HP 8/8 Fabric OS Administrator's Guide v6.4.0 (53-1001763-01, June 2010) - Page 103

Routing Traffic Chapter 4 About this chapter •Routing overview 63 •Inter-switch links 66 •Gateway links 69 •Inter-chassis links 71 •Routing policies 73 •Route selection 76 •Frame order delivery 78 •Lossless Dynamic Load Sharing on ports 79 •Frame Redirection 81 Routing overview Data moves through a fabric from switch to switch and from storage to server along one or more paths that make up a route. Routing policies determine the path for each frame of data. Before the fabric can begin to route, it must discover the route a packet should take to reach the intended destination. Route tables are lists that indicate the next hop to which packets are directed to reach a destination. Route tables include network addresses, the next address in the data path, and a cost to reach the destination network. There are two kinds of routing protocols on intranet networks, Distance Vector and Link State. • Distance Vector is based on hop count. This is the number of switches that a frame passes through to get from the source switch to the destination switch. • Link State is based on a metric value based on a cost. The cost could be based on bandwidth, line speed, or round-trip-time. With the link-state method, switches that discover a route identify the networks to which they are attached, receiving an initial route table from the principal switch. After an initial message is sent out, the switch only notifies the others when changes occur. It is recommended that no more than seven hops occur between any two switches. This limit is not required or enforced by FSPF. Its purpose is to ensure that a frame is not delivered to a destination after R_A_TOV has expired. Unicast, multicast, and broadcast traffic are supported. Both Unicast Class 2 and 3 traffic are supported. Broadcast and multicast are supported in Class 3 only. Fabric OS Administrator's Guide 63 53-1001763-01