Avaya 580 - Manual (Page 424)

13-4 User Guide for the Avaya P580 and P882 Multiservice Switches, v6.1
Chapter 13
What is TCP
Established? TCP Established is a criteria applied by a rule where the “Acknowledge” bit
in a TCP header is examined. If this option is not “checked”, the rule will
apply to the packets whose Acknowledge bit is clear (0). If the option is
checked, packets that have the Acknowledge bit set will be affected by the
rule.
The Acknowledge bit in the TCP header, when 0, indicates that the packet is
an initial “call” to the destination. The host sending the message will clear
the bit (0). The host that responds to the message will set the bit(1)
indicating this message is a response. Effectively the call is now
“Established”. All subsequent packets between these two hosts for this
session will have the Acknowledge bit set.
For example: Suppose the Avaya Multiservice switch has interfaces to
“Outside” networks as well as interfaces to “Inside” networks. The Outside
networks need access to a Web server and should be denied access to any
other resource within the Inside network.
Hosts on the Inside networks should have full access to all other resources
on the Inside.
The Web server itself should not be able to establish any new connections to
the Outside but should be able to pass traffic to the other Inside networks.
Assume the following abbreviations:
WS = Web Server.
IN = Inside Networks
ON = Outside Networks
Any = Both Inside and Outside Networks