22.12.2012 Views

Front cover - IBM Redbooks

Front cover - IBM Redbooks

Front cover - IBM Redbooks

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

Session-layer proxies<br />

Although application-level proxies are considered highly secure, they require a<br />

high degree of technical configuration and support. To help solve this problem,<br />

session-layer proxies, also referred to as circuit-level proxies, were developed.<br />

Session-layer proxies are much like application-level proxies. A session-layer<br />

gateway establishes a proxy connection between an internal user and an<br />

external host. However, unlike application-level proxies, session-layer proxies<br />

control the flow of data at the session layer. Working at the session layer means<br />

that the proxy actually establishes a virtual circuit between the client and the host<br />

on a session-by-session basis. Discussions on the advantages and<br />

disadvantages of either type can be found in numerous places. For example, see<br />

the following URL:<br />

http://www.aventail.com<br />

It is important to note the difference between a session-layer proxy and a stateful<br />

packet filter. Unlike stateful packet filters, a session-layer proxy inspects all<br />

packets, so the throughput is generally lower.<br />

SOCKS<br />

SOCKS is an IETF standard (RFC-1928) generic proxy protocol for<br />

TCP/IP-based applications. The SOCKS protocol provides a flexible framework<br />

for developing secure communications by supporting the integration of other<br />

security technologies.<br />

SOCKSv5 is an IETF (Internet Engineering Task Force) approved standard<br />

(RFC 1928), generic proxy protocol for TCP/IP-based networking applications.<br />

The SOCKS protocol provides a flexible framework for developing secure<br />

communications by easily integrating other security technologies.<br />

SOCKS consists of two components, a server and a client. The SOCKS proxy<br />

server is implemented at the application layer, while the SOCKS client is<br />

implemented between the OSI application and transport layers. It is a<br />

session-layer proxy. The basic function of SOCKS is to enable hosts on one side<br />

of a SOCKS proxy server to access hosts on the other side of a SOCKS server<br />

without requiring direct ITCP/IP connectivity. The relationship of the SOCKS<br />

proxy server to the OSI stack is shown Figure 4-2.<br />

Chapter 4. Security components and layers 119

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!