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RIB Management

RIB Management is a module of NFD 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 namespace ndn:/localhost/nfd/rib.
RIB Management commands are also available under namespace ndn:/localhop/nfd/rib.

RIB Entry

A RIB Entry maintains a list of routes associated with a particular namespace.

A RIB Entry contains:

  • Name prefix
  • a list of Routes

Route

A route indicates that contents under 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 via AutoPrefixPropagation
  • autoreg(=64): indicates a Route toward an end host connected to this router, registered automatically by the nfd-autoreg tool
  • autoconf(=66): indicates a Route toward a remote router that this end host has connected to, registered automatically by the ndn-autoconfig tool

Route cost

Cost indicates the preference among multiple routes with same Name prefix.
The nexthop face on a route with lower cost is preferred.

Unlike IP routing, the nexthop face to use is decided by forwarding strategy.
Route cost is a suggestion to strategy; 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; overrides CHILD_INHERIT. This flag applies on the prefix: if any route of a prefix has this flag, the prefix will have this flag.

Example:

Name prefix Nexthop FaceId CHILD_INHERIT CAPTURE
/ 1 yes no
/ 2 no no
/A 3 yes no
/A/B/C 4 yes no
/D 5 yes yes
/D 6 yes no
  • 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:

Name prefix Nexthop FaceId Origin Cost CHILD_INHERIT CAPTURE
/A 1 static 10 no no
/A 1 nlsr 20 yes no
/A 2 static 30 no no
/A/B 1 static 40 yes no
/A/B 2 static 50 yes no
/A/B/C 3 static 60 yes no
/A/B/C/D 4 static 70 yes yes

The corresponding FIB should be:

Name prefix Nexthop records
/A (face=1,cost=10) (face=2,cost=30)
/A/B (face=1,cost=40) (face=2,cost=50)
/A/B/C (face=1,cost=40) (face=2,cost=50) (face=3,cost=60)
/A/B/C/D (face=4,cost=70)

Control Commands

ControlCommand management-module: rib

Register a route

command-verb: register

This command adds a route to the RIB.

This command can also be accepted on ndn:/localhop/nfd management prefix, in addition to the default ndn:/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.
If Name exceeds this limit, the command fails with code 414.

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

Origin defaults to app(=0).

Cost defaults to zero.

Flags is the inclusive OR of route inheritance flags.
CHILD_INHERIT=1, CAPTURE=2.
It defaults to CHILD_INHERIT.

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

If a route of same Name, FaceId, and Origin exists, its Cost and Flags are updated, and its lifetime is extended to now + ExpirationPeriod.

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

Alternatively, application may use Prefix Announcement Protocol to register prefixes to itself.

Unregister a route

command-verb: unregister

This command removes a route from the RIB.

This command can also be accepted on ndn:/localhop/nfd management prefix, in addition to the default ndn:/localhost/nfd management prefix.

ControlParameters fields:

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

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

Origin defaults to app(=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 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 a Status Dataset at ndn:/localhost/nfd/rib/list.

Multiple routes of same Name prefix are organized into a RIB entry.
Each RIB entry is represented by a RibEntry block:

RibEntry = RIB-ENTRY-TYPE TLV-LENGTH
             Name
             1*Route

Route    = ROUTE-TYPE TLV-LENGTH
             FaceId
             Origin
             Cost
             Flags
             [ExpirationPeriod]

Flags is inclusive OR of route inheritance flags, encoded in the same way as register command.

ExpirationPeriod is the remaining lifetime of a route, or omitted if it's Infinity.

Routable Prefixes Dataset

RIB Management collects a list of routable prefixes and publishes them as a published as a Status Dataset at ndn:/localhost/nfd/rib/routable-prefixes and ndn:/localhop/nfd/rib/routable-prefixes.

Generally, a routable 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 via AutoPrefixPropagation 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 a Name block in the dataset.

TLV-TYPE assignments

Type Assigned value Assigned value (hex)
RibEntry 128 0x80
Route 129 0x81

Updated by Davide Pesavento over 4 years ago · 31 revisions