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Assignment 5 Solution

    • Please finish the lab according to this file

– submit the report of lab 5 based on the lab report template.

– submit your source code in zip file. (5.3.zip)

            ▪ comments is MUST

            ▪ DO NOT copy paste any existing source code of DNS resolver

Assignment 5.1

    • make an DNS query which will invoke the EDNS0

–  Screenshot on this command and its output

    • capture the packages using Wireshark

–  what is the content of this query message

            ▪ Find the name, type and class of this query

            ▪ How can you tell this DNS query is based on EDNS0

            ▪ From this query massage , can it handle DNSSEC security RRs or not

–  what is the content of this response message

            ▪ Is there any answers, what’s the ttl of each answer

            ▪ Is there any authority RRs, what’s the type of each RR

            ▪ Is there any special additional RRs with OPT type, what does its ‘Do bit’ say: Does it accept DNSSEC security RRs or not

Assignment 5.2


    • Make the query by using query method of “dns resolver”(a python package)

– To query the type A value of www.163.com based on TCP and UDP stream respectively

    • capture the related TCP stream and UDP stream using Wireshark
–  Screenshot on this two commands .
what’s the default transport lay protocol while invoke DNS query
–  Screenshot on the TCP stream of query by TCP.
how many TCP packets are captured in this stream, Which port is used?
–  Screenshot on the UDP stream of query by UDP.
how many UDP packets are captured in this stream, Which port is used?

– Is there any difference on DNS query and response message while using TCP and UDP respectively

Assignment 5.3 (Class A Only)

implement a local resolver

    • Function:

–  Listen and accept DNS queries.

            ▪ Support common query types: A, AAAA, CNAME, TXT, NS, MX

            ▪ EDNS implementation is not required.

–  Forward query to a upstream DNS resolver (or a public DNS server).

–  Check out the response and send response to your clients.

–  Maintain a cache of DNS query-response of all results.

    • Test method:

–  using dig sending query to your resolver

    • *comments is MUST

    • *DO NOT copy paste any existing source code of DNS resolver.

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