01 basico redes

Module 1: Internetworking Basics

Before begin…

1-3 : Networking Fundamentals—Internetworking HVS . Universidad Autónoma de Yucatán I.S.C Henry Ventura Sabido

Cisco Icons and Symbols


Cisco Icons and Symbols


Computer Basics

PC COMPONENTS

PC’s are the building block of the networks. They have many of the same parts and systems as the other network devices, such as router and switches. You should understand the functions of the following components in case the need to troubleshooting arises.


CPU


Expansion Slot


Floppy Disk Drive


Motherboard


PC Vs. Laptop


Network Interface Card


NIC Installation


Units Information


Base 2 Numbering System


Binary-to-Decimal Conversion


Base 2 Number System


Binary And Decimal Translation

27 26 25 24 23 22 21 20

128 64 32 16 8 4 2 1

10011101

128+16+8+4+1= 157


Binary And Decimal Translation

Decimal Hexadecimal Binary 0 0 0000 1 1 0001 2 2 0010 3 3 0011 4 4 0100 5 5 0101 6 6 0110 7 7 0111 8 8 1000 9 9 1001

10 A 1010 11 B 1011 12 C 1100 13 D 1101 14 E 1110 15 F 1111


Computer Basics

Internal Storage Memory A thin plate on which integrated circuit are placed Printed circuit Board A silicon chip that contains a CPU Microprocessor

Used to store and retrieve data from nonvolatile storage media

Hard Disk Drive A device for reading and writing to floppy disk Floppy disk drive An opening in the computer for expansion card Expansion Slot

A printed circuit board that can be inserted for additional functionality

Expansion Card

The computer “brain” where nearly all calculations are performed.

Central Processing Unit (CPU) Compact Disc Read-only memory CD-ROM Drive

Wires that connect the internal components to the CPU

Bus Function Component


Computer Basics

An interface that allows other devices to be connected and disconnected without resetting the system.

Universal Serial Bus (USB) An interface that communicate 1 bit at a time Serial Port

An interface that communicates more than 1 bit of information at a time. Usually used to connect devices such as printer

Parallel port A PCB that provides network access Network Card

A device that connects to pieces of equipment (a mouse and computer, for example)

Interface A connector for expansion card Socket The computer’s “main” box System Unit Prerecorded or “startup” memory Read-only Memory (ROM)

A temporary storage place for data while programs are in use. If the computer loses power, all data in RAM that was not saved is lost.

Random Access Memory (RAM)

Function Component


Reading….

Unit : 1 Topic: 1

“Introduction to Networking”


Homework to Next Class

Decimal to Binary Binary to Decimal

Decimal to Hexadecimal

Hexadecimal to Decimal

1) 85 11001100 142 0B 2) 163 01110110 25 A1 3) 45 00101011 44 45 4) 98 10011001 192 59 5) 124 01001100 201 F0 6) 146 01100000 68 1C 7) 78 10011010 99 63 8) 110 10111100 115 79 9) 246 11111001 224 AA

10) 163 01110110 169 6D 11) 210 00010101 248 0F 12) 155 10101101 55 AC 13) 186 11101001 193 FB 14) 228 10110100 10 C5 15) 137 00111001 207 89


Revisión Investigación I

1) Qué es una red de datos? y cuáles son sus aplicaciones?.

2) Qué es una red de voz? Y cuáles son sus aplicaciones?

3) Tipos de redes existentes en la Industria.

4) Aplicaciones de una red de voz y datos en la industria actual.

5) Evolución y Nuevas tendencias de las redes en la actualidad?


¿Que es una Red?

Existen varias definiciones acerca de que es una red, algunas de las cuales son:

•  Conjunto de operaciones centralizadas o distribuidas, con el fin de compartir recursos "hardware y software".

•  Sistema de transmisión de datos que permite el intercambio de información entre ordenadores.

•  Conjunto de nodos "computador" conectados entre sí.

En español: Una red son dos ó más computadoras con sus periféricos asociados conectadas por un medio de comunicación.


Ventajas de las Redes

•  Trabajar lejos de la Oficina: Cuando se encuentra viajando o en la casa puede conectarse a la red de la oficina para intercambiar mensajes y archivos.

•  Eliminar los Tenis: Se refiere a la manera física de trasladar la información de una computadora a otra para intercambiar información. Una red elimina esta necesidad.

•  Compartir Información: Las redes permiten compartir los datos y programas. Por lo tanto puede intercambiar documentos, correo electrónico, video, sonido e imágenes.

•  Compartir equipo: Las computadoras conectadas a una red pueden compartir equipo, tal como una impresora o un modem.


Aplicaciones de Red

Una red local proporciona la facilidad de compartir recursos entre sus usuarios. Esto es:

•  Compartir Ficheros. Es la prestación principal de las redes locales. La aplicación básica consiste en utilizar ficheros de otros usuarios, sin necesidad de utilizar el disquete.

•  Impresión en Red. Permiten que sus usuarios puedan acceder a impresoras de calidad y alto precio sin que suponga un desembolso prohibitivo.

•  Aplicaciones en Red. El tipo de aplicaciones más importante son los programas de correo electrónico.

•  Acceso a aplicaciones. •  Internet.


Clasificación de las Redes

Según la extensión geográfica: LAN (Local Area Network) MAN (Metropolitan Area Network) WAN (Wide Area Network)

Según la topología:

Red en anillo Red en árbol Red en malla Red en bus Red en estrella

Según el medio de transmisión:

Red cableada Red inalámbrica


Agenda

• Networking History • OSI Reference Model

• How a LAN Is Built

•  LAN Topologies

•  LAN/WAN Devices

Networking History


Evolution of Internetworking History

•  The first networks were time-sharing networks that used mainframes and attached terminals. Such environments were implemented using IBM's System Networks Architectures (SNA) and Digital's Digital Equipment Corporation (DECnet) network architecture.

•  Local area Networks (LAN) evolved around the PC revolution. LANs allowed multiple users in a relatively small geographical area to exchange files and messages, and to access shared resources such as file servers.

•  Wide area Networks (WAN) interconnect LANs across normal telephone lines (and other media), thereby interconnecting geographically dispersed users.

•  Today, high-speed LANs and Switched internetworks are becoming widely used. These internetworks operate at very high speeds and support high-bandwidth applications such as voice and video conferencing.


Early Networks

• Samuel Morse • Alexander Graham Bell

• Emile Baudot


Telephone Network

Analog Network

Bell Telephone


Telephone Network

Bell Atlantic MCI

AT&T

Pacific Bell


1960s–1970s Communications

IBM Host Computer Systems Network Architecture (SNA) •  Application Programs •  Database •  Printing

Low-Speed Access Lines

Digital Network


Problem…


Analog and Digital Signals

Digital Transmission— 1’s and 0’s

On or Off Computer-speak

1 0 1 0 0 1 1 0 1 “1” bit “0” bit

Start Bit

Stop Bit

Analog Transmission— Wires or wireless,

Audio tones Info conveyed through

signal amplitude, frequency, and phase


Solution—Modems

• Modem—Modulator/Demodulator Translates digital computer signals to analog signals which the telephone world can understand and vice versa


Solution—Modems

•  Modem—Modulator/Demodulator Translates digital computer signals to analog signals which the telephone world can understand and vice versa

Modem Modem

POTS (Plain Old Telephone Service)

Mainframe Host

POTS


Another Solution—Multiplexing

Baseband—Carries only one signal at a time

Broadband—Able to carry multiple signals simultaneously

Multiplexer—Allows multiple signals to be carried across a single physical medium

Mainframe Host


Broadband— !Wide-Area Network !(WAN)!

Baseband— !Local-Area Network!(LAN)!

Baseband versus Broadband



Digital Digital

Mainframe Host

Sunnyvale Branch

Headquarters, San Francisco

POTS



Dialup Modem Connection

Morgan Hill Branch

Digital

Mainframe Host

Headquarters, San Francisco

Digital Digital

Dedicated Leased Lines

Sunnyvale Branch

POTS


Birth of the Personal Computer

•  Applications •  File storage

•  Processing power

•  Printing options

•  Smart terminals


The Internet—1970s and 1980s

•  ARPANET—Advanced Research Projects Agency Network, Dept. of Defense

–  Developed in mid 1960s –  Funded research to universities and companies –  First packet-switched network built by BBN—Dec 1969 –  Many LANs connected to the ARPANET with TCP/IP –  Shut down in 1990 due to newer networks emerging

•  NSFNET—National Science Foundation, late 1970s –  High-speed successor to ARPANET –  Six supercomputers: San Diego, Boulder, Champaign,

Pittsburgh, Ithaca, and Princeton –  Supercomputers given a microcomputer which spoke TCP/IP –  Overloaded from the word “go”


1990s—Global Internetworking

•  1992—1 major backbone, 3,000 networks, 200K computers •  1995—Multiple backbones, hundreds of regional nets, tens of thousands

of LAN’s, millions of hosts, tens of millions of users Doubling every year!


Introduction to Internetworking

An internetwork is a collection of individual networks, connected by intermediate networking devices, that functions as a single large network.

Internetworking refers to the industry, products, and procedures that meet the challenge of creating and administering internetworks.


Internetworking Benefits

Connectivity - The challenge of connectivity is to support communication between disparate technologies, such as different media types or speeds.

Reliability - Reliable service is a must in any

internetwork. Individual users and whole organizations are dependent on getting consistent, reliable access to network resources.


Internetworking Benefits

Management - Network management must provide

centralized support and troubleshooting capabilities in an internetwork. Configuration, security, performance, and other issues must be adequately addressed in order for the internetwork to function smoothly.

Flexibility - Flexibility is a necessity in the face of network expansion, new applications and services, and other such factors.


Needs for Internetworking

Three problems gave birth to the internetworking industry:

•  Isolated LANs -- Electronic communication between

different offices or departments was impossible. •  Duplication of resources -- The same hardware and

software had to be supplied to each office or department. A separate, complete support staff had to be deployed at each site.

•  Lack of network management -- There was no centralized way to manage and troubleshoot networks.

OSI Reference Model


Agenda

•  The Layered Model •  Layers 4–7: Transport,

Session, Presentation, and Application Layers

•  Layer 3: Network Layer •  Layers 1 & 2: Physical &

Data Link Layers

The Layered Model


Open Systems Interconnection (OSI) Reference Model Overview

The Open Systems Interconnection (OSI) reference model is a conceptual model composed of seven layers, each specifying particular network functions. The OSI model describes how information from a software application in one computer moves through a network medium to a software application in another computer. The model was developed by the International Organization for Standardization (ISO) in 1984. It is now considered the primary architectural model for intercomputer communications.


Open Systems Interconnection (OSI) Reference Model Overview

The Open Systems Interconnection (OSI) reference model is a standardized framework for network functions and schemes. It breaks otherwise-complex network interactions into simple elements, wich lets developers modularize design efforts. This methods allows many independent developers to work on separate network functions, which can be applied in a “plug and play” manner.


Layered Communication

Source: Tanenbaum, 1996

I like rabbits

L: Dutch Ik hou van konijnen

Fax #:--- L: Dutch Ik hou van konijnen

Message

Information for the Remote Translator

Information for the Remote Secretary

Location A



I like rabbits





J’aime les lapins

Information for the Remote Translator

Information for the Remote Secretary

Location A Location B

Message



I like rabbits





J’aime les lapins

Information for the remote translator

Information for the remote secretary

Location A Location B

1

2

3 Layers

Message


Why a Layered Network Model?

7   Application

7   Presentation

7   Session

7   Transport

7   Network

7   Data Link

1 Physical

•  Reduces complexity (one big problem to seven smaller ones)

•  Standardizes interfaces •  Facilitates modular

engineering •  Assures interoperable

technology •  Accelerates evolution •  Simplifies teaching and

learning


Why a Layered Network Model?


Devices Function at Layers

7   Application

7   Presentation

7   Session

7   Transport

7   Network

7   Data Link

1 Physical

NIC Card

Hub


Host Layers

7 Application

6 Presentation

5 Session

4 Transport

3   Network

2 Data Link

1 Physical

Host layers: Provide accurate data delivery between computers }


Media Layers

Host layers: Provide accurate data delivery between computers

(Upper layers)

Media layers: Control physical delivery of messages over the network (Lower layers)

} } Application

Presentation

Session

Transport

Network

Data Link

Physical


Layer Functions

Provides network services to application processes (such as electronic mail, file transfer, and terminal emulation)

7 Application


Layer Functions

Network services to applications

•  Ensures data is readable by receiving system

•  Format of data •  Data structures •  Negotiates data transfer

syntax for application layer

7 Application

6 Presentation Data representation


Layer Functions

Inter-host communication •  Establishes, manages, and

terminates sessions between applications

!

7 Application

6 Presentation

5 Session


Data representation


Layer Functions

!

7 Application

6 Presentation

5 Session

Transport 4

Inter-host communication


Data representation

End-to-end connection reliability •  Concerned with data transport

issues between hosts •  Data transport reliability •  Establishes, maintains, and

terminates virtual circuits •  Fault detection and recovery •  Information flow control


Layer Functions

7 Application

6 Presentation

5 Session

Transport 4

Network 3



Data representation

End-to-end connection reliability

Addresses and best path •  Provides connectivity and path

selection between two end systems

•  Domain of routing


Layer Functions

!

7 Application

6 Presentation

5 Session

Transport 4

Network 3

Data Link 2



Data representation


Addresses and best path

Access to media •  Provides reliable transfer of data

across media •  Physical addressing, network

topology, error notification, flow control

Physical 1


Layer Functions

!

7 Application

6 Presentation

5 Session

Transport 4

Network 3

Data Link 2

Physical 1



Data representation


Addresses and best path

Access to media

Binary transmission •  Wires, connectors, voltages,

data rates


Layered Interchange

!

Application

Presentation

Session

Transport

Network

Data Link

Physical

PDU

Segment

Packet

Frame

Bit

Upper Layer Data

Data Network Header

Transport Header Upper Layer Data

MAC Header Data

01011101010010000101000101

FCS

LLC Header Data FCS


7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

Host A

Peer-to-Peer Communications

Application

Presentation

Session

Transport

Network

Data Link

Physical Bits

Frames

Packets

Segments

Host B


OSI Communication Process


Data Encapsulation

Application

Presentation

Session

Transport

Network

Physical

Data Link

Application

Presentation

Session

Transport

Network

Physical

Data Link

Host A Host B

Data } {


Data Encapsulation

Application

Presentation

Session

Transport

Network

Physical

Data Link

Application

Presentation

Session

Transport

Network

Physical

Data Link

Data } { Data Network

Header

Host A Host B


Data Encapsulation

Application

Presentation

Session

Transport

Network

Physical

Data Link

Application

Presentation

Session

Transport

Network

Physical

Data Link


Header

Frame Header

Frame

Trailer Data Network

Header

Host A Host B


Data Encapsulation

Application

Presentation

Session

Transport

Network

Physical

Data Link

Application

Presentation

Session

Transport

Network

Physical

Data Link


Header

Frame Header

Frame

Trailer Data Network

Header

0101101010110001

Host A Host B


Data Encapsulation


What is a Protocol?

A protocol is a formal set of rules and conventions that govern how computers exchange information over a network medium. A protocol implements the functions of one or more layers of the OSI Model.

There are a wide variety of communication protocols:

•  LAN Protocols: Ethernet, Token Ring, FDDI

•  WAN Protocols: Frame Relay, PPP

•  Routing Protocols: RIP, EIGRP

•  Routed Protocols: TCP/IP


Remaining Chapter Sequence

Network Applications

End-to-end Services

Routing

Data Transmission


ISO Hierarchy of Networks

Nomenclatura OSI: End System: Pc’s Intermediate System: Routers Area: Local Network Autonomous System: Network Organization

Layers 4–7: Transport, Session, Presentation, and Application Layers


Application Layer

Word Processor

Presentation Graphics Spreadsheet

Database

Design/Manufacturing

Project Planning

Others

COMPUTER APPLICATIONS

Electronic Mail

File Transfer Remote Access

Client-Server Process

Information Location

Network Management

Others

NETWORK APPLICATIONS INTERNETWORK

APPLICATIONS

Electronic Data Interchange

World Wide Web E-Mail Gateways

Special-Interest Bulletin Boards

Financial Transaction Services

Internet Navigation Utilities

Conferencing (Voice, Video, Data)

Others •  Internetwork applications

can extend beyond the enterprise (i.e., to suppliers, etc.)


Presentation Layer

ASCII EBCDIC Encrypted

• Text • Data

login:

PICT TIFF JPEG GIF

• Graphics • Visual images

• Sound

• Video MPEG QuickTime

MIDI

•  Provides code formatting and conversion for applications


Session Layer

•  Network File System (NFS) •  Structured Query Language (SQL) •  Remote-Procedure Call (RPC) •  X Window System •  AppleTalk Session Protocol (ASP) •  DEC Session Control Protocol (SCP)

Service Request

Service Reply

•  Coordinates applications as they interact on different hosts

Layers 4: Transport Layers

© 1999, Cisco Systems, Inc. www.cisco.com


Transport Layer

•  Segments upper-layer applications •  Establishes an end-to-end connection •  Sends segments from one end host to another •  Optionally, ensures data reliability


Transport Layer— Segments Upper-Layer Applications

Electronic Mail

File Transfer

Application

Presentation

Session

Segments

Data Application

Port Transport Data

Application Port

Terminal

Session


Multiplexing Basics

Multiplexing is a process in which multiple data channels are combined into a single data or physical channel at the source. Multiplexing can be implemented at any of the OSI layers. Demultiplexing is the process of separating multiplexed data channels at the destination.


Transport Layer— Establishes Connection

Synchronize

Synchronize

Acknowledge

Negotiate Connection

Receiver

Data Transfer

Connection Established

(Send Segments)

Sender


Connection-Oriented Sessions

Connection-oriented service involves three phases:


Connectionless Network Service

Connectionless network service does not predetermine the path from the source to the destination system, nor are packet sequencing, data throughput, and other network resources guaranteed. Each packet must be completely addressed because different paths through the network might be selected for different packets, based on a variety of influences. Each packet is transmitted independently by the source system and is handled independently by intermediate network devices.


Transport Layer— Sends Segments with Flow Control

Transmit

Buffer Full Not Ready Stop Process Segments

Buffer OK Ready Go

Resume Transmission

Receiver Sender


Buffering

Buffering is used by network devices to temporarily store bursts of excess data in memory until they can be processed.


Source Quench Messages

Source quench messages are used by receiving devices to help prevent their buffers from overflowing.


Transport Layer— Reliability with Windowing

• Window Size = 1

Sender

Send 1 Receive 1

Receiver

Ack 2

Send 2 Receive 2 Ack 3

Sender

Send 1 Send 2

Receive 1 Receive 2

Receiver

• Window Size = 3

Send 3 Receive 3 Ack 4

Send 4


Reliability with Windowing

Windowing is a flow-control scheme in which the source device requires an acknowledgement from the destination after a certain number of packets have been transmitted.


Transport Layer— An Acknowledgement Technique

Sender Receiver

Send 2 Send 1

Send 3 Ack 4

Send 5 Send 4

Send 6 Ack 5

Send 5 Ack 7

1 2 3 4 5 6 7 1 2 3 4 5 6 7


Error Checking Basics Error-checking schemes determine whether transmitted data has become corrupted or otherwise damaged in traveling from source to destination. Error checking is implemented at a number of the OSI layers. One common error-checking scheme is the cyclic redundancy check (CRC).


Transport to Network Layer

End-to-End Segments

Routed Packets


Summary

•  The ISO/OSI reference model describes network applications

•  Presentation layer formats and converts network application data to represent text, graphics, images, video, and audio

•  Session-layer functions coordinate communication interactions between applications.

•  Reliable transport-layer functions include: –  Multiplexing –  Flow control –  Reliability with Windowing

Layer 3: Network Layer



Network layer

The network layer provides routing and related functions that allow multiple data links to be combined into an internetwork. This is accomplished by the logical addressing (as opposed to the physical addressing) of devices. The network layer supports both connection-oriented and connectionless service from higher-layer protocols.

www.cisco.com © 1999, Cisco Systems, Inc.

What is Routing?


What Is Routing?

•  Routing is: – Finding a path between a source and

destination (path determination) – Moving information across an internetwork

from a source to a destination (switching*) – Very complex in large networks because

of the many potential intermediate nodes

•  A router is: – A network layer device that forwards packets

from one network to another and determines the optimal path for forwarding network traffic

* The term “switching”, when used to describe a router’s function, is different from a switch (the network device).


Routing Table 192.168.3.0 Frame Relay 192.168.1.0 Ethernet 192.168.2.0 FDDI

Network 192.168.2.0 FDDI

Network 192.168.3.0 Frame Relay

Remote Location

Network 192.168.1.0 Ethernet

Main Site

Routers—Layer 3


• LAN-to-LAN connectivity • LAN-to-WAN connectivity

• Remote access

Where are Routers Used?


Path Determination

1

2

3

4

5

6

7

8 9

10 11

•  Routers find the best path through the network

–  Routing tables contain route information

–  Network addresses represent the path of media connections to a destination

Which Path?


Path Determination

•  Routers find the best path through the network

–  Routing tables contain route information

–  Network addresses represent the path of media connections to a destination


Network Layer: Communicate Path

1

2

3

4

5

6

7

8 9

10 11

•  Addresses represent the path of media connections

•  Routing helps contain broadcasts


Routing Tables

•  Routing algorithms –  Initialize and maintain

routing tables to help with path determination

•  Route information types –  Destination/next-hop associations –  Path desirability –  Vary depending on routing algorithm

•  Message = Routing table maintenance communications –  Routing update messages –  Link-state advertisement

To Reach Send

Network: To:

27 Node A 57 Node B 17 Node C 24 Node B 11 Node B 72 Node A


Routing Algorithm Goals

•  Optimality –  Selecting the best route based on metrics and

metric weightings used in the calculation

•  Simplicity and low overhead –  Efficient routing algorithm functionality with a

minimum of software and utilization overhead

•  Robustness and stability –  Correct performance in the face of unusual

or unforeseen circumstances (e.g., high load)

•  Rapid convergence –  Fast agreement, by all routers, on optimal routes

•  Flexibility –  Quick and accurate adaptation to changes in

router availability, bandwidth, queue size, etc.


Routing Metrics

•  Path length –  Total hop count or sum of cost per network link

•  Reliability –  Dependability (bit error rate) of each network link

•  Delay –  Useful because it depends on bandwidth, queues, network

congestion, and physical distance

•  Communication cost

–  Operating expenses of links (private versus public)

•  Bandwidth and load


Hierarchical versus Flat Address Space


Network and Node Addresses

Network Node

1

2

1 2 3

1

3 1

1.1

2.1

3.1

1.2

1.3

•  Network address—Path part used by the router •  Node address—Specific port or device on the network

1

2

3


Addressing Examples: Protocol Addressing Variations

Network Node/Host Protocol Address Address General 1. 4

TCP/IP 10. 8.2.48

Novell IPX 1aceb0b 0000.0c00.6e25

AppleTalk 10. 1.

X.25 DNIC NTN NTN: National Terminal Number


Address Assignment

Addresses are assigned to devices in one of three ways:

• Static: Static addresses are assigned by a network administrator. Static address does not change until the network administrator manually changes it. • Dynamic: Dynamic addresses are obtained by devices when they attach to a network. • Server: Addresses assigned by a server are given to devices as they connect to the network. Server assigned addresses are recycled for reuse as devices disconnect. A device is therefore likely to have a different address each time it connects to the network.


131.108.0.0 INTERNET

131.108.1.0

131.108. 2 .0 131.108. 3 .0

131.108. 5 .0

131.108. 4 .0

131.108. 8 .0 131.108. 6 .0

131.108. 7 .0

131.108. 10 .0

131.108. 9 .0

Subnetwork Addressing

Manufacturing

R&D

Subdividing address space into smaller blocks

–  Helps organize network

–  Security (keeps HR separately addressable)

–  Scalability—Keeps traffic to appropriate segments

–  Allows single, summarized routing entry (131.108.0.0) to be advertised to external networks

–  Specific route entries (131.108.8.0) required only for routers in the subnetted block

HR


Network Layer: Path Switching

• Each router provides its services to support upper layer functions

X Y

A A

C C


Routers: Path Switching (Layer 3)


Network Layer Protocol Operations

• Each router provides its services to support upper layer functions

B B

X Y

A A

C C

Presentation

Data Link Physical

Data Link Physical

Router A Router B Router C

Data Link Physical

Data Link Network Transport Session Presentation Application

Physical

Host X Host Y

Data Link Network Transport Session

Application

Physical

Network Network Network


Multiprotocol Routing

IP 15.17.132.6

IP 15.16.42.8

IP 15.16.50.3

Routing Tables

IP

Token Ring

Token Ring

AppleTalk 200.167

AppleTalk 100.110

Apple IPX 4b.0800.0121.ab13

IPX 3a.0800.5678.12ab

Novell

DECnet 5.8

DECnet 10.1

DEC

VAX

VAX

•  Routers pass traffic from all routed protocols over the internetwork


Routed Versus Routing Protocol

• Routed protocol used between routers to direct user traffic

1.0 2.0

3.0

1.1 2.1 3.1

Destination Network

Network Protocol

Protocol Name

Examples: IP, IPX, AppleTalk, DECnet Exit Port

to Use


Routed Versus Routing Protocol

• Routed protocol used between routers to direct user traffic

Examples: IP, IPX, AppleTalk, DECnet

• Routing protocol used only between routers to maintain routing tables

Examples: RIP, IGRP, OSPF


Static Versus Dynamic Routes

Uses a protocol route that a network administrator enters into the router

Static Route

Uses a route that a network protocol adjusts automatically for topology or traffic changes

Dynamic Route


Static Routing

“Stub” Network

A

B

•  Manual table updates by a network administrator

•  Benefits –  Reflects administrator’s special

topology knowledge –  Private—Not conveyed to other

routers in updates –  Avoids the overhead of dynamic

routing

•  Stub network –  When a node is accessible by

only one path, a static route is sufficient

–  Point-to-point or circuit-switched connection

connection with no need Only a single network

for routing updates


Summary

• Routers move data across networks from a source to a destination

• Routers determine the optimal path for forwarding network traffic

• Routing protocols communicate reachability information between routers

Layers 1 & 2: Physical & Data Link

Layers



Data Link layer

The data link layer provides reliable transit of data across a physical network link.


Data Link Sublayer

The Logical Link Control (LLC) sublayer of the data link layer manages communications between devices over a single link of a network. Logical Link Control (LLC) is the upper sublayer of the OSI data link layer. 1.  The LLC sublayer is primarily concerned with:

Multiplexing protocols transmitted over the MAC layer (when transmitting) and demultiplexing them (when receiving). that make it possible for several network protocols (IP, IPX, Appletalk) to coexist within a multipoint network and to be transported over the same network media

2.  Providing flow control and detection and retransmission of dropped packets, if requested.

LLC is defined in the IEEE 802.2 specification.


Data Link Sublayer

The Media Access Control (MAC) sublayer of the data link layer manages protocol access to the physical network medium.


Physical layer The physical layer defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between communicating network systems. Different data link layer specifications define different network and protocol characteristics, including the following:

•  Physical addressing •  Network topology •  Error notification •  Sequencing of frames •  Flow control


Physical & Data link Layer

The physical and data link layers are usually implemented together in hardware/software combination solutions. Examples include: hubs, switches, and network adapters, and their applicable software drivers, as well as the media or cables used to connect network nodes. The IEEE (Institute of Electrical and Electronics Engineers) created several standards under the 802 series.


Remaining Chapter Sequence

Application User Interface Telnet, HTTP

Presentation Encryption and other processing ASCII /EBCDIC

Session Manages multiple Applications Operating System

Transport Provides reliable or best-effor delivery and some error correction

TCP, UDP, SPX

Network Provides logical addressing used by routers and the network hierarchy.

IP, IPX

Data link Creates frames from bits of data Uses MAC Address to access endpoints Provides error detection but not correction

802.3 802.2 HDLC, Frame relay

Physical Specifies voltage, wire speed, and cable pin outs

EIA/TIA V.35

OSI MODEL

LAN

WAN


En español…..

Exercises


Internetworking Addressing

Internetwork addresses identify devices uniquely or as a member of a group. Addressing schemes vary depending on the protocol family and the layer of the OSI model. Three types of internetwork addresses are commonly used:

• Data link layer addresses • Media Access Control (MAC) addresses • Network layer addresses


Physical and Logical Addressing

0000.0c12.3456


Data Link layer Addresses

A data link layer address uniquely identifies each physical network connection of a network device. Data link addresses are sometimes referred to as physical or hardware addresses. End systems typically have only one physical network connection, and thus have only one data link address. Routers and other internetworking devices typically have multiple physical network connections.


Data Link layer Addresses


Network layer Addresses

A network layer address identifies an entity at the network layer of the OSI reference model.They are sometimes called virtual or logical addresses. The relationship of a network address with a device is logical and unfixed. It is typically based either on physical network characteristics (the device is on a particular network segment) or on groupings that have no physical basis


MAC Address

MAC addresses are 48 bits in length and are expressed as 12 hexadecimal digits:

•The first 6 hexadecimal digits are the manufacturer identification (or vendor code), called the Organizational Unique Identifier (OUI). These 6 digits are administered by the IEEE. •The last 6 hexadecimal digits are the interface serial number or another value administered by the specific vendor.


MAC Address

24 bits

ROM RAM

24 bits

0000.0c12. 3456 Serial Number Vendor Code

•  MAC address is burned into ROM on a network interface card


Address Resolution

Address resolution is the process of mapping network addresses to Media Access Control (MAC) addresses. This process is accomplished using the Address Resolution Protocol (ARP).

When a network address is successfully associated with a MAC address, the network device stores the information in the ARP cache.


Address Resolution on a single LAN


Address resolution Across LAN


Routers: Path Switching (Layer 3)


Hello Protocol

The Hello protocol is a network layer protocol that allows network devices to identify one another and indicate that they are still functional.


Summary

• OSI reference model describes building blocks of functions for program-to-program communications between similar or dissimilar hosts

• Layers 4–7 (host layers) provide accurate data delivery between computers

• Layers 1–3 (media layers) control physical delivery of data over the network

Exercises

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Technology

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