1. EdgeNet2006 Summit1 Virtual LAN as A Network Control Mechanism Tzi-cker Chiueh Computer Science Department Stony Brook University

2. EdgeNet2006 Summit2 Ethernet Routing Spanning tree topology Source Learning to populate the forwarding table Broadcast if dont know what to do Question: How to control the routes on large L2 networks of commodity Ethernet switches? VLAN

3. EdgeNet2006 Summit3 Virtual LAN (IEEE 802.1Q) Originally proposed to support multiple IP subnets on a L2 network without L3 routers VLAN limits the scope of a broadcast packet 4-byte 802.1Q header inserted between SRC MAC and Type/Length 2-byte 802.1Q tag type = 0x8100 3 bits for priority (IEEE 802.1P) 1 bit for Canonical Format Indicator 12 bits for VLAN ID

4. EdgeNet2006 Summit4

5. 5 VLAN in Practice 802.1Q tag is added at the hosts or edge switches Packets are exchanged between two VLANs through a router Conceptually, each VLAN is like a physical LAN that has its own Spanning tree L2 routing table 802.1S allows per-VLAN spanning tree Number of VLANs supported in real switches is hundreds VLAN specification is port-based or host-based Configuration can be based on SNMP or web requests or CLI

6. EdgeNet2006 Summit6 Viking Project Goal: A network resource management system for campus-wide L2 network backbone or Metro Ethernet Services A large number of low-port-density switches vs. a small number of high-port-density switches Larger geographic coverage More cost-effective (economy of scales) More redundancy at the physical connectivity level Higher aggregate back-plane throughput

7. EdgeNet2006 Summit7 Problem with Existing Ethernet Main problem: single spanning tree Inefficient Inflexible routing Longer failure recovery

8. EdgeNet2006 Summit8 Traffic Engineering Constantly measure traffic load matrix Compute an active-backup path for each node pair to balance loads among links and use shorter links whenever possible mesh rather than tree Force a paths route by setting up a dedicated logical VLAN for it ATM-like behavior on Ethernet Need to combine multiple logical VLANs into one physical VLAN, which corresponds to a spanning tree; active and path paths belong to different VLANs

9. EdgeNet2006 Summit9 Big Picture Each host in a single IP subnet participates in multiple VLANs, and uses different VLANs to reach different destination Fast failure recovery: Switch to a different 802.1S VLAN to reach a destination when the current VLAN fails The failure recovery time of the Viking prototype is less than 500 msec, most of which is SNMP trap Next step: Edge-based traffic shaping and 802.1P for QoS guarantee

10. EdgeNet2006 Summit10

11. EdgeNet2006 Summit11 IGMP Snooping Why: Avoid using L2 broadcast when supporting L3 multicast How: Snoop on IGMP packets to infer a L2 distribution tree for an IP multicast group on top of a L2 networks spanning tree Supported by most commodity Ethernet switches Real switches can only track a small number of IP multicast groups Configuration: Sending IGMP packets to the root, which acts as the default router

12. EdgeNet2006 Summit12 Cassini Project Goal: Leverage commodity Ethernet switches as building block for storage area network Multicast is an important primitive Idea: Use VLAN/IGMP snooping to support tree-based L2 multicast Transparent Reliable Multicast: Multiple L3 connections (e.g. TCP) layered on on top of a L2 multicast connection ACK/Retransmission on individual L3 unicast connection

13. EdgeNet2006 Summit13

14. EdgeNet2006 Summit14 Conclusion Many innovative features in commodity Ethernet switches that are largely exploited CLI or SNMP or HTTP provides the possibility of on-the-fly reconfiguration according to workloads and/or hardware health status Interesting application scenarios: Large-scale L2 network Storage area network Compute cluster interconnect: program-specific topology

15. EdgeNet2006 Summit15 Thank You! Questions?

16. EdgeNet2006 Summit16 Mariner Project Goal: Leverage advanced features of commodity Gigabit Ethernet switches to build scalable compute cluster interconnects (~1000 nodes) Programmable application-specific interconnect topology Fault management: asynchronous state check- pointing and pessimistic message logging Scalable multicast state management

17. EdgeNet2006 Summit17