ZyXEL Communications 1000 User Manual

 Chapter 34 IDP

ZyWALL USG 1000 User’s Guide

Create custom signatures for new attacks or attacks peculiar to your network. 
Custom signatures can also be saved to/from your computer so as to share with 
others. 

You need some knowledge of packet headers and attack types to create your own 
custom signatures. 

These are the fields in an Internet Protocol (IP) version 4 packet header. 

Figure 411   IP v4 Packet Headers

 The header fields are discussed below:  

Table 157   IP v4 Packet Headers 

Version

The value 4 indicates IP version 4.

IHL

IP Header Length is the number of 32 bit words forming the total 
length of the header (usually five).

Type of Service

The Type of Service, (also known as Differentiated Services Code 
Point (DSCP)) is usually set to 0, but may indicate particular 
quality of service needs from the network.

Total Length

This is the size of the datagram in bytes. It is the combined length 
of the header and the data. 

Identification

This is a 16-bit number, which together with the source address, 
uniquely identifies this packet. It is used during reassembly of 
fragmented datagrams.

Flags

Flags are used to control whether routers are allowed to fragment 
a packet and to indicate the parts of a packet to the receiver.

Fragment Offset

This is a byte count from the start of the original sent packet.