I'm using HWserout, but I don't think I could do much better using TXint. It isn't the sending time that is the problem, it is the large amount of processing I have to do with the packets.
SNMP requires that I do lexicographical sorts (1.2.1.3.1.1.1.4.2.1 is before 1.2.1.3.1.1.1.4.2.1.1 and 1.2.1.3.1.1.1.4.2.1 is after 1.2.1.3.1.1.1.3.9.9.9.9.9.9.9)
Even if you get sent a string that does not match one that you have (internally) in your list, you have to pick the first item in your list that (lexicographically) comes after the received string,
then grab the appropriate data, perform encryption on certain bytes (3 different types, depending on the data), re-assemble the variable-length packets, calculate the LRCs, and send.
And some of the data is a (calculated) number 40 bits long.