RIB Management¶

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

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
• selflearning(=129): indicates a route installed by the self-learning forwarding strategy
• 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¶

The routing cost of a nexthop face for a Name prefix is the lowest cost among all Routes toward this nexthop face that can apply to this Name prefix.

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=20) (face=2,cost=50)
/A/B/C	(face=1,cost=20) (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

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
              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