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