Quick SNMP Payload Structure Question

[Josha Bronson <dmuz () slartibartfast angrypacket com>]

Hey folks,

Trying to work on generating arbitrary SNMP request packets, but for the
life of me I can not figure out how the second byte of the payload data
is calculated. I *think* that it is some sort of length signifier...  I
think there are also other length based bytes that might need to be
calculated elsewhere in the payload.

What I am trying to do is figure out what bytes need to be modified in a
basic payload structure so that I can drop in different communities,
only altering the bytes necessary.

I've already used ethereal's excellent packet analysis, but it does not
say what the significance is of all the packets, including the second
byte.

Any quick answers or links are greatly appreciated.

-- 
Josha Bronson
dmuz () angrypacket com
AngryPacket Security