Postacademic Interuniversity Course in Information Technology – Module C1p1 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

Postacademic Interuniversity Course in Information Technology – Module C1p2 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

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

Postacademic Interuniversity Course in Information Technology – Module C1p4 Datagram Routing Based upon routing tables a b c d 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

Postacademic Interuniversity Course in Information Technology – Module C1p5 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

Postacademic Interuniversity Course in Information Technology – Module C1p6 Best route consequences a b c d Risk of congestion Idle

Postacademic Interuniversity Course in Information Technology – Module C1p7 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

Postacademic Interuniversity Course in Information Technology – Module C1p8 Virtual Circuit Number a b c d a>b a>c a>d b>c b>d a>b d>c a>d b>d b>c a>c d>c a>c a>d b>c b>d Each virtual circuit is identified by a specific number on each physical link

Postacademic Interuniversity Course in Information Technology – Module C1p9 Forwarding Tables a b c d > >3.21

Postacademic Interuniversity Course in Information Technology – Module C1p10 Permanent Virtual Circuit Forwarding tables set-up and cleared by network manager through “separate” network a b c d a>c11a>c > >3.21 “Separate” signaling network Signaling and data packets travel through different (virtual) circuits

Postacademic Interuniversity Course in Information Technology – Module C1p11 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.

Postacademic Interuniversity Course in Information Technology – Module C1p12 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

Postacademic Interuniversity Course in Information Technology – Module C1p13 Internal vs. External Policies Network services (NUI) Connection oriented Connectionless Network operation (NNI) Connection oriented Connectionless

Postacademic Interuniversity Course in Information Technology – Module C1p14 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