212777-A, February 2002 217CHAPTER 9Virtual Matrix ArchitectureVirtual Matrix Architecture (VMA) is a hybrid architecture that takes full advantage of the dis-tributed processing capability in Alteon Web switches. With VMA, the switch makes optimaluse of system resources by distributing the workload to multiple processors, thereby improvingswitch performance and increasing session capacity. VMA also removes the topology con-straints introduced by using Direct Access Mode (DAM).The number of concurrent sessions per switch, with VMA enabled, is given below: AD4 and A184: 512K AD3 and A180E: 336K AD2: 256KFor better switch performance and higher session capacities, it is recommended that youenable VMA, especially when using Bandwidth Management and Content Intelligent Switch-ing for multiple frames processing (up to 4500 bytes).Proxy IP Addresses and VMABy default, VMA is enabled on the Web switch (/cfg/slb/adv/matrix). If you areupgrading to Web OS from a previous release, however, VMA will be initially disabled if aproxy IP address is configured for any port on the switch. VMA requires that if any port is con-figured with a proxy IP address, then all ports (except port 9) must be configured with a uniqueproxy IP address prior to enabling VMA.With VMA, the concept of a per-port session table doesn’t apply; instead, there is a global ses-sion table. To identify which processor should process responses to proxied requests, a uniqueproxy IP address must be configured on each port (except port 9). The action of the unusedproxy IP addresses can be disabled using /cfg/slb/port x/proxy dis.
