BGP LS support

Overview

BGP Link State, as defined in RFC 7752, defines a way in which an IGP node can export and transport its link state database using BGP. In the context of MPLS TE this database contains not only topology information but also the extensions required to perform traffic engineering. Making these bits available to a northbound entity (hence the "North-Bound Distribution" in the RFC title) can be useful in areas like LSP optimization, custom path computation, monitoring, etc.

ExaBGP can be used as such northbound entity, receiving and decoding BGP-LS information from a device and then probably feeding this data to a separate process. With the information received you could then perform offline CSPF computations, link monitoring and many more.

Configuration

A working ExaBGP configuration could look like the following:

process parsed-route-backend { run /home/ruissalo/exabgp/etc/exabgp/processes/file.py; encoder json; }

`neighbor 10.30.4.3 {`
    `local-address 10.30.4.2;`
    `local-as 65050;`
    `peer-as 65000;`
    `family { `
	`bgpls bgp-ls;`
	`}`


`api {`
	`processes [ parsed-route-backend ];`
	`receive {`
		`parsed;`
		`update;`
	`}`
`}  `


`}`

Where file.py is just a python script that reads from stdin and dumps the data into a file. This file will then contain update information like the following:

{ "exabgp": "3.5.0", "time": 1483605300.29, "host" : "ruissalo", "pid" : 10697, "ppid" : 10666, "counter": 12, "type": "update", "neighbor": { "address": { "local": "10.0.0.2", "peer": "10.0.0.1" }, "asn": { "local": "65050", "peer": "65000" }, "direction": "receive", "message": { "update": { "attribute": { "origin": "igp", "as-path": [ 65000 ], "confederation-path": [], "bgp-ls": { "node-name": "R1", "area-id": "490002", "local-te-router-id": "172.16.0.201" } }, "announce": { "bgpls bgp-ls": { "10.0.0.1": [ { "ls-nlri-type": 1, "l3-routing-toplogy": 0, "protocol-id": 2, "node-descriptors": { "autonomous-system": "65000", "router-id": "172000160201" }, "nexthop": "10.0.0.1" } ] } } } } } }

{ "exabgp": "3.5.0", "time": 1483605300.33, "host" : "ruissalo", "pid" : 10697, "ppid" : 10666, "counter": 13, "type": "update", "neighbor": { "address": { "local": "10.0.0.2", "peer": "10.0.0.1" }, "asn": { "local": "65050", "peer": "65000" }, "direction": "receive", "message": { "update": { "attribute": { "origin": "igp", "as-path": [ 65000 ], "confederation-path": [], "bgp-ls": { "admin-group-mask": [0], "maximum-link-bandwidth": 125000000.0, "maximum-reservable-link-bandwidth": 125000000.0, "unreserved-bandwidth": [125000000.0, 125000000.0, 125000000.0, 125000000.0, 125000000.0, 125000000.0, 125000000.0, 125000000.0], "te-metric": "10", "igp-metric": "10" } }, "announce": { "bgpls bgp-ls": { "10.0.0.1": [ { "ls-nlri-type": 2, "l3-routing-toplogy": "0", "protocol-id": 2, "local-node-descriptors": { "autonomous-system": "65000", "router-id": "172000160002" }, (...)

Json output format

TODO

You can check here for details on how to set up a Juniper device to enable the distribution of link state information.

Submitting bugs

Before submitting any bug report make sure link state data is actually being exported from the TED:

Junos:

show route table lsdist.0

lsdist.0: 29 destinations, 29 routes (29 active, 0 holddown, 0 hidden) + = Active Route, - = Last Active, * = Both

NODE { AS:65000 ISO:1720.0000.0202.00 ISIS-L2:0 }/1152 *[IS-IS/18] 4w1d 21:35:17 Fictitious

NODE { AS:65000 ISO:1720.0016.0001.00 ISIS-L2:0 }/1152 *[IS-IS/18] 4w1d 21:36:43 Fictitious

LINK { Local { AS:65000 ISO:1720.0016.0001.00 }.{ IPv4:10.0.0.3 } Remote { AS:65000 ISO:1720.0016.0011.00 }.{ IPv4:10.0.0.2 } ISIS-L2:0 }/1152

And that it is also being advertised to the ExaBGP neighbor:

show route advertising-protocol bgp 10.30.4.3 | match "NODE|LINK|PREFIX"