RIB Management¶

• Table of contents
• RIB Management
  • RIB Entry
  • Route
    • Route origin
    • Route cost
    • Route inheritance
    • Effective routing cost
  • Control Commands
    • Register a route
    • Register a route with Prefix Announcement object
      • Example
    • Unregister a route
    • Semantics of successful responses
  • RIB Dataset
  • Routable Prefixes Dataset
  • TLV-TYPE assignments

RIB Management is a module ofNFD Management protocol.
It provides:

• commands to register and unregister routes
• a dataset of routes
• a dataset of routable prefixes

RIB Management commands and datasets are available under namespacendn:/localhost/nfd/rib.
RIB Management commands are also available under namespacendn:/localhop/nfd/rib.

RIB Entry¶

ARIB Entry maintains a list of routes associated with a particular namespace.

A RIB Entry contains:

• Name prefix
• a list of Routes

Route¶

Aroute indicates that data with a certain name prefix may be available via a certain nexthop.

A route contains:

• Name prefix
• nexthop FaceId
• origin
• cost
• route inheritance flags

Route origin¶

Origin is a value in [0, 65535] range that indicates who is announcing a route.

• app (=0): indicates a Route toward a local producer application.
• static (=255): indicates a static route.
• nlsr (=128): indicates a route installed by NLSR routing protocol.
• prefixann (=129): indicates a route installed by a prefix announcement.
• client (=65): indicates a Route toward an end host connected to this router, installed viaAutoPrefixPropagation.
• autoreg (=64): indicates a Route toward an end host connected to this router, registered automatically by thenfd-autoreg tool.
• autoconf (=66): indicates a Route toward a remote router that this end host has connected to, registered automatically by thendn-autoconfig tool.

Route cost¶

Cost indicates the preference among multiple routes with same Name prefix.

Generally, the nexthop face on a route with lower cost is preferred. Unlike IP routing, in NDN the nexthop face to use is decided by the forwarding strategy. Route cost is a suggestion to the strategy: the strategy MAY consider route cost when making forwarding decisions.

Route inheritance¶

Each route can have two route inheritance flags:

• CHILD_INHERIT: indicates that this route may be used even if a longer prefix is matched.This flag applies on a single route.
• CAPTURE: indicates that no shorter prefix can be used; overridesCHILD_INHERIT.This flag applies on the prefix: if any route of a prefix has this flag, the prefix will have this flag.

Example:

• Interest /A/P can go to face 1 and 3.
  • It cannot go to face 2, because that route has CHILD_INHERIT=no.
• Interest /A/B/C/Q can go to face 1, 3, and 4.
• Interest /D/R can go to face 5 and 6.
  • It cannot go to face 1, because one of the routes on /D sets CAPTURE=yes.
• Interest /S can go to face 1 and 2.

Effective routing cost¶

To determine the routing cost of a nexthop face for FIB entry:

1. Collect all routes whose name is a prefix of the FIB entry name and has the nexthop face.
2. Select the routes with longest prefix. This could select multiple routes if they have distinct origins.
3. Use the lowest cost among these routes.

Example:

The corresponding FIB should be:

Control Commands¶

ControlCommandmanagement-module:rib

Register a route¶

command-verb:register

This command adds a route to the RIB.

This command can also be accepted onndn:/localhop/nfd management prefix, in addition to the defaultndn:/localhost/nfd management prefix.

ControlParameters fields:

• Name (required)
• FaceId (optional)
• Origin (optional)
• Cost (optional)
• Flags (optional)
• ExpirationPeriod (optional)

Name is the name prefix of the route. A forwarder MAY impose a limit on the length of the name prefix. The current limit in NFD is 32 name components. IfName exceeds this limit, the command fails with code 414.

FaceId is the FaceId returned byFace Management. IfFaceId is omitted or is set to zero, it is implied as the requesting face (self registration).

Origin defaults toapp (=0).

Cost defaults to zero.

Flags is the inclusive OR of the following route inheritance flags:

• CHILD_INHERIT = 1
• CAPTURE = 2

The default isCHILD_INHERIT.

ExpirationPeriod gives the duration (in milliseconds) for which this route is effective. AfterExpirationPeriod has elapsed, or when the face fails, the route is removed.ExpirationPeriod defaults to infinity.

If a route of sameName,FaceId, andOrigin exists, itsCost andFlags are updated and its lifetime is extended to now +ExpirationPeriod.

If the command succeeds, <body> in ControlResponse block contains the updated ControlParameters:

• Name: Name prefix
• FaceId: nexthop FaceId (not zero)
• Origin: route origin
• Cost: route cost
• Flags: inclusive OR of route inheritance flags
• ExpirationPeriod: remaining lifetime (in milliseconds), or omitted if it's infinity

Register a route with Prefix Announcement object¶

This command announces a prefix using aPrefixAnnouncement object.

The RIB management module accepts this command as asigned Interest with the following name:

/localhost/nfd/rib/announce/<params-sha256>/localhop/nfd/rib/announce/<params-sha256>

The Interest's ApplicationParameters element carries the prefix announcement object.
The RIB management module converts this command into an equivalentrib/register command. The route'sOrigin is set to "prefix announcement" (=129).
The response is the same as therib/register command.

Example¶

Interest  Name /localhop/nfd/rib/announce/params-sha256=607a2bc7653eea18b47e92b84edc58bab5aaa321d4efb39ceeccc6cafbcbb3d1  MustBeFresh  ApplicationParameters    PrefixAnnouncement  InterestSignatureInfo  InterestSignatureValue

Assuming the enclosed PrefixAnnouncement is the one shown in thePrefixAnnouncement example, the RIB management module should interpret the above command in the same way as arib/register command with the following ControlParameters:

• Name:/net/example
• Origin: 129
• ExpirationPeriod: 3600000; optionally, constrained by the ValidityPeriod of the PrefixAnnouncement

Unregister a route¶

command-verb:unregister

This command removes a route from the RIB.

This command can also be accepted onndn:/localhop/nfd management prefix, in addition to the defaultndn:/localhost/nfd management prefix.

ControlParameters fields:

• Name (required)
• FaceId (optional)
• Origin (optional)

FaceId is the FaceId returned byFace Management. IfFaceId is omitted or is set to zero, it is implied as the requesting face (self unregistration).

Origin defaults toapp (=0).

Self unregistration is unnecessary if the client is quitting. The forwarder SHOULD automatically remove routes belonging to a closed face.
A client needs self unregistration when it stops serving a name prefix, but intends to continue execution.

If the route does not exist, this command does nothing, but is still considered successful.

If the command succeeds, <body> in ControlResponse block contains the updated ControlParameters:

• Name: unchanged
• FaceId: nexthop FaceId (not zero)
• Origin: unchanged if request specifies;app (=0) if request omits

Semantics of successful responses¶

Successful responses from these commands indicate that RIB Management has received and authorized the command, and will perform the requested updates shortly.
RIB and FIB updates are asynchronous, and they are not necessarily completed when the response is sent.

RIB Dataset¶

Routes are published as aStatus Dataset atndn:/localhost/nfd/rib/list.

Multiple routes of the same Name prefix are organized into aRIB entry. Each RIB entry is represented by aRibEntry block:

RibEntry = RIB-ENTRY-TYPE TLV-LENGTH             Name             1*RouteRoute    = ROUTE-TYPE TLV-LENGTH             FaceId             Origin             Cost             Flags             [ExpirationPeriod]

• Flags is the inclusive OR of route inheritance flags, encoded in the same way as theregister command.
• ExpirationPeriod is the remaining lifetime of a route. This field is omitted if the route has infinite lifetime.

Routable Prefixes Dataset¶

RIB Management collects a list of routable prefixes and publishes it as aStatus Dataset atndn:/localhost/nfd/rib/routable-prefixes andndn:/localhop/nfd/rib/routable-prefixes.

Generally, aroutable prefix is a name prefix that satisfies one of the following:

• The prefix is advertised into a routing protocol from this router.
• The prefix can be registered onto a connected router viaAutoPrefixPropagation from this end host, and falls under a routable prefix of that router.

This means, generally, a local producer can have reasonable belief that it would be able to receive Interests expressed elsewhere in the network, if it registers a prefix under a routable prefix. However, since the network is a dynamic and distributed system, global reachability cannot be guaranteed even if a routable prefix is used.

Each routable prefix is represented by aName block in the dataset.

TLV-TYPE assignments¶