Size of zone transfers

[James Hall-Kenney]

We have been doing some testing of zone transfers between an 8.2.1 master
(10.184.0.28) and an 8.2.1 slave (10.184.0.29) in a lab environment. We did
the testing using a tool called NetXray on a laptop.  All 3 devices were
connected into a hub which was not connected to anything else.

We transferred the zones by deleting the zone file on the slave and then
running named-xfer from the command line.

The results:
zone 1:
File sizes:
- on master:     615000
- on slave:      711821
Data transferred over the wire:
- packets:       1233
- data:          1067506
Records:         20549

zone 2 had similar results. In both cases, the zone transfer was successful.

The question was raised as to why there was such disparity between the data
sizes.  The difference between files on the master & slave is easily
explained as the $TTL value is added to each record as the data on the slave
is written.  However the additional over the wire traffic is hard to
determine.

Looking at the packet capture, the Net-Xray tool believes that there were a
number or malformed or "errored" DNS packets in the capture.  Looking at the
packet contents, they had invalid names in the the Question part of the
packet and a number of other errors.  Retries of these would explain the
disparity in data sizes.

I guess my question is - "is this normal?".  If not, my only guess as to why
it is occuring is insufficient hardware for the name servers - they are
SPARC 5's doing nothing but DNS.

Any ideas?  I can post the packet captures if they would help.

Cheers

J.