Re: [Idr] 4-byte AS community encoding (was re: wide communities)

[Robert Raszuk <[e-mail]>]

Hi Jeff,

>>> Also last but not least the draft
>>> dhrao-idr-4octet-extcomm-generic-subtype does not define a notion of AS
>>> specific communities which clearly may have good applications even at
>>> customer-ISP boundary.
>>
>> That is not its intended purpose.  Again, see my original comment about
>> proceeding with the additional functionality work covered by wide and
>> flexible communities.
>
> It was suggested to me off-list that I may have misunderstood what you meant
> by "AS specific communities".  Could you clarify?

With pleasure  ...

I meant when AS number carried in the community is not to just indicate 
like in original RFC 1997 the AS number who inserted given community. It 
is to indicate the AS on which given community is to be executed.

Example:

I am a customer and you are ISP. You are peering to upstream A and B. I 
am paying you for my transit but really would like to avoid going via 
your upstream A.

The simplest thing to accomplish this is for me to inject a A:Prepend 
what would mean that when you advertise my prefix(es) to ISP A and B you 
will prepend your AS few times when advertising it to ISP A and not B.

I really have live networks asking for such ability today as the only 
way to achieve this currently is via manual operational policy on the 
peering points for you as my provider if you are to continue to be my 
provider :).

Cheers,
R.