Circuit Level gateways works at the session layer of OSI model. The TCP
handshaking between packets for determining whether a session requested is
legitimate or not is monitored by Circuit level gateways. The information that
is passed to a remote computer through a circuit level gateway will appear as
if originated from the gateway. The above process is useful for information
hiding about protected networks. CL gateways are inexpensive.
The following are the advantages of Circuit Level Gateways:
- Private network data hiding
- Avoidance of filtering individual packets
- Flexible in developing address schemes
- Don’t need a separate proxy server for each application
- Simpler to implement
The following are the disadvantages of Circuit Level Gateways:
- Active content can not be scanned or disallowed commands.
- Can only handle TCP connections – new extensions proposed for UDP
- TCP/IP stacks are mandatorily be modified by vendor for using CL Gateways.
