Packet forwarding

Packet forwarding is the relaying of packets from one network segment to another by nodes in a computer network.

Decisions

At nodes where multiple outgoing links are available, the choice of which, all, or any to use for forwarding a given packet requires a decision-making process that, while simple in concept, is sometimes bewilderingly complex. Since a forwarding decision must be made for every packet handled by a node, the total time required for this can become a major limiting factor in overall network performance. Much of the design effort of high-speed routers and switches has been focused on making rapid forwarding decisions for large numbers of packets.

The forwarding decision is generally made using one of two processes: routing, which uses information encoded in a device's address to infer its ___location on the network, or bridging, which makes no assumptions about where addresses are located and depends heavily on broadcasting to locate unknown addresses. The heavy overhead of broadcasting has led to the dominance of routing in large networks, particularly the Internet; bridging is largely relegated to small networks where the overhead of broadcasting is tolerable. However, since large networks are usually composed of many smaller networks linked together, it would be inaccurate to state that bridging has no use on the Internet; rather, its use is localized.

Methods

A node can use one of two different methods to forward packets: store-and-forward or cut-through switching.^[1]

See also

• Equal-cost multi-path routing
• Forwarding information base
• Node-to-node data transfer
• Per-hop behaviour
• Port forwarding

References

1. Stefan Haas (1998). The IEEE 1355 Standard: Developments, Performance and Application in High Energy Physics (PDF) (Thesis). p. 58. Retrieved 2015-01-16.