1. Postacademic Interuniversity Course in Information Technology – Module C1p1 Chapter 5 Multiplexing

2. Postacademic Interuniversity Course in Information Technology – Module C1p2 Contents Link multiplexing –Circuit switching Synchronous Time-domain Multiplexing –Packet Switching Statistical Time-domain Multiplexing Connection oriented vs. Connectionless –Datagrams & Routing –Virtual Circuits & Forwarding Internal vs. External policies

3. Postacademic Interuniversity Course in Information Technology – Module C1p3 Contents Link multiplexing –Circuit switching Synchronous Time-domain Multiplexing –Packet Switching Statistical Time-domain Multiplexing Connection oriented vs. Connectionless –Datagrams & Routing –Virtual Circuits & Forwarding Internal vs. External policies

4. Postacademic Interuniversity Course in Information Technology – Module C1p4 Circuit vs. Packet Switching A resource multiplexing issue !!! Main shared resource in networks = transmission capacity between nodes How to share such resource optimally among several users ? Shared resource examples Fixed transmission capacity

5. Postacademic Interuniversity Course in Information Technology – Module C1p5 Contents Link multiplexing –Circuit switching Synchronous Time-domain Multiplexing –Packet Switching Statistical Time-domain Multiplexing Connection oriented vs. Connectionless –Datagrams & Routing –Virtual Circuits & Forwarding Internal vs. External policies

6. Postacademic Interuniversity Course in Information Technology – Module C1p6 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. Postacademic Interuniversity Course in Information Technology – Module C1p7 Circuit Switching Fixed transmission capacity Also used for data communications A predefined share is allocated to each user. The allocation remains valid until revocation, whether it is used or not. Charges are duration based.

8. Postacademic Interuniversity Course in Information Technology – Module C1p8 Circuit Switched Routing Each switching node has a routing table Giving, when the circuit is established, the outgoing link to be used for each destination. Routing tables are set up by network management. They are, in general static, sometimes even implicit. For mobile user dynamic tables are required a b d c a:1 b:2 c:3 d:3 a:1 b:1 c:3 d:2 1 2 3 1 2 3

9. Postacademic Interuniversity Course in Information Technology – Module C1p9 Time Domain Multiplexing 1001 0 1 0 1 Synchronous time domain multiplexing is The main technique used for circuit switching 1001 0 1 0 1 S

10. Postacademic Interuniversity Course in Information Technology – Module C1p10 Contents Link multiplexing –Circuit switching Synchronous Time-domain Multiplexing –Packet Switching Statistical Time-domain Multiplexing Connection oriented vs. Connectionless –Datagrams & Routing –Virtual Circuits & Forwarding Internal vs. External policies

11. Postacademic Interuniversity Course in Information Technology – Module C1p11 Packet Switching (Invented by Paul Baran, 1960) Fixed transmission capacity 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.

12. Postacademic Interuniversity Course in Information Technology – Module C1p12 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

13. Postacademic Interuniversity Course in Information Technology – Module C1p13 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

14. Postacademic Interuniversity Course in Information Technology – Module C1p14 Contents Link multiplexing –Circuit switching Synchronous Time-domain Multiplexing –Packet Switching Statistical Time-domain Multiplexing Connection oriented vs. Connectionless –Datagrams & Routing –Virtual Circuits & Forwarding Internal vs. External policies

15. Postacademic Interuniversity Course in Information Technology – Module C1p15 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

16. Postacademic Interuniversity Course in Information Technology – Module C1p16 Contents Link multiplexing –Circuit switching Synchronous Time-domain Multiplexing –Packet Switching Statistical Time-domain Multiplexing Connection oriented vs. Connectionless –Datagrams & Routing –Virtual Circuits & Forwarding Internal vs. External policies

17. Postacademic Interuniversity Course in Information Technology – Module C1p17 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

18. Postacademic Interuniversity Course in Information Technology – Module C1p18 Routing Tables in Connectionless networks For ALL POSSIBLE destination addresses, they give the “best” outgoing link, but –the best can be different for different applications –the best can get congested For EACH packet routing table needs to be consulted Routing tables need to be updated regularly –Set of possible destinations can change –Set of available links can change –Destinations can be mobile

19. Postacademic Interuniversity Course in Information Technology – Module C1p19 Best route consequences a b c d 11 1 1 1 Risk of congestion Idle

20. Postacademic Interuniversity Course in Information Technology – Module C1p20 Contents Link multiplexing –Circuit switching Synchronous Time-domain Multiplexing –Packet Switching Statistical Time-domain Multiplexing Connection oriented vs. Connectionless –Datagrams & Routing –Virtual Circuits & Forwarding Internal vs. External policies

21. Postacademic Interuniversity Course in Information Technology – Module C1p21 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

22. Postacademic Interuniversity Course in Information Technology – Module C1p22 Forwarding Tables a b c d 1121 10 1 2 3 1 2 3 1.11>3.101.10>3.21

23. Postacademic Interuniversity Course in Information Technology – Module C1p23 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

24. Postacademic Interuniversity Course in Information Technology – Module C1p24 Forwarding Tables in Connection Oriented networks For Each V. C. in use, they give the outgoing link –Different v.c. can connect the same end-points. –Resources can be reserved for a v.c. –They can be changed dynamically to follow mobiles Routing tables are only needed to establish a new V.C.

25. Postacademic Interuniversity Course in Information Technology – Module C1p25 Contents Link multiplexing –Circuit switching Synchronous Time-domain Multiplexing –Packet Switching Statistical Time-domain Multiplexing Connection oriented vs. Connectionless –Datagrams & Routing –Virtual Circuits & Forwarding Internal vs. External policies

26. Postacademic Interuniversity Course in Information Technology – Module C1p26 Internal vs. External Policies Network services (NUI) Connection oriented Connectionless Network operation (NNI) Connection oriented Connectionless

27. Postacademic Interuniversity Course in Information Technology – Module C1p27 Introduced concepts Multiplexing Circuit Switching Synchronous time multiplexing Packet Switching Statistical time multiplexing Datagrams and routing Virtual Circuits & packet forwarding Resource reservation for a Virtual Circuit Internal vs. External policies