On 5/22/2004 5:00 PM, Jim Lyon wrote:
For really big complicated domains, they may need to work harder, but
can still avoid the need to fall back to TCP. HotMail, for example, has
published Caller ID records (which are of a size similar to what we're
contemplating). No TCP is required -- in fact, their DNS server doesn't
even accept TCP connections. If the biggest email handler on the planet
can do it without TCP, then everyone probably can, too. (Yes, they use
indirection through 3 other records. The biggest handful of ISPs might
be expected to need to do the same.)
Yes, n-level redirection will be required, at best.
Hotmail is actually a pretty good practical example of sizing problems:
[ 17:13:46 -- goose:/var/log/ ]
[ ehall$ ] dig @ns1.hotmail.com. hotmail.com. any
; <<>> DiG 9.2.2 <<>> @ns1.hotmail.com. hotmail.com. any
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 47044
;; flags: qr aa rd; QUERY: 1, ANSWER: 11, AUTHORITY: 4, ADDITIONAL: 12
;; QUESTION SECTION:
;hotmail.com. IN ANY
;; ANSWER SECTION:
hotmail.com. 3600 IN A 64.4.32.7
hotmail.com. 3600 IN A 64.4.33.7
hotmail.com. 3600 IN MX 5 mx1.hotmail.com.
hotmail.com. 3600 IN MX 5 mx2.hotmail.com.
hotmail.com. 3600 IN MX 5 mx3.hotmail.com.
hotmail.com. 3600 IN MX 5 mx4.hotmail.com.
hotmail.com. 3600 IN NS ns1.hotmail.com.
hotmail.com. 3600 IN NS ns2.hotmail.com.
hotmail.com. 3600 IN NS ns3.hotmail.com.
hotmail.com. 3600 IN NS ns4.hotmail.com.
hotmail.com. 3600 IN SOA ns1.hotmail.com.
dns.hotmail.com. 2004052101 28800 3600 604800 3600
;; AUTHORITY SECTION:
hotmail.com. 3600 IN NS ns1.hotmail.com.
hotmail.com. 3600 IN NS ns2.hotmail.com.
hotmail.com. 3600 IN NS ns3.hotmail.com.
hotmail.com. 3600 IN NS ns4.hotmail.com.
;; ADDITIONAL SECTION:
mx1.hotmail.com. 3600 IN A 65.54.252.99
mx1.hotmail.com. 3600 IN A 64.4.50.99
mx1.hotmail.com. 3600 IN A 65.54.166.99
mx1.hotmail.com. 3600 IN A 64.4.50.50
mx2.hotmail.com. 3600 IN A 65.54.252.230
mx2.hotmail.com. 3600 IN A 65.54.190.7
mx2.hotmail.com. 3600 IN A 65.54.166.230
mx2.hotmail.com. 3600 IN A 65.54.190.50
mx3.hotmail.com. 3600 IN A 65.54.253.99
mx3.hotmail.com. 3600 IN A 65.54.167.5
mx3.hotmail.com. 3600 IN A 64.4.50.239
mx3.hotmail.com. 3600 IN A 64.4.50.179
;; Query time: 85 msec
;; SERVER: 216.200.206.140#53(ns1.hotmail.com.)
;; WHEN: Sat May 22 17:14:31 2004
;; MSG SIZE rcvd: 501
^^^ overflow limits triped, bailing!
You lopped off the mx4 RRset, and you left off the NS hosts too (you
should be giving them preference over the MX additional-data btw). The
lack of TCP support means that a full answer set is not possible.
If I prime my cache with discrete data, I get:
[ 17:19:35 -- goose:/var/log/ ]
[ ehall$ ] dig @localhost. hotmail.com. any +vc
...
;; Query time: 27 msec
;; SERVER: 127.0.0.1#53(localhost.)
;; WHEN: Sat May 22 17:19:46 2004
;; MSG SIZE rcvd: 541
^^^ doh!
I can see why you would want/need to use some other owner name regardless
of the type, but that's a good reason *against* a practice, not a good
reason *for* stuffing entire XML documents into the system.
Please, use an RR that holds a URL pointing to an XML document instead.
--
Eric A. Hall http://www.ehsco.com/
Internet Core Protocols http://www.oreilly.com/catalog/coreprot/