Assignment 8

The assignment is due Sunday, July 18, 11.59 pm EDT. Submission Guidelines

1. Programming problem: Building on the previous assignment, extend your audio application to provide better RTCP support for multicast. The application should adjust the interval between RTCP packets according to the number of members in the group, using the RTCP scaling rules. You should also implement unconditional reconsideration.

   The program should display, to stdout, when RTCP packets have been sent and received, as well as the current estimate of the group size. The printout should include the most important elements of the RTCP packets. Show all these in your sample output.

2. Review problem: After hearing about how phones are line-powered, your friend has discovered a new way to light the house. He wants to put a transformer on the phone jack and connect light bulbs. This, he says, also works when the power goes out during a storm. Find out whether this would work and, if so, how much light you could generate from that.
3. Find out the SIP server address for the domain iptel.org and then, using telnet, create and capture a SIP OPTIONS request.
4. ENUM: Find out the SIP and email address for the phone number +436644204100. Hint: see RFC 2916.
5. Review question: We talked about telephony routing for both traditional circuit-switched services and VoIP. Describe the functionality and contrast it with normal routing (e.g., using OSPF and BGP) in terms of similarities and differences.
6. Review question: Why does the INVITE transaction in SIP use an ACK and the OPTIONS (and BYE) one doesn't?
7. Review question: Why could SIP not use end-to-end reliability mechanisms (for UDP)?
8. What problems would you run into when running SIP behind a NAT?