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Re: I-D ACTION:draft-ietf-dnsind-rfc2052bis-00.txt
> Could you summarize what the changes are and why they are being made?
> My quick scan of the new version didn't immediately pick up on
> anything, but I didn't do a detailed comparison. I'm just sort of
> curious since I hadn't heard anything about doing a rev to RFC2052
> until the announcement came out. I'd have thought at least a quick
> mention at Chicago given that DNSIND didn't use all its allotted
> time...
>
> -MAP
The only difference is the putting back in of the _'s that the RFC Editor
took out of the draft I'd submitted for Experimental status. To wit:
@@ -42,39 +52,42 @@
(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
+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.
+ example zone file near the end of this 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
+ _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.
+ Numbers or locally. An underscore (_) is prepended to the
+ service identifier to avoid collisions with DNS labels that
+ occur in nature.
Some widely used services, notably POP, don't have a single
universal name. If Assigned Numbers names the service
@@ -83,7 +96,9 @@
The Service is case insensitive.
Proto
- TCP and UDP are at present the most useful values
+ The symbolic name of the desired protocol, with an underscore
+ (_) prepended to prevent collisions with DNS labels that occur
+ in nature. _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.
@@ -182,31 +194,40 @@
All round numbers, wrote Dr. Johnson, are false, and these numbers
are very round: A reply packet has a 30-byte overhead plus the name
- of the service ("telnet.tcp.asdf.com" for instance); each SRV RR adds
- 20 bytes plus the name of the target host; each NS RR in the NS
+ of the service (``_telnet._tcp.asdf.com'' for instance); each SRV RR
+ adds 20 bytes plus the name of the target host; each NS RR in the NS
section is 15 bytes plus the name of the name server host; and
finally each A RR in the additional data section is 20 bytes or so,
and there are A's for each SRV and NS RR mentioned in the answer.
@@ -233,14 +244,14 @@
A SRV-cognizant client SHOULD use this procedure to locate a list of
servers and connect to the preferred one:
- Do a lookup for QNAME=service.protocol.target, QCLASS=IN,
+ Do a lookup for QNAME=_service._protocol.target, QCLASS=IN,
QTYPE=SRV.
If the reply is NOERROR, ANCOUNT>0 and there is at least one SRV
RR which specifies the requested Service and Protocol in the
reply:
If there is precisely one SRV RR, and its Target is "."
(the root domain), abort.
Else, for all such RR's, build a list of (Priority, Weight,
@@ -308,7 +364,7 @@
or NS RR's.)
- A future standard could specify that a SRV RR whose Protocol was
- TCP and whose Service was SMTP would override RFC 974's rules
+ _TCP and whose Service was _SMTP would override RFC 974's rules
with regard to the use of an MX RR. This would allow firewalled
organizations with several SMTP relays to control the load
distribution using the Weight field.
@@ -316,6 +372,7 @@
- Future protocols could be designed to use SRV RR lookups as the
means by which clients locate their servers.
+
Fictional example
This is (part of) the zone file for asdf.com, a still-unused domain:
@@ -326,20 +383,20 @@
NS server.asdf.com.
NS ns1.ip-provider.net.
NS ns2.ip-provider.net.
- ftp.tcp SRV 0 0 21 server.asdf.com.
- finger.tcp SRV 0 0 79 server.asdf.com.
+ _ftp._tcp SRV 0 0 21 server.asdf.com.
+ _finger._tcp SRV 0 0 79 server.asdf.com.
; telnet - use old-slow-box or new-fast-box if either is
; available, make three quarters of the logins go to
; new-fast-box.
- telnet.tcp SRV 0 1 23 old-slow-box.asdf.com.
-Gulbrandsen & Vixie Experimental [Page 6]
+Gulbrandsen and Vixie Proposed [Page 7]
-RFC 2052 DNS SRV RR October 1996
+RFC 2052bis DNS SRV RR September 1998
+ _telnet._tcp SRV 0 1 23 old-slow-box.asdf.com.
SRV 0 3 23 new-fast-box.asdf.com.
; if neither old-slow-box or new-fast-box is up, switch to
; using the sysdmin's box and the server
@@ -347,22 +404,22 @@
SRV 1 0 23 server.asdf.com.
; HTTP - server is the main server, new-fast-box is the backup
; (On new-fast-box, the HTTP daemon runs on port 8000)
- http.tcp SRV 0 0 80 server.asdf.com.
+ _http._tcp SRV 0 0 80 server.asdf.com.
SRV 10 0 8000 new-fast-box.asdf.com.
; since we want to support both http://asdf.com/ and
; http://www.asdf.com/ we need the next two RRs as well
- http.tcp.www SRV 0 0 80 server.asdf.com.
+ _http._tcp.www SRV 0 0 80 server.asdf.com.
SRV 10 0 8000 new-fast-box.asdf.com.
; SMTP - mail goes to the server, and to the IP provider if
; the net is down
- smtp.tcp SRV 0 0 25 server.asdf.com.
+ _smtp._tcp SRV 0 0 25 server.asdf.com.
SRV 1 0 25 mailhost.ip-provider.net.
@ MX 0 server.asdf.com.
MX 1 mailhost.ip-provider.net.
; NNTP - use the IP providers's NNTP server
- nntp.tcp SRV 0 0 119 nntphost.ip-provider.net.
+ _nntp._tcp SRV 0 0 119 nntphost.ip-provider.net.
; IDB is an locally defined protocol
- idb.tcp SRV 0 0 2025 new-fast-box.asdf.com.
+ _idb._tcp SRV 0 0 2025 new-fast-box.asdf.com.
; addresses
server A 172.30.79.10
old-slow-box A 172.30.79.11
@@ -377,98 +434,42 @@
; backup A RR for www.asdf.com
www A 172.30.79.10
; NO other services are supported
- *.tcp SRV 0 0 0 .
- *.udp SRV 0 0 0 .
+ *._tcp SRV 0 0 0 .
+ *._udp SRV 0 0 0 .
- In this example, a telnet connection to "asdf.com." needs an SRV
- lookup of "telnet.tcp.asdf.com." and possibly A lookups of "new-
- fast-box.asdf.com." and/or the other hosts named. The size of the
+ In this example, a telnet connection to ``asdf.com.'' needs an SRV
+ lookup of ``_telnet._tcp.asdf.com.'' and possibly A lookups of ``new-
+ fast-box.asdf.com.'' and/or the other hosts named. The size of the
SRV reply is approximately 365 bytes:
30 bytes general overhead
- 20 bytes for the query string, "telnet.tcp.asdf.com."
- 130 bytes for 4 SRV RR's, 20 bytes each plus the lengths of "new-
+ 20 bytes for the query string, ``_telnet._tcp.asdf.com.''
-Gulbrandsen & Vixie Experimental [Page 7]
+Gulbrandsen and Vixie Proposed [Page 8]
-RFC 2052 DNS SRV RR October 1996
+RFC 2052bis DNS SRV RR September 1998
- fast-box", "old-slow-box", "server" and "sysadmins-box" -
- "asdf.com" in the query section is quoted here and doesn't
+ 130 bytes for 4 SRV RR's, 20 bytes each plus the lengths of ``new-
+ fast-box'', ``old-slow-box'', ``server'' and ``sysadmins-box'' -
+ ``asdf.com'' in the query section is quoted here and doesn't
need to be counted again.
75 bytes for 3 NS RRs, 15 bytes each plus the lengths of
- "server", "ns1.ip-provider.net." and "ns2" - again, "ip-
- provider.net." is quoted and only needs to be counted once.
+ ``server'', ``ns1.ip-provider.net.'' and ``ns2'' - again, ``ip-
+ provider.net.'' is quoted and only needs to be counted once.
120 bytes for the 6 A RR's mentioned by the SRV and NS RR's.
-Refererences
-
- RFC 1918: Rekhter, Y., Moskowitz, R., Karrenberg, D., de Groot, G.,
- and E. Lear, "Address Allocation for Private Internets",
- RFC 1918, February 1996.
-
- RFC 1916 Berkowitz, H., Ferguson, P, Leland, W. and P. Nesser,
- "Enterprise Renumbering: Experience and Information
- Solicitation", RFC 1916, February 1996.
-
- RFC 1912 Barr, D., "Common DNS Operational and Configuration
- Errors", RFC 1912, February 1996.
-
- RFC 1900: Carpenter, B., and Y. Rekhter, "Renumbering Needs Work",
- RFC 1900, February 1996.
-
- RFC 1920: Postel, J., "INTERNET OFFICIAL PROTOCOL STANDARDS",
- STD 1, RFC 1920, March 1996.
- RFC 1814: Gerich, E., "Unique Addresses are Good", RFC 1814, June
- 1995.
-
- RFC 1794: Brisco, T., "DNS Support for Load Balancing", April 1995.
-
- RFC 1713: Romao, A., "Tools for DNS debugging", November 1994.
-
- RFC 1712: Farrell, C., Schulze, M., Pleitner, S., and D. Baldoni,
- "DNS Encoding of Geographical Location", RFC 1712, November
- 1994.
-
- RFC 1706: Manning, B. and R. Colella, "DNS NSAP Resource Records",
- RFC 1706, October 1994.
-
- RFC 1700: Reynolds, J., and J. Postel, "ASSIGNED NUMBERS",
- STD 2, RFC 1700, October 1994.
-
- RFC 1183: Ullmann, R., Mockapetris, P., Mamakos, L., and
- C. Everhart, "New DNS RR Definitions", RFC 1183, November
- 1990.
-
-
-
-
-Gulbrandsen & Vixie Experimental [Page 8]
-
-RFC 2052 DNS SRV RR October 1996
-
-
- RFC 1101: Mockapetris, P., "DNS encoding of network names and other
- types", RFC 1101, April 1989.
-
- RFC 1035: Mockapetris, P., "Domain names - implementation and
- specification", STD 13, RFC 1035, November 1987.
-
- RFC 1034: Mockapetris, P., "Domain names - concepts and
- facilities", STD 13, RFC 1034, November 1987.
+Refererences
- RFC 1033: Lottor, M., "Domain administrators operations guide",
- RFC 1033, November 1987.
+ RFC 1034: Mockapetris, P., ``Domain names - concepts and
+ facilities'', RFC 1034, November 1987.
- RFC 1032: Stahl, M., "Domain administrators guide", RFC 1032,
- November 1987.
+ RFC 974: Partridge, C., ``Mail routing and the domain system'', RFC
+ 974, January 1986.
- RFC 974: Partridge, C., "Mail routing and the domain system",
- STD 14, RFC 974, January 1986.
Security Considerations
@@ -490,74 +491,17 @@
host names and addresses. The authors do not see any practical
effect of this.
- We assume that as the DNS-security people invent new features, DNS
- servers will return the relevant RRs in the Additional Data section
- when answering an SRV query.
-
-
-
-
-
-
-
-
-
-
-Gulbrandsen & Vixie Experimental [Page 9]
-
-RFC 2052 DNS SRV RR October 1996
-
-
Authors' Addresses
- Arnt Gulbrandsen
- Troll Tech
- Postboks 6133 Etterstad
- N-0602 Oslo
- Norway
-
- Phone: +47 22646966
- EMail: agulbra@troll.no
-
-
- Paul Vixie
- Vixie Enterprises
- Star Route 159A
- Woodside, CA 94062
-
- Phone: (415) 747-0204
- EMail: paul@vix.com
-
-
-
-
-
-
-
-
-
+ Arnt Gulbrandsen Paul Vixie
+ Troll Tech Internet Software Consortium
+ Postboks 6133 Etterstad 950 Charter Street
+ N-0602 Oslo, Norway Redwood City, CA 94063
+ +47 22646966 +1 650 779 7001
+ <agulbra@troll.no> <paul@vix.com>
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Gulbrandsen & Vixie Experimental [Page 10]
-
+Gulbrandsen and Vixie Proposed [Page 9]
+
\ No newline at end of file