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London Internet Exchange Point Update

Learn about LINX's growth, second site launch, new backbone, traffic issues, Member expansion in UK & beyond, infrastructure evolution, and address migration, including challenges and solutions.

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London Internet Exchange Point Update

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  1. London Internet ExchangePoint Update Keith Mitchell, Executive Chairman NANOG15 Meeting Denver, Jan 1999

  2. LINX Update • LINX now has 63 members • Second site now in use • New Gigabit backbone in place • Renumbered IXP LAN • Some things we have learned! • Statistics • What’s coming in 1999

  3. What is the LINX ? • UK National IXP • Not-for-profit co-operative of ISPs • Main aim to keep UK domestic Internet traffic in UK • Increasingly keeping EU traffic in EU

  4. LINX Status • Established Oct 94 by 5 member ISPs • Now has 7 FTE dedicated staff • Sub-contracts co-location to 2 neutral sites in London Docklands: • Telehouse • TeleCity • Traffic doubling every 4-6 months !

  5. Now totals 63 +10 since Oct 98 Recent UK members: RedNet XTML Mistral ICLnet Dialnet Recent non-UK members: Carrier 1 GTE Above Net Telecom Eireann Level 3 LINX membership

  6. LINX Members by Country

  7. Second Site • Existing Telehouse site full until 99Q3 extension ready • TeleCity is new dedicated co-lo facility, 3 miles from Telehouse • Awarded LINX contract by open tender (8 submissions) • LINX has 16-rack suite • Space for 800 racks

  8. Second Site • LINX has diverse dark fibre between sites (5km) • Same switch configuration as Telehouse site • Will have machines to act as hot backups for the servers in Telehouse • Will have a K.root server behind a transit router soon

  9. LINX Traffic Issues • Bottleneck was inter-switch link between Catalyst 5000s • Cisco FDDI could no longer cope • 100baseT nearly full • Needed to upgrade to Gigabit backbone within existing site 98Q3

  10. Gigabit Switch Options • Looked at 6 vendors: • Cabletron/Digital, Cisco, Extreme, Foundry, Packet Engines, Plaintree • Some highly cost-effective options available • But needed non-blocking, modular, future-proof equipment, not workgroup boxes

  11. Old LINX Infrastructure • 5 Cisco Switches: • 2 x Catalyst 5000, 3 x Catalyst 1200 • 2 Plaintree switches • 2 x WaveSwitch 4800 • FDDI backbone • Switched FDDI ports • 10baseT & 100baseT ports • Media convertors for fibre ether (>100m)

  12. Old LINX Topology

  13. New Infrastructure • Catalyst and Plaintree switches no longer in use • Catalyst 5000s appeared to have broadcast scaling issues regardless of Supervisor Engine • Plaintree switches had proven too unstable and unmanageable • Catalyst 1200s at end of useful life

  14. New Infrastructure • Packet Engines PR-5200 • Chassis based 16 slot switch • Non-blocking 52Gbps backplane • Used for our core, primary switches • One in Telehouse, one in TeleCity • Will need a second one in Telehouse within this quarter • Supports 1000LX, 1000SX, FDDI and 10/100 ethernet

  15. New Infrastructure • Packet Engines PR-1000: • Small version of PR-5200 • 1U switch; 2x SX and 20x 10/100 • Same chipset as 5200 • Extreme Summit 48: • Used for second connections • Gives vendor resiliency • Excellent edge switch - low cost per port and • 2x Gigabit, 48x 10/100 ethernet

  16. New Infrastructure • Topology changes: • Aim to be able to have major failure in one switch without affecting member connectivity • Aim to have major failures on inter-switch links with out affecting connectivity • Ensure that inter-switch connections are not bottlenecks

  17. New backbone • All primary inter-switch links are now gigabit • New kit on order to ensure that all inter-switch links are gigabit • Inter-switch traffic minimised by keeping all primary and all backup traffic on their own switches

  18. IXP Switch Futures • Vendor claims of 1000baseProprietary 50km+ range are interesting • Need abuse prevention tools: • port filtering, RMON • Need traffic control tools: • member/member bandwidth limiting and measurement

  19. Address Transition • Old IXP LAN was 194.68.130/24 • New allocation 195.66.224/19 • New IXP LAN 195.66.224/23 • “Striped” allocation on new LAN • 2 addresses per member, same last octet • About 100 routers involved

  20. Address Migration Plan • Configured new address(es) as secondaries • Brought up peerings with their new addresses • When all peers are peering on new addresses, stopped old peerings • Swap over the secondary to the primary IP address

  21. Address Migration Plan • Collector dropped peerings with old 194.68.130.0/24 addresses • Anyone not migrated at this stage lost direct peering with AS5459 • Eventually, old addresses no longer in use

  22. What we have learned • ... the hard way! • Problems after renumbering • Some routers still using /24 netmask • Some members treating the /23 network as two /24s • Big problem if proxy ARP is involved! • Broadcast traffic bad for health • We have seen >50 ARP requests per second at worst times.

  23. ARP Scaling Issues • Renumbering led to lots of ARP requests for unused IP addresses • ARP no-reply retransmit timer fixed time-out • Maintenance work led to groups of routers going down/up together • Synchronised “waves” of ARP requests

  24. New MoU Prohibitions • Proxy ARP • ICMP redirects • Directed broadcasts • Spanning Tree • IGP broadcasts • All non-ARP MAC layer broadcasts

  25. Statistics • LINX total traffic • 300 M/sec avg, 405 M/sec peak • Routing table • 9,200 out of 55,000 routes • k.root-servers • 2.2 Mbit/sec out, 640 Kbit/sec in • nic.uk • 150 Kbit/sec out, 60 Kbit/sec in

  26. Statistics and looking glass at http://www2.linx.net/

  27. Things planned for ‘99 • Infrastructure spanning tree implementation • Completion of Stratum-1 NTP server • Work on an ARP server • Implementation of route server • Implementation of RIPE NCC test traffic box

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