1. CIS 725 Telephone protocols

2. Telephone systems Circuited switched system Call control software

3. OCM = originating call machine TCM = terminating call machine A places a call to B An OCM for A is instantiated with initial state as idle When signal reaches B, a TCM for B is instantiated

6. Off_hook dialtone number ringing ringback Off_hook connect Off_hook dialtone number busy

7. -C places a call to A - An OCM for C is instantiated -A TCM for A is instantiated with state as busy

8. -C places a call to B - An OCM for C is instantiated -A TCM for B is instantiated with state as busy

9. Off_hook dialtone number ringing ringback Off_hook connect Off_hook dialtone number ringback CW_alert Flash_hook On_hold connect Call waiting feature

10. Feature Interaction Limited terminal equipment Same key used for different purposes Example: CW and 3WC A is talking to B C calls B B receives the call; Call is accepted by CW; issues a tone to B Now, CW is in state ready to accept # from B

11. Before listening to the tone, B presses # to call D using 3WC CW will intercept # and connect to B to C instead.

12. Call control interactions: 911 calls: only emergency operator can terminate the call

13. Distributed Interactions: Call number delivery vs call number blocking Call screening vs call forwarding

14. Interaction Detection Model each feature using a formal model Depending on the current state, a feature may or may not accept a signal Fi = accepts a signal S in state si Fj = accepts a signal S in state sj Can Fi and Fj be in the states si and sj simultaneously

15. Explore all reachable states and check whether si and sj are simultaneously reachable If you find interaction then avoid them

16. Assign priorities Assign priorities and use layering Example: CW and CF: CW has priority over CF

17. Feature at layer N processes a signal before a feature at layer N - 1 If feature N does not accept a signal, it passes it to the next layer

18. - CW has priority over CF

19. - CW has priority over 3WC

20. Multimedia systems Different streams of data What are the new requirements QoS requirements: - picture quality, brightness, color, tint - jitter, glitches, lip_sync, delay

21. Intra-media requirements Latency: - elapsed time from packet generation to packet playback - low latency: real-time applications - high latency: email

22. Jitter: - disruption in continuous playback - low jitter for real-time applications Packet loss: - % of packets lost - video = packet loss could be high - text = low packet loss Successive packet loss

23. Intermedia requirements Asynchrony: - synchronization between different streams - tight synch for tele-conferencing

24. Conflicts between QoS parameters Jitter and latency conflict - To control jitter, value of latency must be large enough to smooth out variations in network Asynchrony conflicts with latency

25. Specifying QoS parameters Latency - two thresholds: lat_max, lat_min Jitter Gap_max Packet loss pktloss_max over time time_pktloss % of successive packet loss

26. Asynchrony: Async_negthres, Async_posthres

27. QoS Control Can be implemented inside the network - streams are synchronized - virtual circuit-based systems Can be implemented at end-systems Combination of both techniques

28. Inter-media synchronization Use a single channel to send all types of data - perfect synchronization Master/slave channels - use one of the media as the master and synchronize others with respect to this channel

29. Marker-based synchronization: - periodically insert markers in the streams; - wait for markers to arrive on all streams

30. QoS Protocol Design Receiver-based QoS control QoS control module: - computes the playback time for each pkt - monitors QoS packets - adjusts the playback time - may buffer packets or drop them

31. Playback time Each QoS parameters influences the playback time. Latency Jitter Asynchrony

32. Real-time Transport protocol(RTP) Application Level Framing: - application knows its own needs - application knows how to segment data * Defines format for data packets (RTP) and control packets (RTCP) * Provides timing-related information to the application to process packets and make decisions