SPRING C. FilsfilsInternet-Draft Cisco Systems, Inc.Intended status: Standards Track J. LeddyExpires: June 24, 2018 Comcast D. Voyer D. Bernier Bell Canada D. Steinberg Steinberg Consulting R. Raszuk Bloomberg LP S. Matsushima SoftBank D. Lebrun Universite catholique de Louvain B. Decraene Orange B. Peirens Proximus S. Salsano Universita di Roma "Tor Vergata" G. Naik Drexel University H. Elmalky Ericsson P. Jonnalagadda M. Sharif Barefoot Networks A. Ayyangar Arista S. Mynam Dell Force10 Networks W. Henderickx Nokia A. Bashandy K. Raza D. Dukes F. Clad P. Camarillo, Ed. Cisco Systems, Inc. December 21, 2017 SRv6 Network Programmingdraft-filsfils-spring-srv6-network-programming-03Filsfils, et al. Expires June 24, 2018 [Page 1]
Internet-Draft SRv6 Network Programming December 2017Abstract This document describes the SRv6 network programming concept and its most basic functions.Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described inRFC 2119 [RFC2119].Status of This Memo This Internet-Draft is submitted in full conformance with the provisions ofBCP 78 andBCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is athttps://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on June 24, 2018.Copyright Notice Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject toBCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.Filsfils, et al. Expires June 24, 2018 [Page 2]
Internet-Draft SRv6 Network Programming December 2017Table of Contents1. Introduction . . . . . . . . . . . . . . . . . . . . . . . .52. Terminology . . . . . . . . . . . . . . . . . . . . . . . . .53. SRv6 Segment . . . . . . . . . . . . . . . . . . . . . . . .64. Functions associated with a Local SID . . . . . . . . . . . .84.1. End: Endpoint . . . . . . . . . . . . . . . . . . . . . .104.2. End.X: Endpoint with Layer-3 cross-connect . . . . . . .104.3. End.T: Endpoint with specific IPv6 table lookup . . . . .11 4.4. End.DX2: Endpoint with decapsulation and Layer-2 cross- connect . . . . . . . . . . . . . . . . . . . . . . . . .12 4.5. End.DX2V: Endpoint with decapsulation and VLAN L2 table lookup . . . . . . . . . . . . . . . . . . . . . . . . .12 4.6. End.DT2U: Endpoint with decapsulation and unicast MAC L2 table lookup . . . . . . . . . . . . . . . . . . . . . .13 4.7. End.DT2M: Endpoint with decapsulation and L2 table flooding . . . . . . . . . . . . . . . . . . . . . . . .14 4.8. End.DX6: Endpoint with decapsulation and IPv6 cross- connect . . . . . . . . . . . . . . . . . . . . . . . . .15 4.9. End.DX4: Endpoint with decapsulation and IPv4 cross- connect . . . . . . . . . . . . . . . . . . . . . . . . .15 4.10. End.DT6: Endpoint with decapsulation and specific IPv6 table lookup . . . . . . . . . . . . . . . . . . . . . .16 4.11. End.DT4: Endpoint with decapsulation and specific IPv4 table lookup . . . . . . . . . . . . . . . . . . . . . .17 4.12. End.DT46: Endpoint with decapsulation and specific IP table lookup . . . . . . . . . . . . . . . . . . . . . .174.13. End.B6: Endpoint bound to an SRv6 policy . . . . . . . .18 4.14. End.B6.Encaps: Endpoint bound to an SRv6 encapsulation policy . . . . . . . . . . . . . . . . . . . . . . . . .194.15. End.BM: Endpoint bound to an SR-MPLS policy . . . . . . .194.16. End.S: Endpoint in search of a target in table T . . . .204.17. SR-aware application . . . . . . . . . . . . . . . . . .204.18. Non SR-aware application . . . . . . . . . . . . . . . .214.19. Flavours . . . . . . . . . . . . . . . . . . . . . . . .214.19.1. PSP: Penultimate Segment Pop of the SRH . . . . . .214.19.2. USP: Ultimate Segment Pop of the SRH . . . . . . . .215. Transit behaviors . . . . . . . . . . . . . . . . . . . . . .225.1. T: Transit behavior . . . . . . . . . . . . . . . . . . .225.2. T.Insert: Transit with insertion of an SRv6 Policy . . .22 5.3. T.Encaps: Transit with encapsulation in an SRv6 Policy . 235.4. T.Encaps.L2: Transit with encapsulation of L2 frames . .236. Operation . . . . . . . . . . . . . . . . . . . . . . . . . .246.1. Reserved FUNC opcodes . . . . . . . . . . . . . . . . . .246.2. Counters . . . . . . . . . . . . . . . . . . . . . . . .246.3. Flow-based hash computation . . . . . . . . . . . . . . .256.4. O-bit processing . . . . . . . . . . . . . . . . . . . .256.5. End.OTP: OAM Endpoint with Timestamp and Punt . . . . . .26Filsfils, et al. Expires June 24, 2018 [Page 3]
Internet-Draft SRv6 Network Programming December 20177. Basic security for intra-domain deployment . . . . . . . . .267.1. SEC 1 . . . . . . . . . . . . . . . . . . . . . . . . . .277.2. SEC 2 . . . . . . . . . . . . . . . . . . . . . . . . . .277.3. SEC 3 . . . . . . . . . . . . . . . . . . . . . . . . . .277.4. SEC 4 . . . . . . . . . . . . . . . . . . . . . . . . . .288. Control Plane . . . . . . . . . . . . . . . . . . . . . . . .288.1. IGP . . . . . . . . . . . . . . . . . . . . . . . . . . .288.2. BGP-LS . . . . . . . . . . . . . . . . . . . . . . . . .298.3. BGP IP/VPN . . . . . . . . . . . . . . . . . . . . . . .298.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . .299. Illustration . . . . . . . . . . . . . . . . . . . . . . . .309.1. Simplified SID allocation . . . . . . . . . . . . . . . .309.2. Reference diagram . . . . . . . . . . . . . . . . . . . .319.3. Basic security . . . . . . . . . . . . . . . . . . . . .319.4. SR-IPVPN . . . . . . . . . . . . . . . . . . . . . . . .329.5. SR-Ethernet-VPWS . . . . . . . . . . . . . . . . . . . .339.6. SR-EVPN-FXC . . . . . . . . . . . . . . . . . . . . . . .349.7. SR-EVPN . . . . . . . . . . . . . . . . . . . . . . . . .359.7.1. EVPN Bridging . . . . . . . . . . . . . . . . . . . .359.7.2. EVPN Multi-homing with ESI filtering . . . . . . . .379.7.3. EVPN Layer-3 . . . . . . . . . . . . . . . . . . . .389.7.4. EVPN Integrated Routing Bridging (IRB) . . . . . . .389.8. SR TE for Underlay SLA . . . . . . . . . . . . . . . . .399.8.1. SR policy from the Ingress PE . . . . . . . . . . . .399.8.2. SR policy at a midpoint . . . . . . . . . . . . . . .409.9. End-to-End policy with intermediate BSID . . . . . . . .419.10. TI-LFA . . . . . . . . . . . . . . . . . . . . . . . . .429.11. SR TE for Service chaining . . . . . . . . . . . . . . .439.12. OAM . . . . . . . . . . . . . . . . . . . . . . . . . . .449.12.1. Ping to a SID function . . . . . . . . . . . . . . .449.12.2. End-to-end ping using End.OTP . . . . . . . . . . .449.12.3. Segment-by-segment ping using the O-bit . . . . . .4410. Benefits . . . . . . . . . . . . . . . . . . . . . . . . . .4510.1. Seamless deployment . . . . . . . . . . . . . . . . . .4510.2. Integration . . . . . . . . . . . . . . . . . . . . . .4610.3. Security . . . . . . . . . . . . . . . . . . . . . . . .4711. IANA Considerations . . . . . . . . . . . . . . . . . . . . .4712. Work in progress . . . . . . . . . . . . . . . . . . . . . .4713. Acknowledgements . . . . . . . . . . . . . . . . . . . . . .4714. Contributors . . . . . . . . . . . . . . . . . . . . . . . .4715. References . . . . . . . . . . . . . . . . . . . . . . . . .4715.1. Normative References . . . . . . . . . . . . . . . . . .4715.2. Informative References . . . . . . . . . . . . . . . . .47Appendix A. Additional Contributors . . . . . . . . . . . . . .49 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . .49Filsfils, et al. Expires June 24, 2018 [Page 4]
Internet-Draft SRv6 Network Programming December 20171. Introduction Segment Routing leverages the source routing paradigm. An ingress node steers a packet through a ordered list of instructions, called segments. Each one of these instructions represents a function to be called at a specific location in the network. A function is locally defined on the node where it is executed and may range from simply moving forward in the segment list to any complex user-defined behavior. The network programming consists in combining segment routing functions, both simple and complex, to achieve a networking objective that goes beyond mere packet routing. This document illustrates the SRv6 Network Programming concept and aims at standardizing the main segment routing functions to enable the creation of interoperable overlays with underlay optimization and service chaining. Familiarity with the Segment Routing Header [I-D.ietf-6man-segment-routing-header] is assumed.2. Terminology SRH is the abbreviation for the Segment Routing Header. We assume that the SRH may be present multiple times inside each packet. NH is the abbreviation of the IPv6 next-header field. NH=SRH means that the next-header field is 43 with routing type 4. When there are multiple SRHs, they must follow each other: the next- header field of all SRH except the last one must be SRH. The effective next-header (ENH) is the next-header field of the IP header when no SRH is present, or is the next-header field of the last SRH. In this version of the document, we assume that there is no other extension header than the SRH. These will be lifted in future versions of the document. SID: A Segment Identifier which represents a specific segment in segment routing domain. The SID type used in this document is IPv6 address (also referenced as SRv6 Segment or SRv6 SID). A SID list is represented as <S1, S2, S3> where S1 is the first SID to visit, S2 is the second SID to visit and S3 is the last SID to visit along the SR path.Filsfils, et al. Expires June 24, 2018 [Page 5]
Internet-Draft SRv6 Network Programming December 2017 (SA,DA) (S3, S2, S1; SL) represents an IPv6 packet with: - IPv6 header with source and destination addresses respectively SA and DA and next-header is SRH - SRH with SID list <S1, S2, S3> with SegmentsLeft = SL - Note the difference between the <> and () symbols: <S1, S2, S3> represents a SID list where S1 is the first SID and S3 is the last SID. (S3, S2, S1; SL) represents the same SID list but encoded in the SRH format where the rightmost SID in the SRH is the first SID and the leftmost SID in the SRH is the last SID. When referring to an SR policy in a high-level use-case, it is simpler to use the <S1, S2, S3> notation. When referring to an illustration of the detailed behavior, the (S3, S2, S1; SL) is more convenient. - The payload of the packet is omitted. SRH[SL] represents the SID pointed by the SL field in the first SRH. In our example, SRH[2] represents S1, SRH[1] represents S2 and SRH[0] represents S3. FIB is the abbreviation for the forwarding table. A FIB lookup is a lookup in the forwarding table. When a packet is intercepted on a wire, it is possible that SRH[SL] is different from the DA.3. SRv6 Segment An SRv6 Segment is a 128-bit value. "SID" (abbreviation for Segment Identifier) is often used as a shorter reference for "SRv6 Segment". An SRv6-capable node N maintains a "My Local SID Table". This table contains all the local SRv6 segments explicitly instantiated at node N. N is the parent node for these SIDs. A local SID of N can be an IPv6 address associated to a local interface of N but it is not mandatory. Nor is the My Local SID table populated by default with all IPv6 addresses defined on node N. In most use-cases, a local SID will NOT be an address associated to a local interface of N. A local SID of N could be routed to N but it does not have to be. Most often, it is routed to N via a shorter-mask prefix. Let's provide a classic illustration.Filsfils, et al. Expires June 24, 2018 [Page 6]
Internet-Draft SRv6 Network Programming December 2017 Node N is configured with a loopback0 interface address of C1::1/40 originated in its IGP. Node N is configured with two SIDs: C1::100 and C2::101. The entry C1::1 is not defined explicitly as an SRv6 SID and hence does not appear in the "My Local SID Table". The entries C1::100 and C2::101 are defined explicitly as SRv6 SIDs and hence appear in the "My Local SID Table". The network learns about a path to C1::/40 via the IGP and hence a packet destined to C1::100 would be routed up to N. The network does not learn about a path to C2::/40 via the IGP and hence a packet destined to C2::101 would not be routed up to N. A packet could be steered to a non-routed SID C2::101 by using a SID list <...,C1::100,C2::101,...> where the non-routed SID is preceded by a routed SID to the same node. This is similar to the local vs global segments in SR-MPLS. Every SRv6 local SID instantiated has a specific instruction bound to it. This information is stored in the "My Local SID Table". The "My Local SID Table" has three main purposes: - Define which local SIDs are explicitly instantiated - Specify which instruction is bound to each of the instantiated SIDs - Store the parameters associated with such instruction (i.e. OIF, NextHop,...) We represent an SRv6 local SID as LOC:FUNCT where LOC is the L most significant bits and FUNCT is the 128-L least significant bits. L is called the locator length and is flexible. Each operator is free to use the locator length it chooses. Most often the LOC part of the SID is routable and leads to the node which owns that SID. Often, for simplicity of illustration, we will use a locator length of 64 bits. This is just an example. Implementations must not assume any a priori prefix length. The FUNCT part of the SID is an opaque identification of a local function bound to the SID. Hence the name SRv6 Local SID. A function may require additional arguments that would be placed in the rightmost-bits of the 128-bit space. In such case, the SRv6 Local SID will have the form LOC:FUNCT:ARGS.Filsfils, et al. Expires June 24, 2018 [Page 7]
Internet-Draft SRv6 Network Programming December 2017 These arguments may vary on a per-packet basis and may contain information related to the flow, service, or any other information required by the function associated to the SRv6 Local SID. For to this reason, the "My Local SID Table" matches on a per longest-prefix-match basis. A node may receive a packet with an SRv6 SID in the DA without an SRH. In such case the packet should still be processed by the Segment Routing engine.4. Functions associated with a Local SID Each entry of the "My Local SID Table" indicates the function associated with the local SID. We define hereafter a set of well-known functions that can be associated with a SID.Filsfils, et al. Expires June 24, 2018 [Page 8]
Internet-Draft SRv6 Network Programming December 2017 End Endpoint function The SRv6 instantiation of a prefix SID End.X Endpoint function with Layer-3 cross-connect The SRv6 instantiation of a Adj SID End.T Endpoint function with specific IPv6 table lookup End.DX2 Endpoint with decapsulation and Layer-2 cross-connect L2VPN use-case End.DX2V Endpoint with decapsulation and VLAN L2 table lookup EVPN Flexible cross-connect use-cases End.DT2U Endpoint with decapsulation and unicast MAC L2 table lookup EVPN Bridging unicast use-cases End.DT2M Endpoint with decapsulation and L2 table flooding EVPN Bridging BUM use-cases with ESI filtering End.DX6 Endpoint with decapsulation and IPv6 cross-connect IPv6 L3VPN use (equivalent of a per-CE VPN label) End.DX4 Endpoint with decapsulation and IPv4 cross-connect IPv4 L3VPN use (equivalent of a per-CE VPN label) End.DT6 Endpoint with decapsulation and IPv6 table lookup IPv6 L3VPN use (equivalent of a per-VRF VPN label) End.DT4 Endpoint with decapsulation and IPv4 table lookup IPv4 L3VPN use (equivalent of a per-VRF VPN label) End.DT46 Endpoint with decapsulation and IP table lookup IP L3VPN use (equivalent of a per-VRF VPN label) End.B6 Endpoint bound to an SRv6 policy SRv6 instantiation of a Binding SID End.B6.Encaps Endpoint bound to an SRv6 encapsulation Policy SRv6 instantiation of a Binding SID End.BM Endpoint bound to an SR-MPLS Policy SRv6/SR-MPLS instantiation of a Binding SID End.S Endpoint in search of a target in table T The list is not exhaustive. In practice, any function can be attached to a local SID: e.g. a node N can bind a SID to a local VM or container which can apply any complex function on the packet. We call N the node who has an explicitly defined local SID S and we detail the function that N binds to S. At the end of this section we also present some flavours of these well-known functions.Filsfils, et al. Expires June 24, 2018 [Page 9]
Internet-Draft SRv6 Network Programming December 20174.1. End: Endpoint The Endpoint function ("End" for short) is the most basic function. When N receives a packet whose IPv6 DA is S and S is a local End SID, N does: 1. IF NH=SRH and SL > 0 2. decrement SL 3. update the IPv6 DA with SRH[SL] 4. FIB lookup on updated DA ;; Ref1 5. forward accordingly to the matched entry ;; Ref2 6. ELSE 7. drop the packet ;; Ref3 Ref1: The End function performs the FIB lookup in the forwarding table associated to the ingress interface Ref2: If the FIB lookup matches a multicast state, then the related RPF check must be considered successful Ref3: a local SID could be bound to a function which authorizes the decapsulation of an outer header (e.g. IPinIP) or the punting of the packet to TCP, UDP or any other protocol. This however needs to be explicitly defined in the function bound to the local SID. By default, a local SID bound to the well-known function "End" only allows the punting to OAM protocols and neither allows the decapsulation of an outer header nor the cleanup of an SRH. As a consequence, an End SID cannot be the last SID of an SRH and cannot be the DA of a packet without SRH. This is the SRv6 instantiation of a Prefix SID [I-D.ietf-spring-segment-routing].4.2. End.X: Endpoint with Layer-3 cross-connect The "Endpoint with cross-connect to an array of layer-3 adjacencies" function (End.X for short) is a variant of the End function. When N receives a packet destined to S and S is a local End.X SID, N does: 1. IF NH=SRH and SL > 0 2. decrement SL 3. update the IPv6 DA with SRH[SL] 4. forward to layer-3 adjacency bound to the SID S ;; Ref1 5. ELSE 6. drop the packet ;; Ref2Filsfils, et al. Expires June 24, 2018 [Page 10]
Internet-Draft SRv6 Network Programming December 2017 Ref1: If an array of adjacencies is bound to the End.X SID, then one entry of the array is selected based on a hash of the packet's header. Ref2: An End.X function only allows punting to OAM and does not allow decaps. An End.X SID cannot be the last SID of an SRH and cannot be the DA of a packet without SRH. The End.X function is required to express any traffic-engineering policy. This is the SRv6 instantiation of an Adjacency SID [I-D.ietf-spring-segment-routing]. If a node N has 30 outgoing interfaces to 30 neighbors, usually the operator would explicitly instantiate 30 End.X SIDs at N: one per layer-3 adjacency to a neighbor. Potentially, more End.X could be explicitly defined (groups of layer-3 adjacencies to the same neighbor or to different neighbors). Note that with SR-MPLS, an AdjSID is typically preceded by a PrefixSID. This is unlikely in SRv6 as most likely an End.X SID is globally routed to N. Note that if N has an outgoing interface bundle I to a neighbor Q made of 10 member links, N may allocate up to 11 End.X local SIDs for that bundle: one for the bundle itself and then up to one for each member link. This is the equivalent of the L2-Link Adj SID in SR- MPLS [I-D.ietf-isis-l2bundles].4.3. End.T: Endpoint with specific IPv6 table lookup The "Endpoint with specific IPv6 table lookup" function (End.T for short) is a variant of the End function. When N receives a packet destined to S and S is a local End.T SID, N does: 1. IF NH=SRH and SL > 0 ;; Ref1 2. decrement SL 3. update the IPv6 DA with SRH[SL] 4. lookup the next segment in IPv6 table T associated with the SID 5. forward via the matched table entry 6. ELSE 7. drop the packet Ref1: The End.T SID must not be the last SIDFilsfils, et al. Expires June 24, 2018 [Page 11]
Internet-Draft SRv6 Network Programming December 2017 The End.T is used for multi-table operation in the core.4.4. End.DX2: Endpoint with decapsulation and Layer-2 cross-connect The "Endpoint with decapsulation and Layer-2 cross-connect to OIF" function (End.DX2 for short) is a variant of the endpoint function. When N receives a packet destined to S and S is a local End.DX2 SID, N does: 1. IF NH=SRH and SL > 0 2. drop the packet ;; Ref1 3. ELSE IF ENH = 59 ;; Ref2 4. pop the (outer) IPv6 header and its extension headers 5. forward the resulting frame via OIF associated to the SID 6. ELSE 7. drop the packet Ref1: An End.DX2 SID must always be the last SID, or it can be the Destination Address of an IPv6 packet with no SRH header. Ref2: We conveniently reuse the next-header value 59 allocated to IPv6 No Next Header [RFC2460]. When the SID is of function End.DX2 and the Next-Header=59, we know that an Ethernet frame is in the payload without any further header. An End.DX2 function could be customized to expect a specific VLAN format and rewrite the egress VLAN header before forwarding on the outgoing interface. One of the applications of the End.DX2 function is the L2VPN use- case.4.5. End.DX2V: Endpoint with decapsulation and VLAN L2 table lookup The "Endpoint with decapsulation and specific VLAN L2 table lookup" function (End.DX2V for short) is a variant of the endpoint function. When N receives a packet destined to S and S is a local End.DX2V SID, N does:Filsfils, et al. Expires June 24, 2018 [Page 12]
Internet-Draft SRv6 Network Programming December 2017 1. IF NH=SRH and SL > 0 2. drop the packet ;; Ref1 3. ELSE IF ENH = 59 ;; Ref2 4. pop the (outer) IPv6 header and its extension headers 5. lookup the exposed inner VLANs in L2 table T 6. forward via the matched table entry 7. ELSE 8. drop the packet Ref1: An End.DX2V SID must always be the last SID, or it can be the Destination Address of an IPv6 packet with no SRH header. Ref2: We conveniently reuse the next-header value 59 allocated to IPv6 No Next Header [RFC2460]. When the SID is of function End.DX2V and the Next-Header=59, we know that an Ethernet frame is in the payload without any further header. An End.DX2V function could be customized to expect a specific VLAN format and rewrite the egress VLAN header before forwarding on the outgoing interface. The End.DX2V is used for EVPN Flexible cross-connect use-cases.4.6. End.DT2U: Endpoint with decapsulation and unicast MAC L2 table lookup The "Endpoint with decapsulation and specific unicast MAC L2 table lookup" function (End.DT2U for short) is a variant of the endpoint function. When N receives a packet destined to S and S is a local End.DT2U SID, N does: 1. IF NH=SRH and SL > 0 2. drop the packet ;; Ref1 3. ELSE IF ENH = 59 ;; Ref2 4. pop the (outer) IPv6 header and its extension headers 5. learn he exposed inner MAC SA in L2 table T ;; Ref3 6. lookup the exposed inner MAC DA in L2 table T 7. forward via the matched T entry else to all L2OIF in T 8. ELSE 9. drop the packet Ref1: An End.DT2U SID must always be the last SID, or it can be the Destination Address of an IPv6 packet with no SRH header. Ref2: We conveniently reuse the next-header value 59 allocated to IPv6 No Next Header [RFC2460]. When the SID is of function End.DT2UFilsfils, et al. Expires June 24, 2018 [Page 13]
Internet-Draft SRv6 Network Programming December 2017 and the Next-Header=59, we know that an Ethernet frame is in the payload without any further header. Ref3: In EVPN, the learning of the exposed inner MAC SA is done via control plane. The End.DT2U is used for EVPN Bridging unicast use cases.4.7. End.DT2M: Endpoint with decapsulation and L2 table flooding The "Endpoint with decapsulation and specific L2 table flooding" function (End.DT2M for short) is a variant of the endpoint function. This function may take an argument: "Arg.FE2". It is an argument specific to EVPN ESI filtering. It is used to exclude a specific OIF from L2 table T flooding. The Arg.FE2 SID is merged with an End.DT2M function by bit ORing operation to form an End.DT2M(FE2)single SID. When N receives a packet destined to S and S is a local End.DT2M SID, N does: 1. IF NH=SRH and SL > 0 2. drop the packet ;; Ref1 3. ELSE IF ENH = 59 ;; Ref2 4. pop the (outer) IPv6 header and its extension headers 5. learn the exposed inner MAC SA in L2 table T ;; Ref3 6. forward on all L2OIF excluding the one specified in Arg.FE2 7. ELSE 8. drop the packet Ref1: An End.DT2M SID must always be the last SID, or it can be the Destination Address of an IPv6 packet with no SRH header. Ref2: We conveniently reuse the next-header value 59 allocated to IPv6 No Next Header [RFC2460]. When the SID is of function End.DT2M and the Next-Header=59, we know that an Ethernet frame is in the payload without any further header. Ref3: In EVPN, the learning of the exposed inner MAC SA is done via control plane The End.DT2M is used for EVPN Bridging BUM use case with ESI filtering capability.Filsfils, et al. Expires June 24, 2018 [Page 14]
Internet-Draft SRv6 Network Programming December 20174.8. End.DX6: Endpoint with decapsulation and IPv6 cross-connect The "Endpoint with decapsulation and cross-connect to an array of IPv6 adjacencies" function (End.DX6 for short) is a variant of the End and End.X functions. When N receives a packet destined to S and S is a local End.DX6 SID, N does: 1. IF NH=SRH and SL > 0 2. drop the packet ;; Ref1 3. ELSE IF ENH = 41 ;; Ref2 4. pop the (outer) IPv6 header and its extension headers 5. forward to layer-3 adjacency bound to the SID S ;; Ref3 6. ELSE 7. drop the packet Ref1: The End.DX6 SID must always be the last SID, or it can be the Destination Address of an IPv6 packet with no SRH header. Ref2: 41 refers to IPv6 encapsulation as defined by IANA allocation for Internet Protocol Numbers Ref3: Selected based on a hash of the packet's header (at least SA, DA, Flow Label) One of the applications of the End.DX6 function is the L3VPN use-case where a FIB lookup in a specific tenant table at the egress PE is not required. This would be equivalent to the per-CE VPN label in MPLS[RFC4364].4.9. End.DX4: Endpoint with decapsulation and IPv4 cross-connect The "Endpoint with decapsulation and cross-connect to an array of IPv4 adjacencies" function (End.DX4 for short) is a variant of the End and End.X functions. When N receives a packet destined to S and S is a local End.DX4 SID, N does: 1. IF NH=SRH and SL > 0 2. drop the packet ;; Ref1 3. ELSE IF ENH = 4 ;; Ref2 4. pop the (outer) IPv6 header and its extension headers 5. forward to layer-3 adjacency bound to the SID S ;; Ref3 6. ELSE 7. drop the packetFilsfils, et al. Expires June 24, 2018 [Page 15]
Internet-Draft SRv6 Network Programming December 2017 Ref1: The End.DX4 SID must always be the last SID, or it can be the Destination Address of an IPv6 packet with no SRH header. Ref2: 4 refers to IPv4 encapsulation as defined by IANA allocation for Internet Protocol Numbers Ref3: Selected based on a hash of the packet's header (at least SA, DA, Flow Label) One of the applications of the End.DX4 function is the L3VPN use-case where a FIB lookup in a specific tenant table at the egress PE is not required. This would be equivalent to the per-CE VPN label in MPLS[RFC4364].4.10. End.DT6: Endpoint with decapsulation and specific IPv6 table lookup The "Endpoint with decapsulation and specific IPv6 table lookup" function (End.DT6 for short) is a variant of the End function. When N receives a packet destined to S and S is a local End.DT6 SID, N does: 1. IF NH=SRH and SL > 0 2. drop the packet ;; Ref1 3. ELSE IF ENH = 41 ;; Ref2 4. pop the (outer) IPv6 header and its extension headers 5. lookup the exposed inner IPv6 DA in IPv6 table T 6. forward via the matched table entry 7. ELSE 8. drop the packet Ref1: the End.DT6 SID must always be the last SID, or it can be the Destination Address of an IPv6 packet with no SRH header. Ref2: 41 refers to IPv6 encapsulation as defined by IANA allocation for Internet Protocol Numbers One of the applications of the End.DT6 function is the L3VPN use-case where a FIB lookup in a specific tenant table at the egress PE is required. This would be equivalent to the per-VRF VPN label in MPLS[RFC4364]. Note that an End.DT6 may be defined for the main IPv6 table in which case and End.DT6 supports the equivalent of an IPv6inIPv6 decaps (without VPN/tenant implication).Filsfils, et al. Expires June 24, 2018 [Page 16]
Internet-Draft SRv6 Network Programming December 20174.11. End.DT4: Endpoint with decapsulation and specific IPv4 table lookup The "Endpoint with decapsulation and specific IPv4 table lookup" function (End.DT4 for short) is a variant of the End function. When N receives a packet destined to S and S is a local End.DT4 SID, N does: 1. IF NH=SRH and SL > 0 2. drop the packet ;; Ref1 3. ELSE IF ENH = 4 ;; Ref2 4. pop the (outer) IPv6 header and its extension headers 5. lookup the exposed inner IPv4 DA in IPv4 table T 6. forward via the matched table entry 7. ELSE 8. drop the packet Ref1: the End.DT4 SID must always be the last SID, or it can be the Destination Address of an IPv6 packet with no SRH header. Ref2: 4 refers to IPv4 encapsulation as defined by IANA allocation for Internet Protocol Numbers One of the applications of the End.DT4 is the L3VPN use-case where a FIB lookup in a specific tenant table at the egress PE is required. This would be equivalent to the per-VRF VPN label in MPLS[RFC4364]. Note that an End.DT4 may be defined for the main IPv4 table in which case and End.DT4 supports the equivalent of an IPv4inIPv6 decaps (without VPN/tenant implication).4.12. End.DT46: Endpoint with decapsulation and specific IP table lookup The "Endpoint with decapsulation and specific IP table lookup" function (End.DT46 for short) is a variant of the End function. When N receives a packet destined to S and S is a local End.DT46 SID, N does:Filsfils, et al. Expires June 24, 2018 [Page 17]
Internet-Draft SRv6 Network Programming December 2017 1. IF NH=SRH and SL > 0 2. drop the packet ;; Ref1 3. ELSE IF ENH = 4 ;; Ref2 4. pop the (outer) IPv6 header and its extension headers 5. lookup the exposed inner IPv4 DA in IPv4 table T 6. forward via the matched table entry 7. ELSE IF ENH = 41 ;; Ref2 8. pop the (outer) IPv6 header and its extension headers 9. lookup the exposed inner IPv6 DA in IPv6 table T 10. forward via the matched table entry 11. ELSE 12. drop the packet Ref1: the End.DT46 SID must always be the last SID, or it can be the Destination Address of an IPv6 packet with no SRH header. Ref2: 4 and 41 refer to IPv4 and IPv6 encapsulation respectively as defined by IANA allocation for Internet Protocol Numbers One of the applications of the End.DT46 is the L3VPN use-case where a FIB lookup in a specific tenant table at the egress PE is required. This would be equivalent to the per-VRF VPN label in MPLS[RFC4364]. Note that an End.DT46 may be defined for the main IP table in which case and End.DT46 supports the equivalent of an IPinIPv6 decaps (without VPN/tenant implication).4.13. End.B6: Endpoint bound to an SRv6 policy The "Endpoint bound to an SRv6 Policy" is a variant of the End function. When N receives a packet destined to S and S is a local End.B6 SID, N does: 1. IF NH=SRH and SL > 0 ;; Ref1 2. do not decrement SL nor update the IPv6 DA with SRH[SL] 3. insert a new SRH ;; Ref2 4. set the IPv6 DA to the first segment of the SRv6 Policy 5. forward according to the first segment of the SRv6 Policy 6. ELSE 7. drop the packet Ref1: An End.B6 SID, by definition, is never the last SID. Ref2: In case that an SRH already exists, the new SRH is inserted in between the IPv6 header and the received SRHFilsfils, et al. Expires June 24, 2018 [Page 18]
Internet-Draft SRv6 Network Programming December 2017 Note: Instead of the term "insert", "push" may also be used. The End.B6 function is required to express scalable traffic- engineering policies across multiple domains. This is the SRv6 instantiation of a Binding SID [I-D.ietf-spring-segment-routing].4.14. End.B6.Encaps: Endpoint bound to an SRv6 encapsulation policy This is a variation of the End.B6 behavior where the SRv6 Policy also includes an IPv6 Source Address A. When N receives a packet destined to S and S is a local End.B6.Encaps SID, N does: 1. IF NH=SRH and SL > 0 2. decrement SL and update the IPv6 DA with SRH[SL] 3. push an outer IPv6 header with its own SRH 4. set the outer IPv6 SA to A 5. set the outer IPv6 DA to the first segment of the SRv6 Policy 6. forward according to the first segment of the SRv6 Policy 7. ELSE 8. drop the packet Instead of simply inserting an SRH with the policy (End.B6), this behavior also adds an outer IPv6 header. The source address defined for the outer header does not have to be a local SID of the node.4.15. End.BM: Endpoint bound to an SR-MPLS policy The "Endpoint bound to an SR-MPLS Policy" is a variant of the End.B6 function. When N receives a packet destined to S and S is a local End.BM SID, N does: 1. IF NH=SRH and SL > 0 ;; Ref1 2. decrement SL and update the IPv6 DA with SRH[SL] 3. push an MPLS label stack <L1, L2, L3> on the received packet 4. forward according to L1 5. ELSE 6. drop the packet Ref1: an End.BM SID, by definition, is never the last SID. The End.BM function is required to express scalable traffic- engineering policies across multiple domains where some domains support the MPLS instantiation of Segment Routing.Filsfils, et al. Expires June 24, 2018 [Page 19]
Internet-Draft SRv6 Network Programming December 2017 This is an SRv6 instantiation of a SR-MPLS Binding SID [I-D.ietf-spring-segment-routing].4.16. End.S: Endpoint in search of a target in table T The "Endpoint in search of a target in Table T" function (End.S for short) is a variant of the End function. When N receives a packet destined to S and S is a local End.S SID, N does: 1. IF NH=SRH and SL = 0 ;; Ref1 2. drop the packet 3. ELSE IF match(last SID) in specified table T 4. forward accordingly 5. ELSE 6. apply the End behavior Ref1: By definition, an End.S SID cannot be the last SID, as the last SID is the targeted object. The End.S function is required in information-centric networking (ICN) use-cases where the last SID in the SRv6 SID list represents a targeted object. If the identification of the object would require more than 128 bits, then obvious customization of the End.S function may either use multiple SIDs or a TLV of the SR header to encode the searched object ID.4.17. SR-aware application Generally, any SR-aware application can be bound to an SRv6 SID. This application could represent anything from a small piece of code focused on topological/tenant function to a much larger process focusing on higher-level applications (e.g. video compression, transcoding etc.). The ways in which an SR-aware application can binds itself on a local SID depends on the operating system. Let us consider an SR-aware application running on a Linux operating system. A possible approach is to associate an SRv6 SID to a target (virtual) interface, so that packets with IP DA corresponding to the SID will be sent to the target interface. In this approach, the SR-aware application can simply listen to all packets received on the interface. A different approach for the SR-aware app is to listen to packets received with a specific SRv6 SID as IPv6 DA on a given transport port (i.e. corresponding to a TCP or UDP socket). In this case, the app can read the SRH information with a getsockopt Linux system callFilsfils, et al. Expires June 24, 2018 [Page 20]
Internet-Draft SRv6 Network Programming December 2017 and can set the SRH information to be added to the outgoing packets with a setsocksopt system call.4.18. Non SR-aware application [I-D.xu-clad-spring-sr-service-chaining] defines a set of additional functions in order to enable non SR-aware applications to be associated with a SRv6 Local SID.4.19. Flavours We present the PSP and USP variants of the functions End, End.X and End.T. For each of these functions these variants can be enabled or disabled either individually or together.4.19.1. PSP: Penultimate Segment Pop of the SRH After the instruction 'update the IPv6 DA with SRH[SL]' is executed, the following instructions must be added: 1. IF updated SL = 0 & PSP is TRUE & O-bit = 0 & A-bit = 0 ;; Ref1 2. pop the top SRH ;; Ref2 Ref1: If the SRH.Flags.O-bit or SRH.Flags.A-bit is set, PSP of the SRH is disabled.Section 6.1 specifies the pseudocode needed to process the SRH.Flags.O-bit. Ref2: The received SRH had SL=1. When the last SID is written in the DA, the End, End.X and End.T functions with the PSP flavour pop the first (top-most) SRH. Subsequent stacked SRH's may be present but are not processed as part of the function.4.19.2. USP: Ultimate Segment Pop of the SRH We insert at the beginning of the pseudo-code the following instructions: 1. IF SL = 0 & NH=SRH & USP=TRUE ;; Ref1 2. pop the top SRH 3. restart the function processing on the modified packet ;; Ref2 Ref1: The next header is an SRH header Ref2: Typically SL of the exposed SRH is > 0 and hence the restarting of the complete function would lead to decrement SL, update the IPv6 DA with SRH[SL], FIB lookup on updated DA and forward accordingly to the matched entry.Filsfils, et al. Expires June 24, 2018 [Page 21]
Internet-Draft SRv6 Network Programming December 20175. Transit behaviors We define hereafter the set of basic transit behaviors. T Transit behavior T.Insert Transit behavior with insertion of an SRv6 Policy T.Encaps Transit behavior with encapsulation in an SRv6 policy T.Encaps.L2 T.Encaps behavior of the received L2 frame This list can be expanded in case any new functionality requires it.5.1. T: Transit behavior As per [RFC2460], if a node N receives a packet (A, S2)(S3, S2, S1; SL=2) and S2 is neither a local address nor a local SID of N then N forwards the packet without inspecting the SRH. This means that N treats the following two packets with the same performance: - (A, S2) - (A, S2)(S3, S2, S1; SL=2) A transit node does not need to count by default the amount of transit traffic with an SRH extension header. This accounting might be enabled as an optional behavior leveraging SEC4 behavior described later in this document.Section 7.4 A transit node MUST include the outer flow label in its ECMP hash[RFC6437].5.2. T.Insert: Transit with insertion of an SRv6 Policy Node N receives two packets P1=(A, B2) and P2=(A,B2)(B3, B2, B1; SL=1). B2 is neither a local address nor SID of N. N steers the transit packets P1 and P2 into an SRv6 Policy with one SID list <S1, S2, S3>. The "T.Insert" transit insertion behavior is defined as follows: 1. insert the SRH (B2, S3, S2, S1; SL=3) ;; Ref1, Ref1bis 2. set the IPv6 DA = S1 3. forward along the shortest path to S1 Ref1: The received IPv6 DA is placed as last SID of the inserted SRH.Filsfils, et al. Expires June 24, 2018 [Page 22]
Internet-Draft SRv6 Network Programming December 2017 Ref1bis: The SRH is inserted before any other IPv6 Routing Extension Header. After the T.Insert behavior, P1 and P2 respectively look like: - (A, S1) (B2, S3, S2, S1; SL=3) - (A, S1) (B2, S3, S2, S1; SL=3) (B3, B2, B1; SL=1)5.3. T.Encaps: Transit with encapsulation in an SRv6 Policy Node N receives two packets P1=(A, B2) and P2=(A,B2)(B3, B2, B1; SL=1). B2 is neither a local address nor SID of N. N steers the transit packets P1 and P2 into an SR Encapsulation Policy with a Source Address T and a Segment list <S1, S2, S3>. The T.Encaps transit encapsulation behavior is defined as follows: 1. push an IPv6 header with its own SRH (S3, S2, S1; SL=2) 2. set outer IPv6 SA = T and outer IPv6 DA = S1 3. set outer payload length, traffic class and flow label ;; Ref1 4. update the next_header value ;; Ref1 5. decrement inner Hop Limit or TTL ;; Ref1 6. forward along the shortest path to S1 After the T.Encaps behavior, P1 and P2 respectively look like: - (T, S1) (S3, S2, S1; SL=2) (A, B2) - (T, S1) (S3, S2, S1; SL=2) (A, B2) (B3, B2, B1; SL=1) The T.Encaps behavior is valid for any kind of Layer-3 traffic. This behavior is commonly used for L3VPN with IPv4 and IPv6 deployements. The SRH MAY be omitted when the SRv6 Policy only contains one segment and there is no need to use any flag, tag or TLV. Ref 1: As described in [RFC2473] (Generic Packet Tunneling in IPv6 Specification)5.4. T.Encaps.L2: Transit with encapsulation of L2 frames While T.Encaps encapsulates the received IP packet, T.Encaps.L2 encapsulates the received L2 frame (i.e. the received ethernet header and its optional VLAN header is in the payload of the outer packet).Filsfils, et al. Expires June 24, 2018 [Page 23]
Internet-Draft SRv6 Network Programming December 2017 If the outer header is pushed without SRH then the DA must be a SID of type End.DX2, End.DX2V, End.DT2U or End.DT2M and the next-header must be 59 (IPv6 NoNextHeader). The received Ethernet frame follows the IPv6 header and its extension headers. Else, if the outer header is pushed with an SRH, then the last SID of the SRH must be of type End.DX2, End.DX2V, End.DT2U or End.DT2M and the next-header of the SRH must be 59 (IPv6 NoNextHeader). The received Ethernet frame follows the IPv6 header and its extension headers.6. Operation6.1. Reserved FUNC opcodes The following SRv6 LocalSID function opcodes are reserved: - Opcode 0: Invalid - Opcode 1-63: Reserved - Opcode 1: End with PSP - Opcode 2: End with USP - Opcode ~0 (all 1s): Wildcard The SRv6 LocalSID argument value "0" means "No argument".6.2. Counters Any SRv6 capable node SHOULD implement the following set of combined counters (packets and bytes): - CNT1: Per entry of the "My Local SID Table", traffic that matched that SID and was processed correctly. - CNT2: Per SRv6 Policy, traffic steered into it and processed correctly. Furthermore, an SRv6 capable node maintains an aggregate counter CNT0 tracking the IPv6 traffic that was received with a destination address matching a local interface address that is not a local SID and the next-header is SRH with SL>0. We remind that this traffic is dropped as an interface address is not a local SID by default. A SID must be explicitly instantiated.Filsfils, et al. Expires June 24, 2018 [Page 24]
Internet-Draft SRv6 Network Programming December 20176.3. Flow-based hash computation When a flow-based selection within a set needs to be performed, the source address, the destination address and the flow-label MUST be included in the flow-based hash. This occurs when the destination address is updated and a FIB lookup is performed and multiple ECMP paths exist to the updated destination address. This occurs when End.X is bound to an array of adjacencies. This occurs when the packet is steered in an SR policy whose selected path has multiple SID lists [I-D.filsfils-spring-segment-routing-policy].6.4. O-bit processing [I-D.ietf-6man-segment-routing-header] defines the Segment Routing Header (SRH) Flag O-bit. This document defines the usage of the O-bit in the SRH. Implementation of the O-bit is optional. If a node does not support the O-bit, then upon reception it simply ignores it. If a node supports the O-bit, it can optionally advertise its potential via node capability advertisement in IGP [ID.TBA]. The SRH.Flags.O-bit implements the "punt a timestamped copy and forward" behavior. We insert at the beginning of the pseudo-code the following instructions: 1. Timestamp a local copy of the packet. ;; Ref1 2. Punt the copied packet to CPU for SW processing (slow-path);; Ref2 Ref1: Timestamping is done ASAP at the ingress pipeline (in hardware). As timestamping is done on a copy of the packet which is locally punted, timestamp value can be carried in the local packet header. Ref2: Hardware (microcode) just punts the packet. There is no requirement for the hardware to manipulate any TLV in SRH (or elsewhere). Software (slow path) implements the required OAM mechanism. Timestamp is not carried in the packet forwarded to the next hop.Filsfils, et al. Expires June 24, 2018 [Page 25]
Internet-Draft SRv6 Network Programming December 20176.5. End.OTP: OAM Endpoint with Timestamp and Punt Many scenarios require punting of SRv6 OAM packets at the desired nodes in the network. The "OAM Endpoint with Timestamp and Punt" function (End.OTP for short) represents a special OAM function to implement the timestamp and punt behavior for an OAM packet. This function uses the reserved opcode TBA (To be assigned by IANA). When N receives a packet destined to S and S is a local End.OTP SID, N does: 1. Timestamp the packet ;; Ref1 2. Punt the packet to CPU for SW processing (slow-path) ;; Ref2 Ref1: Timestamping is done ASAP at the ingress pipeline (in hardware). A timestamped packet is locally punted, timestamp value can be carried in local packet header. Ref2: Hardware (microcode) only punts the packet. There is no requirement for the hardware to manipulate any TLV in the SRH (or elsewhere). Software (slow path) implements the required OAM mechanisms.7. Basic security for intra-domain deployment We use the following terminology: An internal node is a node part of the domain of trust. A border router is an internal node at the edge of the domain of trust. An external interface is an interface of a border router towards another domain. An internal interface is an interface entirely within the domain of trust. The internal address space is the IP address block dedicated to internal interfaces. An internal SID is a SID instantiated on an internal node. The internal SID space is the IP address block dedicated to internal SIDs. External traffic is traffic received from an external interface to the domain of trust.Filsfils, et al. Expires June 24, 2018 [Page 26]
Internet-Draft SRv6 Network Programming December 2017 Internal traffic is traffic the originates and ends within the domain of trust. The purpose of this section is to document how a domain of trust can operate SRv6-based services for internal traffic while preventing any external traffic from accessing the internal SRv6-based services. It is expected that future documents will detail enhanced security mechanisms for SRv6 (e.g. how to allow external traffic to leverage internal SRv6 services).7.1. SEC 1 An SRv6 router MUST support an ACL on the external interface that drops any traffic with SA or DA in the internal SID space. A provider would generally do this for its internal address space to prevent access to internal addresses and in order to prevent spoofing. The technique is extended to the local SID space. The typical counters of an ACL are expected.7.2. SEC 2 An SRv6 router MUST support an ACL with the following behavior: 1. IF (DA == LocalSID) && (SA != internal address or SID space) 2. drop This prevents access to local SIDs from outside the operator's infrastructure. Note that this ACL may not be enabled in all cases. For example, specific SIDs can be used to provide resources to devices that are outside of the operator's infrastructure. When an SID is in the form of LOC:FUNCT:ARGS the DA match should be implemented as a prefix match covering the argument space of the specific SID i.s.o. a host route. The typical counters of an ACL are expected.7.3. SEC 3 As per the End definition, an SRv6 router MUST only implement the End behavior on a local IPv6 address if that address has been explicitly enabled as a segment. This address may or may not be associated with an interface. This address may or may not be routed. The only thing that matters isFilsfils, et al. Expires June 24, 2018 [Page 27]
Internet-Draft SRv6 Network Programming December 2017 that the local SID must be explicitly instantiated and explicitly bound to a function (the default function is the End function).7.4. SEC 4 An SRv6 router should support Unicast-RPF on source address on external interface. This is a generic provider technique applied to the internal address space. It is extended to the internal SID space. The typical counters to validate such filtering are expected.8. Control Plane In an SDN environment, one expects the controller to explicitly provision the SIDs and/or discover them as part of a service discovery function. Applications residing on top of the controller could then discover the required SIDs and combine them to form a distributed network program. The concept of "SRv6 network programming" refers to the capability for an application to encode any complex program as a set of individual functions distributed through the network. Some functions relate to underlay SLA others to overlay/tenant, others to complex applications residing in VM and containers. The specification of the SRv6 control-plane is outside the scope of this document. We limit ourselves to a few important observations.8.1. IGP The End and End.X SIDs express topological functions and hence are expected to be signaled in the IGP together with the flavours PSP and USP [I-D.bashandy-isis-srv6-extensions]. The presence of SIDs in the IGP do not imply any routing semantics to the addresses represented by these SIDs. The routing reachability to an IPv6 address is solely governed by the classic, non-SID-related, IGP information. Routing is not governed neither influenced in any way by a SID advertisement in the IGP. These two SIDs provide important topological functions for the IGP to build FRR/TI-LFA solution and for TE processes relying on IGP LSDB to build SR policies.Filsfils, et al. Expires June 24, 2018 [Page 28]
Internet-Draft SRv6 Network Programming December 20178.2. BGP-LS BGP-LS is expected to be the key service discovery protocol. Every node is expected to advertise via BGP-LS its SRv6 capabilities (e.g. how many SIDs in can insert as part of an T.Insert behavior) and any locally instantiated SID[I-D.ietf-idr-bgp-ls-segment-routing-ext][I-D .ietf-idr-te-lsp-distribution].8.3. BGP IP/VPN The End.DX46, End.DT46 and End.DX2 SIDs are expected to be signaled in BGP[I-D.dawra-idr-srv6-vpn].8.4. Summary The following table summarizes which SID would be signaled in which signaling protocol. +------------------+-----+--------+------------+ | | IGP | BGP-LS | BGP IP/VPN | +------------------+-----+--------+------------+ | End (PSP, USP) | X | X | | | End.X (PSP, USP) | X | X | | | End.T (PSP, USP) | X | X | | | End.DX2 | | X | X | | End.DX2V | | X | X | | End.DT2U | | X | X | | End.DT2M | | X | X | | End.DX6 | X | X | X | | End.DX4 | | X | X | | End.DT6 | X | X | X | | End.DT4 | | X | X | | End.DT46 | | X | X | | End.B6 | | X | | | End.B6.Encaps | | X | | | End.B6.BM | | X | | | End.S | | X | | | End.OTP | X | X | X | +------------------+-----+--------+------------+ Table 1: SRv6 LocalSID signaling The following table summarizes which transit capability would be signaled in which signaling protocol.Filsfils, et al. Expires June 24, 2018 [Page 29]
Internet-Draft SRv6 Network Programming December 2017 +-------------+-----+--------+------------+ | | IGP | BGP-LS | BGP IP/VPN | +-------------+-----+--------+------------+ | T | | X | | | T.Insert | | X | | | T.Encaps | | X | | | T.Encaps.L2 | | X | | +-------------+-----+--------+------------+ Table 2: SRv6 transit behaviors signaling The previous table describes generic capabilities. It does not describe specific instantiated SID. For example, a BGP-LS advertisement of the T capability of node N would indicate that node N supports the basic transit behavior. The T.Insert behavior would describe the capability of node N to instantiation a T.Insert behavior, specifically it would describe how many SIDs could be inserted by N without significant performance degradation. Same for T.Encaps (the number potentially lower as the overhead of the additional outer IP header is accounted). The reader should also remember that any specific instantiated SR policy (via T.Insert or T.Encaps) is always assigned a Binding SID. He should remember that BSIDs are advertised in BGP-LS as shown in Table 1. Hence, it is normal that Table 2 only focuses on the generic capabilities related to T.Insert and T.Encaps as Table 1 advertises the specific instantiated BSID properties.9. Illustration We introduce a simplified SID allocation technique to ease the reading of the text. We document the reference diagram. We then illustrate the network programming concept through different use- cases. These use-cases have been thought to allow straightforward combination between each other.9.1. Simplified SID allocation To simplify the illustration, we assume: A::/4 is dedicated to the internal SRv6 SID space B::/4 is dedicated to the internal address space We assume a location expressed in 48 bits and a function expressed in 80 bitsFilsfils, et al. Expires June 24, 2018 [Page 30]
Internet-Draft SRv6 Network Programming December 2017 Node k has a classic IPv6 loopback address Bk::/128 which is advertised in the IGP Node k has Ak::/48 for its local SID space. Its SIDs will be explicitly allocated from that block Node k advertises Ak::/48 in its IGP Function 0:0:0:0:1 (function 1, for short) represents the End function with PSP support Function 0:0:0:0:C2 (function C2, for short) represents the End.X function towards neighbor 2 Each node K has: An explicit SID instantiation Ak::1/128 bound to an End function with additional support for PSP An explicit SID instantiation Ak::Cj/128 bound to an End.X function to neighbor J with additional support for PSP9.2. Reference diagram Let us assume the following topology where all the links have IGP metric 10 except the link 23 which is 100. Nodes A, 1 to 8 and B are considered within the network domain while nodes CE-A and CE-B are outside the domain. 4------5---9 / | \ / 3 | 6 \ | / A--1--- 2------7---8--B / \ CE-A CE-B Tenant100 Tenant100 with IPv4 20/8 Figure 1: Reference topology9.3. Basic security Any edge node such as 1 would be configured with an ACL on any of its external interface (e.g. from CE-A) which drops any traffic with SA or DA in A::/4. See SEC 1 (Section 7.1).Filsfils, et al. Expires June 24, 2018 [Page 31]
Internet-Draft SRv6 Network Programming December 2017 Any core node such as 6 could be configured with an ACL with the SEC2 (Section 7.2) behavior "IF (DA == LocalSID) && (SA is not in A::/4 or B::/4) THEN drop". SEC 3 (Section 7.3) protection is a default property of SRv6. A SID must be explicitly instantiated. In our illustration, the only available SIDs are those explicitly instantiated. Any edge node such as 1 would be configured with Unicast-RPF on source address on external interface (e.g. from CE-A). See SEC 4 (Section 7.4).9.4. SR-IPVPN Let us illustrate the SR-IPVPN use-case applied to IPv4. Nodes 1 and 8 are configured with a tenant 100, each respectively connected to CE-A and CE-B. Node 8 is configured with a local SID A8::D100 of function End.DT4 bound to tenant IPv4 table 100. Via BGP signaling or an SDN-based controller, Node 1's tenant-100 IPv4 table is programmed with an IPv4 SR-VPN route 20/8 via SRv6 policy <A8::D100>. When 1 receives a packet P from CE-A destined to 20.20.20.20, P looks up its tenant-100 IPv4 table and finds an SR-VPN entry 20/8 via SRv6 policy <A8::D100>. As a consequence, 1 pushes an outer IPv6 header with SA=A1::0, DA=A8::D100 and NH=4. 1 then forwards the resulting packet on the shortest path to A8::/40. When 8 receives the packet, 8 matches the DA in its My LocalSID table, finds the bound function End.DT4(100) and confirms NH=4. As a result, 8 decaps the outer header, looks up the inner IPv4 DA in tenant-100 IPv4 table, and forward the (inner) IPv4 packet towards CE-B. The reader can easily infer all the other SR-IPVPN IP instantiations:Filsfils, et al. Expires June 24, 2018 [Page 32]
Internet-Draft SRv6 Network Programming December 2017 +---------------------------------+----------------------------------+ | Route at ingress PE(1) | SR-VPN Egress SID of egress PE(8)| +---------------------------------+----------------------------------+ | IPv4 tenant route with egress | End.DT4 function bound to | | tenant table lookup | IPv4-tenant-100 table | +---------------------------------+----------------------------------+ | IPv4 tenant route without egress| End.DX4 function bound to | | tenant table lookup | CE-B (IPv4) | +---------------------------------+----------------------------------+ | IPv6 tenant route with egress | End.DT6 function bound to | | tenant table lookup | IPv6-tenant-100 table | +---------------------------------+----------------------------------+ | IPv6 tenant route without egress| End.DX6 function bound to | | tenant table lookup | CE-B (IPv6) | +---------------------------------+----------------------------------+9.5. SR-Ethernet-VPWS Let us illustrate the SR-Ethernet-VPWS use-case. Node 1 is configured with an ethernet VPWS service: - Local attachment circuit: Ethernet interface from CE-A - Local End.DX2 bound to the local attachment circuit: A1::DC2A - Remote End.DX2 SID: A8::DC2B Node 8 is configured with an ethernet VPWS service: - Local attachment circuit: Ethernet interface from CE-B - Local End.DX2 bound to the local attachment circuit: A8::DC2B - Remote End.DX2 SID: A1::DC2A These configurations can either be programmed by an SDN controller or partially derived from a BGP-based signaling and discovery service. When 1 receives a packet P from CE-A, 1 pushes an outer IPv6 header with SA=A1::0, DA=A8::DC2B and NH=59. Note that no additional header is pushed. 1 then forwards the resulting packet on the shortest path to A8::/40. When 8 receives the packet, 8 matches the DA in its My LocalSID table and finds the bound function End.DX2. After confirming that the next-header=59, 8 decaps the outer IPv6 header and forwards the inner Ethernet frame towards CE-B.Filsfils, et al. Expires June 24, 2018 [Page 33]
Internet-Draft SRv6 Network Programming December 2017 The reader can easily infer the Ethernet VPWS use-case: +------------------------+-----------------------------------+ | Route at ingress PE(1) | SR-VPN Egress SID of egress PE(8) | +------------------------+-----------------------------------+ | Ethernet VPWS | End.DX2 function bound to | | | CE-B (Ethernet) | +------------------------+-----------------------------------+9.6. SR-EVPN-FXC Let us illustrate the SR-EVPN-FXC use-case (Flexible cross-connect service). Node 1 is configured with an EVPN-FXC service: - Local attachment circuit: Ethernet interface from CE1-A over VLAN 100 - Local attachment circuit: Ethernet interface from CE2-A over VLAN 200 - Local End.DX2 bound to the local attachment circuit: A1::DC2A - Remote End.DX2 SID: A8::DC2B Node 8 is configured with an EVPN-FXC service: - Local attachment circuit: Ethernet interface from CE1-B over VLAN 100 - Local attachment circuit: Ethernet interface from CE2-B over VLAN 200 - Local End.DX2 bound to the local attachment circuit: A8::DC2B - Remote End.DX2 SID: A1::DC2A These configurations can either be programmed by an SDN controller or derived from a BGP-based EVPN-FXC service. EVPN route Type-1 is used for that purpose. When node 1 receives a packet P from CE-A, it pushes an outer IPv6 header with SA=A1::0, DA=A8::DC2B and NH=59. Note that no additional header is pushed. Node 1 then forwards the resulting packet on the shortest path to A8::/40.Filsfils, et al. Expires June 24, 2018 [Page 34]
Internet-Draft SRv6 Network Programming December 2017 When node 8 receives the packet, it matches the IP DA in its My LocalSID table and finds the bound function End.DX2V. After confirming that the next-header=59, node 8 decaps the outer IPv6 header, performs a VLAN loopkup in table T1 and forwards the inner Ethernet frame to matching interface e.g. for VLAN 100, packet is forwarded to CE1-B and for VLAN 200, packet is forwarded to CE2-B. The reader can easily infer the Ethernet FXC use-case:+------------------------------------+------------------------------------+| Route at ingress PE (1) | SR-VPN Egress SID of egress PE (8) |+------------------------------------+------------------------------------+| EVPN-FXC | End.DX2V function bound to || | CE1-B / CE2-B (Ethernet) |+------------------------------------+------------------------------------+9.7. SR-EVPN There are few use cases to illustrate under SR-EVPN: bridging (unicast and multicast), multi-homing ESI filtering, EVPN L3, EVPN- IRB.9.7.1. EVPN Bridging Node 1 is configured with an EVPN bridging service (E-LAN service): - Local attachment circuit: Ethernet interface from CE-A - Local End.DT2U bound to a local layer2 table T1 where EVPN is enable: A1::D2AA. That SID is used to attract unicast traffic - Local End.DT2M bound to the same local layer2 table T1 where EVPN is enable: A1::D2AF:0. That SID is used to attract BUM traffic Node 4 is configured with an EVPN bridging service: - Local attachment circuit: Ethernet interface from CE-B - Local End.DT2U bound to a local layer2 table T1 where EVPN is enable: A4::D2BA. That SID is used to attract unicast traffic - Local End.DT2M bound to the same local layer2 Table T1 where EVPN is enable: A4::D2BF:0. That SID is used to attract BUM traffic Node 8 is configured with an EVPN bridging service: - Local attachment circuit: Ethernet interface from CE-CFilsfils, et al. Expires June 24, 2018 [Page 35]
Internet-Draft SRv6 Network Programming December 2017 - Local End.DT2U bound to a local layer2 table T1 where EVPN is enable: A8::D2CA. That SID is used to attract unicast traffic - Local End.DT2M bound to the same local layer2 Table T1 where EVPN is enable: A8::D2CF:0/112. That SID is used to attract BUM traffic The End.DT2M SID are exchanged between nodes via BGP-based EVPN route-3. Upon reception of EVPN Type-3 routes, each node build its own replication list per layer2 table T1. On node 1, the replication list looks like: A4::D2BF:0, A8::D2CF:0. On node 4, the replication list looks like: A1::D2AF:0, A8::D2CF:0. On node 8, the replication list looks like: A1:D2AF:0, A4:D2BF:0. In the case of ingress replication, Ingress PE transmitting the BUM traffic stream replicates the traffic using that list. When node 1 receives a BUM packet P from CE-A, it replicates that packet to remote nodes. For node 4, it pushes an outer IPv6 header with SA=A1::0, DA=A4::D2BF:0 and NH=59. For node 8, it performs the same operation but DA=A8::D2CF:0. Note that no additional header is pushed. Node 1 then forwards the resulting packet on the shortest path for each replication e.g. A4::D2BF:0/112 and A8::D2CF:0/112. When node 4 receives the packet, it matches the DA in its My LocalSID table and finds the bound function End.DT2M and its related layer2 table T1. After confirming that the next-header=59, node 4 decaps the outer IPv6 header and forwards the inner Ethernet frame to all layer-2 output interface found to table T1. Similar processing is also performed by node 8 upon packet reception. This example is the same for any BUM stream coming from CE-B and CE-C. Node 1,4 and 8 are also performing software MAC learning to exchange MAC reachability information (unicast traffic) via BGP among themselves. Each MAC being learned in software are exchanged using BGP-based EVPN route type-2. When node 1 receives an unicast packet P from CE-A, it learns its MAC-SA=CEA in software. Node 1 transmits that MAC and its associated SID A1::D2AA using BGP-based EVPN route-type 2 to all remote nodes. When node 4 receives an unicast packet P from CE-B destinated to MAC- DA=CEA, it performs a L2 table T1 MAC-DA lookup to find the associated SID. It pushes an outer IPv6 header with SA=A4::0, DA=A1::D2AA and NH=59. Note that no additional header is pushed.Filsfils, et al. Expires June 24, 2018 [Page 36]
Internet-Draft SRv6 Network Programming December 2017 Node 4 then forwards the resulting packet on the shortest path to A1::/40. Similar processing is also performed by node 8.9.7.2. EVPN Multi-homing with ESI filtering In L2 network, traffic loop avoidance is a MUST. In EVPN all-active multi-homing scenario, ESI filtering feature enforce that requirement. Node 1 and node 2 are peering partners of a redundancy group where the access CE-A is connected in an all-active multi-homing way with these two nodes. Node 1 is configured with an EVPN bridging service (E-LAN service): - Local attachment circuit: Ethernet interface from CE-A - Local Arg.FE2 bound to the attachment circuit: 0xC1 - Local End.DT2M bound to the same local layer2 table T1 where EVPN is enable: A1::D2AF:0/112. That SID is used to attract BUM traffic Node 2 is configured with an EVPN bridging service: - Local attachment circuit: Ethernet interface from CE-A - Local Arg.FE2 bound to the attachment circuit: 0xC2 - Local End.DT2M bound to the same local layer2 Table T1 where EVPN is enable: A2::D2BF:0. That SID is used to attract BUM traffic The End.DT2M SID are exchanged between nodes via BGP-based EVPN route type-3. Upon reception of EVPN Type-3 routes, each node build its own replication list per layer2 table T1. The Arg.FE2 SID are exchange between nodes via BGP ESI-filtering extended community attached to BGP-based EVPN route type-1. Upon reception of EVPN route type-1 and type-3, node 1 merges the End.DT2M SID and the Arg.FE2 SID from node 2; its peering partner. Its replication list looks like A2::D2BF:C1. Similar procedure is performed by node 2. When node 1 receives a BUM packet P from CE-A, it replicates that packet to remote nodes. For node 2, it pushes an outer IPv6 header with SA=A1::0, DA=A2::D2BF:C1 and NH=59. Note that no additionalFilsfils, et al. Expires June 24, 2018 [Page 37]
Internet-Draft SRv6 Network Programming December 2017 header is pushed. Node 1 then forwards the resulting packet on the shortest path for each replication e.g. A2::D2BF:00/112. Again, similar processing is also performed by node 8 upon packet reception9.7.3. EVPN Layer-3 EVPN layer-3 works exactly in the same way of IPVPN. Please refer to SR-IPVPN section9.7.4. EVPN Integrated Routing Bridging (IRB) EVPN IRB brings Layer-2 and Layer-3 together. It uses BGP-based EVPN route type-2 to achieve Layer-2 intra-subnet and Layer-3 inter-subnet forwarding. The EVPN route type-2 maintain the associated of a MAC/ IP association. Node 1 is configured with an EVPN IRB service: - Local attachment circuit: Ethernet interface from CE-A - Local End.DT2U bound to a local layer2 table T1 where EVPN is enable: SID = A1::D2AA. That SID is used to attract unicast L2 traffic - Local End.DT2 bound to tenant IPv4 table 100: SID = A1::D3AA. That SID is used to attract L3 traffic Node 8 is configured with an EVPN IRB service: - Local attachment circuit: Ethernet interface from CE-C - Local End.DT2U bound to a local layer2 table T1 where EVPN is enable: SID = A8::D2CB. That SID is used to attract unicast L2 traffic - Local End.DT2 bound to tenant IPv4 table 100: SID = A8::D3CB. That SID is used to attract L3 traffic Each ARP/ND request learned by each node are exchanged using BGP- based EVPN route type-2. When node 1 receives an ARP/ND packet P from a host (10.10.10.10) on CE-A destined to 20.20.20.20, it learns its MAC-SA=CEA in software. It also learns the ARP/ND entry (IP SA=10.10.10.10) in its cache. Node 1 transmits that MAC/IP and its associated L2 SID A1::D2AA and L3 SID A1::D3AA using BGP-based EVPN route-type 2 to all remote nodes.Filsfils, et al. Expires June 24, 2018 [Page 38]
Internet-Draft SRv6 Network Programming December 2017 When node 8 receives a packet P from CE-C destined to 10.10.10.10 from a host (20.20.20.20), P looks up its tenant-100 IPv4 table and finds an SR-VPN entry for that prefix. As a consequence, node 8 pushes an outer IPv6 header with SA=A8::0, DA=A1::D3AA and NH=4. Node 8 then forwards the resulting packet on the shortest path to A1::/40. EVPN inter-subnet forwarding is then achieved. When node 8 receives a packet P from CE-C destined to 10.10.10.10 from a host (10.10.10.11), P looks up its L2 table T1 MAC-DA lookup to find the associated SID. It pushes an outer IPv6 header with SA=A8::0, DA=A1::D2AA and NH=59. Note that no additional header is pushed. Node 8 then forwards the resulting packet on the shortest path to A1::/40. EVPN intra-subnet forwarding is then achieved.9.8. SR TE for Underlay SLA9.8.1. SR policy from the Ingress PE Let's assume that node 1's tenant-100 IPv4 route "20/8 via A8::D100" is programmed with a color/community that requires low-latency underlay optimization [I-D.filsfils-spring-segment-routing-policy]. In such case, node 1 either computes the low-latency path to the egress node itself or delegates the computation to a PCE. In either case, the location of the egress PE can easily be found by looking for who originates the SID block comprising the SID A8::D100. This can be found in the IGP's LSDB for a single domain case, and in the BGP-LS LSDB for a multi-domain case. Let us assume that the TE metric encodes the per-link propagation latency. Let us assume that all the links have a TE metric of 10, except link 27 which has TE metric 100. The low-latency path from 1 to 8 is thus 1245678. This path is encoded in a SID list as: first a hop through A4::C5 and then a hop to 8. As a consequence the SR-VPN entry 20/8 installed in the Node1's Tenant-100 IPv4 table is: T.Encaps with SRv6 Policy <A4::C5, A8::D100>. When 1 receives a packet P from CE-A destined to 20.20.20.20, P looks up its tenant-100 IPv4 table and finds an SR-VPN entry 20/8. As a consequence, 1 pushes an outer header with SA=A1::0, DA=A4::C5, NH=SRH followed by SRH (A8::D100, A4::C5; SL=1; NH=4). 1 then forwards the resulting packet on the interface to 2.Filsfils, et al. Expires June 24, 2018 [Page 39]
Internet-Draft SRv6 Network Programming December 2017 2 forwards to 4 along the path to A4::/40. When 4 receives the packet, 4 matches the DA in its My LocalSID table and finds the bound function End.X to neighbor 5. 4 notes the PSP capability of the SID A4::C5. 4 sets the DA to the next SID A8::D100. As 4 is the penultimate segment hop, it performs PSP and pops the SRH. 4 forwards the resulting packet to 5. 5, 6 and 7 forwards along the path to A8::/40. When 8 receives the packet, 8 matches the DA in its My LocalSID Table and finds the bound function End.DT(100). As a result, 8 decaps the outer header, looks up the inner IPv4 DA in tenant-100 IPv4 table, and forward the (inner) IPv4 packet towards CE-B.9.8.2. SR policy at a midpoint Let us analyze a policy applied at a midpoint on a packet without SRH. Packet P1 is (A1::, A8::D100). Let us consider P1 when it is received by node 2 and let us assume that that node 2 is configured to steer A8::/40 in a transit behavior T.Insert associated with SR policy <A4::C5>. In such a case, node 2 would send the following modified packet P1 on the link to 4: (A1::, A4::C5)(A8::D100, A4::C5; SL=1). The rest of the processing is similar to the previous section. Let us analyze a policy applied at a midpoint on a packet with an SRH. Packet P2 is (A1::, A7::1)(A8::D100, A7::1; SL=1). Let us consider P2 when it is received by node 2 and let us assume that node 2 is configured to steer A7::/40 in a transit behavior T.Insert associated with SR policy <A4::C5, A9::1>. In such a case, node 2 would send the following modified packet P2 on the link to 4: (A1::, A4::C5)(A7::1, A9::1, A4::C5; SL=2)(A8::D100, A7::1; SL=1)Filsfils, et al. Expires June 24, 2018 [Page 40]
Internet-Draft SRv6 Network Programming December 2017 Node 4 would send the following packet to 5: (A1::, A9::1)(A7::1, A9::1, A4::C5; SL=1)(A8::D100, A7::; SL=1) Node 5 would send the following packet to 9: (A1::, A9::1)(A7::1, A9::1, A4::C5; SL=1)(A8::D100, A7::1; SL=1) Node 9 would send the following packet to 6: (A1::, A7::1)(A8::D100, A7::1; SL=1) Node 6 would send the following packet to 7: (A1::, A7::1)(A8::D100, A7::1; SL=1) Node 7 would send the following packet to 8: (A1::, A8::D100)9.9. End-to-End policy with intermediate BSID Let us now describe a case where the ingress VPN edge node steers the packet destined to 20.20.20.20 towards the egress edge node connected to the tenant100 site with 20/8, but via an intermediate SR Policy represented by a single routable Binding SID. Let us illustrate this case with an intermediate policy which both encodes underlay optimization for low-latency and the service chaining via two SR- aware container-based apps. Let us assume that the End.B6 SID A2::B1 is configured at node 2 and is associated with midpoint T.Insert policy <A4::C5, A9::A1, A6::A2>. A4::C5 realizes the low-latency path from the ingress PE to the egress PE. This is the underlay optimization part of the intermediate policy. A9::A1 and A6::A2 represent two SR-aware NFV applications residing in containers respectively connected to node 9 and 6. Let us assume the following ingress VPN policy for 20/8 in tenant 100 IPv4 table of node 1: T.Encaps with SRv6 Policy <A2::B1, A8::D100>. This ingress policy will steer the 20/8 tenant-100 traffic towards the correct egress PE and via the required intermediate policy that realizes the SLA and NFV requirements of this tenant customer. Node 1 sends the following packet to 2: (A1::, A2::B1) (A8::D100, A2::B1; SL=1) Node 2 sends the following packet to 4: (A1::, A4::C5) (A6::A2, A9::A1, A4::C5; SL=2)(A8::D100, A2::B1; SL=1)Filsfils, et al. Expires June 24, 2018 [Page 41]
Internet-Draft SRv6 Network Programming December 2017 Node 4 sends the following packet to 5: (A1::, A9::A1) (A6::A2, A9::A1, A4::C5; SL=1)(A8::D100, A2::B1; SL=1) Node 5 sends the following packet to 9: (A1::, A9::A1) (A6::A2, A9::A1, A4::C5; SL=1)(A8::D100, A2::B1; SL=1) Node 9 sends the following packet to 6: (A1::, A6::A2) (A8::D100, A2::B1; SL=1) Node 6 sends the following packet to 7: (A1::, A8::D100) Node 7 sends the following packet to 8: (A1::, A8::D100) which decaps and forwards to CE-B. The benefits of using an intermediate Binding SID are well-known and key to the Segment Routing architecture: the ingress edge node needs to push fewer SIDs, the ingress edge node does not need to change its SR policy upon change of the core topology or re-homing of the container-based apps on different servers. Conversely, the core and service organizations do not need to share details on how they realize underlay SLA's or where they home their NFV apps.9.10. TI-LFA Let us assume two packets P1 and P2 received by node 2 exactly when the failure of link 27 is detected. P1: (A1::, A7::1) P2: (A1::, A7::1)(A8::D100, A7::1; SL=1) Node 2's pre-computed TI-LFA backup path for the destination A7:: is <A4::C5>. It is installed as a T.Insert transit behavior. Node 2 protects the two packets P1 and P2 according to the pre- computed TI-LFA backup path and send the following modified packets on the link to 4: P1: (A1::, A4::C5)(A7::1, A4::C5; SL=1) P2: (A1::, A4::C5)(A7::1, A4::C5; SL=1) (A8::D100, A7::1; SL=1) Node 4 then sends the following modified packets to 5: P1: (A1::, A7::1) P2: (A1::, A7::1)(A8::D100, A7::1; SL=1)Filsfils, et al. Expires June 24, 2018 [Page 42]
Internet-Draft SRv6 Network Programming December 2017 Then these packets follow the rest of their post-convergence path towards node 7 and then go to node 8 for the VPN decaps.9.11. SR TE for Service chaining We have illustrated the service chaining through SR-aware apps in a previous section. We illustrate the use of End.AS function [I-D.xu-clad-spring-sr-service-chaining] to service chain an IP flow bound to the internet through two SR-unaware applications hosted in containers. Let us assume that servers 20 and 70 are respectively connected to nodes 2 and 7. They are respectively configured with SID spaces A020::/40 and A070::/40. Their connected routers advertise the related prefixes in the IGP. Two SR-unaware container-based applications App2 and App7 are respectively hosted on server 20 and 70. Server 20 (70) is configured explicitly with an End.AS SID A020::2 for App2 (A070::7 for App7). Let us assume a broadband customer with a home gateway CE-A connected to edge router 1. Router 1 is configured with an SR policy which encapsulates all the traffic received from CE-A into a T.Encaps policy <A020::2, A070::7, A8::D0> where A8::D0 is an End.DT4 SID instantiated at node 8. P1 is a packet sent by the broadband customer to 1: (X, Y) where X and Y are two IPv4 addresses. 1 sends the following packet to 2: (A1::0, A020::2)(A8::D0, A070::7, A020::2; SL=2; NH=4)(X, Y). 2 forwards the packet to server 20. 20 receives the packet (A1::0, A020::2)(A8::D0, A070::7, A020::2; SL=2; NH=4)(X, Y) and forwards the inner IPv4 packet (X,Y) to App2. App2 works on the packet and forwards it back to 20. 20 pushes the outer IPv6 header with SRH (A1::0, A070::7)(A8::D0, A070::7, A020::2; SL=1; NH=4) and sends the (whole) IPv6 packet with the encapsulated IPv4 packet back to 2. 2 and 7 forward to server 70. 70 receives the packet (A1::0, A070::7)(A8::D0, A070::7, A020::2; SL=1; NH=4)(X, Y) and forwards the inner IPv4 packet (X,Y) to App7. App7 works on the packet and forwards it back to 70. 70 pushes the outer IPv6 header with SRH (A1::0, A8::D0)(A8::D0, A070::7, A020::2;Filsfils, et al. Expires June 24, 2018 [Page 43]
Internet-Draft SRv6 Network Programming December 2017 SL=0; NH=4) and sends the (whole) IPv6 packet with the encapsulated IPv4 packet back to 7. 7 forwards to 8. 8 receives (A1::0, A8::D0)(A8::D0, A070::7, A020::2; SL=0; NH=4)(X, Y) and performs the End.DT4 function and sends the IP packet (X, Y) towards its internet destination.9.12. OAM This section illustrates the use of O-bit and End.OTP SID by describing the ping use-case.9.12.1. Ping to a SID function Consider the case where the user wants to ping a remote SID function A8::DC4B, via A4::C5, from node 1. Node 1 constructs the ping packet (B1::0, A4::C5)(A8::DC4B, A4::C5, SL=1; NH=ICMPv6)(ICMPv6 Echo Request). When node 8 receives the ICMPv6 echo request with DA set to A8::DC4B and next header set to ICMPv6, it silently drops it (see security section for details). To solve this problem, the initiator needs to mark the ICMPv6 echo request as an OAM packet. The OAM packets are identified either by setting the O-bit in the SRH or by inserting an End.OTP SID at the appropriate place in the SRH.9.12.2. End-to-end ping using End.OTP Consider the same example where the user wants to ping a remote SID function A8::DC4B , via A4::C5, from node 1. To force a punt of the ICMPv6 echo request at the node 8, node 1 inserts the End.OTP SID just before the target SID A8::DC4B in the SRH, i.e., packet as it leaves node 1 looks like (B1::0, A4::C5)(A8::DC4B, A8::OTP, A4::C5; SL=2; NH=ICMPv6)(ICMPv6 Echo Request). When the node 8 receives the packet (B1::0, A8::OTP)(A8::DC4B, A8::OTP, A4::C5 ; SL=1; NH=ICMPv6)(ICMPv6 Echo Request), it processes the End.OTP SID. The packet gets punted to ICMPv6 process for processing. The ICMPv6 process checks if the next SID in SRH (target SID A8::DC4B) is locally programmed or not and responds to the ICMPv6 Echo Request, accordingly.9.12.3. Segment-by-segment ping using the O-bit Consider the same example where the user wants to ping a remote SID function A8::DC4B, via A4::C5, from node 1. However, in this ping, the node1 wants to get a response from each segment node in the SRH. In other words, in the segment-by-segment ping case, the node 1Filsfils, et al. Expires June 24, 2018 [Page 44]
Internet-Draft SRv6 Network Programming December 2017 expects a response from node 4 and node 8 for their respective local SID function. To force a punt of the ICMPv6 echo request at node 4 and node 8, node 1 sets the O-bit in the SRH. The packet, as it leaves node 1, looks like (B1::0, A4::C5)(A8::DC4B, A4::C5; SL=1, Flags.O=1; NH=ICMPv6)(ICMPv6 Echo Request). When the node 4 receives the packet (B1::0, A4::C5)(A8::DC4B, A4::C5; SL=1, Flags.O=1; NH=ICMPv6)(ICMPv6 Echo Request) packet a time- stamped copy of the packet gets punted to the ICMPv6 process for processing. Node 4 continues to apply the A4::C5 SID function on the original packet and forwards it, accordingly. As SRH.Flags.O=1, Node4 also disables the PSP flavour, i.e., does not remove the SRH. The ICMPv6 process at node4 checks if its local SID (A4::C5) is locally programmed or not and responds to the ICMPv6 Echo Request, accordingly. Please note that if node 4 does not support the O-bit, it simply ignores it and process the local SID, A4::C5. When the node 8 receives the packet (B1::0, A8::DC4B)(A8::DC4B, A4::C5; SL=0, Flags.O=1; NH=ICMPv6)(ICMPv6 Echo Request), it processes the O-bit in SRH. A time-stamped copy of the packet gets punted to the ICMPv6 process for processing. The ICMPv6 process at node 8 checks if its local SID (A8::DC4B) is locally programmed or not and responds to the ICMPv6 Echo Request, accordingly. Support for the O-bit is part of the node capability advertisement. That enables node 1 to know which segment nodes are capable of responding to the ICMPv6 echo request.10. Benefits10.1. Seamless deployment The VPN use-case can be realized with SRv6 capability deployed solely at the ingress and egress PE's. All the nodes in between these PE's act as transit routers as per [RFC2460]. No software/hardware upgrade is required on all these nodes. They just need to support IPv6 per [RFC2460]. The SRTE/underlay-SLA use-case can be realized with SRv6 capability deployed at few strategic nodes. It is well-known from the experience deploying SR-MPLS that underlay SLA optimization requires few SIDs placed at strategic locations. This was illustrated in our example with the low- latency optimization which required the operator to enable oneFilsfils, et al. Expires June 24, 2018 [Page 45]
Internet-Draft SRv6 Network Programming December 2017 single core node with SRv6 (node 4) where one single and End.X SID towards node 5 was instantiated. This single SID is sufficient to force the end-to-end traffic via the low-latency path. The TI-LFA benefits are collected incrementally as SRv6 capabilities are deployed. It is well-know that TI-LFA is an incremental node-by-node deployment. When a node N is enabled for TI-LFA, it computes TI- LFA backup paths for each primary path to each IGP destination. In more than 50% of the case, the post-convergence path is loop- free and does not depend on the presence of any remote SRv6 SID. In the vast majority of cases, a single segment is enough to encode the post-convergence path in a loop-free manner. If the required segment is available (that node has been upgraded) then the related back-up path is installed in FIB, else the pre- existing situation (no backup) continues. Hence, as the SRv6 deployment progresses, the coverage incrementally increases. Eventually, when the core network is SRv6 capable, the TI-LFA coverage is complete. The service chaining use-case can be realized with SRv6 capability deployed at few strategic nodes. The service-chaining deployment is again incremental and does not require any pre-deployment of SRv6 in the network. When an NFV app A1 needs to be enabled for inclusion in an SRv6 service chain, all what is required is to install that app in a container or VM on an SRv6-capable server (Linux 4.10 or FD.io 17.04 release). The app can either be SR-aware or not, leveraging the proxy functions described in this document. By leveraging the various END functions it can also be used to support any current PNF/VNF implementations and their forwarding methods (e.g. Layer 2). The ability to leverage SR TE policies and BSIDs also permits building scalable, hierarchical service-chains.10.2. Integration The SRv6 network programming concept allows integrating all the application and service requirements: multi-domain underlay SLA optimization with scale, overlay VPN/Tenant, sub-50msec automated FRR, security and service chaining.Filsfils, et al. Expires June 24, 2018 [Page 46]
Internet-Draft SRv6 Network Programming December 201710.3. Security The combination of well-known techniques (SEC1, SEC2, SEC4) and carefully chosen architectural rules (SEC3) ensure a secure deployment of SRv6 inside a multi-domain network managed by a single organization. Inter-domain security will be described in a companion document.11. IANA Considerations This document has no actions for IANA.12. Work in progress We are working on a extension of this document to provide Yang modelling for all the functionality described in this document.13. Acknowledgements TBD.14. Contributors Stefano Previdi, Dave Barach, Mark Townsley, Peter Psenak, Paul Wells, Robert Hanzl, Dan Ye, Patrice Brissette, Gaurav Dawra, Faisal Iqbal, Zafar Ali, Jaganbabu Rajamanickam, David Toscano, Asif Islam, Jianda Liu, Yunpeng Zhang, Jiaoming Li, Narendra A.K, Mike Mc Gourty, Bhupendra Yadav, Sherif Toulan, Satish Damodaran, John Bettink, Kishore Nandyala Veera Venk, Jisu Bhattacharya and Saleem Hafeez substantially contributed to the content of this document.15. References15.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels",BCP 14,RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>.15.2. Informative References [I-D.bashandy-isis-srv6-extensions] Ginsberg, L., Bashandy, A., Filsfils, C., and B. Decraene, "IS-IS Extensions to Support Routing over IPv6 Dataplane",draft-bashandy-isis-srv6-extensions-01 (work in progress), September 2017.Filsfils, et al. Expires June 24, 2018 [Page 47]
Internet-Draft SRv6 Network Programming December 2017 [I-D.dawra-idr-srv6-vpn] Dawra, G., Filsfils, C., Dukes, D., Brissette, P., Camarillo, P., Leddy, J., daniel.voyer@bell.ca, d., daniel.bernier@bell.ca, d., Steinberg, D., Raszuk, R., Decraene, B., and S. Matsushima, "BGP Signaling of IPv6- Segment-Routing-based VPN Networks",draft-dawra-idr-srv6-vpn-02 (work in progress), October 2017. [I-D.filsfils-spring-segment-routing-policy] Filsfils, C., Sivabalan, S., Raza, K., Liste, J., Clad, F., Hegde, S., Lin, S., bogdanov@google.com, b., Horneffer, M., Steinberg, D., Decraene, B., and S. Litkowski, "Segment Routing Policy for Traffic Engineering",draft-filsfils-spring-segment-routing-policy-03 (work in progress), October 2017. [I-D.ietf-6man-segment-routing-header] Previdi, S., Filsfils, C., Raza, K., Leddy, J., Field, B., daniel.voyer@bell.ca, d., daniel.bernier@bell.ca, d., Matsushima, S., Leung, I., Linkova, J., Aries, E., Kosugi, T., Vyncke, E., Lebrun, D., Steinberg, D., and R. Raszuk, "IPv6 Segment Routing Header (SRH)",draft-ietf-6man-segment-routing-header-07 (work in progress), July 2017. [I-D.ietf-idr-bgp-ls-segment-routing-ext] Previdi, S., Psenak, P., Filsfils, C., Gredler, H., and M. Chen, "BGP Link-State extensions for Segment Routing",draft-ietf-idr-bgp-ls-segment-routing-ext-03 (work in progress), July 2017. [I-D.ietf-idr-te-lsp-distribution] Previdi, S., Dong, J., Chen, M., Gredler, H., and J. Tantsura, "Distribution of Traffic Engineering (TE) Policies and State using BGP-LS",draft-ietf-idr-te-lsp-distribution-07 (work in progress), July 2017. [I-D.ietf-isis-l2bundles] Ginsberg, L., Bashandy, A., Filsfils, C., Nanduri, M., and E. Aries, "Advertising L2 Bundle Member Link Attributes in IS-IS",draft-ietf-isis-l2bundles-07 (work in progress), May 2017. [I-D.ietf-spring-segment-routing] Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing Architecture",draft-ietf-spring-segment-routing-13 (work in progress), October 2017.Filsfils, et al. Expires June 24, 2018 [Page 48]
Internet-Draft SRv6 Network Programming December 2017 [I-D.xu-clad-spring-sr-service-chaining] Clad, F., Xu, X., Filsfils, C., daniel.bernier@bell.ca, d., Decraene, B., Yadlapalli, C., Henderickx, W., Salsano, S., and S. Ma, "Segment Routing for Service Chaining",draft-xu-clad-spring-sr-service-chaining-00 (work in progress), December 2017. [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification",RFC 2460, DOI 10.17487/RFC2460, December 1998, <https://www.rfc-editor.org/info/rfc2460>. [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6 Specification",RFC 2473, DOI 10.17487/RFC2473, December 1998, <https://www.rfc-editor.org/info/rfc2473>. [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)",RFC 4364, DOI 10.17487/RFC4364, February 2006, <https://www.rfc-editor.org/info/rfc4364>. [RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme, "IPv6 Flow Label Specification",RFC 6437, DOI 10.17487/RFC6437, November 2011, <https://www.rfc-editor.org/info/rfc6437>.Appendix A. Additional Contributors Patrice Brissete Cisco Systems, Inc. Canada Email: pbrisset@cisco.com Zafar Ali Cisco Systems, Inc. United States of America Email: zali@cisco.comAuthors' Addresses Clarence Filsfils Cisco Systems, Inc. Belgium Email: cf@cisco.comFilsfils, et al. Expires June 24, 2018 [Page 49]
Internet-Draft SRv6 Network Programming December 2017 John Leddy Comcast United States of America Email: john_leddy@cable.comcast.com Daniel Voyer Bell Canada Canada Email: daniel.voyer@bell.ca Daniel Bernier Bell Canada Canada Email: daniel.bernier@bell.ca Dirk Steinberg Steinberg Consulting Germany Email: dws@dirksteinberg.de Robert Raszuk Bloomberg LP United States of America Email: robert@raszuk.net Satoru Matsushima SoftBank 1-9-1,Higashi-Shimbashi,Minato-Ku Tokyo 105-7322 Japan Email: satoru.matsushima@g.softbank.co.jpFilsfils, et al. Expires June 24, 2018 [Page 50]
Internet-Draft SRv6 Network Programming December 2017 David Lebrun Universite catholique de Louvain Belgium Email: david.lebrun@uclouvain.be Bruno Decraene Orange France Email: bruno.decraene@orange.com Bart Peirens Proximus Belgium Email: bart.peirens@proximus.com Stefano Salsano Universita di Roma "Tor Vergata" Italy Email: stefano.salsano@uniroma2.it Gaurav Naik Drexel University United States of America Email: gn@drexel.edu Hani Elmalky Ericsson United States of America Email: hani.elmalky@gmail.com Prem Jonnalagadda Barefoot Networks United States of America Email: prem@barefootnetworks.comFilsfils, et al. Expires June 24, 2018 [Page 51]
Internet-Draft SRv6 Network Programming December 2017 Milad Sharif Barefoot Networks United States of America Email: msharif@barefootnetworks.com Arthi Ayyangar Arista United States of America Email: arthi@arista.com Satish Mynam Dell Force10 Networks United States of America Email: satish_mynam@dell.com Wim Henderickx Nokia Belgium Email: wim.henderickx@nokia.com Ahmed Bashandy Cisco Systems, Inc. United States of America Email: bashandy@cisco.com Kamran Raza Cisco Systems, Inc. Canada Email: skraza@cisco.com Darren Dukes Cisco Systems, Inc. Canada Email: ddukes@cisco.comFilsfils, et al. Expires June 24, 2018 [Page 52]
Internet-Draft SRv6 Network Programming December 2017 Francois Clad Cisco Systems, Inc. France Email: fclad@cisco.com Pablo Camarillo Garvia (editor) Cisco Systems, Inc. Spain Email: pcamaril@cisco.comFilsfils, et al. Expires June 24, 2018 [Page 53] draft-filsfils-spring-srv6-network-programming-03
| Document | Document type | This is an older version of an Internet-Draft whose latest revision state is "Replaced". This document is an Internet-Draft (I-D). Anyone may submit an I-D to the IETF. This I-D isnot endorsed by the IETF and hasno formal standing in theIETF standards process. | |
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| Authors | Clarence Filsfils,John Leddy,Daniel Voyer,Daniel Bernier,Dirk Steinberg,Robert Raszuk,Satoru Matsushima,David Lebrun,Bruno Decraene,Bart Peirens,Stefano Salsano,Gaurav Naik,Hani Elmalky,Prem Jonnalagadda,Milad Sharif,Arthi Ayyangar,Satish Mynam,Wim Henderickx,Ahmed Bashandy,Syed Kamran Raza,Darren Dukes,Francois Clad,Pablo Camarillo | ||
| Replaced by | draft-ietf-spring-srv6-network-programming RFC 8986 | ||
| RFC stream | (None) | ||
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