rtbrick-bngblaster/docs/bgp.md

BGP

The Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems (AS) on the internet. BGP is classified as a path-vector routing protocol, and it makes routing decisions based on paths, network policies, or rule-sets configured by a network operator.

Following an example BGP configuration with one session.

{
    "interfaces": {
        "network": [
            {
                "interface": "eth1",
                "address": "10.0.1.2/24",
                "gateway": "10.0.1.1"
            }
        ]
    },
    "bgp": [
        {
            "local-ipv4-address": "10.0.1.2",
            "peer-ipv4-address": "10.0.1.1",
            "raw-update-file": "test.bgp",
            "local-as": 65001,
            "peer-as": 65001
        }
    ]
}

BGP Sessions

Every BGP session is opened with the capabilities for the following address families:

• IPv4 unicast
• IPv4 labelled unicast
• IPv6 unicast
• IPv6 labelled unicast

Limitations

BGP authentication is currently not supported but already planned as enhancement in one of the next releases.

RAW Update Files

The BNG Blaster is able to inject BGP messages from a pre-compiled RAW update file into the defined sessions. A RAW update file is not more than a pre-compiled binary stream of BGP messages, typically but not limited to update messages.

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 +                                                               +
 |                                                               |
 +                                                               +
 |                           Marker                              |
 +                                                               +
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |          Length               |      Type     | ...
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++
 .
 .
 .
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 +                                                               +
 |                                                               |
 +                                                               +
 |                           Marker                              |
 +                                                               +
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |          Length               |      Type     | ...
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++

Those files can be created using the included BGP RAW update generator script bgpupdate or manually using libraries like scapy or converters from PCAP or MRT files.

The configured raw-update-file under the BGP session is loaded during Blaster startup phase and send as soon as the session is established.

The bgp-raw-update command allows to send further updates during the session lifetime.

$ sudo bngblaster-cli run.sock bgp-raw-update file update1.bgp

This allows in example to load a full table after session has started and manually trigger a series of changes using incremental updates files.

All BGP RAW update files are loaded once and can than be used by multiple sessions. Meaning if two or more sessions reference the same file identified by file name, this file is loaded once into memory and used by multiple sessions.

Therefore for incremental updates, it may makes sense to pre-load via bgp-raw-update-files configuration.

{
    "bgp": [
        {
            "local-ipv4-address": "10.0.1.2",
            "peer-ipv4-address": "10.0.1.1",
            "raw-update-file": "start.bgp",
            "local-as": 65001,
            "peer-as": 65001
        }
    ],
    "bgp-raw-update-files": [
        "update1.bgp",
        "update2.bgp"
    ]
}

Incremental updates not listed here will be loaded dynamically as soon as referenced by first session.

BGP RAW Update Generator

The BGP RAW update generator is a simple tool to generate BGP RAW update streams for use with the BNG Blaster.

$ bgpupdate --help
usage: bgpupdate [-h] [-a ASN] -n ADDRESS [-N N] -p PREFIX [-P N] [-m LABEL]
                 [-M N] [-l LOCAL_PREF] [-f FILE] [-w] [--end-of-rib]
                 [--append] [--pcap FILE] [--log-level {warning,info,debug}]

optional arguments:
  -h, --help            show this help message and exit
  -a ASN, --asn ASN     autonomous system number
  -n ADDRESS, --next-hop-base ADDRESS
                        next-hop base address (IPv4 or IPv6)
  -N N, --next-hop-num N
                        next-hop count
  -p PREFIX, --prefix-base PREFIX
                        prefix base network (IPv4 or IPv6)
  -P N, --prefix-num N  prefix count
  -m LABEL, --label-base LABEL
                        label base
  -M N, --label-num N   label count
  -l LOCAL_PREF, --local-pref LOCAL_PREF
                        local preference
  -f FILE, --file FILE  output file
  -w, --withdraw        withdraw prefixes
  --end-of-rib          add end-of-rib message
  --append              append to file if exist
  --pcap FILE           write BGP updates to PCAP file
  --log-level {warning,info,debug}
                        logging Level

The python BGP RAW update generator is a python script which uses scapy to build BGP messages. Therefore this tool can be easily modified, extend or used as blueprint for your own tools to generate valid BGP update streams.