Tutorial 9 – Computer Systems
Tutorial 9 – Computer Systems
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Transport layer protocols
Transport layer protocols provide logical communication between
application processes running on different hosts (it goes directly to
the specific process) and only resides on those hosts
A network layer protocol provides logical communication between
hosts (NOT the specific processes, Transport layer does this!)
Logical communication is another way to say “end-to-end”, i.e. it is as if
the applications or hosts are directly in communication with each other
Example of transport layer protocols
UDP: user data protocol
TCP: transmission control protocol
Transport layer protocols
Transport layer protocols extend network layer protocols by
providing process to process delivery service for applications
through multiplexing and demultiplexing
Multiplexing: Transport layer gathers data chunks from different
sockets, encapsulates each data chunk with header info to create
segments, and passes these segments to network layer
Demultiplexing: At receiving end, transport layer identifies the
receiving socket and then directs data in transport layer to
correct socket
Transport layer protocol header contain port numbers which
identify exact process this information needs to go to. Network
layer headers only contain IP addresses that identify only host
and not the processes inside
Transport layer protocols extend network layer protocols by
providing process to process delivery service for
applications through multiplexing and demultiplexing
Multiplexing vs. demultiplexing
What is reliable data
No corrupted data
Not lost or duplicated
Not out of order
TCP provides reliable data transfer
Examples of when you would use TCP and when you would use UDP?
TCP: Email, remote terminal access, web, file transfer since these all need reliable data
UDP: DNS, Routing table updates (if we’re missing an update, then just send another one),
network management data SNMP (simple network management protocol) (this usually
happens when network is congested, so congestion controlled data transfer would be
hard to achieve)
connectionless
congestion control
flow control
reliable data transfer
connection oriented
A socket does not mean the actual connection. It is an endpoint
instance of a specific communication line.
How do we establish logical communication over TCP?
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