1 / 20

Congestion Mitigation

Congestion Mitigation. Trying to maximise performance between MFN’s network and a peer’s network over some busy PNIs. Hello, Good Evening. Joe Abley jabley@mfnx.net Toolmaker, Token Canadian Metromedia Fiber Network. Background.

pamala
Download Presentation

Congestion Mitigation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Congestion Mitigation Trying to maximise performance between MFN’s network and a peer’s network over some busy PNIs

  2. Hello, Good Evening Joe Abley jabley@mfnx.net Toolmaker, Token Canadian Metromedia Fiber Network

  3. Background • There are frequent periods of congestion between our network and a peer’s network in Europe • The peer is a major operator in the region, and evil forces are preventing us from simply lighting up new fibre • We need to work with what we have in place already

  4. Characteristics of Problem • The peer is home to a lot of broadband subscribers • Transient hot-spots in content hosted within MFN’s network cause localised congestion in some PNIs, with other PNIs showing headroom • We get paid for shifting packets (if we don’t carry the packets, we don’t get paid)

  5. State of Play: Day One

  6. Goals • Identify the important consumers of traffic in and beyond the peer’s network • Once we can characterise the major traffic sinks, we can try and balance them out across our various PNIs • Hopefully this will make the PNIs less sensitive to bursty traffic • We expect to have to keep measuring and rebalancing

  7. Tools • Ixia IxTraffic • Gumption • Unix-based BGP speaker that participates in the IBGP mesh • Gives us route history • SeeFlow • Smart NetFlow collector which talks to Gumption • Awk • We always have awk

  8. Infrastructure • NetFlow traffic to be collected in-band from GSR12012s • Single IxTraffic box: • FreeBSD 4.5, i386, dual 700MHz P3, 2GB RAM • Overkill • Load average occasionally peaks above 0.07 • 10GB filesystem for storing routing and flow data in • Located in Virginia • MRTG-like thing (duck) which also lives in VA on a different box gives us nice visibility of congestion trends

  9. Exporting Flow Data • Flow switching needs to be turned on in a maint window, because it makes the routers belch impolitely • All interfaces that can contribute towards traffic sent towards the peer get “ip route-cache flow sampled” • See kiddie script! See router die! • Export config is trivial: ip flow-export source Loopback0 ip flow-export version 5 peer-as ip flow-export destination 192.168.38.9 3871 ip flow-sampling-mode packet-interval 1000 • Note low sampling rate of 1:1000.

  10. Collecting Flow Data • SeeFlow is configured to populate net2net and aspath matrices (“buckets”) • We suspect that a lot of data is getting sunk within the peer network, hence net2net • We could be wrong, and aspath matrices are cool, so we collect those too • Buckets chew up about 50MB of disk per day (all routers)

  11. Initial Discoveries • All the traffic is being sunk within the peer network, and not in a downstream network • Damn • All the traffic is being sunk into a single /12 advertisement • Damn • We need better granularity if we are going to be able to spread the demand across our PNIs

  12. ASPATH Matrices [jabley@nautilus]$ seeasp -s 3320 ./dtag.agg | more Facets: TimeInterval : 05/09/2002 15:00:03.663492 - 06/05/2002 04:57:58.747866 PDT SuperDataFacet : Facets: RouterIpv4Addr : 209.249.254.142 RouterName : pr1.fra1.de.mfnx.net Facets: RouterIpv4Addr : 209.249.254.195 RouterName : mpr2.vie3.at.mfnx.net Facets: RouterIpv4Addr : 216.200.254.246 RouterName : mpr1.ams1.nl.mfnx.net AS P PktsThru BytesThru PktsTo BytesTo PktsTotal BytesTotal ----- - ---------- ------------ ---------- ------------ ---------- ------------ 0 - 0 0 371.203M 143.286G 371.203M 143.286G AAAA P 1.816M 333.567M 108.112M 36.705G 109.928M 37.038G BBBB - 0 0 1.516M 191.657M 1.516M 191.657M CCCC - 0 0 33.173K 23.932M 33.173K 23.932M DDDD - 9 5.118K 35.555K 23.064M 35.564K 23.069M EEEE - 12.567K 7.998M 3.663K 2.413M 16.230K 10.411M FFFF - 917 704.260K 16.872K 9.642M 17.789K 10.346M GGGG - 2.187K 1.406M 22.323K 8.250M 24.510K 9.656M HHHH - 0 0 30.447K 8.587M 30.447K 8.587M IIII - 0 0 10.658K 7.427M 10.658K 7.427M JJJJ - 0 0 27.932K 7.029M 27.932K 7.029M

  13. Net2Net Matrices 172.184.0.0/13 -> A.A.0.0/12 13001989 5601247858 172.184.0.0/13 -> A.A.0.0/12 12983375 5592070913 62.4.67.0/24 -> B.B.0.0/11 9459634 1687041555 62.4.67.0/24 -> B.B.0.0/11 9443861 1677536483 172.176.0.0/14 -> A.A.0.0/12 7113026 2985029679 172.176.0.0/14 -> A.A.0.0/12 7099648 2977787074 62.80.115.0/24 -> C.C.0.0/11 6873518 1236318991 62.4.67.0/24 -> A.A.0.0/12 6689319 1180741686 62.4.82.0/24 -> A.A.0.0/12 6611879 1171430532 62.4.67.0/24 -> C.C.0.0/11 3469776 629221553 62.4.82.0/24 -> C.C.0.0/11 3433970 625422145 62.4.67.0/24 -> D.0.0.0/13 2422913 442942807 62.4.67.0/24 -> D.0.0.0/13 2407651 470778890 62.4.65.96/27 -> A.A.0.0/12 1981446 287218317 62.80.116.0/24 -> E.E.0.0/15 1802114 378062358 62.4.67.0/24 -> F.F.0.0/14 1510412 315282857 62.4.67.0/24 -> F.F.0.0/14 1421497 277014582 62.4.65.96/27 -> B.B.0.0/11 1341063 378931389 62.4.81.128/27 -> B.B.0.0/11 1330058 378268227 172.185.0.0/16 -> A.A.0.0/12 1077841 446966211 172.185.0.0/16 -> A.A.0.0/12 1073445 443555367

  14. Destination Prefix Histogram destination net megabytes proportion A.A.0.0/12 21478 59% B.B.0.0/11 6494 18% C.C.0.0/11 4388 12% D.0.0.0/13 1365 3% F.F.0.0/14 1033 2% G.G.0.0/15 416 1% H.H.0.0/14 311 0% I.I.I.0/21 160 0% J.J.0.0/15 117 0% K.K.0.0/19 89 0%

  15. Drilling down into A.A.0.0/12 • Ask peer to advertise longer prefixes within the /12, so we can measure the traffic per prefix • Wait for response • GOTO 10 • Maybe we can fix this ourselves

  16. /home/dlr/bin/bgpd • We injected 15 covered /16 prefixes into IBGP, with a NEXT_HOP that lay within the remaining /16 • All tagged no-export, to avoid messing with the peer’s public route policy • Strictly local-use within AS6461

  17. More Collection • The increased granularity gives us better visibility into the traffic sinks within the peer network • We will try to spread the traffic over the available PNIs so we can weather bursts of demand more effectively • We will also continue to let the peer know what we are doing • You never know, they may be listening

  18. New Dest Prefix Histogram destination net megabytes proportion B.B.0.0/11 1912 14% A.76.0.0/16 1530 11% C.C.0.0/11 1516 11% A.73.0.0/16 1120 8% A.72.0.0/16 1024 7% A.64.0.0/12 874 6% A.74.0.0/16 683 5% A.70.0.0/16 696 5% A.68.0.0/16 601 4% A.66.0.0/16 437 3%

  19. State of Play: Day N

  20. Conclusions • “Light more fibre” is not always a realistic strategy • You are not always your peer’s number one priority, so it’s nice to be able to take matters into your own hands • Distributing the heavy traffic sinks across different PNIs makes bursty demand less unpleasant • Routing plus flow data = Power. Or something.

More Related