Introduction of Network

04 Nov 2017 Tags:

network

Internet, that is what we are surrounded by. We learn that it is network of networks, an infrastructure for providing network applications and it provides program interface for application. Last semester I’ve taken a web system programming class, programming a web application and learn about http and jsp as a preview of network.

Internet, Web and Protocol

Internet

network of networks
infrastructure for providing network applications
provides program interface for application

Web(World Wide Web)

just one of the way to send information in internet (another example might be a Mail Service (port : 25))
uses http for Protocol
hyper text and URLs

Protocol

an agreement of message format, order and actions to operate when messsage is transmitted/received for communication between hosts.

Internet Elements

host/terminal/end system
access network
physical media
network core

1. access network

Residential(home) access network
Enterprise access network
Mobile access network.

  a. Residential(home) access network
  Techniques used at home access network are ADSL(asymmetric digital subscriber line) and Cable. ADSL modem at home is conneted to the centeral office, which has dsl multiplexer. Then, the central office connects the line to ISP. 
On the other hand, cables are connected to headend(Cable Modem Termination System). CMTS connects the line to ISP.

  b. Enterprise access network( Ethernet )

  c. Mobile access network 

  Techniques used for mobile access nets are divided by the range it could cover. Wireless LAN is for local. WAN is for wide area, works in cellular units. There are also PAN and etc.

2. Phsical Media

Guided Medias : Copper, Coaxial, fiber Optic Cable
Unguided Medias : radio, satellites

3. Network Core

Global ISPS
Regional ISP and CDN (Content Distributon Network)

Global ISPs have much bigger range than Regionl ISPS. CDN is served at core ~ access networks but depends on where and how it is served. It could be ‘enter deep’ near the accenss network or could be ‘bring home’ at upper layer than access network.</pre>

How does the hosts exchange messages?

There used to be 3 ways ; circuit switching, message swiching, packet swtiching but, message swiching has been depreciated.

circuit switching

Resouces used for exchanging messages such as physical links are dedicated and determined before the actual transmission. There must be a setup before always. Therefore, messages are guaranteed. Usually used for telephone wires.

packet switching

Messages are torn down into ‘packets’ and sent by one hop between routers. Since this method is based by ‘store and forward’, the packets could not move until the full parcket arrived at the destination router. Unlike circuit swiching, this could handle more users(cliets) with composure.
However if the rate of arriving packet exceed the butffer of router or the rare of transmission of router, the packet will be dropped or lost.

lynring24 blog