Date: Fri, 30 Jul 2010 17:38:55 +0200 From: Martin Barry <marty@supine.com> Subject: SingTel (AS7473) is only announcing ConnectPlus (AS9911)        routes to       Level3 (AS3356) in SJC? To: nanog@nanog.org

Anyone on the list who can offer an explanation about the following scenario? We have taken this up with providers at either end but it will take awhile to filter up to the ASes in question.

We were seeing a London to Singapore connection go via San Jose causing a 50%+ increase in latency.

It appears that SingTel (AS7473) is only announcing ConnectPlus (AS9911) routes to Level3 (AS3356) in SJC.

However they have many adjacencies in many countries and other routes of both AS7473 and it's other downstreams don't appear to be affected (although I haven't tested them all).

Traceroutes are appended at the end but to see for yourself use 202.176.222.0 as a BGP or traceroute query in the Level3 looking glass for both London and any other location, then compare with 167.172.93.0

Checking another large AS at random, they see AS7473 announcing AS9911 routes in London.

thanks Marty

At first I wanted to say this looks like a policy move on 7473's part but on further investigation I'm not sure if they're punishing themselves or doing some very specific traffic routing possible for balancing purposes. Noticing in Leve'3 bgp output they're a customer  Show Level 3 (London, England) BGP routes for 202.176.222.212 BGP routing table entry for 202.176.222.0/24 Paths: (2 available, best #1) 7473 9911 AS-path translation: { APNIC-AS-2-BLOCK APNIC-AS-3-BLOCK } car2.SanJose1 (metric 44128) Origin IGP, metric 100, localpref 100, valid, internal, best Community: North_America Lclprf_100 Level3_Customer United_States San_Jose 7473:10000 7473:20000 7473:41101 Prepend_2_to_AS1668 Prepend_2_to_AS13680 Originator: car2.SanJose1 7473 9911 AS-path translation: { APNIC-AS-2-BLOCK APNIC-AS-3-BLOCK } car2.SanJose1 (metric 44128) Origin IGP, metric 100, localpref 100, valid, internal Community: North_America Lclprf_100 Level3_Customer United_States San_Jose 7473:10000 7473:20000 7473:41101 Prepend_2_to_AS1668 Prepend_2_to_AS13680 Originator: car2.SanJose1 I was inclined to believe it was related to cost, especially seeing the prepend for AOL (1668), but began to dimiss that as I saw two known _peers_ haul the traffic to the west coast as well: Router: gin-l78-mcore3 Site: GB, London - L78, VSNL LONTX01 STRATFORD Command: show ip bgp 202.176.222.212 BGP routing table entry for 202.176.222.0/24 Bestpath Modifiers: deterministic-med Paths: (3 available, best #2) 13 16 7473 9911 laa-icore1. (metric 3100) from laa-mcore3. (laa-mcore3.) Origin IGP, valid, internal Community: Peer route North America West Coast Los Angeles (LAA, LMR) Originator: laa-icore1. 7473 9911 pdi-icore1. (metric 3095) from pdi-mcore4. (pdi-mcore4.) Origin IGP, valid, internal, best Community: Peer route North America West Coast Palo Alto (PDI) Originator: pdi-icore1. and- 1 74 ms 75 ms 75 ms 10gigabitethernet2-3.core1.nyc4.he.net (72.52.92.77) 2 130 ms 149 ms 147 ms 10gigabitethernet5-3.core1.lax1.he.net (72.52.92.226) 3 131 ms 130 ms 139 ms laxeq-ds2-peer1.singtel.com (206.223.123.120) 4 131 ms 130 ms 139 ms ge-1-0-0-0.laxow-cr2.ix.singtel.com (203.208.149.118) In terms of figuring it out for sure I dont think L3 will tell you anything as they probably don't know. SingTel's your best bet but good luck with that unless you become a customer. I'm going to vote backbone traffic balancing by SingTel.