HP StorageWorks Enterprise File Services WAN Accelerator Deployment Guide (November 2005)

44 5 - CONFIGURING CONNECTION FORWARDING
If you have one path (through HP EFS WAN Accelerator-2) from the client to
the server and a different path (through HP EFS WAN Accelerator-3) from the
server to the client, you need to enable in-path connection forwarding and
configure the HP EFS WAN Accelerators to communicate with each other.
These HP EFS WAN Accelerators are called neighbors and exchange
connection information to redirect packets to each other.
Figure 5-1. Connection Forwarding in an Asymmetric Network
For example, in Figure 5-1 packets from the Client to the Server go through HP
EFS WAN Accelerator-2 while packets from the server to the Client go through
HP EFS WAN Accelerator-3. The connection is intercepted by HP EFS WAN
Accelerator-1 and HP EFS WAN Accelerator-2 because the first Transmission
Control Protocol (TCP) packet went through HP EFS WAN Accelerator-2.
Because HP EFS WAN Accelerator-3 sees the packets but HP EFS WAN
Accelerator-2 has the relevant information to optimize them, HP EFS WAN
Accelerator-3 redirects the packets from the Server to the Client back to HP
EFS WAN Accelerator-2 so that the connection can be intercepted and
optimized correctly by HP EFS WAN Accelerator-2.
Neighbors in
Connection
Forwarding
Neighbors can be placed in the same physical site or in different sites but the
latency between them should be small because the packets travelling between
them are not optimized.
TIP: If the neighbors are placed on the same physical site, consider installing and
configuring an HP EFS WAN Accelerator with multiple pairs of ports (for example,
Four-Port Copper Gigabit-Ethernet Bypass) and connecting the multiple links to
intercept all packets coming back from the server without performing connection
forwarding.
Load-Balancing Connection forwarding can also be used in networks where there is packet
load-balancing on the server-side, because it does not matter which path the
packets take when they come back from the server. Connection forwarding
cannot perform packet load-balancing on the client-side (that is, there is no
redirection on the client-side).