Jonathan,
If you use a MIB Browser to walk the MIB, you will see the interface information. The transmit utilization is (to my knowledge) does not have a standard MIB OIB in the SNMP MibII library, but can be obtained via a method found on
http://www.faqs.org/faqs/snmp-faq/part1/, which states:
(DELTA(ifInOctets) + DELTA(ifOutOctets)) * 8
-------- * 100
(DELTA(sysUpTime) / 100) * 1 540 000
where DELTA(attribute) means the difference of the value
of attribute between two polls. Of course, the values for
ifInOctets, ifOutOctets and sysUpTime should be requested
in one single PDU.
For work, I use a great program to walk MIB's from a company called iReasoning (
http://www.ireasoning.com) that I've found more than valuable. As an example if what I looked at when browsing the MIB, load RFC1213 and UCD-SNMP-MIB into your MIB Tree. If you need more help, let me know. Thanks!
Mike