Implementing Advanced Services Today – Routing & Multicast

1. Implementing Advanced Services Today– Routing & Multicast ken lindahl Chair, Internet2 Routing Working Group lindahl@ack.berkeley.edu Campus Focused Workshop on Advanced Networking San Diego, CA 4 December 2000

2. Routing Campus Focused Workshop on Advanced Networking

3. Routing Working Group • Chair: ken lindahl, UC Berkeley • current topics: • Explicit Routing • Internet2 Routing Registry (I2db) • Internet2/Commodity Internet Routing Asymmetry • http://www.internet2.edu/routing/ Campus Focused Workshop on Advanced Networking

4. Internet2 / Commodity Internet Routing Asymmetry • traffic between two Internet2 sites uses Abilene in one direction and commodity Internet in the other. • reduced performance: lower bandwidth, greater latency, greater jitter, higher packet loss • reported by Hank Nussbacher at Spring 2000 Members Meeting • http://www.internet-2.org.il/i2-asymmetry/ • very pronounced cases can be seen in the Abilene Connector mrtg graphs (Joe St Sauver) • http://monon.uits.iupui.edu/abilene/ Campus Focused Workshop on Advanced Networking

5. Asymmetry example #1Abilene Connector mrtg graphs • e.g. Georgetown (NYCM Connector) 11/30/2000 in/ max in (to Abilene) out /max out(from Abilene) http://monon.uits.iupui.edu/abilene/nycm/georgetown-bits.html Campus Focused Workshop on Advanced Networking

6. Asymmetry example #2Abilene Connector mrtg graphs • e.g. Cornell (NYCM Connector) 11/30/2000 in/ max in (to Abilene) out /max out(from Abilene) http://monon.uits.iupui.edu/abilene/nycm/cornell-bits.html Campus Focused Workshop on Advanced Networking

7. Abilene Connector mrtg graphsLimitations • Abilene Connector mrtg graphs won’t show asymmetry in many cases, e.g.: • campus connects to a gigaPoP • Abilene graphs will show aggregated statistics for all campuses connected to the gigaPoP, tending to hide asymmetry for a single campus. • gigaPoP and campus graphs might reveal asymmetry. • but, some gigaPoPs offer “shared” ISP; campuses may have a single link to gigaPoP for both Internet2 and commodity traffic. • campus mrtg graphs won’t reveal asymmetry in this case. Campus Focused Workshop on Advanced Networking

8. Abilene Connector mrtg graphsLimitations • Abilene Connector mrtg graphs won’t show asymmetry in many cases, e.g.: • parts of the campus network are routed asymmetrically • incorrect BGP configuration prevents some campus prefixes from being announced • some campus subnets don’t reach Internet2 connection; instead, follow campus default to commodity Internet. Campus Focused Workshop on Advanced Networking

9. source: The Asymmetry of Internet2, Hank Nussbacher, March 2000, http://www.internet-2.org.il/i2-asymmetry/ Asymmetry example #3Asymmetry of Internet-2, slide 17 Campus Focused Workshop on Advanced Networking

10. source: The Asymmetry of Internet2, Hank Nussbacher, March 2000, http://www.internet-2.org.il/i2-asymmetry/ Asymmetry example #4Asymmetry of Internet-2, slide 18 • slide 18 from Hank’s talk Campus Focused Workshop on Advanced Networking

11. source: The Asymmetry of Internet2, Hank Nussbacher, March 2000, http://www.internet-2.org.il/i2-asymmetry/ Asymmetry example #5Asymmetry of Internet-2, slide 20 Campus Focused Workshop on Advanced Networking

12. Routing Asymmetry • estimated 30% of Internet2 exhibits this sort of asymmetry • The Asymmetry of Internet-2, Hank Nussbacher, March 2000 • in some cases, campuses are aware of the issue; need to upgrade network equipment to fix. Campus Focused Workshop on Advanced Networking

13. source: The Asymmetry of Internet2, Hank Nussbacher, March 2000, http://www.internet-2.org.il/i2-asymmetry/ Detecting Asymmetry Detecting AsymmetryNussbacher’s Looking Glass test Campus Focused Workshop on Advanced Networking

14. Detecting Asymmetry • campus Surveyor or NLANR AMP might be able to detect asymmetry http://www.advanced.org/surveyor/ http://amp.nlanr.net/ • typically located near the campus Internet2 link, so might not detect asymmetries affecting interior subnets. • traceroute to Internet2 sites from interior subnets • will reveal instances where outbound data is via the commodity Internet. • time-intensive. • not available to network engineers at other sites. Campus Focused Workshop on Advanced Networking

15. Detecting Asymmetry • Abilene Core Node Router Proxy can be used to check campus BGP announcements • doesn’t really show that data will be delivered correctly • … but if the BGP announcements are incorrect, packets are unlikely to take the desired path. • Summary: several incomplete and/or inadequate tools exist. Routing WG will investigate this issue and try to find a solution. • participants will be welcomed! to join, see http://www.internet2.edu/routing/ Campus Focused Workshop on Advanced Networking

16. Interior routing • what’s to say? • encourage use of link-state IGP, e.g. OSPF, EIGRP (cisco proprietary). • generally, not necessary to redistribute external routes into IGP; instead use default to deliver packets to border router, let BGP do the work from there. • most importantly, make sure the packets are following intended paths. Campus Focused Workshop on Advanced Networking

17. port duplex mis-matches • not routing, per se… • some think this is the most commonly seen performance killer in the Internet today. • often is the result of autonegotiation failure between connected devices. • YMMV, consider disabling autonegotiation; rely on manually configured speed and duplex... • … especially on switch-to-switch and switch-to-router links (how often do these change speed or duplex?) Campus Focused Workshop on Advanced Networking

18. Multicast Campus Focused Workshop on Advanced Networking

19. Multicast Working Group • Chair: Kevin Almeroth, UC Santa Barbara • currently focused on encouraging campus deployment of IP multicast • http://www.internet2.edu/multicast/ disclaimer: content of this presentation should be blamed on ken, not Kevin. Campus Focused Workshop on Advanced Networking

20. Internet2 Multicast Architecture • PIM Sparse-Mode • avoids periodic flooding of all multicast groups; important for high-bandwidth Internet2 multicast applications. • MBGP on border routers • allows non-congruent unicast and multicast topologies; important when a site does not use it’s ISP for multicast. • MSDP between neighboring ASs • communicate Sender Active information to RPs in all external PIM domains. • for details, see NCNE Multicast page; • http://www.ncne.org/faq/multicast.html Campus Focused Workshop on Advanced Networking

21. PIM issues • version: should be PIMv2 • vendor interoperability (e.g. Nortel: PIMv2 SM only) • cisco: requires IOS 12.0 or later • auto-RP vs. BootStrap Router (BSR) • auto-RP is cisco-proprietary; supports cisco’s v1/v2 interoperability mode; requires Sparse-Dense-Mode (interior interfaces only); works with administratively scoped zones • BSR is part of PIMv2 spec, supports vendor interoperability; may not work with administratively scoped zones (still true?) Campus Focused Workshop on Advanced Networking

22. Monitoring Multicast • NLANR Beacon • loss • one-waydelay • jitter • out-of-orderarrivals • duplication Campus Focused Workshop on Advanced Networking

23. Monitoring Multicast • NLANR Beacon • documentation and source (java), available at http://dast.nlanr.net/Projects/Beacon/ • Abilene Beacon page • http//palpatine.ucs.indiana.edu:9999/ • only two sites currently; not ready for prime-time? • suggestion: deploy Beacons around campus to monitor campus multicast; also one at/near border to peer with GigaPoP and other campuses. Campus Focused Workshop on Advanced Networking

24. Monitoring Multicast • Abilene multicast tools • Multicast Route Viewer, MSDP logger, SDR Monitorhttp://www.abilene.iu.edu/index.cgi?page=multicast • SDR Monitor at UCSB • http://steamboat.cs.ucsb.edu/sdr-monitor/ • shows whether SDR announcements from your campus are getting out • also, gives an idea of what SDR announcements your campus should be able see • list of multicast monitoring and debugging tools http://www.ncne.nlanr.net/faq/mcast_eng_faq.html#42 Campus Focused Workshop on Advanced Networking

25. Multicast bandwidth control usingrate-limiting • cisco routers support configurable rate-limits on interfacesip multicast rate-limit out 4000 ip multicast rate-limit in 4000 • limits total {in,out}bound multicast to 4Mbps • when configured limit is exceeded, multicast packets are dropped indiscriminately • some multicast is pretty important and should not be dropped: OSPF, PIM messages, NTP • can use access-lists to exempt well-known groups from rate-limiting Campus Focused Workshop on Advanced Networking

26. Multicast bandwidth control using administratively scoped zones • parts of the campus network that are not able to handle high-bandwidth multicast (e.g. >10Mbps) need protection • if the sender is on your campus and you can influence the group address that is used, administratively scoped multicast boundaries can keep users in bandwidth-challenged parts of the network from joining high-bandwidth sessions. • but you probably can’t control sessions that originate from outside your campus. • configuration can be complicated, involving multiple RPs and multiple RP mapping agents, each carefully scoped. • c.f. Developing IP Multicast Networks, Beau Williamson, Cisco Press Campus Focused Workshop on Advanced Networking

27. Constraining multicast flooding –IGMP Snooping vs CGMP • IGMP Snooping • switch inspects IGMP membership reports from hosts to determine which ports a group should be forwarded out • can be CPU intensive (switch must inspect all multicast packets). • implementations appear to differ among vendors. • CGMP • switch forwards IGMP membership reports to router; router uses CGMP to tell the switch which ports a group should be forwarded out • moves CPU load to the router (minimal) • cisco proprietary Campus Focused Workshop on Advanced Networking

28. Constraining multicast flooding –IGMP Snooping vs CGMP • use one or the other on switched LANs that have connected hosts • Issue: leave latency • IGMPv1 hosts do not send IGMP Leave Group messages, so forwarding state on switch must time out. (Affects both IGMP snooping and CGMP). • Issue: does not work on router ports • routers don’t send host membership reports, so neither IGMP snooping nor CGMP works on router ports. Don’t use either on a backbone switch with only routers attached. Campus Focused Workshop on Advanced Networking

29. the next thing: SSM • Source-Specific Multicast • addresses scalability issue of earlier forms of multicast • receivers specify desired source when joining group • source and group information learned via non-multicast means (e.g. web page) • requires IGMPv3 for (S,G) joins • some host implementations are available • requires support in last-hop router (cisco EFT images now, supported releases soon) • cisco offers 2 interim workarounds: IGMPv3lite and URD (URL Rendezvous Directory) Campus Focused Workshop on Advanced Networking

30. the next thing: SSM • cisco informationhttp://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121newft/121t/121t3/dtssm.htm • U of Oregon SSM trialhttp://videolab.uoregon.edu/projects.html • IETF WGhttp://www.ietf.org/html.charters/ssm-charter.html Campus Focused Workshop on Advanced Networking