Information Technology Reference
In-Depth Information
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Back-end
Storage Servers
Front-end
Clients with Integrated Proxy
Figure 9.3
The proxy-at-client architecture
transmits the data to the clients. Therefore, to request
B
bytes of data, we need 2
B
bytes
of transmission and 2
B
bytes of reception. Hence, this approach requires even more pro-
cessing and network bandwidth than the proxy-at-server architecture. Moreover, additional
hardware and network links are required to host and connect the proxies.
9.2.3 Proxy-At-Client
The third approach is to integrate the proxy into the client, as shown in Figure 9.3. This
can be done by adding a proxy software module into the operating system or within the
application. Under this architecture, a proxy requests the servers to send data directly to the
client computer. After processing by the proxy, video data are then passed directly to the client
application without further network communications. Hence, to retrieve
B
bytes from the
servers, we only need
B
bytes of transmission from the servers and
B
bytes of reception at the
client.
Compared to the proxy-at-server and independent proxy architectures, the proxy-at-client
architecture requires only half the amount of data transfer and does not need separate hardware
for the proxies. The primary advantage of the proxy-at-server and independent proxy archi-
tectures is client transparency, i.e., the complexity of communicating with multiple servers is
hidden by the proxy. However, some experimental studies [13, 14] have shown that the extra
complexity involved is negligible, even when running the client in low-end PC machines.
On the other hand, if the computer running a proxy fails (hardware failure, network failure,
etc.) under the proxy-at-server and the independent proxy architecture, the service of all clients
serving by the proxy will be disrupted. Conversely, the same situation will only affect a single
client in the proxy-at-client architecture because each proxy serves only one client and the
proxy runs at the client host.
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