Chapter 1: Internetworking - PowerPoint PPT Presentation

1 / 26
About This Presentation
Title:

Chapter 1: Internetworking

Description:

Chapter 1: Internetworking Internetworking Basics Network segmentation How bridges, switches, and routers are used to physically segment a network – PowerPoint PPT presentation

Number of Views:189
Avg rating:3.0/5.0
Slides: 27
Provided by: ax09
Category:

less

Transcript and Presenter's Notes

Title: Chapter 1: Internetworking


1
Chapter 1 Internetworking
  • Internetworking Basics
  • Network segmentation
  • How bridges, switches, and routers are used to
    physically segment a network
  • How routers are used to create internetwork
  • OSI model

2
Internetworking Models
  • Most networks are designed as a stack of layers,
    each one built upon the one below it. Why?

Host 1
Host 2
Layer 3 protocol
Layer 3
Layer 3
Layer 2/3 interface
Layer 2 protocol
Layer 2
Layer 2
Layer 1/2 interface
Layer 1 protocol
Layer 1
Layer 1
Physical Medium
3
  • Each layer provides services to the higher
    levels.
  • Each layer behaves as a black box.
  • Layer n on one machine talks to layer n on
    another machines.
  • The corresponding layer in the layered structure
    are called peers.
  • The communication between peers must follow
    certain rules, known as protocol.
  • No data are directly transferred between layers.
    Actual communication is through a physical medium
    below layer 1.

4
An Analogy
Professor A
Professor B
I like rabbits
Jaime bien les lapins
Message
Chinese French
Information for the remote translator
Urdu English
Translator
Translator
L Dutch
L Ducth
Ik vind konijnen leuk
Ik vind konijnen leuk
use Dutch
Secretary
Secretary
Information for the remote secretary
Fax
Fax
L Ducth
L Ducth
Ik vind konijnen leuk
Ik vind konijnen leuk
use fax
5
Open Systems Interconnection (OSI) Reference Model
Application
  • Provides user interface
  • Initiates services

Presentation
  • Transfer data into standard format before
    transmission

The upper levels
Session
  • Keeps data different applications data separate
  • Control the data exchange

Transport
  • End-to-end data error free data transmission

Network
  • Logical addressing for data packets Routing and
    error handling

The lower levels
Data Link
  • NIC software function
  • How data in packaged
  • Error detection

Physical
  • Moves bits between devices
  • Specifies voltages, cables, and cables

6
Reasons for Layering
  • Simplifies the network model
  • Enables programmers to specialize in a particular
    level or layer of the networking model
  • Provides design modularity
  • Encourages interoperability
  • Allows for standardized interfaces to be produced
    by networking vendors

7
The Application Layer (Layer 7)
  • The layer where users communicate to the computer
  • Contains protocols and utilities that provides
    services to network applications
  • (True/False) MsWord, Eudora Mail, Netscape are in
    the application layer.
  • Eudora (application) uses SMTP (Simple Mail
    Transfer Protocol) (protocol).
  • E-mail
  • Message formats such as RFC 822
  • SMTP, POP3 (Post Office Protocol Version 3), IMAP
    (Internet Message Access Protocol)
  • WWW
  • HTML (The HyperText Markup Language), XML
    (eXtensible Markup Language), XSL (eXtensible
    Style Language)
  • HTTP (The HyperText Transfer Protocol)

8
The Presentation Layer (Layer 6)
  • The presentation layer prepares the data from the
    application layer for transmission over the
    network or from the network to the application
    layer.
  • Include protocols specifying how to represent
    data (MPEG, JPEG, PIC, WAV)
  • Responsible for data translation, formatting,
    encryption, compression.
  • We need these services because different
    computers use different internal representation
    for data (integers and characters)

9
The Session Layer (Layer 5)
  • Enables two applications on the network to have
    an ongoing conversation
  • Provide following services
  • Communication setup and teardown
  • Control for data exchange
  • Data synchronization definition
  • Failure recovery
  • Examples
  • Structured Query Language (SQL)
  • X Windows
  • AppleTalk Session Protocol (ASP)

10
The Transport Layer (Layer 4)
  • Provides
  • end-to-end error free data transport services
  • establish a logical connection
  • data segmentation into maximum transmission unit
    size
  • messaging service for session layer
  • Protocols in this layer can be
  • connection-oriented require an acknowledgment
    of the receipt of data packets.
  • connectionless do not require an acknowledgment
    of the receipt of data packets.

11
  • Connection-oriented protocols

sender
receiver
Synchronize
Negotiate connection
Synchronize
Acknowledge
Connection Establish
Virtual Circuit
Data Transfer
12
  • Flow Control
  • The segments delivered back to the sender upon
    their reception
  • Any segment not acknowledged are retransmitted.
  • Segments are sequence back into their proper
    order upon arrival at their destination
  • Manageable data flow is maintained in order to
    avoid congestion

sender
receiver
Buffer full
GO
13
  • Windowing The quantity of data segment (in
    bytes) is sent without receiving an
    acknowledgment (ack) is called a window.

sender
receiver
sender
receiver
Window size of 3
Window size of 1
receive 1
send 1
send 1
ack. 2
send 2
send 2
receive 2
send 3
ack. 3
ack. 4
send 3
send 4
14
  • Acknowledgments

sender
receiver
Positive Acknowledgment with retransmission
1
2
3
4
5
6
1
2
3
4
5
6
send 1
send 2
send 3
ack. 4
send 4
send 5
Connection lost!
send 6
ack. 5
send 5
ack. 7
15
The Network Layer (Layer 3)
  • Provides services
  • to manage devices addressing
  • to tracks the location of devices on the network
  • to determine the best way to move data on the
    network
  • The network layer must transport traffic between
    devices that are not directly connected.
  • Routers are specified at this layer.

16
The Data Link (Layer 2)
  • Services
  • Identification of the source and destination
    nodes via their physical address (Media Access
    Control (MAC) address)
  • Definition of how data is packaged for transport
    as frames
  • Error detection
  • Flow control of information sent across the link
  • Has two sublayers
  • Media Access Control (MAC) 802.3
  • Logical Link Control (LLC) 802.2

17
The Physical Layer (Layer 1)
  • This layer communicates directly with the various
    types of actual communication media
  • Services
  • definition of the physical characteristics of the
    network hardware, including cable and connector
  • Encoding
  • Transmission of signals on the wire

18
Example568B twisted pair wiring scheme
19
Layer 1 Network Devices Repeaters
  • The number of nodes on a network and the length
    of cable used influence the quality of
    communication on the network
  • Attenuation
  • Natural degradation of a transmitted signal over
    distance
  • Repeaters work against attenuation by repeating
    signals that they receive on a network
  • Why are repeaters Layer 1 devices?

20
Layer 1 Network Devices Hubs
  • Generic connection device used to tie several
    networking cables together to create a link
    between different stations on a network

21
  • Hubs that are plugged into electric power are
    called active hubs
  • A hub that merely connects different cables on a
    network and provides no signal regeneration is
    called a passive hub and is not a repeater
  • Hub is a generic term applied to many different
    network-connection devices
  • If a hub in some way segments or subdivides the
    traffic on a network, it is an intelligent, or
    switching, hub
  • For the purpose of the CCNS exam, the term hubby
    itselfis a device that does not segment the
    network

22
Network Segmentation
  • Segmentation
  • Process of breaking a network into smaller
    broadcast or collision domains
  • Ethernet network, which are characterized by IEEE
    802.3 standard, define the use of a Carrier Sense
    Multiple Access with Collision Detection
    (CSMA/CD) access method
  • Backoff algorithm Mathematical calculation
    performed by computers after a collision occurs
    on a CSMA/CD network
  • Backoff period Random time interval used after
    a collision has been detected on an Ethernet
    network

23
Network Segmentation via Bridges
24
Layer 2 Devices Bridges
  • Operate at the Data Link layer of the OSI model
  • Filters traffic between network segments by
    examining the destination MAC address
  • Based on this destination MAC address, the bridge
    either forwards or discards the frame
  • When a client sends a broadcast frame to the
    entire network, the bridge will always forward
    the frame

25
  • Transparent Bridges Also called learning
    bridges because they build a table of MAC
    addresses as they receive frames
  • This means that they learn which addresses are
    on which segments
  • Ethernet networks mainly use transparent bridges
  • Source-routing bridges Rely on the source of
    the frame transmission to provide the routing
    information
  • Usually employed by Token Ring networks
  • Translation bridges Can connect networks with
    different architectures

26
Layer 2 Devices Switches
  • Increase network performance by reducing the
    number of packets transmitted to the rest of the
    network
  • Like bridges, operate at the Data Link layer of
    the OSI model
  • In an Ethernet network, computers are usually
    connected directly to a switch
  • Virtual circuit
  • Private connections between two points created by
    a switch that allows the two points to use the
    entire available bandwidth between those two
    points without contention
Write a Comment
User Comments (0)
About PowerShow.com