Switching technologies, Lecture notes of Communication

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Introduction to Communication Networks

Spring 2007 EECS 122 SPRING 2007

Unit 5 Switching Principles

Prof. Adam Wolisz^

EECS 122 SPRING 2007 Acknowledgements – slides comming from:^ •^ Data and Computer Communication

by Wiliam Stallings (our supplementary textbook) – numerous slides! • Data Communications and Networking

by B.^ Forouzan , Mc Graw Hill, 2004 • Some figures have been used form the earlier issues of theEECS 122 tought by Prof Jean Walrand. • Introduction to Telephones & Telephone Systems

by A. Michael Noll, Artech House, 1986

Prof. Adam Wolisz^

EECS 122 SPRING 2007

Circuit Switching – Principle^ A connection between the ingoing and outgoing segments of thetransmission path is established on demand, for the exclusive useof a pair of end users

• until explicitly released

Prof. Adam Wolisz^

EECS 122 SPRING 2007

Circuit Switching – features^ •^ The whole path is reserved for the single pair of end users -inefficient use of the path if there is bursty traffic^ •^ The delay in transmission of user data is constant,determined^ mainly

by the signal propagation

-^ Explicit setup and release of a switch setting is needed, theintention to setup/release a connection must be conveyedfrom the initiator to each switch (signaling)^ –^ Time is needed for both: propagation of the signalinginformation and operation of each switch, as well aspropagation of the confirmation of path setting •^ During the establishing/releasing the path segments can notbe used – but later the resources are assured!!!^ Perfect for LONG transmissions of flows with prettyconstant bit rate!!!

Prof. Adam Wolisz^

EECS 122 SPRING 2007

Comparison of Switching Techniques- again...^ •^ Burstiness of data^ –^ In many data communication applications, data occur in burstsseparated by idle periods^ –^ This type of intermittent data can often be transmitted moreeconomically by assembling the data into packets (or messages) andinterspersing packets from several channels on one physicalcommunication path

Prof. Adam Wolisz^

EECS 122 SPRING 2007

Message Switching – Principle!^ •^ There does exist a permanent connection between each input andeach output of the switch (like a fully connected matrix or sharedmemory).^ •^ The user generated data units (messages) have to carry informationuniquely defining the route to be chosen (header)

Prof. Adam Wolisz^

EECS 122 SPRING 2007

Message switching

[Fairhurst]

Prof. Adam Wolisz^

EECS 122 SPRING 2007

Serialization^ •^ Small message caught behind big message

Prof. Adam Wolisz^

EECS 122 SPRING 2007 Packet switching

[Fairhurst]

Prof. Adam Wolisz^

EECS 122 SPRING 2007 Delay on the way – summary

[ Source: Dr. Cheng Lehigh Univ.]

Prof. Adam Wolisz^

EECS 122 SPRING 2007

Comparison of switching approaches

[Tannenbaum]

(a) Circuit switching

(b) Message switching

(c) Packet switching

Prof. Adam Wolisz^

EECS 122 SPRING 2007

Effect of Packet Size on Transmission Time

Prof. Adam Wolisz^

EECS 122 SPRING 2007 Cut-thorugh packet switching

[eecs122, walrand]

Prof. Adam Wolisz^

EECS 122 SPRING 2007 Bottleneck...^

[eecs122, walrand]

It is possible to estimate the bottelneck trhoughput sending „back –to-back“ packets of constant length and observing the time differencebetween their Arrival times...