protocol file

Definition of protocol file in The Network Encyclopedia.

What is Protocol File?

A text file that provides resolution of protocol names into their respective RFC-defined protocol numbers on a TCP/IP network. The entries in the protocol file are friendly names for TCP/IP protocol numbers and can be used for well-known service (WKS) records in Domain Name System (DNS) servers and other Windows Sockets applications.

How It Works

The protocol file is in the following location on computers running Microsoft Windows:

  • Windows NT and Windows 2000:


  • Windows 95 and Windows 98:


Each line in the protocol file contains the standard name for a protocol followed by the assigned number as defined in Request for Comments (RFC) 1060, an alias, and an optional comment prefixed with a pound sign (#). The following example comes from the sample protocol file included with Windows 95 and Windows 98:

ip       0     IP       # Internet protocol
icmp 1 ICMP # Internet control message protocol
ggp 3 GGP # Gateway-gateway protocol
tcp 6 TCP # Transmission control protocol

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