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25 Cards in this Set

  • Front
  • Back

Nodal Delay

Delay between nodes on a network

processing delay

The time it takes for routers to process packet headers

transmission delay

The amount of time it takes to push all of the packet bits into the wire.

queueing delay

Delay created when packets arrive faster than they can be processed. Router queues them for processing.

propogation delay

Time it takes for signal to travel from one destination to another.

packet switching

Divides communications into packets that are transmitted individually, in contrast to circuit switching.

circuit switching

Dedicated communications channel is established for the duration of the transmission.

network layer

Handles communication between nodes that may not be directly connected.

addressing and routing at network layer

Addressing - addresses on other networks may not match. Network layer handles this.



Routing - figure out the best path between nodes

IPv4 vs IPv6

IPv4 - 32 bit dotted decimal format



IPv6 - 128 bit hexadecimal separated by colons

Transport Layer

Provides process to process communications. Provides TCP and UDP.

port numbers

docking points for software / programming so a socket can be created and data can be transferred between two computers

TCP

Transport layer protocol. Reliable. Delivers data in same order sent. Error checking. High overhead.

UDP

Transport layer protocol. Best effort. No error checking. Faster than TCP.

TCP vs UDP

The former has much higher overhead but it is more reliable. The latter is best effort and faster.

Client-Server applications

Servers run 24/7. Clients connect to servers, send requests, server responds. An example of relationship is Web servers and web browsers (clients)

Peer-to-Peer applications

All network processes play the same role, but one has to take the role of the "Server" initially to get connected.

Sockets and socket programming

Sockets are used to connect one computer to another.



Socket sock = new Socket(String ip, int port)



Input and output streams can be placed on sockets.

active and passive sockets

Passive sockets are waiting for a connection request. Active sockets are connected.

binding sockets to end point addresses

When a client requests a connection, that socket is bound to client and server by their addresses.

Creating TCP servers and clients

Lame echo

Multi-threaded servers

As soon as connection is received it's passed to its own thread. The server continues to wait for other connection requests.

Binary vs text based protocols

calculator example



Text based require parsing and conversions



Text based are human readable and easily debugged

HTTP, IMAP, POP3, DNS, DHCP

Hypertext transfer Prot. 80


Internet Message Access Prot.


Post Office Prot. 110


Domain Name Server


Dynamic Host Config Prot.

Telnet

Useful in debugging severs. Can connect to sockets and send text based commands.