Installing and Administering PPP

Chapter 5 93
Security Techniques
Packets Overview
Packets Overview
Each stanza represents a template used to find matching packets. The
features you can place in your stanzas correspond to the fields in
network messages. This allows you to filter at the IP level or the
TCP/UDP/ICMP level.
Internet Protocol (IP) Level
Figure 5-1
*RFC-791 (IP)
The fields available at the IP level include the protocol (e.g., 1 [ICMP], 2
[IGMP], 6 [TCP], 8 [EGP], 17 [UDP], etc.), an address (i.e., the source or
destination address) and IP options (e.g., rr, lsrr, etc.), and
fragmentation.
PPP does not provide a filter keyword for matching the version, IHL,
TOS, length, ID, TTL or checksum header fields.