TCP/IPv6 Configuration and Management Manual (G06.24+)

Maximize the Benefit of the NonStop TCP/IPv6
Architecture
HP NonStop TCP/IPv6 Configuration and Management Manual—524523-008
3-7
Distributor Listening Model
The distributor model achieves some parallelism and load-balancing because of the
use of the multiple, back-end server instances. However, the distributor model is
limited by the fact that all data must flow through the distributor to the back-end server
processes through PATHSEND. This situation creates a potential bottle-neck in the
distributor.
Figure 3-3 shows the distributor listener model in conventional TCP/IP. To scale to
accommodate growing computing needs in this conventional TCP/IP example, three
instances of the distributor are running in three processors (3, 4, and 5) distributing
connections to three sets of server instances in three different processors (0, 1, and 2).
When you can achieve scalability in the conventional TCP/IP model by running multiple
distributors in this manner, there are two hops involved in data flow (one inter-process
hop between the distributor and the server and one between the distributor and the
TCP/IP process). In addition, each processor must have its own physical interface
(PIF) on the adapter. Finally, running a TCP/IP process for each distributor, each
distributor appears to be on a different IP host to the outside world.
Figure 3-3. Distributor Listening Model in Conventional TCP/IP
Server Classes
A, D, G
Server Classes
A, D, G
Processor 0
Server Classes
A, D, G
Processor 0
Processor 1
Processor 2
Server Classes
A, D, G
Server Classes
A, D, G
Processor 0
Server Classes
A, D, G
Processor 0
Processor 1
Processor 2
Server Classes
A, D, G
Server Classes
A, D, G
Processor 0
Server Classes
A, D, G
Processor 0
Processor 1
Processor 2
Distributor
TCP/IP
Hop 2
TCP/IP
Distributor
Distributor
TCP/IP
Server Class Send or
Other IPC, Hop 1
LAN
Adapter
LAN
Adapter
LAN
Adapter
Processor 3
Processor 4 Processor 5
Sockets
Three IP hosts
VST110.vsd