[routing-wg] Large BGP Communities beacon in the wild

Exa thomas.mangin at exa-networks.co.uk
Fri Oct 28 08:27:05 UTC 2016


Hello Owen,

While I agree ( and cudos to Job for noticing the issue while the document is still at the draft stage), the current process for allocation is not developer friendly.

For ExaBGP, I also had to squat a code point to implement draft-frs-bgp-operational-message.
I doubt it will eve cause an operational issue, ExaBGP is not used to route packets in anyone's core, but but the current process gave me no choice: it takes implementation to find issues with drafts and/or interrop problems, unexpected behaviours or simply provide a feature to a crying customer even if a draft is never created / never reach RFC status.

I remember reading a draft from John which attempted to allocate some code points for experimentation - my memory is fuzzy on the details sorry - but even then this would require re numbering which is not ideal.

So perhaps in addition to recognising the squatting issue, "we" should look at how the current IETF process works and can be changed to improve experimentation.

Thomas

Sent from my iPad

>  On 27 Oct 2016, at 16:47, Owen DeLong <owen at delong.com> wrote:
> 
> I don’t mind the move to 32, but I hope the vendors are getting appropriately smacked for squatting and that those attributes are not allowed to be misappropriated by the vendors.
> 
> We have a standards process for a reason and vendors simply squatting on numbers is a violation of that process which cannot be allowed to stand unless we wish to establish that as precedent and simply allow vendors to claim numbers as they wish.
> 
> This already happened with the BSD community in their implementation of a pseudo-VRRP like capability and now two different vendors have abused BGP path attributes.
> 
> This is not a good path for us to continue.
> 
> Owen
> 
>> On Oct 26, 2016, at 11:19 PM, Job Snijders <job at ntt.net> wrote:
>> 
>> Dear Internet,
>> 
>> Through this beacon it was discovered that a vendor was squatting on BGP
>> Path Attribute value 30. And another vendor sat on 31.
>> 
>> So, a twisted turn of events, the Large BGP Communities effort has ended up
>> with BGP Path Attribute value 32 - very befitting if you look at the very
>> problem we're trying to solve :-)
>> 
>> The beacon has been updated to use the new IANA assigned value, nothing
>> else was changed. Hopefully we are in the clear this time around!
>> 
>> Please verify if you can see 192.147.168.0/24 and 2001:67c:208c::/48
>> 
>> Kind regards,
>> 
>> Job
>> 
>>> On Tue, Oct 11, 2016 at 05:01:56PM +0200, Job Snijders wrote:
>>> Large BGP Communities are a novel way to signal information between
>>> networks. An example of a Large BGP Communities is: 2914:4056024901:80.
>>> 
>>> Large BGP Communities are composed of three 4-octet integers, separated
>>> by something like a colon. This is easy to remember and accommodates
>>> advanced routing policies in relation to 4-Byte ASNs. It is the tool that has
>>> been missing since 4-octet ASNs were introduced.
>>> 
>>> IANA has made an Early Allocation of the value 30 (LARGE_COMMUNITY) in
>>> the "BGP Path Attributes" registry under the "Border Gateway Protocol
>>> (BGP) Parameters" group.
>>> 
>>> The draft can be read here: https://tools.ietf.org/html/draft-ietf-idr-large-community
>>> 
>>> Additional information about Large BGP Communities can be found here:
>>> http://largebgpcommunities.net/
>>> 
>>> Starting today (2016.10.11), the following two BGP beacons are available
>>> to the general public, with AS_PATH 2914_15562$
>>> 
>>>   Both these prefixes have a Large BGP Community attached:
>>> 
>>>   2001:67c:208c::/48
>>>   192.147.168.0/24
>>> 
>>>   Large BGP Community - 15562:1:1
>>> 
>>> The NLNOG RING BGP Looking Glass is running the latest version of BIRD
>>> which understands the Large BGP Community Path Attribute.
>>> 
>>> IPv4 LG: http://lg.ring.nlnog.net/prefix_detail/lg01/ipv4?q=192.147.168.0/24
>>> IPv6 LG: http://lg.ring.nlnog.net/prefix_detail/lg01/ipv6?q=2001:67c:208c::/48
>>> 
>>> In theory, since this is an optional transitive BGP Path Attribute, all
>>> the Looking Glass' peers should boomerang the Large Community back to
>>> the LG.  However we currently observe that 50 out of 75 peers propagate
>>> the Large BGP Community to the LG.
>>> 
>>> Relevant Router commands to see if you receive the attribute, or whether
>>> one of intermediate networks has stripped the attribute from the route:
>>> 
>>>   IOS: show ip bgp path-attribute unknown 
>>>       shows all prefixes with unknown path attributes.
>>> 
>>>    IOS #2 - like on route views:
>>>        route-views>sh ip bgp 192.147.168.0
>>>         BGP routing table entry for 192.147.168.0/24, version 98399100
>>>         Paths: (39 available, best #30, table default)
>>>           Not advertised to any peer
>>>           Refresh Epoch 1
>>>           701 2914 15562
>>>             137.39.3.55 from 137.39.3.55 (137.39.3.55)
>>>               Origin IGP, localpref 100, valid, external
>>>               unknown transitive attribute: flag 0xE0 type 0x1E length 0xC
>>>                 value 0000 3CCA 0000 0001 0000 0001
>>>               rx pathid: 0, tx pathid: 0
>>>         
>>>   IOS-XR: (you must look at specific prefixes)
>>>       RP/0/RSP0/CPU0:Router#show bgp  ipv6 unicast 2001:67c:208c::/48 unknown-attributes 
>>>       BGP routing table entry for 2001:67c:208c::/48
>>>       Community: 2914:370 2914:1206 2914:2203 2914:3200
>>>       Unknown attributes have size 15
>>>       Raw value:
>>>       e0 1e 0c 00 00 3c ca 00 00 00 01 00 00 00 01 
>>>       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>> 
>>>   JunOS:
>>>       user at JunOS-re6> show route 2001:67c:208c::/48 detail 
>>>       2001:67c:208c::/48 (1 entry, 1 announced)
>>>           AS path: 15562 I
>>>           Unrecognized Attributes: 15 bytes
>>>           Attr flags e0 code 1e: 00 00 3c ca 00 00 00 01 00 00 00 01
>>>                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>> 
>>> A note about router Configurations:
>>> 
>>> Ensure you are not fitlering the path attributes, eg:
>>> 
>>> JunOS:
>>>   [edit protocols bgp]
>>>   user at junos# delete drop-path-attributes 30
>>> 
>>> XR:
>>>   configure
>>>   router bgp YourASN
>>>       attribute-filter group ReallyBadIdea ! avoid creating bogons
>>>       no attribute 30 
>>>     !
>>>   !
>>> 
>>> Contact persons: myself or Jared Mauch or NTT NOC. BGP Session
>>> identifier 83.231.213.230 / 2001:728:0:5000::a92 AS 15562.
>>> 
>>> Kind regards,
>>> 
>>> Job
> 
> 


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