Understanding Wide Area Networks

Lesson 7

Objectives

Skills/Concepts Objective Domain Description

Objective Domain Number

Understanding routing

Understanding routers

2.2

Defining common WAN technologies and connections

Understanding wide area networks (wan’s)

1.3

• Routing is the process of managing the flow of data between network segments and between hosts or routers

• Data is sent along a path according to the IP networks and individual IP addresses of the hosts

• A router is a network device that maintains tables of information about other routers on the network or internetwork

Routing

• A static route is a path that is manually configured and remains constant throughout the router’s operation

• A dynamic route is a path that is generated dynamically by using special routing protocols

Static and Dynamic Routing

Static

Dynamic

• Dynamic routing method has two conceptual parts:• Routing protocol used to convey information about the network environment• Routing Algorithm that determines paths through the network

• Common Dynamic routing protocols:• Distance vector routing protocols: Advertise the number of hops to a network

destination (distance) and the direction a packet can reach a network destination (vector). Sends updates at regularly scheduled intervals, and can take time for route changes to be updated

• Link state routing protocols: Provide updates only when a network link changes state

• Distance Vector Routing• Routing Information Protocol (RIP)

• Link State Routing• Open Shortest Path First (OSPF)

Dynamic Routing

• Routing protocols that enable elements that comprise an autonomous system (AS) to exchange routing information

• For very large networks it is necessary to divide the internetwork into entities known as autonomous systems (AS)

• IGPs exchange routing information within a single AS that operates common routing protocols

• RIP and OSPF are examples of IGPs

Interior Gateway Protocols (IGPs)

AS

AS

RIPOSPF

RIPOSPF

• Distance vector routing protocol that enables the exchange of IP routing information

• Calculates the direction or interface that packets should be forwarded to, as well as the distance from the destination

• Each router maintains a database of the number of hops to a network destination (distance) and the direction a packet can reach a network destination (vector)

• RIP is easy to implement and has a large installed base• Updates are sent periodically

Routing Information Protocol (RIP and RIPv2)

• A link-state protocol that monitors the network for routers that have a change in their link state

• Each router maintains a database of router advertisements called Link State Advertisements (LSAs)

• An LSA consist of a router, attached networks and their configured costs

• Updates are sent when the status of a route is updated

Open Shortest Path First (OSPF)

• A routing protocol that was designed and intended for use between autonomous systems

• Border Gateway Protocol (BGP) is an EGP that enables autonomous systems (AS) to exchange routing information

• BGP is used to enable routing on the Internet

Exterior Gateway Protocols (EGPs)

AS

AS

RIPOSPF

RIPOSPF

BGP

DEMO: Configuring RRAS Server (verify RIP)

• Wide area networks (WANs) connect multiple local area networks together

• WANs connect multiple LANs that can include a home, school, or buildings

• WANs enable network to function without concern to a location

• WAN technologies can include:• Packet Switching: Devices transport packets via shared links• Leased Line: Dedicated point to point connection• Circuit Switching: Dedicated circuit path is created between end points (dial up)• Cell Relay: Similar to packet switching but uses fixed packet lengths

Wide Area Network

• WANs utilize some type of packet switching technology • Packet switching services include X.25 and Frame Relay• Before packet switching, technology such as direct dial-up

connections was used

Packet Switching

• X.25 communications protocol was one of the first implementations of packet switching

• Data Terminal Equipment (DTEs) or a network device, connect to Data Communications Equipment (DCEs), a modem is a DCE enabling communication to the X.25 network

• Dummy terminals can connect to the network using Packet Assembler/Disassembler (PADs) which connect to the DCE

X.25

Modem (DCE)DTE X.25

Network

• Telecommunication companies have thousands of shared circuits / connections from which to select a path• These are known as a circuit set

• The chances of the entire message of packets taking one circuit are slim

• Multiple circuits are being used, and not just one, the entire circuit set is known as the virtual circuit

• This method of data transmission is the core technology for the Internet and most LANs

Virtual Circuits

• There could be several PSE stops along the way• These PSEs disassemble and reassemble the packets• These stops are also known as hops• At the receiving office, the packet is reassembled and the

overhead (header and trailer) is discarded

Hops

• If data fails, X.25 automatically recovers and sends it again• X.25 allows shared access among multiple users on the LAN

• X.25 has full error and flow control• There is also protection from intermediate link failure

• X.25 is not completely fault tolerant, but it is 70% effective

• Pricing is per shared packet sent, not per minute• X.25 is a synchronous, digital transmission. There is less overhead per file

X.25 Advantages

• Frame Relay is the advancement of X.25 packet switching• A standardized wide are network protocol using a form of

packet switching designed for faster connections • It also uses a virtual circuit, but one that is more

advanced. Frame Relay created the “virtual network” that resides in the cloud

Frame Relay

• A permanent virtual circuit is a virtual circuit established for repeated use

• Frame Relay enables multiple sessions to be run simultaneously on the same link

• These connections to the cloud are known as permanent logical links or permanent virtual circuits (PVCs)

• The PVC links the sites together in the cloud, and this is accomplished by using the PSE (packet switching exchange)

Permanent Virtual Circuits

• Leased lines are a connection contract between a provider and a customer

• Frame Relay service must be purchased from an Internet services or telecommunications provider

• With Frame Relay, you must commit to a certain amount of information over time• This is the CIR (committed information rate). The CIR is assigned to each PVC that services the organization’s account

• Because this transmission is full duplex, there can be two CIRs for each PVC

Leased Lines

• A T-carrier or telecommunications carrier system is a cabling and interface system designed to carry data at high speeds

• The basic data transfer rate of the T-carrier system is 64 Kbps, which is known as DS0, which is the digital signaling scheme

• DS1 is the digital signaling scheme for the T1-carrier

T-Carrier Overview

• Countries and their associated T-carrier systems

T-Carrier Systems Comparison

T-Carrier North America Japan Europe

Level 0 – DS0

64 Kbps 64 Kbps 64 Kbps

Level 1 – DS1

1.544 Mbps (T1: 24 user Channels)

1.544 Mbps (J1: 24 user Channels)

1.544 Mbps (E1: 24 user Channels)

Level 3 – DS3

44.736 Mbps (T3: 672 user channels)

32.064 Mbps (J3: 480 user channels)

34.368 Mbps (E3: 512 user channels)

Level 4 – DS4

274.176 Mbps (T4: 4032 user channels)

97.728 Mbps (J4: 1440 user channels)

139.264 Mbps (E4: 2048 user channels)

A digital technology developed to offer faster communication speed than an analog telephone line

• Integrated Services Digital Network (ISDN) is a set of communication standards enabling simultaneous digital transmission of data, fax, voice and video

• ISDN can be broken down into two major categories:• Basic rate ISDN (BRI):

• 128 Kbps - two equal B channels at 64 Kbps each• Generally, devices that connect to BRI lines can handle eight simultaneous

connections to the Internet.• Primary rate ISDN (PRI):

• 1.536 Mbps - runs on a T-1 circuit • 24 equal 64 Kbps B channels for data

ISDN

• Asynchronous transfer mode (ATM) is a cell-based switching technology as opposed to a packet switching technology

• ATM is a high-speed networking technology used to transmit data in cells of a fixed length containing 53 bytes of information

• ATM is a native connection-oriented protocol comprised of a number of related technologies for software, hardware and connection-oriented matter

ATM

• Synchronous Optical Networking (SONET) is a standardized protocol allowing for the transmissions of signals over optical fiber in North America

• Synchronous Digital Hierarchy (SDH) is the standard in Europe

• The standard represents a transport vehicle capable of supporting data rates in the gigabit range, optical interfaces, network management and testing methods

• Before the standard was released, each manufacturer designed its fiber terminal device to its own optical signal interface

SONET

SONET Signal Hierarchy

Level Line Rate DS3 Channels

OC-1 51.84 Mbps 1

OC-3 155.52 Mbps 3

OC-12 622.08 Mbps 12

OC-24 1.244 Gbps 18

OC-48 2.488 Gbps 48

OC-192 9.953 Gbps 192

• Fiber distributed data interface (FDDI) is a standard for transmitting data on fiber optic cables at a rate of around 100 Mbps

• Supports transmission distances beyond 50 miles• The original FDDI standard called for a physical double

ring topology• FDDI is primarily a protocol used on backbone networks

FDDI

• Digital subscriber line (DSL) is a family of technologies that provides data transmissions over local telephone networks

• DSL allows for voice and data to be run over the same line• DSL uses higher frequency bands to transmit data

• xDSL is the standard for the various digital subscriber lines• ADSL (asymmetric digital subscriber lines) The upload and download speed are the different or asymmetrical

• SDSL (symmetrical digital subscriber line) The upload and download speed are the same or symmetrical

DSL

• Broadband cable is used for cable Internet and cable television using the cable television network

• It operates at a higher speed than DSL and rates can range from 384 kbps to 20 Mbps +

Broadband Cable

• POTS/PSTN stands for plain old telephone system/public switched telephone network.

• This is what we use now for “regular” phone lines, and it has been around since the 1940s.

• POTS/PSTN is now digital at the switching office and some central offices, but there analog lines run to people’s homes.

POTS/PSTN

• The differences between static and dynamic routing.• How to install and configure RRAS to function as a network router

and how to install the Routing Information Protocol.• How to define packet switching types, such as X.25 and Frame Relay.• What T-carrier lines are, the different types of lines, and their

Japanese and European counterparts.• The basics about various other wide area networking technologies,

such as ATM, SONET, FDDI, and so on.• An introduction to different personal and small business Internet

connectivity types.

Summary

Additional Resources & Next Steps

Books• Exam 98-366: MTA

Networking Fundamentals (Microsoft Official Academic Course)

Instructor-Led Courses• 40033A: Windows Operating System and

Windows Server Fundamentals: Training 2-Pack for MTA Exams 98-349 and 98-365 (5 Days)

• 40349A: Windows Operating System Fundamentals: MTA Exam 98-349 (3 Days)

• 40032A: Networking and Security Fundamentals: Training 2-Pack for MTA Exams 98-366 and 98-367 (5 Days)

• 40366A: Networking Fundamentals: MTA Exam 98-366 Exams &

Certifications

• Exam 98-366: Networking Fundamentals

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