Here is my reply to Claudio on the IDR list. Copying the IETF list.
------------------------------------------------------
Hi, Claudio:
Not sure if you are aware of the large scale outage that occurred a few
years ago from the leak of the confed related segments by one
implementation. At the time quite a few implementations were resetting
the sessions when receiving such updates.
While discarding the whole AS4_PATH would be simpler and less disruptive
(than session resetting), it would still lose the vital as-path info
contained in the AS4_PATH which can otherwise be recovered by
"repairing" the attribute. That is why the approach specified in the
rfc4893bis is adopted, and it has been implemented widely.
-- Enke
On 6/12/12 7:25 AM, Stewart Bryant wrote:
FYI
Copying to IETF list as this is an IETF LC
Stewart
-------- Original Message --------
Subject: Re: [Idr] Last Call: (BGP Support for Four-octet AS
Number Space) to Proposed Standard
Date: Tue, 12 Jun 2012 15:54:55 +0200
From: Claudio Jeker <cjeker@xxxxxxxxxxxxxxxxx>
To: Stewart Bryant <stbryant@xxxxxxxxx>
CC: <idr@xxxxxxxx>
On Tue, Jun 12, 2012 at 11:30:11AM +0100, Stewart Bryant wrote:
On 01/06/2012 23:00, Claudio Jeker wrote:
>On Fri, Jun 01, 2012 at 11:54:44AM -0700, The IESG wrote:
>>The IESG has received a request from the Inter-Domain Routing WG
(idr) to
>>consider the following document:
>>- 'BGP Support for Four-octet AS Number Space'
>> <draft-ietf-idr-rfc4893bis-06.txt> as Proposed Standard
>>
>>The IESG plans to make a decision in the next few weeks, and solicits
>>final comments on this action. Please send substantive comments to the
>>ietf@xxxxxxxx mailing lists by 2012-06-15. Exceptionally, comments
may be
>>sent to iesg@xxxxxxxx instead. In either case, please retain the
>>beginning of the Subject line to allow automated sorting.
>>
>>Abstract
>>
>>
>> The Autonomous System (AS) number is encoded as a two-octet
entity in
>> the base BGP specification. This document describes extensions
to BGP
>> to carry the Autonomous System numbers as four-octet entities.
This
>> document obsoletes RFC 4893.
>>
>Just for the sake of clarity, OpenBGPD will not do the following:
>
> In addition, the path segment types AS_CONFED_SEQUENCE and
> AS_CONFED_SET [RFC5065] MUST NOT be carried in the AS4_PATH
attribute
> of an UPDATE message. A NEW BGP speaker that receives these path
> segment types in the AS4_PATH attribute of an UPDATE message
from an
> OLD BGP speaker MUST discard these path segments, adjust the
relevant
> attribute fields accordingly, and continue processing the UPDATE
> message. This case SHOULD be logged locally for analysis.
>
>There is no point to do this fiddeling instead we will treat this
like any
>other parse error of AS4_PATH.
>
Claudio
Since this is in last call, I have to ask whether you have objection
to the publication
of the above text, or have any proposed text changes?
I see no reason to enforce AS_CONFED_SEQUENCE and AS_CONFED_SET stripping
on all AS4 implementations. It forces bgp implementations that don't have
confederation support to strip out something that will cause an error in
the regular path and for those systems ignoring the AS4_PATH attribute
is perfectly fine. I do not understand how a workaround needs to be a
MUST for something that is a MUST NOT at the same time? Why MUST we
workaround something that MUST NOT appear? Why do we need to add extra
code that is hard to test and maybe cause for further errors because it
modifies attributes in very uncommon way?
I propose to remove that paragraph entierly since it does only add
complexity to the protocol for no reason and therefor is only a source of
errors without any benefit.