Decimal Keyword Protocol References
0 HOPOPT IPv6 Hop-by-Hop Option [RFC1883]
1 ICMP Internet Control Message RFC792]
2 IGMP Internet Group Management [RFC1112]
3 GGP Gateway-to-Gateway [RFC823]
4 IP IP in IP (encapsulation) [RFC2003]
5 ST Stream [RFC1190,IEN119]
6 TCP Transmission Control [RFC793]
7 CBT CBT [Ballardie]
8 EGP Exterior Gateway Protocol [RFC888,DLM1]
9 IGP Any private interior gateway(used by Cisco for their IGRP) [IANA]
10 BBN-RCC-MON BBN RCC Monitoring [SGC]
11 NVP-II Network Voice Protocol [RFC741,SC3]
12 PUP PUP [PUP,XEROX]
13 ARGUS ARGUS [RWS4]
14 EMCON EMCON [BN7]
15 XNET Cross Net Debugger [IEN158,JFH2]
16 CHAOS Chaos [NC3]
17 UDP User Datagram [RFC768,JBP]
18 MUX Multiplexing [IEN90,JBP] ...

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