1. Circuit-Switched Network
1.1. Connection: Dedicated Path
1.2. Three Phases
1.2.1. Setup Phase
1.2.2. Data Transfer
1.2.3. Teardown
1.3. Efficiency
1.3.1. Computers can remain connected even without activity, hence...
1.3.2. Resources are redundant, and...
1.3.3. ...other connection are deprived until it's terminated
1.4. Delay is Minimal
2. Packet-Switched Networks
2.1. Datagram Networks
2.1.1. Each Packet treated Independently
2.1.2. Packet belong to same message
2.1.2.1. ...may take different paths
2.1.2.2. Arrived destination not in order
2.1.2.3. possibly can be lost
2.1.3. Packet need header
2.1.3.1. so switch where to send them
2.1.4. Message will be divided into packets
2.1.4.1. fixed size
2.1.4.2. variable size
2.1.5. Resources:
2.1.5.1. no reservation
2.1.5.2. allocated based on demand
2.1.6. Done at Network Layer
2.1.7. No Setup & Teardown phases
2.1.8. Each Switch has routing table
2.1.9. a.k.a Connectionless network
2.1.10. issues
2.1.10.1. Efficiency
2.1.10.1.1. Resources only allocated when packet being transferred
2.1.10.1.2. better than circuit-switched network
2.1.10.2. Delay
2.1.10.2.1. Great delay
2.1.10.2.2. Each packet experience "wait" at switch before being forwarded
2.1.10.2.3. not all packet travel through same switches...
2.1.10.2.4. ...hence, delay is not uniform
2.2. Virtual-Circuit Networks
2.2.1. involved Setup & Teardown phases
2.2.1.1. Three Phases
2.2.1.1.1. Setup
2.2.1.1.2. Data Transfer
2.2.1.1.3. Teardown
2.2.2. data transfer as individual packets
2.2.2.1. take same path accross network
2.2.2.2. Arrived in order at destination
2.2.2.3. possibly can be lost
2.2.3. Packet need header
2.2.3.1. to know which next switch to be sent to
2.2.4. is a cross between a circuit-switch network and a datagram network
2.2.5. Resoucrces
2.2.5.1. Allocated
2.2.5.2. or on-demand
2.2.6. all packets follow same path
2.2.7. implement at datalink layet
2.2.8. Addressing
2.2.8.1. Global
2.2.8.1.1. unique address in scope of network
2.2.8.1.2. or internationally in international network
2.2.8.2. Local
2.2.8.2.1. use actual address for data transfer
2.2.8.2.2. is a small number has only switched
2.2.9. Issues
2.2.9.1. Efficiency
2.2.9.1.1. All packets belong to same source
2.2.9.1.2. travel in the same path
2.2.9.1.3. if resources is on-demand: packet may arrive with different delays
2.2.9.2. Delay
2.2.9.2.1. One-time delay for setup
2.2.9.2.2. One-time delay for teardown