On a related note : Do ISPs ever tweak around with Local Prefs and weights so as to select BGP paths with greater AS PATH length? Would it ever make sense for a provider to chose a longer AS PATH length BGP route against a shorter AS PATH length route? Rohit MTech Comp Sc. Institute of Technology Banaras Hindu University ----- Original Message ----- From: "Howard C. Berkowitz" To: Sent: Thursday, September 09, 2004 11:27 PM Subject: Re: ISP Policies At 11:04 AM +0530 9/9/04, Tulip Rasputin wrote: Hi Chris, Or, you just don't want to send traffic through Bill Manning's ASN because you dislike his hawiian T-Shirt Policy? There are probably a few hundred reasosn why you'd avoid an ASN... In general though I'd think that like Michel said: "It's a pain and its doing something that bgp should do for you without lots of messing about" That's why i explicitly asked for some "social/political/etc." reasons where an ISP may not want his traffic to traverse some particular AS number(s). Something which is beyond BGP to determine as of now ! :-) Indiatimes Email now powered by APIC Advantage. Help! HelpClick on the image to chat with me
On Fri, Sep 10, 2004 at 11:36:58AM +0530, Rohit Gupta wrote:
On a related note : Do ISPs ever tweak around with Local Prefs and weights so as to select BGP paths with greater AS PATH length?
Would it ever make sense for a provider to chose a longer AS PATH length BGP route against a shorter AS PATH length route?
Yes many do -> Prefer your customer routes via customer interfaces, over transit and peering interfaces. Higher LP over cust interfaces = more bits = more revenue. There is nothing wrong with this IMO, considering many of them who do this, also provide a community for customers to override this behaviour. -J -- James Jun TowardEX Technologies, Inc. Technical Lead Network Design, Consulting, IT Outsourcing james@towardex.com Boston-based Colocation & Bandwidth Services cell: 1(978)-394-2867 web: http://www.towardex.com , noc: www.twdx.net
RG> Date: Fri, 10 Sep 2004 11:36:58 +0530 RG> From: Rohit Gupta RG> On a related note : Do ISPs ever tweak around with Local RG> Prefs and weights so as to select BGP paths with greater AS RG> PATH length? Definitely. Case in point: I set up a network a few years ago that included a choice between X 1 Y Z 1 and the latter, longer AS_PATH was the lower-latency way to reach most of AS1. A side bonus was that traffic distribution between their upstreams was better. Note that, as others have mentioned, such tweaks are more common on smaller providers that have less splay. RG> Would it ever make sense for a provider to chose a longer AS RG> PATH length BGP route against a shorter AS PATH length route? Yes. See above. Not all AS_PATH hops are created equal, just as not all IP hops are created equal. Eddy -- Everquick Internet - http://www.everquick.net/ A division of Brotsman & Dreger, Inc. - http://www.brotsman.com/ Bandwidth, consulting, e-commerce, hosting, and network building Phone: +1 785 865 5885 Lawrence and [inter]national Phone: +1 316 794 8922 Wichita _________________________________________________________________ DO NOT send mail to the following addresses: davidc@brics.com -*- jfconmaapaq@intc.net -*- sam@everquick.net Sending mail to spambait addresses is a great way to get blocked.
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Rohit Gupta