Hi Jim, Please refer below example.
Assume destination IP is in Asian region. Particular ISP in a different location (Say India) has upstream peering to US POP (Say AT&T) and Asia POP (Say NTT). If we check BGP routing table, assume it shows XX.XX.XX.XX/24 -------->AS - AT&T,AS-XX,AS-Destination -------->AS - NTT,AS-YY,AS-Destination In above case AS-PATH is equal and assume router automatically select path via AT&T. Then end user experiences high latency to reach destination. In such a case, I suggest router need to consider geographic distance to destination and select path via NTT to reach destination by default. Deciding geo distance is a challenge but there are options. Here geo distance means shortest distance to reach IP destination from upstream POP. Current practice is to use community strings, but it depends on upstream ISP capability. Can you comment my idea. Regards Duleept From: UTTARO, JAMES [mailto:ju1...@att.com] Sent: Friday, August 7, 2015 4:09 PM To: Duleep Thilakarathne; 'Robert Raszuk' Cc: 'bess@ietf.org' Subject: Re: [bess] BGP route selection criteria - geographic distance when AS_PATH are equal Duleep, Assuming AS-PATH is equal and AS-Content different how can you know that the internal metrics of each AS are consistent and mirror actual geographic distances? You have to be assured that each administrative domain applies the same metric assignment. I do not believe this is possible when there are multiple administrative domains. Jim Uttaro From: BESS [mailto:bess-boun...@ietf.org] On Behalf Of Duleep Thilakarathne Sent: Friday, August 07, 2015 5:19 AM To: Robert Raszuk Cc: bess@ietf.org<mailto:bess@ietf.org> Subject: Re: [bess] BGP route selection criteria - geographic distance when AS_PATH are equal Hi Raszuk, I went through RFC7311 and my concern is different than RFC 7311. I have analyzed full BGP routing table (541,199 routes) with two tier 1 ISP multi-homing scenario and found nearly 50% of routes have equal AS-PATH length. In this analysis It was considered, there was no route policy applied to influence local preference. According to BGP best path selection algorithm, when AS-PATH lengths are equal, router breaks tie condition based on route internal logic. This does not grantee proper outgoing path selection. Appreciate your concern on above analysis. Regards Duleept From: Robert Raszuk [mailto:rob...@raszuk.net] Sent: Monday, July 27, 2015 2:40 AM To: Duleep Thilakarathne Cc: bess@ietf.org<mailto:bess@ietf.org> Subject: Re: [bess] BGP route selection criteria - geographic distance when AS_PATH are equal Hi Duleep, Please consider RFC 7311 and provide feedback why you think it is not sufficient for your objective. https://tools.ietf.org/html/rfc7311 Best, R. On Sun, Jul 26, 2015 at 9:15 PM, Duleep Thilakarathne <dule...@mobitel.lk<mailto:dule...@mobitel.lk>> wrote: Hi, I would like to suggest to consider geographic distance when AS_PATH are equal in BGP route selection criteria. (as tie breaking rule). Can anybody comment on my idea. Regards Duleept This e-mail and any attachments may contain confidential and privileged information. If you are not the intended recipient, please notify the sender immediately by return e-mail, delete this e-mail and destroy any copies. Any dissemination or use of this information by a person other than the intended recipient is unauthorized and may be illegal. Mobitel (Pvt) Ltd. _______________________________________________ BESS mailing list BESS@ietf.org<mailto:BESS@ietf.org> https://www.ietf.org/mailman/listinfo/bess This e-mail and any attachments may contain confidential and privileged information. If you are not the intended recipient, please notify the sender immediately by return e-mail, delete this e-mail and destroy any copies. Any dissemination or use of this information by a person other than the intended recipient is unauthorized and may be illegal. Mobitel (Pvt) Ltd. This e-mail and any attachments may contain confidential and privileged information. If you are not the intended recipient, please notify the sender immediately by return e-mail, delete this e-mail and destroy any copies. Any dissemination or use of this information by a person other than the intended recipient is unauthorized and may be illegal. Mobitel (Pvt) Ltd.
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