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A DNS RR for specifying the location of services (DNS SRV) (RFC2052)

IP.com Disclosure Number: IPCOM000002603D
Original Publication Date: 1996-Oct-01
Included in the Prior Art Database: 2000-Sep-13
Document File: 8 page(s) / 18K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

A. Gulbrandsen: AUTHOR [+2]

Abstract

This document describes a DNS RR which specifies the location of the server(s) for a specific protocol and domain (like a more general form of MX).

This text was extracted from a ASCII Text document.
This is the abbreviated version, containing approximately 17% of the total text.

Network Working Group A. Gulbrandsen

Request for Comments: 2052 Troll Technologies

Updates: 1035, 1183 P. Vixie

Category: Experimental Vixie Enterprises

October 1996

A DNS RR for specifying the location of services (DNS SRV)

Status of this Memo

This memo defines an Experimental Protocol for the Internet

community. This memo does not specify an Internet standard of any

kind. Discussion and suggestions for improvement are requested.

Distribution of this memo is unlimited.

Abstract

This document describes a DNS RR which specifies the location of the

server(s) for a specific protocol and domain (like a more general

form of MX).

Overview and rationale

Currently, one must either know the exact address of a server to

contact it, or broadcast a question. This has led to, for example,

ftp.whatever.com aliases, the SMTP-specific MX RR, and using MAC-

level broadcasts to locate servers.

The SRV RR allows administrators to use several servers for a single

domain, to move services from host to host with little fuss, and to

designate some hosts as primary servers for a service and others as

backups.

Clients ask for a specific service/protocol for a specific domain

(the word domain is used here in the strict RFC 1034 sense), and get

back the names of any available servers.

Introductory example

When a SRV-cognizant web-browser wants to retrieve

http://www.asdf.com/

it does a lookup of

http.tcp.www.asdf.com

and retrieves the document from one of the servers in the reply. The

example zone file near the end of the memo contains answering RRs for

this query.

The format of the SRV RR

Here is the format of the SRV RR, whose DNS type code is 33:

Service.Proto.Name TTL Class SRV Priority Weight Port Target

(There is an example near the end of this document.)

Service

The symbolic name of the desired service, as defined in Assigned

Numbers or locally.

Some widely used services, notably POP, don't have a single

universal name. If Assigned Numbers names the service

indicated, that name is the only name which is legal for SRV

lookups. Only locally defined services may be named locally.

The Service is case insensitive.

Proto

TCP and UDP are at present the most useful values

for this field, though any name defined by Assigned Numbers or

locally may be used (as for Service). The Proto is case

insensitive.

Name

The domain this RR refers to. The SRV RR is unique in that the

name one searches for is not this name; the example near the end

shows this clearly.

TTL

Standard DNS meaning.

Class

Standard DNS meaning.

Priority

As for MX, the priority of this target host. A client MUST

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