HP StorageWorks Enterprise File Services WAN Accelerator 2.1.5 deployment guide (June 2006)

40 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, HP EFS N4c WAN
Accelerator 4-port NIC Card) 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).