Port Assignments and NetBIOS Names

Every application that intends to receive data from a TCP/IP network calls the TCP/IP service to acquire a port, a 16-bit number unique to that application on that particular host. Any well-formed incoming datagram with that port number in its TCP or UDP header is delivered to that application. Fragmented datagrams only contain port information in the first datagram fragment (fragment 0). By convention, any transmitting application also owns a port number on its host, and it supplies that port number in the destination port field of the datagrams it sends.

TCP Port Assignments

Table B-1 lists the TCP port assignment for each port.

Table B-1: TCP Port Assignments
Port Keyword Protocol

7

ECHO

Echo

9

DISCARD

Discard

11

USERS

Active Users

13

DAYTIME

Daytime

17

QUOTE

Quote of the Day

19

CHARGEN

Character Generator

20

FTP-DATA

File Transfer (Default Data)

21

FTP

File Transfer (Control)

23

TELNET

Telnet

25

SMTP

Simple Mail Transfer

37

TIME

Time

43

NICNAME

Who Is

53

DOMAIN

Domain Name Server

79

FINGER

Finger

101

HOSTNAME

NIC Host Name Server

103

X400

X400

104

X400-SND

X400-SND

113

AUTH

Authentication Service

117

UUCP-PATH

UUCP Path Service

119

NNTP

USENET Network News Transfer Protocol

512

rexec

UNIX rexec (Control)

513

rlogin

UNIX rlogin

514

rsh

UNIX rsh and rcp

515

printer

UNIX Line Printer Remote Spooling

**Table B-1: TCP Port Assignments**
Port	Keyword	Protocol
7	ECHO	Echo
9	DISCARD	Discard
11	USERS	Active Users
13	DAYTIME	Daytime
17	QUOTE	Quote of the Day
19	CHARGEN	Character Generator
20	FTP-DATA	File Transfer (Default Data)
21	FTP	File Transfer (Control)
23	TELNET	Telnet
25	SMTP	Simple Mail Transfer
37	TIME	Time
43	NICNAME	Who Is
53	DOMAIN	Domain Name Server
79	FINGER	Finger
101	HOSTNAME	NIC Host Name Server
103	X400	X400
104	X400-SND	X400-SND
113	AUTH	Authentication Service
117	UUCP-PATH	UUCP Path Service
119	NNTP	USENET Network News Transfer Protocol
512	rexec	UNIX rexec (Control)
513	rlogin	UNIX rlogin
514	rsh	UNIX rsh and rcp
515	printer	UNIX Line Printer Remote Spooling

UDP Port Assignments

Table B-2 lists the UDP port assignment for each port.

Table B-2: UDP Port Assignments
Port Keyword Protocol

7

ECHO

Echo

9

DISCARD

Discard

13

DAYTIME

Daytime

19

CHARGEN

Character Generator

37

TIME

Time

39

RLP

Resource Location Protocol

42

NAMESERVER

Host Name Server

43

NICNAME

Who Is

49

LOGIN

Login Host Protocol

53

DOMAIN

Domain Name Server

67

BOOTPS

Bootstrap Protocol Server

68

BOOTPC

Bootstrap Protocol Client

69

TFTP

Trivial File Transfer Protocol

111

SUNRPC

SUN Remote Procedure Call

123

NTP

Network Time Protocol

126

SNMP

Simple Network Mgmt. Protocol

137

NETBIOS-NS

NETBIOS Name Service

138

NETBIOS-DGM

NETBIOS Datagram Service

139

NETBIOS-SSN

NETBIOS Session Service

161

SNMP

Simple Network Mgmt. Protocol Q/R

162

SNMP-TRAP

SNMP Event Traps

513

rwho

UNIX Broadcast Naming Service

514

syslog

UNIX System Log

517

talk

Two User Interaction

520

RIP

Routing Information Protocol

525

timed

Time Server

Table B-2: **UDP Port Assignments**
Port	Keyword	Protocol
7	ECHO	Echo
9	DISCARD	Discard
13	DAYTIME	Daytime
19	CHARGEN	Character Generator
37	TIME	Time
39	RLP	Resource Location Protocol
42	NAMESERVER	Host Name Server
43	NICNAME	Who Is
49	LOGIN	Login Host Protocol
53	DOMAIN	Domain Name Server
67	BOOTPS	Bootstrap Protocol Server
68	BOOTPC	Bootstrap Protocol Client
69	TFTP	Trivial File Transfer Protocol
111	SUNRPC	SUN Remote Procedure Call
123	NTP	Network Time Protocol
126	SNMP	Simple Network Mgmt. Protocol
137	NETBIOS-NS	NETBIOS Name Service
138	NETBIOS-DGM	NETBIOS Datagram Service
139	NETBIOS-SSN	NETBIOS Session Service
161	SNMP	Simple Network Mgmt. Protocol Q/R
162	SNMP-TRAP	SNMP Event Traps
513	rwho	UNIX Broadcast Naming Service
514	syslog	UNIX System Log
517	talk	Two User Interaction
520	RIP	Routing Information Protocol
525	timed	Time Server

NetBios Names

The NetBIOS naming convention allows 16 characters in a NetBIOS name. Microsoft, however, limits the number of NetBIOS names to 15 characters and uses the 16th character as a NetBIOS suffix. The NetBIOS suffix is used by Microsoft Networking software to identify functionality installed on the registered device. Cisco Systems has adopted the Microsoft NetBIOS naming convention, as a 16th byte of a NetBIOS name is a special character reserved for the suffix.

Table B-3 lists the NetBIOS suffixes used by Microsoft Windows NT. The suffixes are listed in hexadecimal format because many of them are unprintable otherwise.

Table B-3: NetBIOS Names
Name Number(h) Type¹ Usage

<computername>

00

U

Workstation Service.

<computername>

01

U

Messenger Service.

<computername>

03

U

Messenger service name used when receiving and sending messages. This is the name that is registered with the WINS server as the messenger service on the WINS client and is usually appended to the computer name and to the name of the user currently logged on to the computer.

<computername>

06

U

RAS Server Service.

<domain>

1B

U

Domain Master Browser, which clients and browsers use to contact the domain master browser.

<domain>

1D

U

Clients resolve this name to access the master browser for server lists. There is one master browser on a subnet.

<computername>

1F

U

NetDDE service.

<computername>

20

U

File Server Service.

<computername>

21

U

RAS Client Service.

<computername>

BE

U

Network Monitor Agent.

<computername>

BF

U

Network Monitor Application.

<domain>

00

G

Domain Name.

<\\--__MSBROWSE__>

01

G

The name master browsers broadcast to on the local subnet to announce their domains to other master browser. WINS handles this name by returning the broadcast address FFFFFFFF.

<domain>

1C

G

This group name contains a list of the specific addresses of systems that have registered the name. The domain controllers register this name.

<domain>

1E

G

Browsers broadcast to this name and listen on it to elect a master browser. The broadcast is done on the local subnet and should not cross routers.

<groupname>

20

G

A special group name that is registered with WINS servers to identify groups of computers for administrative purposes. For example, "printersg" could be a registered group name used to identify an administrative group of print servers.

¹U means Unique, G means Group.

Name	Number(h)	Type¹	Usage
<computername>	00	U	Workstation Service.
<computername>	01	U	Messenger Service.
<computername>	03	U	Messenger service name used when receiving and sending messages. This is the name that is registered with the WINS server as the messenger service on the WINS client and is usually appended to the computer name and to the name of the user currently logged on to the computer.
<computername>	06	U	RAS Server Service.
<domain>	1B	U	Domain Master Browser, which clients and browsers use to contact the domain master browser.
<domain>	1D	U	Clients resolve this name to access the master browser for server lists. There is one master browser on a subnet.
<computername>	1F	U	NetDDE service.
<computername>	20	U	File Server Service.
<computername>	21	U	RAS Client Service.
<computername>	BE	U	Network Monitor Agent.
<computername>	BF	U	Network Monitor Application.
<domain>	00	G	Domain Name.
<\\--__MSBROWSE__>	01	G	The name master browsers broadcast to on the local subnet to announce their domains to other master browser. WINS handles this name by returning the broadcast address FFFFFFFF.
<domain>	1C	G	This group name contains a list of the specific addresses of systems that have registered the name. The domain controllers register this name.
<domain>	1E	G	Browsers broadcast to this name and listen on it to elect a master browser. The broadcast is done on the local subnet and should not cross routers.
<groupname>	20	G	A special group name that is registered with WINS servers to identify groups of computers for administrative purposes. For example, "printersg" could be a registered group name used to identify an administrative group of print servers.

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