Zhone 2004 ユーザーガイド

A p p l i c a t i o n   N o t e s

keeps information about the flow of a communication session. State 

can be kept for TCP, UDP, and ICMP packets.

keeps information on fragmented packets, to be applied to later frag-

ments.

The quick option is good for rules such as

block in quick from any to any with ipopts

which will match any packet with a non-standard header length (IP options 
present) and abort further processing of later rules, recording a match and also 
that the packet should be blocked.

The "fall-through" rule parsing allows for effects such as this:

block in from any to any port < 6000
pass in from any to any port >= 6000
block in from any to port > 6003

which sets up the range 6000-6003 as being permitted and all others being 
denied. Note that the effect of the first rule is overridden by subsequent rules. 
Another (easier) way to do the same is:

block in from any to any port 6000 <> 6003
pass in from any to any port 5999 >< 6004

Note that both the "block" and "pass" are needed here to effect a result as a 
failed match on the "block" action

pass in quick from any to any port < 1024

would be needed before the first block.

The Call Agent can ask the gateway to collect digits dialed by the user. This 
facility is intended to be used with residential gateways to collect the numbers 
that a user dials; it can also be used with trunking gateways and access 
gateways alike, to collect access codes, credit card numbers and other 
numbers requested by call control services.

One procedure is for the gateway to notify the Call Agent of each individual 
dialed digit, as soon as they are dialed. However, such a procedure generates a 
large number of interactions. It is preferable to accumulate the dialed numbers 
in a buffer, and to transmit them in a single message.