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Network Working Group                                            S. ShahRequest for Comments: 3619                                        M. YipCategory: Informational                                 Extreme Networks                                                            October 2003Extreme Networks'Ethernet Automatic Protection Switching (EAPS)Version 1Status of this Memo   This memo provides information for the Internet community.  It does   not specify an Internet standard of any kind.  Distribution of this   memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2003).  All Rights Reserved.Abstract   This document describes the Ethernet Automatic Protection Switching   (EAPS) (tm) technology invented by Extreme Networks to increase the   availability and robustness of Ethernet rings.  An Ethernet ring   built using EAPS can have resilience comparable to that provided by   SONET rings, at a lower cost and with fewer constraints (e.g., ring   size).1.  Introduction   Many Metropolitan Area Networks (MANs) and some Local Area Networks   (LANs) have a ring topology, as the fibre runs.  The Ethernet   Automatic Protection Switching (EAPS) technology described here works   well in ring topologies for MANs or LANs.   Most MAN operators want to minimise the recovery time in the event   that a fibre cut occurs.  The Ethernet Automatic Protection Switching   (EAPS) technology described here converges in less than one second,   often in less than 50 milliseconds.  EAPS technology does not limit   the number of nodes in the ring, and the convergence time is   independent of the number of nodes in the ring.Shah & Yip                   Informational                      [Page 1]

RFC 3619                 Extreme Networks' EAPS             October 20032.  Concept of Operation   An EAPS Domain exists on a single Ethernet ring.  Any Ethernet   Virtual Local Area Network (VLAN) that is to be protected is   configured on all ports in the ring for the given EAPS Domain.  Each   EAPS Domain has a single designated "master node".  All other nodes   on that ring are referred to as "transit nodes".   Of course, each node on the ring will have 2 ports connected to the   ring.  One port of the master node is designated as the "primary   port" to the ring, while the other port is designated as the   "secondary port".   In normal operation, the master node blocks the secondary port for   all non-control Ethernet frames belonging to the given EAPS Domain,   thereby avoiding a loop in the ring.  Existing Ethernet switching and   learning mechanisms operate per existing standards on this ring.   This is possible because the master node makes the ring appear as   though there is no loop from the perspective of the Ethernet standard   algorithms used for switching and learning.  If the master node   detects a ring fault, it unblocks its secondary port and allows   Ethernet data frames to pass through that port.  There is a special   "Control VLAN" that can always pass through all ports in the EAPS   Domain, including the secondary port of the master node.   EAPS uses both a polling mechanism and an alert mechanism, described   below, to verify the connectivity of the ring and quickly detect any   faults.2.1.  Link Down Alert   When a transit node detects a link-down on any of its ports in the   EAPS Domain, that transit node immediately sends a "link down"   control frame on the Control VLAN to the master node.   When the master node receives this "link down" control frame, the   master node moves from the "normal" state to the ring-fault state and   unblocks its secondary port.  The master node also flushes its   bridging table, and the master node also sends a control frame to all   other ring nodes, instructing them to flush their bridging tables as   well.  Immediately after flushing its bridging table, each node   begins learning the new topology.Shah & Yip                   Informational                      [Page 2]

RFC 3619                 Extreme Networks' EAPS             October 20032.2.  Ring Polling   The master node sends a health-check frame on the Control VLAN at a   user-configurable interval.  If the ring is complete, the health-   check frame will be received on its secondary port, where the master   node will reset its fail-period timer and continue normal operation.   If the master node does not receive the health-check frame before the   fail-period timer expires, the master node moves from the normal   state to the "ring-fault" state and unblocks its secondary port.  The   master node also flushes its bridging table and sends a control frame   to all other nodes, instructing them to also flush their bridging   tables.  Immediately after flushing its bridge table, each node   starts learning the new topology.  This ring polling mechanism   provides a backup in the event that the Link Down Alert frame should   get lost for some unforeseen reason.2.3.  Ring Restoration   The master node continues sending periodic health-check frames out   its primary port even when operating in the ring-fault state.  Once   the ring is restored, the next health-check frame will be received on   the master node's secondary port.  This will cause the master node to   transition back to the normal state, logically block non-control   frames on the secondary port, flush its own bridge table, and send a   control frame to the transit nodes, instructing them to flush their   bridging tables and re-learn the topology.   During the time between the transit node detecting that its link is   restored and the master node detecting that the ring is restored, the   secondary port of the master node is still open -- creating the   possibility of a temporary loop in the topology.  To prevent this,   the transit node will place all the protected VLANs transiting the   newly restored port into a temporary blocked state, remember which   port has been temporarily blocked, and transition into the "pre-   forwarding" state.  When the transit node in the "pre-forwarding"   state receives a control frame instructing it to flush its bridging   table, it will flush the bridging table, unblock the previously   blocked protected VLANs on the newly restored port, and transition to   the "normal" state.Shah & Yip                   Informational                      [Page 3]

RFC 3619                 Extreme Networks' EAPS             October 20033.  Multiple EAPS Domains   An EAPS-enabled switch can be part of more than one ring.  Hence, an   EAPS-enabled switch can belong to more than one EAPS Domain at the   same time.  Each EAPS Domain on a switch requires a separate instance   of the EAPS protocol on that same switch, one instance per EAPS-   protected ring.   One can also have more than one EAPS domain running on the same ring   at the same time.  Each EAPS Domain has its own unique master node   and its own set of protected VLANs.  This facilitates spatial reuse   of the ring's bandwidth.   EAPS Frame Format         0         1          2          3          4        4         12345678 90123456 78901234 56789012 34567890 12345678        +--------+--------+--------+--------+--------+--------+        |         Destination MAC Address (6 bytes)           |        +--------+--------+--------+--------+--------+--------+        |         Source MAC Address (6 bytes)                |        +--------+--------+--------+--------+--------+--------+        |    EtherType    |PRI | VLAN ID    |  Frame Length   |        +--------+--------+--------+--------+--------+--------+        |    DSAP/SSAP    | CONTROL|     OUI = 0x00E02B       |        +--------+--------+--------+--------+--------+--------+        |     0x00bb      |  0x99  |  0x0b  |  EAPS_LENGTH    |        +--------+--------+--------+--------+--------+--------+        |EAPS_VER|EAPSTYPE|  CTRL_VLAN_ID   |    0x0000       |        +--------+--------+--------+--------+--------+--------+        |  0x0000         |    SYSTEM_MAC_ADDR (6 bytes)      |        +--------+--------+--------+--------+--------+--------+        |                 |   HELLO_TIMER   |    FAIL_TIMER   |        +--------+--------+--------+--------+--------+--------+        | STATE  | 0x00   |   HELLO_SEQ     |     0x0000      |        +--------+--------+--------+--------+--------+--------+        |                 RESERVED (0x000000000000)           |        +--------+--------+--------+--------+--------+--------+        |                 RESERVED (0x000000000000)           |        +--------+--------+--------+--------+--------+--------+        |                 RESERVED (0x000000000000)           |        +--------+--------+--------+--------+--------+--------+        |                 RESERVED (0x000000000000)           |        +--------+--------+--------+--------+--------+--------+        |                 RESERVED (0x000000000000)           |        +--------+--------+--------+--------+--------+--------+        |                 RESERVED (0x000000000000)           |        +--------+--------+--------+--------+--------+--------+Shah & Yip                   Informational                      [Page 4]

RFC 3619                 Extreme Networks' EAPS             October 2003      Where:          Destination MAC Address is always 0x00e02b000004.          PRI contains 3 bits of priority, with 1 other bit reserved.          EtherType is always 0x8100.          DSAP/SSAP is always 0xAAAA.          CONTROL is always 0x03.          EAPS_LENGTH is 0x40.          EAPS_VERS is 0x0001.          CTRL_VLAN_ID is the VLAN ID for the Control VLAN in use.          SYSTEM_MAC_ADDR is the System MAC Address of the sending node.          HELLO_TIMER is the value set by the Master Node.          FAIL_TIMER is the value set by the Master Node.          HELLO_SEQ is the sequence number of the Hello Frame.      EAPS Type (EAPSTYPE) values:          HEALTH              = 5          RING-UP-FLUSH-FDB   = 6          RING-DOWN-FLUSH-FDB = 7          LINK-DOWN           = 8          All other values are reserved.      STATE values:          IDLE           = 0          COMPLETE       = 1          FAILED         = 2          LINKS-UP       = 3          LINK-DOWN      = 4          PRE-FORWARDING = 5          All other values are reserved.4.  Security Considerations   Anyone with physical access to the physical layer connections could   forge any sort of Ethernet frame they wished, including but not   limited to Bridge frames or EAPS frames.  Such forgeries could be   used to disrupt an Ethernet network in various ways, including   methods that are specific to EAPS or other unrelated methods, such as   forged Ethernet bridge frames.   As such, it is recommended that users not deploy Ethernet without   some form of encryption in environments where such active attacks are   considered a significant operational risk.  IEEE standards already   exist for link-layer encryption.  Those IEEE standards could be used   to protect an Ethernet's links.  Alternately, upper-layer security   mechanisms could be used if it is more appropriate to the local   threat model.Shah & Yip                   Informational                      [Page 5]

RFC 3619                 Extreme Networks' EAPS             October 20035.  Intellectual Property Rights Notice   The IETF has been notified of intellectual property rights claimed in   regard to some or all of the specification contained in this   document.  For more information, consult the online list of claimed   rights.6.  Acknowledgement   This document was edited together and put into RFC format by R.J.   Atkinson from internal documents created by the authors below.  The   Editor is solely responsible for any errors made during redaction.7.  Editor's Address   R. Atkinson   Extreme Networks   3585 Monroe Street   Santa Clara, CA, 95051 USA   Phone: +1 (408)579-2800   EMail: rja@extremenetworks.com8.  Authors' Addresses   S. Shah   Extreme Networks   3585 Monroe Street   Santa Clara, CA, 95051   Phone: +1 (408)579-2800   EMail: sshah@extremenetworks.com   M. Yip   Extreme Networks   3585 Monroe Street   Santa Clara, CA, 95051   Phone: +1 (408)579-2800   EMail: my@extremenetworks.comShah & Yip                   Informational                      [Page 6]

RFC 3619                 Extreme Networks' EAPS             October 20039.  Full Copyright Statement   Copyright (C) The Internet Society (2003).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assignees.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Shah & Yip                   Informational                      [Page 7]