Homework 1 -- Packet formats

Assume there's a UDP echo server running on the machine armenia.lcs.mit.edu and you are going to send a UDP echo datagram which contains the characters "Hello there" to armenia from the computer arden.cs.unca.edu. In this homework problem, you'll describe the contents of the Ethernet packet send by arden.

Problem 1 - the Ethernet header

Start with the three fields of the Ethernet header. You'll need to fill in a source and destination number along with a type. To help you out, here are some important numbers:

Computer name Ethernet number
arden.cs.unca.edu 08-00-2b-28-fc-a0
unca-gw.ncren.net aa-00-04-00-06-ac
woodfin.cs.unca.edu 00-00-f8-01-81-b5

By the way, unca-gw.ncren.net is the Internet gateway for the UNCA campus.

Protocol name Protocol type
Internet Protocol 2048 or 0x0800
ARP - Address Resolution Protocol) 2054 or 0x0806
DEC LAT (Local Area Transport) 24580 or 0x6004

Problem 2 - IP header

Now go up to the Internet Protocol header. All the numbers you'll need for this level can be obtained by either running the program nslookup or looking at the file /etc/protocols on a Unix computer. By the way, you may have to make up a couple of fields and you can skip the computation of the checksum.

Problem 3 - UDP header

On to the User Datagram Protocol header. To find the numbers you need, look in the file /etc/services.

Problem 4 - UDP data

Finally, what are the contents of the UDP data field?

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