1 mmdump Reference: “mmdump: A Tool for Monitoring Internet Multimedia Traffic” J. van der Merwe, R. Cceres, Y-H. Chu, C. Sreenan. ACM SIGCOMM Computer Communication Review, Volume 30, Issue 5 (October 2000), ISSN: Speaker: Yan-Hsiang Wang Date:

2 Outline Motive Structure Result Conclusion

3 Motive (1/3) Recent years have seen increasing use of the Internet to send and receive audio and video. It is important for network designers to understand the nature of multimedia traffic.

4 Motive (2/3) tcpdump can be used to monitor packets for a particular protocol by filtering based on the appropriate TCP/DUP port number. The multimedia applications use dynamically assigned UDP port numbers.

5 Motive (3/3) This paper presents the design and implementation of mmdump, contains a parsing module for each multimedia control protocol.

6 How mmdump contains a parsing module for each multimedia control protocol. The parsing module identifies individual control sessions in this aggregate control stream, and parses the control messages to extract the dynamically assigned port numbers.

7 tcpdump It builds on top of the libpcap library, which provides two key functions  An abstraction for dealing with different types of network interfaces  The ability to compile a filter expression for use by a packet filter sudo tcpdump –X port 80

8 Multimedia control protocol Real Time Streaming Protocol

9 Multimedia control protocol H.323 More 

10 Structure All packets that arrive on a particular well-known port number are passed to the corresponding parsing module for processing Lookup  Matching of source and destination addresses and port numbers

11 Flow chart

12 State Maintaining state  New session state can be created when the first TCP packet for a particular session is received  Session state can be removed when the TCP FIN packet is received Control connection for RTSP H.245 connection for H.323

13 Sequence Complete higher layer protocol message  Per packet buffer doesn’t take TCP sequence numbers  Simply treats packets in the order in which they were received

14 Change filter Found new port  Dynamically change the filter expression  Between the parsers and the packet filter change_filter() do_filter() – actual filter change takes place Review - libpcap  pcap_compile()  pcap_setfilter() 

15 Garbage Garbage collection  Because of effects such as packet losses or route changes, the probe point might never receive the FIN packet  It has to be performed to remove stale session

16 Result – RTSP (1/2) RealPlayer on Windows plays CNN Headline News

17 Result – RTSP (2/2) Every half hour Peak hours are drastically shifted towards the late evening hours

18 Result – H.323 (1/2) Two Windows PC machines run Microsoft NetMeeting3.1 and they make a video conferencing

19 Result – H.323 (1/2) The amount of control traffic is significantly lower than the amount of data traffic

20 Conclusions This paper has presented a new tool for monitoring multimedia traffic on the Internet Interesting  Multimedia sessions have a rich structure  Zipf-like distribution  RTSP clients can request that servers adjust the transmission rate

21 Zipf-like distribution

22 SET_PARAMETER One use of this method by the RealMedia player is to set the required delivery bandwidth from the server

23 Future work Using it to monitor the QoS in a VoIP testbed Develop a SIP parser Adopting a modified BPF+ that includes complier support for incremental filter updates

24 Reference Zipf distribution  