RE: weird ASPATH in update message

["Matthew Williams" <]

Mr Jianhong,

The ASes in brackets are the "AS-set". In this case, the AS_Path
includes an AS_Sequence, path to AS performing aggregation, and then an
AS_SET, a list of ASes beyond the aggregation point AS23089. When a peer
creates an aggregate from routing info learnt for other ASes, it can
include those ASes in an AS_Set, primarily for preventing routing loops.


See URLs for more info:
http://www.ict.tuwien.ac.at/skripten/datenkomm/print/28-BGPPolicies.pdf
(slide 20, 21)
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ics/icsbgp4.htm#xtocid2
043939

Best regards,
Matthew Williams

---
> Matthew Williams-Bywater (MW243-RIPE)
> Customer Liaison Engineer
> RIPE NCC (www.ripe.net) 

-----Original Message-----
From: owner-ris-users@localhost [
	    
	    
] On
Behalf Of Jianhong Xia
Sent: 02 June 2002 19:51
Subject: weird ASPATH in update message 


Hi,

I downloaded the BGP raw data of update messsage
on 01/31/2002 from Ripe RRC00, and used route_btoa
to get the text file for the update events.

Normally, in the ASPATH part, there are no more than
40 unique ASes, But I found that sometimes there are
more than 100 ASes there and most of them are in brackets.
What does it mean? Why are there so many ASes in this
breacket, "[...]"?

Thanks.
Jianhong

-----------
PS:

Here is an example:

in the file: updates.20020131.1847

....
...

TYPE: BGP4MP/MESSAGE/Update
FROM: 64.211.147.146 AS3549
TO: 193.0.0.1 AS12654
ORIGIN: INCOMPLETE
ASPATH: 3549 701 23089 [1 3 71 151 226 714 852 1221 1668 2140 2497 2856
3303 3320 3360 3489 3599 3703 3758 3908 4546 4628 4637 4657 4694 5006
6253 6 517 6555 6878 6983 7017 7098 7176 7260 7462 7473 7543 7914 8011
8052 8112 8153 9739 9824 10199 10311 10530 10625 10656 10796 10829 10838
10910 10911  10947 10994 11015 11060 11101 11351 11354 11426 11427 11492
11521 11532 11567 11707 11853 11854 11908 11955 12021 12042 12083 12169
12179 12180 122 62 12270 12271 13343 13367 13373 13471 13560 13581 13606
13632 14011 14265 14366 14412 14465 14606 14743 14764 14803 14893 15009
16924 17011 17361 1 7506 17676 18440 18509 18565 18806 18834 18988 19019
19262 19444 19541 19568 19577 19648 19831 20001 20231 22504 24604]
NEXT_HOP: 64.211.147.146
AGGREGATOR: AS23089 157.130.101.226
COMMUNITY: 3549:2256 3549:30840
ANNOUNCE
  65.215.97.0/24