Circuit and Packet Switching (ITS323, L19, Y15)

[mahmoudalqawasimi]

Dear Steven, thanks a lot for your effort, it is really helpful for me as a telecomm. Engineer .

really appreciated 👍

[JanacMeena]

• How many cables we need to contact 6 computers together?
○ 15
§ 6A, 5B, 4C, 3D, 2E, 1F
○ Switching nodes allow us to connect many computers without having direct connections
§ They do not create or consume data, they just forward it to the right place
○ A sends to node 4, sends to 5, etc.
○ Choosing a path is called routing
• Multiplexing is used for parallel input
○ Frame shifting…
• Internet uses packet switching
• Circuit switching
○ Old telephone lines used manual circuit switching where ladies would change the circuits
○ Now we use automated circuit switching
○ Creating a dedicated communication path between two stations
○ Switching lines need to support enough capacity to support multiple connection
○ Adding capacity is costly and wasteful if it is not used frequently
○ If 1mbps is reserved for connection A, then it will always take up 1mbps capacity, even if it only uses 0.1mbps
• Packet switching
○ Break data into small packets
○ More efficient, allows for sharing capacity
○ 2 types, data gram and virtual
○ Datagram
§ Source station sends a few packets, 123
§ The packets independently travel along the different paths of switching nodes
§ Packets are put together at the end
○ A queue is maintained if capacity is reached

[TheTacticalDood]

- point-to-point networks are not cost-effective
- switched networks are more economical
- use routers (aka. gateways or switches) to forward data
- need not be fully-connected
- multiple paths increase performance and reliability
- using shared links concurrently requires multiplexing
- shared links needs high capacity (i.e., throughput)
- or assumption on link usage
- circuit switching allocates resources
- guarantees good performance
- not optimal from network operator's view
- a resource allocated but not fully utilized is suboptimal
- not suitable when sending rate varies (i.e., Internet)
- datagram packet switching breaks data into small datagrams or packets
- no resource allocation
- router queues incoming packets may drop them