Switching

Techniques

Packet Switching

Distinguish

Between

Datagram Packet

Switching And

Virtual Circuit

Switching

Message

Switching ‐ What

Is Message

Switching?

Circuit Switching

‐ What Is Circuit

Switching?

Cell Switching

(ATM)

What Is Time

Space Switching?

Point‐To‐Point

Protocol (PPP)

PPP Protocol

What Are

Difference

Between

Circuits,

Channels And

Multichanneling?

Comparison

Between Virtual

Circuit And

Datagram

Computer

FundamentalComputer

NetworkingComputer

NetworkComm.

NetworksNetwork

Tech.Multiple

AccessSwitching

IP Address

SysRouting

Services /

App.Security

Structured

Query (SQL)Java Script

HTML Language

Cascading Style

SheetC Programming

(Theory)C Programming

(Pratical)Visual Basic

C++

ProgrammingJava

ProgrammingJava Servlet

Java Server

PagesComputer

GraphicsElectronic

CommerceManagement

(MIS)Data Structures

Software

EngineeringDigital

BY DINESH THAKUR

Conceived in the 1960's, packet switchingis  a  more  recent  technology  than  circuitswitching which addresses a disadvantageof  circuit  switching:  the  need  to  allocateresources for a circuit, thus incurring linkcapacity wastes when  no  data  flows  on  acircuit.

 

Packet  switching  introduces  the  idea  ofcutting data on a  flow  into packets whichare  transmitted  over  a  network  withoutany resource being allocated. If no data isavailable  at  the  sender  at  some  pointduring  a  communication,  then  no  packetis  transmitted  over  the  network  and  noresources are wasted.

 

Distinguish between Datagram Packet switching andvirtual Circuit switching

Search

HOME TECHNOLOGY MOTIVATION ARTICLE DISCUSSION FORUM ABOUT US

Packet Switching

And Circuit

Switching

Difference

Between Virtual

Circuit (VC) And

Permanent

Virtual Circuit

(PVC)

What Are The

Point‐To‐Point

Protocol (PPP)

Four Distinct

Phases?

ATM Structure

Cell Relay ‐ What

Is Cell Relay?

Wavelength

Division

Multiplexing

(WDM)

Logical Channels

What Is Duplex?

ElectronicsC# Programming

Database System

Struts 2 Tutorial

Follow Us

+1   Recommend this on Google

Figure : Datagram Packet Switching. Packets from a given flow are independentand a router can forward two packets from the same flow on two different links.

 

 

 

 

 

 

 

 

 

 

 

 

Since  each  packet  is  processed  individually  by  a  router,  allpackets sent by a host to another host are not guaranteed to usethe  same  physical  links.  If  the  routing  algorithm  decides  tochange  the  routing  tables  of  the  network  between  the  instantstwo packets are sent, then these packets will take different pathsand can even arrive out of order.

 

In this Figure for instance, packets use two different paths to gofrom User  1  to  User  5.  Second,  on  a  network  topology  changesuch  as  a  link  failure,  the  routing  protocol  will  automaticallyrecompute  routing  tables  so  as  to  take  the  new  topology  intoaccount  and  avoid  the  failed  link.  As  opposed  to  circuitswitching, no additional traffic engineering algorithm is requiredto reroute traffic.

 

Virtual circuit packet switching

Figure: Virtual circuit packet switching. All packets from the sameflow use the same virtual circuit.

 

 

 

 

 

 

 

 

 

 

 

Virtual  circuit  packet  switching  (VC­switching)  is  a  packetswitching  technique  which  merges  datagram  packet  switchingand  circuit  switching  to  extract  both  of  their  advantages.  VCswitching  is  a  variation  of  datagram  packet  switching  wherepackets  flow  on  so­called  logical  circuits  for  which  no  physicalresources like frequencies or time slots are allocated (see Figure).

 

Each  packet  carries  a  circuit  identifier,  which  is  local  to  a  linkand updated  by  each  switch  on  the  path  of  the  packet  from  itssource  to  its  destination.  A  virtual  circuit  is  defined  by  thesequence of  the mappings between a  link  taken by packets andthe circuit identifier packets carry on this link. In VC­switching,routing is performed at circuit establishment time to keep packetforwarding fast.

 

Other advantages of VC­switching include the traffic engineeringcapability of circuit switching, and the resources usage efficiencyof datagram packet switching. Nevertheless, a main issue of VC­Switched networks is the behavior on a topology change.

 

As  opposed  to  Datagram  Packet  Switched  networks  whichautomatically recompute routing tables on a topology change likea  link  failure,  in  VC­switching  all  virtual  circuits  that  passthrough  a  failed  link  are  interrupted.  Hence,  rerouting  in  VC­switching relies on traffic engineering techniques.

 

There  are  a  number  of  important  differences  between  virtualcircuit  and  datagram  networks.  The  choice  strongly  impactscomplexity  of  the  different  types  of  node.  Use  of  datagramsbetween intermediate nodes allows relatively simple protocols atthis  level,  but  at  the  expense  of  making  the  end  (user)  nodesmore complex when end­to­end virtual circuit service is desired.

 

The  Internet  transmits  datagrams  between  intermediate  nodesusing IP. Most Internet users need additional  functions such asend­to­end error and sequence control  to give a reliable service(equivalent  to  that  provided  by  virtual  circuits).  This  reliabilitymay  be  provided  by  the  Transmission  Control  Protocol  (TCP),which is used end­to­end across the Internet, or by applicationssuch as the trivial file transfer protocol (TFTP) running on top ofthe User Datagram Protocol (UDP)

Connect Us On FaceBook and Google+

Dinesh Thakur is a Technology Columinist and founder of Computer Notes and Technology Motivation. Mail Me At (@Computer

Notes)