CS 447 Networks and Data Communication Comparison of Circuit-Switching, Virtual-Circuit and Datagram Data Transmissions Department of Computer Science Southern Illinois University Edwardsville Fall, 2015 Dr. Hiroshi Fujinoki E-mail: hfujino@siue.edu

CS 447 Networks and Data Communication Circuit Switching Data Transmission Host A Host X Host Y Host B Switch S1 Switch S2 Switch S3 Switch S4 Switch S5 Signaling Message (Path Setup) Routing Routing ACK ACK ACK ACK Routing Routing

CS 447 Networks and Data Communication Circuit Switching Data Transmission File Host A Host X Host Y Host B Switch S1 Switch S2 Switch S3 Switch S4 Switch S5 Dedicated Pipe (path) Blocked

CS 447 Networks and Data Communication Circuit Switching Data Transmission  Path set-up is required before data transmission starts Major Properties:  Data will be transferred as a continuous stream of bits  All data (all bits) follow exactly the same path (order of bits transmitted by a sender is preserved at a receiver)  No resource sharing (a path is dedicated resource for your transmission)  Path set-up delay is always required  Once data transmission starts, no overhead (i.e., node major switching delay) at each switch on a path (since the path is set up).  Transmission rate is guaranteed (your data will be delivered within certain amount of time).  Highest cost data transmission (= highest quality)

CS 447 Networks and Data Communication Datagram Data Transmission 1 2 3 File Host A Host X Host Y Host B Switch S1 Switch S2 Switch S3 Switch S4 Switch S5 3 2 1 Routing

CS 447 Networks and Data Communication Datagram Data Transmission Host A Host X Host Y Host B Switch S1 Switch S2 Switch S3 Switch S4 Switch S5 3 2 1 Routing

CS 447 Networks and Data Communication Datagram Data Transmission Host A Host X Host Y Host B Switch S1 Switch S2 Switch S3 Switch S4 Switch S5 Routing 3 2 1 Routing

CS 447 Networks and Data Communication Datagram Data Transmission Host A Host X Host Y Host B Switch S1 Switch S2 Switch S3 Switch S4 Switch S5 1 3 2

CS 447 Networks and Data Communication Datagram Data Transmission Host A Host X Host Y Host B Switch S1 Switch S2 Switch S3 Switch S4 Switch S5 3 1 2

CS 447 Networks and Data Communication Datagram Data Transmission Host A Host X Host Y Host B Switch S1 Switch S2 Switch S3 Switch S4 Switch S5 2 3 1

CS 447 Networks and Data Communication Datagram Data Transmission Host A Host X Host Y Host B Switch S1 Switch S2 Switch S3 Switch S4 Switch S5 1 2 3 1 2 3

CS 447 Networks and Data Communication Datagram Data Transmission More packets than S1 can handle could arrive Host A Host X Host Y Host B Switch S1 Switch S2 Switch S3 Switch S4 Switch S5 3 2 1 3 2 1

CS 447 Networks and Data Communication Datagram Data Transmission Switches in datagram networks are called “routers” Host A Host X Host Y Host B Switch S1 Switch S2 Switch S3 Switch S4 Switch S5 Packet Dropped 3 3 2 2 1 1 NACK (Error)

CS 447 Networks and Data Communication Datagram Data Transmission Major Properties:  Path set-up is NOT required before data transmission starts  Data will be transferred as a collection of packets  All packets may not follow the same path (order of bits transmitted by a sender is NOT preserved at a receiver)  Network resource is shared  Path set-up delay is NOT required  After data transmission starts, high overhead (i.e., major switching delay) at each switch on a path (error control and flow control are performed for each packet plus “routing” now have to be performed for every packet).  Transmission rate is NOT guaranteed (“Best-Effort Service).  Lowest cost data transmission (= lowest quality)

CS 447 Networks and Data Communication Datagram Data Transmission Dropped packet Host A Host X Host Y Host B Switch S1 Switch S2 Switch S3 Switch S4 Switch S5 NACK (Error) 3 Even a NACK message could be lost

CS 447 Networks and Data Communication Virtual Circuit Data Transmission Path set-up is same as Circuit-Switching Host A Host X Host Y Host B Switch S1 Switch S2 Switch S3 Switch S4 Switch S5 Signaling Message (Path Setup) Routing ACK

CS 447 Networks and Data Communication Virtual Circuit Data Transmission 1 2 3 File Host A Host X Host Y Host B Switch S1 Switch S2 Switch S3 Switch S4 Switch S5 3 2 1 1 2 1 2 3 1 3 2 Shared Pipe 1 1 2 3 2 (High priority is to host A - but X can send data as best-effort service)

CS 447 Networks and Data Communication Virtual Circuit Data Transmission Major Properties:  Path set-up is required before data transmission starts  Data will be transferred as a collection of packets  All data (all packets) follow exactly the same path (order of bits transmitted by a sender is preserved at a receiver)  Network resource can be shared (because data is transferred as packets)  Path set-up delay is required  After data transmission starts, some overhead (i.e., some switching delay) at each switch on a path (error control and flow control are performed for each packet).  Transmission rate is guaranteed (your data will be delivered within certain amount of time).  Medium cost data transmission (= medium quality)

CS 447 Networks and Data Communication Factors Circuit-Switching Virtual Circuit Datagram ISDN, ATM, Examples Public Telephone Internet Frame Relay Resource Sharing NO YES YES Dedicated Paths YES NO NO Continuous Transmission YES NO NO Path-setup in advance YES YES NO Busy signal if dest. busy YES YES NO Major delay Path setup delay Path setup delay Packet routing

CS 447 Networks and Data Communication Factors Circuit-Switching Virtual Circuit Datagram No overhead after TX starts? YES YES NO (Packet header) (Packet header) Routing delay? NO No (Almost 0) YES (High) Guaranteed Tx Bandwidth? YES YES NO Advantages Guaranteed Quality Guaranteed Quality Resource sharing Resource sharing Low cost Non-blocking High cost Best Effort Service Disadvantages High cost Poor security Blocking service Blocking service Reliable, Delay-sensitive Service that needs To be available 24Hrs Applications Delay-sensitive Text-base