1. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 1 Telecommunications Concepts Chapter 1.6 Multiplexing & Routing

2. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 2 Contents Multiplexing Circuit switching –Frequency domain multiplexing –Synchronous time domain multiplexing Packet switching –Connectionless = datagrams –Connection oriented = Virtual circuit Side-tracks – routing – Network coding

3. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 3 Contents Multiplexing Circuit switching –Frequency domain multiplexing –Synchronous time domain multiplexing Packet switching –Connectionless = datagrams –Connection oriented = Virtual circuit Side-tracks – routing – Network coding

4. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 4 Circuit vs. Packet Switching A resource multiplexing issue !!! Main shared resource in networks = transmission capacity between nodes How to share such resource optimally? Shared resource examples Fixed transmission capacity

5. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 5 Contents Multiplexing Circuit switching –Frequency domain multiplexing –Synchronous time domain multiplexing Packet switching –Connectionless = datagrams –Connection oriented = Virtual circuit Side-tracks – routing – Network coding

6. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 6 Circuit Switching Fixed transmission capacity The preferred multiplexing technique in the traditional telephony world. A predefined share is allocated to each user. The allocation remains valid until revocation, whether it is used or not. Charges are duration based.

7. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 7 Contents Multiplexing Circuit switching –Frequency domain multiplexing –Synchronous time domain multiplexing Packet switching –Connectionless = datagrams –Connection oriented = Virtual circuit Side-tracks – routing – Network coding

8. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 8 Frequency Domain Multiplexing sin(  t) sin(  t) X cos((  t  2 cos((  t  2 cos((  t  2 + ~ / ~ Modulation allows shifting the frequency spectrum: frequency 0 power Ω Example: amplitude modulation of carrier at frequency Ω by signal at frequency ω Other modulation techniques have a similar effect

9. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 9 FDM in broadcasting Mod Ω1Ω1 Ω2Ω2 Baseband signal Carrier Mod Ω3Ω3 Ω1Ω1 Baseband signal Local Oscillator Mod Ω3Ω3 Ω1Ω1

10. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 10 FDM in broadcasting frequency VTMRTBFVRTRTLTF1 7-8 MHz frequency PremiereNostalgieCampusStuBru 50 KHz FM radio: 105.50 87.60 Cable TV:

11. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 11 Contents Multiplexing Circuit switching –Frequency domain multiplexing –Synchronous time domain multiplexing Packet switching –Connectionless = datagrams –Connection oriented = Virtual circuit Side-tracks – routing – Network coding

12. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 12 Time Domain Multiplexing Synchronous Unique bit pattern to delimit frames 1001 0 1 0 1 1001 0 1 0 1 XX

13. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 13 Contents Multiplexing Circuit switching –Frequency domain multiplexing –Synchronous time domain multiplexing Packet switching –Connectionless = datagrams –Connection oriented = Virtual circuit Side-tracks – routing – Network coding

14. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 14 Packet Switching (Invented by Paul Baran, 1960) The preferred multiplexing technique in the data world. Data streams are separated in data packets. Packets belonging to different streams are intermixed for transmission over the shared link. Packets are eventually queued while waiting for access to the shared resource. Charges can be volume based. Fixed transmission capacity

15. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 15 Circuit vs. Packet Switching Peak data rate / Average data rate –Voice : ~2 (both speakers talk 50% of time) –Data : >> 2 (think and processing times > transmission times) t Typical voice traffic Typical data traffic

16. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 16 Circuit vs. Packet Switching Circuit Switching –  peak data rates <= transmission capacity »Acceptable for voice and image transmission »wasteful of resources for data transmission –Fixed total delay Packet Switching –  average data rates <= transmission capacity »Optimal use of transmission capacity »Congestion control to handle traffic peaks –Variable total delay »caused by queuing in front of shared resource »problematic for transmission of voice or images

17. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 17 Contents Multiplexing Circuit switching –Frequency domain multiplexing –Synchronous Time domain multiplexing Packet switching –Connectionless = datagrams –Connection oriented = Virtual circuit Side-tracks – routing – Network coding

18. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 18 Connection oriented vs. Connectionless Circuit Switching –Intrinsically connection oriented Packet Switching –Connectionless »Each packet carries the destination address »Routing decisions to be made for each packet »Typical example : Internet Protocol –Connection oriented : Virtual Circuits »Each packet carries a local identifier (VCN) of the data flow it belongs to »Routing decisions at virtual circuit set-up. »Typical examples : X25, Frame Relay, ATM

19. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 19 Internal vs. External Policies Network services (NUI) Connection oriented Connectionless Network operation (NNI) Connection oriented Connectionless

20. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 20 Contents Multiplexing Circuit switching –Frequency domain multiplexing –Synchronous Time domain multiplexing Packet switching –Connectionless = datagrams –Connection oriented = Virtual circuit Side-tracks – routing – Network coding

21. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 21 Datagram Routing Based upon routing tables a b c d 1 2 3 3 2 1 4 4 3 2 1 2 1 3 a:1 b:2 c:3 d:3 a:3 b:3 c:2 d:2 a:3 b:3 c:1 d:1 a:3 b:3 c:1 d:2

22. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 22 Contents Multiplexing Circuit switching –Frequency domain multiplexing –Synchronous Time domain multiplexing Packet switching –Connectionless = datagrams –Connection oriented = Virtual circuit Side-tracks – routing – Network coding

23. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 23 Routing Routing table gives next hop on best route to all destination nodes Best route is application dependant –Shortest latency –Highest throughput –Lowest cost Best route can change –Nodes can go down or can become congested –Links can be interrupted Routing tables maintained by exploring periodically the network

24. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 24 Finding the best route Example : Distance Vector Routing E B C A D ? VUB, 7 VUB, 20 VUB, 5 VUB, 10 1 3 4 1 What is E’s shortest path to VUB ?

25. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 25 Finding the best route Example : Distance Vector Routing E B C A D VUB, 7 VUB, 20 VUB, 5 VUB, 10 1 3 4 1 VUB, 8 Known as Old ARPANET routing Based on Bellman-Ford algorithm Base of Routing Information Protocol

26. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 26 Best route consequence a b c d 11 1 1 1 Risk of congestion Idle

27. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 27 Routing in large networks Complete routing tables impossible in large networks Hierarchical routing is the solution –Routing table restricted to one level of hierarchy

28. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 28 Contents Multiplexing Circuit switching –Frequency domain multiplexing –Synchronous Time domain multiplexing Packet switching –Connectionless = datagrams –Connection oriented = Virtual circuit Side-tracks – routing – Network coding

29. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 29 Virtual Circuit Number a b c d a>b a>c a>d 10 11 12 b>c b>d a>b 11 12 21 d>c a>d b>d 11 20 21 b>c a>c d>c 20 21 22 a>c a>d b>c b>d 10 11 12 13 Each virtual circuit is identified by a specific number on each physical link

30. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 30 Forwarding Tables a b c d 1121 10 1 2 3 1 2 3 1.11>3.101.10>3.21

31. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 31 Permanent Virtual Circuit Forwarding tables set-up and cleared by network manager through “separate” network a b c d a>c11a>c21 1 2 3 1 2 3 1.11>3.101.10>3.21 “Separate” signaling network Signaling and data packets travel through different (virtual) circuits

32. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 32 Contents Multiplexing Circuit switching –Frequency domain multiplexing –Synchronous Time domain multiplexing Packet switching –Connectionless = datagrams –Connection oriented = Virtual circuit Side-tracks – routing – Network coding

33. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 33 Network Coding Classical packet routing a b c d 3 3 All links : t b/s m1: a > d m2: c > b Bottleneck: 2t b/s needed

34. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 34 Network Coding Message merging a b c d 3 3 All links : t b/s m1: a > d m2: c > b m1 m2 t b/s needed + m1 m2 m1 + + m2 m1 m2 + +

35. J.Tiberghien - VUB09-06-K.Steenhaut & J.Tiberghien - VUB 35 Introduced concepts Circuit switching for uniform traffic –Fixed bandwidth multiplexing »FDM vs. TDM –Connection oriented Packet switching for bursty traffic –Statistical multiplexing –Connectionless : datagrams –Connection oriented : Virtual circuits »Switched vs. permanent virtual circuits Routing –Centralized vs. decentralized –Best route, but risk for unbalanced loads