3Com 10014299 manual Configure Fast, Forwarding

362CHAPTER 22: CONFIGURING IP PERFORMANCE

Configure Fast	Message forwarding efficiency is a key feature evaluating router performance.
Forwarding	According to regular flow, when a message arrives, the router will copy it from the
	interface memory to the main CPU. The CPU specifies the network ID from the IP
	address, consults with the routing table to get the best path to forward the
	message, and creates MAC frame suitable for output of the message. The created
	MAC frame is copied to the output queue via DMA (Direct Memory Access), and
	during this process the main system bus is passed twice. This process can be
	repeated for message forwarding.
	In the Fast forwarding, cache is used to process messages. After the first message
	is forwarded by searching routing table, corresponding exchange information is
	generated in the cache, and forwarding of the following same messages can be
	realized by directly searching the cache. This practice greatly simplifies the queuing
	of IP messages, cuts down the route finding time and improves forwarding
	throughput of IP messages. Since the forwarding table in the cache has been
	optimized, much quicker searching speed can be obtained.
	The 3Com Router supports Fast forwarding on various high-speed link interfaces,
	such as Ethernet, synchronous PPP, frame relay and HDLC.
	Besides, the 3Com Router also supports Fast forwarding when firewall is
	configured.
	Fast forwarding implemented via the 3Com Router contains the following
	features:
	■ Support fast forwarding on all types of high-speed link interfaces, including
	Ethernet, synchronous PPP, frame-relay and HDLC etc.
	■ Provide fast forwarding when the firewall is configured.
	■ Support load sharing and improve packets forwarding efficiency greatly.
	The performance of Fast forwarding sometimes will be affected by some
	characteristics such as message queue management and message header
	compression. Fast forwarding is not conducted for fragmented messages.
	Fast-forwarding Configuration includes:

■Enable/Disable fast-forwarding on an interface

■Configure fast-forwarding table size

1Enable/Disable fast-forwarding on an interface

You can disable fast-forwarding as needed. For example, if load sharing is required when forwarding packets, fast-forwarding should be disabled in the forwarding direction of the interface.

Perform the following configuration in interface view.

Table 395 Enable/Disable fast-forwarding on an interface

Operation	Command
Enable fast-forwarding in both directions of the	ip fast-forwarding
interface
Enable fast-forwarding on the inbound interface	ip	fast-forwarding	inbound
Enable fast-forwarding on the outbound interface	ip	fast-forwarding	outbound