GS1920v2 Series User’s Guide
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APPENDIX B
Common Services
The following table lists some commonly-used services and their associated protocols and port numbers. 
For a comprehensive list of port numbers, ICMP type or code numbers and services, visit the IANA 
(Internet Assigned Number Authority) web site.
• Name: This is a short, descriptive name for the service. You can use this one or create a different one, 
if you like.
• Protocol: This is the type of IP protocol used by the service. If this is TCP/UDP, then the service uses the 
same port number with TCP and UDP. If this is User-Defined, the Port(s) is the IP protocol number, not 
the port number.
• Port(s): This value depends on the Protocol. Please refer to RFC 1700 for further information about port 
numbers.
•If the Protocol is TCP, UDP, or TCP/UDP, this is the IP port number.
•If the Protocol is USER, this is the IP protocol number.
• Description: This is a brief explanation of the applications that use this service or the situations in which 
this service is used.
Table 248   Commonly Used Services
NAME PROTOCOL PORT(S) DESCRIPTION
AH (IPSEC_TUNNEL) User-Defined 51 The IPSEC AH (Authentication Header) tunneling 
protocol uses this service.
AIM/New-ICQ TCP 5190 AOL’s Internet Messenger service. It is also used 
as a listening port by ICQ.
AUTH TCP 113 Authentication protocol used by some servers.
BGP TCP 179 Border Gateway Protocol.
BOOTP_CLIENT UDP 68 DHCP Client.
BOOTP_SERVER UDP 67 DHCP Server.
CU-SEEME TCP
UDP
7648
24032
A popular videoconferencing solution from 
White Pines Software.
DNS TCP/UDP 53 Domain Name Server, a service that matches 
web names (for example www.zyxel.com) to IP 
numbers.
ESP (IPSEC_TUNNEL) User-Defined 50 The IPSEC ESP (Encapsulation Security Protocol) 
tunneling protocol uses this service.
FINGER TCP 79 Finger is a UNIX or Internet related command 
that can be used to find out if a user is logged 
on.
FTP TCP
TCP
20
21
File Transfer Program, a program to enable fast 
transfer of files, including large files that may not 
be possible by email.
H.323 TCP 1720 NetMeeting uses this protocol.
HTTP TCP 80 Hyper Text Transfer Protocol – a client or server 
protocol for the world wide web.