41902 Lecture Notes - Lecture 2: Inter-Process Communication, Application Layer, Computer Network
Network Fundamentals:
Chapter 2: Application Layer
Chapter 2.1: Principles of network applications
Application Architectures:
Client-server:
Server: always on, permanent IP address, data centres for scaling purposes
Clients: include devices like phone, laptop, etc. , communicate with server, irregular connection,
dynamic IP address (changes with different locations and wi-fi), do not communicate directly to each
other and communicate to a server
Peer-to-peer (P2P):
Peer devices communicate with minimal to no reliance on a server, requesting and receiving services
fro other oeted hosts alled peers. Deies are like liets ad hae irregular oetio ad
dynamic IP addresses. In peer-to-peer, the device that requests information is considered the client
and the device that waits for communication is the server.
Process: a program running within a host. Two processes communicate using inter-process
communication (defined by OS). Processes communicate by exchanging messages.
Client process: imitates communication. Server process: waits to be contacted.
Applications P2P architectures have client processes & server processes.
A process sends/receives message to/from its socket (analogous to a door). Sending process relies
o trasport ifrastruture o other side of the door/soket to delier essages to soket a
receiving process.
A packet can get lost within a computer network. It can overflow a buffer in a router, or be discarded
by a host or router after having some of its bits corrupted.
Addressing processes:
To receive messages, a process must have an identifier. Host devices have a unique 32-bit IP address
used to identify them on a network. However IP address alone is not enough to identify an
application or process running (e.g. webpage, email, etc.) as many process are run simultaneously on
the same host. Therefore, an identifier must also have a port number.
App-layer protocol:
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Document Summary
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