Computer Networks 1

Network applications

Web application, video/audio streaming, real-time video/audio streaming

Netwrok connectivity

Point-to-point link, Multiple-access link

Switched networks

Circuit switching network, Packet switching network

Circuit switching network

establishes a dedicated circuit across a sequence of links and then allows the source node to send a stream of bits

Packet switching

send discrete blocks of data to each other. A block of data is called packet/message. Switched networks typically use a strategy called store-and-forward

switch

node responsible for storing and forwarding packets

host

node that use a network

router/gateway

switch that is connected to two or more networks

routing

process of determining, by the switch, how to forward the message to its destination

multiplexing

sharing of a system resource among multiple users

STDM

Synchronous time-division multiplexing, divide time into equal parts and allow each data flow to be sent over during this period

FDM

frequency division multiplexing, transmit each data flow over the link at a different frequency

Statistical multiplexing

data frames are forwarded to the nodes based on their request

channel

connects one process to another, allows for communication between processes

Request/Reply channel

ensures that every message sent by one side is received by the other side and that only one copy of each message is delivered

Message stream channel

support: one-way and two-way traffic. The message stream channel doesn't have to guarantee that all messages are delivered, however, it needs to ensure that those messages arrive in the same order in which they were sent

OSI/7 layer architecture

Physical, Data, Network, Transmission, Session, Presentation, Appliaction layers

Physical Layer

handlers the transmission of raw bits over a communication channel

Data Layer

collects a stream of bits into a larger aggregate called a frame

Network Layer

handles routing among nodes within a packet-switched network

Transport Layer

implements a process-to-process channel of communication

Session Layer

provides name space that is used to tie together the transport streams

Presentation Layer

decide on format of data exchanged between peers

Application Layer

include HTTP enabling web browsers to request pages from web servers

protocol

communication service used to exchange messages. Protocol must have service and peer interface

API

Application Programming Interface- interface provided by the OS allowing for executing protocols

socket

point where a local application process attaches to the network

bandwidth

ratio of bits per second that can be transmitted on the link

latency

describe how long does it takes a message to travel from one end of network to the other one

Delay X Bandwidth product

inform us about number of bits that must be transmitted before the first bit arrives to the receiver