nanog mailing list archives
Re: Long AS Path
From: Tom Beecher <beecher () beecher cc>
Date: Wed, 21 Jun 2017 13:33:16 -0400
Usually when someone starts griping about RTT between destinations more than about 6 time zones apart, I start to talk to them about refraction indicies, platform specific switching delay differences, stuff like that. Normally I can chase them away or put them to sleep well before getting to 'I can break a lot of things, but physics is not one of them.' A longer ASN path is not an automatic signifier of a longer latency path. It can just as easily be a lower latency path that happens to traverse a expensive link that AS doesn't like to use normally, but wants a backup. Or maybe they have congestion inside their AS from that way in and want to influence traffic away from it. Or maybe they just read that chapter and thought it was a cool setting without knowing what it did. On Wed, Jun 21, 2017 at 12:42 PM, Bob Evans <bob () fiberinternetcenter com> wrote:
My cut off is 6 ASNs - more than 6 and it never makes it to the FIB. However, for this to be viable with plenty of unique prefixes to maintain a large table, we have lots and lots of direct big and small peers and much more than the usual amount of transit neighbors in our network. Silicon Valley companies are very demanding for the fasted path with the lowest number of router hops. ASN hops almost always lead to more router hops in the trace. We have customers that call us if everything is fine and they want to shave off milliseconds to favorite destinations. Picky, picky, picky. I am wondering how may other networks get requests (more like demands) from customers wanting you to speed packets up to and from a specific office in India or China. Customers knowing nothing about their office ISP overseas. BTW, it's almost always they have the cheapest congested shared office connection in the building overseas (especially in India). So they can't do anything there except "pretend" about the bandwidth available. About all they know is the IP address of the VPN and they were told they have a full gig connection. Sure they have a gig port, but it's on a switch together with 10 building neighbors that all also have a gig port on a circuit to the building that no one can maintain a gig for more than 3 ms. Go ahead try and fix that latency packet dropping issue with a firewall on both ends with SPI turned on in both directions. It's your fault if you cant make it better. After all their VPN from London to Bangalore works fine. And the ones in China all work fine to and from Australia. Anyways, I always wondered is it just me or do others get these kind of requests? Thank You Bob Evans CTOSteinar, What reason is there to filter them? They are not a significant fraction of BGP paths. They cause no harm. It's just your sense of tidiness. You might consider contacting one of the operators to see if they do have a good reason you haven't considered. But absent a good reason *to*filterthem, I would let BGP mechanics work as intended. -mel beckman On Jun 21, 2017, at 12:57 AM, "sthaug () nethelp no" <sthaug () nethelp no> wrote:Just wondering if anyone else saw this yesterday afternoon ? Jun 20 16:57:29:E:BGP: From Peer 38.X.X.X received Long AS_PATH=3D AS_SEQ(2= ) 174 12956 23456 23456 23456 23456 23456 23456 23456 23456 23456 23456 234= 56 23456 23456 23456 23456 23456 23456 23456 23456 23456 23456 23456 23456 = 23456 23456 23456 23456 23456 ... attribute length (567) More than configur= ed MAXAS-LIMITThere are quite a few examples of people using stupidly long AS paths. For instance 177.23.232.0/24 *[BGP/170] 00:52:40, MED 0, localpref 105 AS path: 6939 16735 28163 28163 28163 28163 28163 28163 28163 28163 28163 28163 28163 28163 28163 28163 28163 28163 262401 262401 262401 262401 262401 262401 262401 262401 262401 262401 262401 262401 262401 262401 262401 262401 262949 52938 52938 52938 52938 52938 52938 52938 52938 52938 52938 52938 I I currently have 27 prefixes in my Internet routing table with 40 or more ASes in the AS path (show route aspath-regex ".{40,}"). I see no valid reason for such long AS paths. Time to update filters here. I'm tempted to set the cutoff at 30 - can anybody see a good reason to permit longer AS paths? Steinar Haug, Nethelp consulting, sthaug () nethelp no
Current thread:
- Re: Long AS Path, (continued)
- Re: Long AS Path Mel Beckman (Jun 21)
- Re: Long AS Path Pierfrancesco Caci (Jun 21)
- Re: Long AS Path jim deleskie (Jun 22)
- Re: Long AS Path Mel Beckman (Jun 22)
- Re: Long AS Path Bob Evans (Jun 21)
- Re: Long AS Path Saku Ytti (Jun 21)
- Re: Long AS Path Jon Lewis (Jun 22)
- Re: Long AS Path Stephen Satchell (Jun 22)
- Re: Long AS Path Ryan L (Jun 23)