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Protocol Numbers

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In an IP header, the Protocol field identifies the service in the next higher level in the protocol stack to which data is passed. Table C.4 shows these commonly used IP protocol numbers. Protocol numbers are used to configure firewalls, routers and proxies.

Table C.4 Common Protocol Numbers

Service

Protocol Number

Internet Control Message Protocol (ICMP)

1

Transmission Control Protocol (TCP)

6

User Datagram Protocol (UDP)

17

General Routing Encapsulation (PPTP data over GRE)

47

Authentication Header (AH) IPSec

51

Encapsulation Security Payload (ESP) IPSec

50

Exterior Gateway Protocol (EGP)

8

Gateway-Gateway Protocol (GGP)

3

Host Monitoring Protocol (HMP)

20

Internet Group Management Protocol (IGMP)

88

MIT Remote Virtual Disk (RVD)

66

OSPF Open Shortest Path First

89

PARC Universal Packet Protocol (PUP)

12

Reliable Datagram Protocol (RDP)

27

Reservation Protocol (RSVP) QoS

46