LAN and WAN Technologies Networking/internetworking Hardware

LAN and WAN Technologies

Networking/internetworking Hardware and Software

Preliminaries in Network Design

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Networking and internetworking

• Networking

connecting of a computer or device (station, host, end-system,

end-node) to another

• Internetworking

connecting of a network to another

• Protocol

a set of rules that controls how communications take place

• Local Area Network (LAN):

in general connecting stations geographically close to each other,

e.g., within a building

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• Wide Area Network (WAN):

connecting multiple LANs

Remark: Speed cannot be used to differentiate LANs from WANs any

more. Traditionally, WANs were slower in speed than LANs. WANs

can be faster than LANs nowadays however – the maximum speed of

a WAN can be higher than that of a LAN.

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Internetworking Technology



��

��The OSI Model



��

��The OSI Model

• developed by the International Organization for Standardization

(ISO)



��

��The OSI Model


(ISO)

• Seven layers: physical, data link, network, transport, session, pre-

sentation, and application layers



��

��The OSI Model


(ISO)

• Seven layers: physical, data link, network, transport, session, pre-

sentation, and application layers

? Physical

defines the electrical, mechanical, procedural, and functional spe-

cifications – transmission of (raw) signals (bits)

? Data link

provides a reliable transit of data across a physical link, concerned

with physical addressing, network topology, line discipline, error

notification, the ordered delivery of frames, and flow control.

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? Network layer

It provides connectivity and path selection between two end

systems. Routing occurs at this layer.

Protocols examples

• TCP/IP

? Layer 3 and above protocol

? can be implemented on a LAN or WAN

• LAN Protocols

? layers 1 and 2 of the OSI model

? Ethernet (derivatives: Fast Ethernet, Gigabit Ethernet and 10

Gigabit Ethernet)

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? Token ring

? FDDI (Fiber Distributed Data Interface)

• WAN Protocols

? ATM

? X.25

? Frame relay

��

��WAN Protocols

operates at layers 1 and 2 of the OSI model

• High Level Data Link Control (HDLC)

HDLC is the primary protocol used for point-to-point serial lines

• Frame Relay

? a packet-switched service

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? permanent virtual circuits (PVCs)

? switched virtual circuits (SVCs)

? lower rate, not so expensive

• Asynchronous Transfer Mode (ATM)

? packet-switched network

? packets are of fixed length, called cells of 53 bytes long

? can carry both voice and data

? in general expensive

• Integrated Services Digital Network (ISDN)

a circuit-switched service digital dial-up, use the existing telephone

local loop circuits offers two simultaneous connections (each of 64

kbps)

• Digital Subscriber Line (DSL)/Cable modem

rate of a few Mbps

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Routed versus Routing Protocols

• A routed protocol contains network, Layer 3, and addressing infor-

mation

enables the protocol to be directed from one network to another.

• A routing protocol provides support to a routed protocol by sharing

routing information

distributed among routers.

Routed protocols Routing Protocols

TCP/IP RIP, OSPF, EIGRP,BGP

IPX/SPX RIP, EIGRP, NLSP

AppleTalk RTMP, EIGRP

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��

��Protocols in other layers

Transmission Control Protocol/Internet Protocol (TCP/IP)

• most commonly used protocol

• used on the Internet exclusively

TCP/IP protocols does not quite follow the OSI model.

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OSI model TCP/IP

Application FTP, HTTP, Telnet

Presentation

Session

Transport TCP, UDP

Network IP, ARP, ICMP

Data link LAN/WAN Protocols

Physical Physical

• The Internet Protocol IP

provides a best-effort, connectionless packet delivery service

• The Address Resolution Protocol (ARP)

used to discover the link address (e.g., IP address), or media access

control (MAC, also known as hardware address) (e.g. Ethernet

address)

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• The Internet Control Message Protocol (ICMP)

? used to report network errors, refer to the ping command.

TCP/IP Transport layer

• the basis for all user data traffic

• TCP

TCP is a connection-oriented.

• UDP

UDP is a connectionless protocol.

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TCP/IP application layer

• File Transfer Protocol (FTP)

to transfer files between hosts

• Hypertext Transfer Protocol (HTTP)

web page access

• Telnet

a terminal emulation application

TCP/IP Routing Protocols

• RIP

? the first TCP/IP routing protocol

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? distance vector protocol, uses a hop count metric

? at most 15 hops

? does not support multiple subnet masks

? RIP version 2

∗ enables multiple subnet masks, 255 hops

∗ a classless protocol

• Interior Gateway Routing Protocol (IGRP)

? Cisco proprietary

? distance vector routing protocol

? The Enhanced IGRP (EIGRP)

∗ integrates several link-state

∗ capabilities with several distance vector capabilities

∗ supports multiple subnet masks and is a classless protocol

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• Open Shortest Path First (OSPF)

? a link-state routing protocol

? supports multiple subnet masks

? a classless protocol

? supports an unlimited number of hops

• The Border Gateway Protocol (BGP)

? the routing protocol of the Internet

? performs routing between multiple autonomous systems (ASs)

? also a classless protocol

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��

��IP Addressing

• An IP address is composed of 32 bits.

• can be represented in binary dotted or decimal dotted

? artificially inserting three dots to divide the 32 bits into four

groups, each of 8 bits

• divided to a network portion and a host portion

• Devices on the same LAN will have the same network portion but

a unique host portion.

To determine the network portion, a mask is used.

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��

��Network (subnet) mask

• A network mask (32 bits) is used to determine the network portion

• format: all 1’s followed by all 0’s

• The network is always represented by a binary 1 in the subnet mask.

? Classical (classful) IP divides the address space into Class A, B,

and C networks by dividing the 32-bit address on 8-bit (byte)

boundaries.

? Classless IP divides, or subnets, these classic networks into smaller

networks by breaking them on bit boundaries.

• Subnetting:

borrows bits from the host portion

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Internetwork Packet Exchange/Sequenced Packet Exchange

(IPX/SPX) protocol suite

• Novell NetWare

AppleTalk protocol

• Apple Computer Inc.

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Network Topology Overview

• Ethernet

• Ring

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Basic Ethernet

• developed in the late 70s at the Palo Alto Research Center (PARC)

of Xerox

• Variation: 10 Gigabit, Gigabit and Fast Ethernet

• Ethernet is simply a group of devices that access a common shared

medium, a cable, to exchange information.

? Operations: Carrier Sense Multiple Access and Collision Detection

(CSMA/CD) – collisions deterorate throughput performance

? A broadcast network: collison domain and broadcast domain

• Network equipment for an Ethernet network: hubs, bridges/switches,

and routers.

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Ethernet types

• denoted as e.g., 10BaseT, Speed-Signaling-Media

• Speed (the first part): the speed in Mbps

• Signaling: the signaling type

Base: baseband signaling

• Media: the media type

Media type:

• T: unshielded twisted pair (UTP) cable

The maximum transmission distance is 100 meters

• F: fiber-optic cable.

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The maximum transmission distance depends on the specific sub-

type. e.g., for FB, the maximum transmission distance is 2000

meters.

Hubs

• Networking equipment, also known as repeaters since they just

repeat what they receive

• can be used to extend networks

• may not have too many hubs

• not suitable for large and complex networks

? Maximum 4 repeaters between source and destination (Ethernet)

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Bridges/Switches

• Networking equipment that operate at layer 2 of the OSI model

• segment traffic based on layer-2 or MAC addresses

• to isolate user traffic

• To reduce the number of users in a collision domain

? Collision domain:

the same shared media

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• Bridges segment a network into several collision domains

• The collision domains are still considered the same LAN

• The use of more repeaters (for Ethernet) is made possible

��

��Routers

• Segment broadcast domains (the whole LAN network)

• Routers will never propagate a broadcast.

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• A router is also the boundary of a LAN.

• Connects two LANs or connects a LAN with a WAN

• Operates at layer 3 of the OSI model

• more complex and expensive

• require more configuration

Routers base their decisions on network and sub-network addresses. A

subnet mask is used to extract the network address. For example (IP)

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• host address 158.132.148.222 AND subnet mask 255.255.254.0 gi-

ves net address 158.132.148.0

• host address 158.132.149.222 AND subnet mask 255.255.254.0 gi-

ves net address 158.132.148.0

Routing protocols classification

• distance vector

• link state

Distance Vector Link StateRIP OSPF

IGRP NLSP

IPX RIP IS-IS

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NLSP: the NetWare Link-Service Protocol, similar to OSPF and

Intermediate System-to-Intermediate System (IS-IS), developed to

overcome many of the issues associated with IPX RIP.

Seven layer model and networking equipment

Commonly used symbols

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Ring Topology

Stations are (logically) connected in a ring topology.

Physically, stations are connected in a star topology. (Remarks:

stations in an Ethernet are connected in a star topology.)

Bridges, switches, and routers behave almost identically to their

Ethernet counterparts.��

��Fiber Distributed Data Interface (FDDI)

• 100 Mbps

• token-passing LAN technology

• dual fiber-optic rings

• often used as a high-speed backbone.

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LAN to LAN/WAN Routers

LAN Hubs, bridges, switches, (switch-routers)

WAN to LAN Firewall, network address translation (NAT)

��

��Routers

• small-office

inexpensive, does not support FDDI and ATM

Example: Cisco 2500 series

(fixed LAN ports, 2 WAN interface cards (WICs))

• mid-range

Example: Cisco 4000/3600 series

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three modular slots for network processing modules (NPMs);

(Each NPM holds one or more (Ethernet/ATM/DS3) ports.) A

maximum of two high-speed interfaces

• high-end routers

Examples: 7000/7500 series and the Cisco 12000 Gigabit Switch

Router (GSR) series

used at the core of your network as a backbone router or the

core of service provider and enterprise IP backbones

��

��LAN Switches

• used to connect end users to the network

• provide large quantities of ports

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• Examples: Cisco 2900XL and 3500XL series, Cisco Catalyst 1900

switches

��

��Other Hardware

• ISDN/DSL routers

Example: Cisco 700 and 800 series

• Remote Access Routers

• Firewall

Example: Cisco’s PIX

• ATM switches

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��

��Software

• Internetworking Operating System (IOS) Software

Example: Cisco

makes the routing decisions on a router

• The Linux OS

? the route command (for static routing)

? zebra: a set of programs that implement various routing algorithms

(e.g., RIP, OSPF)

? iptables: firewall and NAT

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Related issues

• Networking technology used

• Hardware

��

��Framework Triplet (Triangle)

Media Protocols

Transport

• related to layers 2 and 3 of the OSI model

• helps identify possible solutions

? Protocol problems

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? Media problems

? Transport problems

��

��Protocols problems

Examples:

• RIP cannot be used with Variable Length Subnet Masks (VLSMs)

• NETBIOS cannot be routed

��

��Media

• related to layer 2

• Example

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? 10 stations to a hub in a 10 Mpsb Ethernet, maximum 1 Mbps

for each station

? 10 stations to switch in 10 Mbps Ethernet, maximum 10 Mbps

for each station

∗ microsegmenting: each station resides in their own collision

domain

• Similarly in a token ring network: a layer 2 device can reduce the

number of devices in a ring and hence reduce the waiting time.

• Media problem example in a WAN:

100Kbps of traffic cannot be transmitted on a circuit of rate 64

Kbps

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��

��Transport

• Specific types of traffic cannot be carried in a network

• Example

analog (native voice) signal cannot be carried on Ethernet

• speed of the network:

use a faster network

• voice and data traffic over a WAN circuit

? ATM

? Multiprotocol label switching (MPLS)

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Design Principles��

��Example: Hierarchical Design - The Three-Layer Approach

Three layers

• the core layer

provides the backbone transport services

• the distribution layer

provides policybased connectivity

• the access layer

provides end-user access to the network

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Advantages

• Easier to understand

• Easier to troubleshoot

• Easier to grow

��

��The Core Layer

• the backbone of the network

• provides reliable, high-speed communications to all distribution

layers of the network

• can encompass both WAN and LAN technologies

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• High reliability: crucial

• Redundancy and fault tolerance

• Adaptability

• Limited size or diameter

• Low latency and fast processing

• Manageability

��

��The Distribution Layer

• the interface between the core and the access layers

• policy-based connectivity

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• implemented in routers and switches

• Route redistribution and address summarization:

various routing protocols

• Media translations

• Network Address Translation (NAT)

• QoS

• Access-list filtering: restrict any unwanted traffic

• Encryption:

not in the core layer since it will introduces latency

not in the access layer (it would imply multiple encryption processes.)

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��

��The Access Layer

• provides network access for all end stations

• generally implemented with hubs and switches

• raw network connectivity

��

��Summary

• Two design fundamentals

? the framework triangle

? the three-layer hierarchy

• Fundamentals of technology and equipment

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Documents

LAN and WAN Technologies Networking/internetworking Hardware