This object identifies the internet protocol number
in the packets. These IP protocol numbers are defined
in the Network Group Request For Comments(RFC) documents.
For example, Cisco commonly used protocol includes:
1 - Internet Control Message Protocol (ICMP)
2 - Internet Gateway Message Protocol (IGMP)
4 - IP in IP tunneling
6 - Transmission Control Protocol (TCP)
9 - Cisco's IGRP routing protocol (IGRP)
17 - User Datagram Protocol (UDP)
47 - Cisco's GRE tunneling (GRE)
50 - Encapsulation Security Payload
51 - Authentication Header Protocol
88 - Cisco's EIGRP routing protocol
89 - OSPF routing protocol
94 - KA9Q NOS compatible IP over IP tunneling
103 - Protocol Independent Multicast
108 - Payload Compression Protocol.