Introduction to networking - Ch.2 Layering
We will talk about the layers one by one.
Layers
- Each node has a layer
- Layer is distributed
Physical layer
- Moves bits between physically connected end-systems
- Internet - technology to move bits over wires/wireless/satellite
DataLink layer
- Frame - set of bits that belongs together
- Using MAC - Medium Access sublayer address
- Have idle marker, Begin marker and End marker
- First layer of software
- Usually bundle both physical and datalink layer on adaptor E.g. Ethernet Card
- Common technology: Ethernet, PPP, FDDI, SONET, HDLC
* Remember Ethernet will be probably OK
Network Layer
- Allowing an end-system to communicate with other end-system by computing a route between systems
- Provide unique network address - IP address
- Logically concatenates set of links to form an end-to-end link
- In router / switches, Participate in routing protocol, responsible for forwarding packets, choose which packets to drop, schedule the transmission order of packets
Transport Layer
- Do Error-control, flow-control, multiplexing
- Error-control - retransmit lost packets, detect, discard and retransmit corrupted packets
- Flow-control - Control the traffic between end-to-end
- Supports connection-oriented or connectionless service
- TCP provides error control, flow control and multiplexing
- UDP provides only multiplexing
Session Layer
- Not common in practice
- Duplex - if transport layer is simplex, concatenates two transport endpoints together
- Expedited data delivery - allows some messages to skip ahead in end-system queues, by using a separate low-delay transport layer endpoint
- Synchronization - Allows users to place marks in data stream and to roll back to a pre-specified mark
- *Not common in internet
Presentation Layer
- Encrypt data
- Usually ad-hoc
- Work with application data but not "headers"
- *Not common in Internet
Application Layer
- Applications that use the network
- E.g. IE/firefox/foxy
