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Circuit Switching and Packet Switching. ENTC 345 Dr. Ana Goulart Assistant Professor. Announcements. Reading: Stallings Chapter 1 and 2 Chapter 10 TA: Aninda@neo.tamu.edu Office hours: Mondays 5 to 8 pm (T 101) Hw # 1 due today. Review. M/M/1 example – incoming link information

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circuit switching and packet switching

Circuit Switching and Packet Switching

ENTC 345

Dr. Ana Goulart

Assistant Professor

announcements
Announcements
  • Reading: Stallings
    • Chapter 1 and 2
    • Chapter 10
  • TA: Aninda@neo.tamu.edu
    • Office hours: Mondays 5 to 8 pm (T 101)
  • Hw # 1 due today
review
Review
  • M/M/1 example – incoming link information
  • Hw#1: Examples of simulations and applications
  • How was the first lab?
on opnet traffic
On Opnet – Traffic
  • Applications and Profiles

Application Models: generate typical application traffic patterns

Examples: FTP

Email

Remote Login

Video Conferencing

Database

HTTP

Print

Voice

Custom

Standard applications

on opnet
On Opnet
  • Standard applications
    • Client/Server Model
    • Two-tier architecture

* Sessions: single conversation

between client/server

* Traffic organized into sessions

request

Client

Server

response

applications and profiles
Applications and Profiles
  • Applications: simple traffic sources, or complex protocols, or discrete set of tasks
  • Application Profile: user’s behavior
    • Specify application he/she uses
    • how long and how often
applications and profiles7
Applications and Profiles

Application Profile: user’s behavior

  • Example: start time, duration, repeatability, parallel applications or serial applications

Profile 1 : Serial

Email

HTTP

Email

HTTP

FTP

Profile 2 : Parallel

Email

FTP

application model hierarchy
Application Model Hierarchy

Profile

Profile Object

Application

Application Object

Tasks

Task Object

(Custom applications)

Phase

lab 1 small internetwork
Lab 1 – Small Internetwork

Application and Profile

Objects – database

steps
Steps:
  • Create application – add row 1
  • Create profile – set attributes
  • Workstation object - Assign profile to desired workstations
  • Server object – assign service type (application)
  • Example: How would you model the traffic at the library’s subnet?
a network configuration
A Network Configuration

ISP

(page 30 - Stallings)

R

Internet

Residential

user

Subscriber

connection

R

R

R

ATM

switch

Firewall

host

Ethernet

switch

R

Private WAN

Server

LAN PCs

wide area network
Wide Area Network

Important concepts:

Circuit switching

Packet switching

Frame relay

ATM (Asynchronous Transfer Mode)

wide area networks
Wide Area Networks

Important concepts:

Circuit switching –

- fixed routes, dedicated path between 2 stations

- on each link, a logical channel is dedicated to

the connection

- data transmitted along the dedicated path as

rapidly as possible

Packet switching –

- data sent in a sequence of packets

- each packet passed from node to node along

some path

- at each node, the entire packet is received,

stored briefly and transmitted to next node

circuit switching
Circuit Switching

A

B

- data transmitted along the dedicated path as rapidly as possible

packet switching
Packet Switching

A

R

Internet

R

R

R

B

At each node, the entire packet is received, stored briefly and transmitted to next node

What is the primary framework to model this behavior and analyze delays?

circuit switching x packet switching
Circuit switching x Packet switching

Timing of events:

Queuing delay

Call request signal

Pkt 1

Pkt 2

Circuit

establishment

Propagation delay

Pkt 3

Time

Time

Transmission delay

Call accept

signal

Data

A

B

C

D

B

C

D

A

Packet switching

Circuit switching

delays in circuit switching
Delays in Circuit switching

Timing of events:

Call request signal

Circuit

establishment

After connection is established,

Information is transmitted at a

fixed data rate.

Node delays are negligible.

Advantages?

Disadvantages?

Time

Propagation delay

Data

B

C

D

A

Packet switching

Circuit switching

circuit switching x packet switching18
Circuit switching x Packet switching

Timing of events:

Queuing delay

Call request signal

Pkt 1

Pkt 2

Pkt 3

Circuit

establishment

Propagation delay

Time

Time

Transmission delay

Call accept

signal

Data

A

B

C

D

B

C

D

A

Packet switching

Circuit switching

packet switching delays
Packet switching delays

Pkt 1

Transmission delay

Total delay from A to B

Propagation delay

Queuing delay + Processing

Pkt 1

What is the Throughput?

A

B

C

Packet switching

throughput
Throughput

Pkt 1

Transmission delay

T = Total delay from A to B

Propagation delay

Queuing delay + Processing

Pkt 1

What is the Throughput?

L = size of packet (bits)

Throughtput = L / T

A

B

C

Packet switching

throughput21
Throughput

What else can impact the throughput?

- Packet losses

- The type of recovery mechanism

Pkt 1

Transmission delay

X

T = Total delay from A to B

Propagation delay

Queuing delay + Processing

What is the Throughput?

L = size of packet (bits)

Throughput = L / T

As delay increases, the

throughput decreases

B

A

Packet switching

impact of packet size
Impact of packet size
  • Effect of packet size on transmission time

(figure 10.11, page 314 Stallings)

    • Smaller packets => higher service rate (or smaller transmission times)
      • Service rate on the outgoing link
        • μ = Capacity (bits/sec)

Packet size (bits/packet)

virtual circuit packet switching
Virtual Circuit Packet Switching
  • Datagram packet switching
    • No dedicated route for the conversation or session
  • Virtual Circuit Packet Switching
    • Dedicated route for the conversation or session
    • Additional Call setup delay
virtual circuit switching internal
Virtual Circuit switching (internal)

Timing of events:

Call request signal

Circuit

establishment

Time

Call accept

signal

Pkt 1

Data

Pkt 2

Pkt 3

B

C

D

A

Circuit switching

Packet switching

virtual circuits external
Virtual circuits (external)
  • Logical path (or connections) between two stations

Example: X.25 standard

Physical level – interface between station and

packet switched network

Link level – reliable data transfer across the physical

link (LAP-B)

Network level – virtual circuit service, enables users

to set-up logical connections

Packet switching

Network

frame relay
Frame relay
  • Designed to eliminate the overhead of X.25
  • Virtual circuits or logical connections carried at the link layer
  • Call control signaling (separate)
  • No hop-by-hop flow control (error and flow control should be taken care by another higher layer protocol