WAN and Internet Access (Tutorial11)

Introduction

• What is Wide Area Networking? 

• How Internet access works 

• Types of telecommunications services 

• How to determine Internet access needs 

• Steps in implementing a WAN connection

What is Wide Area Networking?

• A WAN is a network that is created using the services of the telephone company to connect LANs separated by large geographical distances 
• WANs require the use of special WAN protocols and devices 
• These protocols are usually part of a company’s Internet access 
• WANs introduce a new level of complexity to internetworking – such as coordinating with outside organisations eg your telecommunications provider

Characteristics are:

• Connections are low bandwidth, with speeds from 56kbps to 2Mbps 
• A single Wan connection is shared by all devises on the LAN (bottleneck) – sometimes a second link is installed for the sake of redundancy 
• WANs cover a large geographical area 
• WAN technologies include Point-to-Point Protocol (PPP), Asynchronous Transfer Mode (ATM), ISDN, DSL, dial-up access and Frame Relay 
• WAN devices include routers, modems and WAN switches

How Internet access works?

• Having set up the Internet at home you have in effect established a WAN.

Internet Access at Home

• Initiate Dialup Software 
• Commands sent to modem 
• ISP is dialled 
• Modem uses ‘local loop’ – pair of copper wires 
• Signal goes to Local Exchange 
• A Switch forwards the call to the often distant ISP                    

• Between the Exchange and the IPS is a multichannel trunk 
• Calls are multiplexed on that link 
• Calls are demultiplexed and separated to modems in a bank 
• The user’s modem and the modem in the bank handshake – a speed is established and data transferred 
• High speed Internet connections for a company is not too dissimilar to this

Planning Internet Access

• How will the connection be used ? 
• How important is the connection to the company ? 
• What infrastructure already exists ? 
• Balance need for bandwidth, reliability of connection, quality of service provider, quality of telco, cost 
• Future Applications ? 
• Video Conferencing/Streaming 
• E-Commerce 
• Virtual Private Network

Telecommunications Services

Circuit Switching

• ‘Creates’ channels as required 
• Essentially for voice data 
• Passive 

Packet Switching

• Transfer of data between two points over a shared medium 
• Sends packets across the network using the ‘best’ path 
• Burst-like in nature – an efficient solution 
• Cost is based upon usage

WAN Technologies

Point-to-Point Protocol 

Advantages

• Well tested and implemented 
• Offers excellent throughput 
• Supports most network protocols 
• Simple to implement 

Disadvantages

• Less flexible for rapidly expanding multiple sites 
• ‘Expensive’ 
• Requires dedicated leased lines

ISDN

• Touted as the solution to residential and SMEs in the ’80s as a means of providing integrated data/voice 
• Due to costs has not been widely adopted 

Advantages

• Runs on existing phone lines 
• Supports voice, data and fax on one line 
• Good for video conferencing

Disadvantages

• Comparatively expensive 
• Only provides 128K – can go up in multiples 
• Less flexible for growth and cost than other WAN technologies 
• Not available everywhere 
• Can be ‘difficult’ to implement 

Digital Subscriber Line (DSL)

• ‘New’ technology 
• Best option for Residential/SME customers 
• Asymmetrical DSL (ADSL) and Symmetrical DSL 

Advantages

• Now becoming affordable 
• Good download speeds 
• Runs over normal copper line 
• Data and voice can be simultaneous 

Disadvantages

• ‘New’ means has yet to establish a reliability track record 
• Not available everywhere –BT have introduced satellite broadband (at a a price !)

Data over Cable

• Standard – Data Over Cable System Interface Specification (ITU-T J.112) 
• Known as cable-modem technology 
• Good Bandwidth/price ratio (cheap) 
• Provided by cable TV companies 

Advantages

• Speeds up to 10Mbps 
• Uses existing TV cable 
• Cheap 

Disadvantages

• Not available in all areas 
• Shared medium – speeds can drop

Frame Relay

• Introduced in 1992 
• Communicates faster than X.25 (because it does not have error correction) 

Advantages

• Widely adopted, International 
• High Capacity switched core offers scalability 
• Flexible, allows expansion and growth 

Disadvantages

• Minimal error correction 
• Connection-oriented service, can cause latency on slow links 
• ‘Expensive’

Remote Access Technology

Remote Access Technology is a technology which allow user to perform administrative task and allow to run application on remote machine by giving an environment like they are working locally .

Remote Access Technologies Components

• Dial-up Remote Access 
• Telnet 
• Terminal Services 

Remote Access Server

Remote servers are the technology used to allow users not connected to the local area network (LAN) to have access to the LAN. Once connected to the server the remote user has access to all the files, shared drives and processes they have been given permission to interact with. Users are authenticated before they are allowed into the LAN. Authentication is a form of security that is configured to identify the user and protect the local area network and its data.

Security Protocols

A sequence of operations that ensure protection of data. Used with a communications protocol, it provides secure delivery of data between two parties. 

Access Control

• Authenticates user identity. Authorizes access to specific resources based on permissions level and policies. 

Key Management

• Create, distribute and maintain the keys. 

Encryption Algorithm

• The cryptographic cipher combined with various methods for encrypting the text. 

Message Integrity

• Ensures that the encrypted message has not been tampered with. 

Authentication Protocols

Authentication is a fundamental aspect of system security. It confirms the identity of any user trying to log on to a domain or access network resources. Windows Server 2003 family authentication enables single sign-on to all network resources.

CHAP

• Challenge Handshake Authentication Protocol is a three way handshake protocol which is considered more secure than PAP. Authentication Protocol. 

EAP 

• Extensible Authentication Protocol is used between a dial-in client and server to determine what authentication protocol will be used. 

PAP

• Password Authentication Protocol is a two way handshake protocol designed for use with PPP. Authentication Protocol Password Authentication Protocol is a plain text password used on older SLIP systems. It is not secure. 

DES

• Data Encryption Standard for older clients and servers. 

RADIUS

• Remote Authentication Dial-In User Service used to authenticate users dialing in remotely to servers in a organization's network. 

S/Key 

• A one time password system, secure against replays. 

Telnet

• Telnet is a user command and an underlying TCP/IP protocol for accessing remote computers. Through Telnet, an administrator or another user can access someone else's computer remotely. On the Web, HTTP and FTP protocols allow you to request specific files from remote computers, but not to actually be logged on as a user of that computer. With Telnet, you log on as a regular user with whatever privileges you may have been granted to the specific application and data on that computer. 

Network Address Translation

• Network Address Translation, an Internet standard that enables a local-area network to use one set of IP addresses for internal traffic and a second set of addresses for external traffic. A NAT box located where the LAN meets the Internet makes all necessary IP address translations.NAT serves three main purposes: 
• Provides a type of firewall by hiding internal IP addresses 
• Enables a company to use more internal IP addresses. Since they're used internally only, there's no possibility of conflict with IP addresses used by other companies and organizations. 
• Allows a company to combine multiple ISDN connections into a single Internet connection.

Virtual Private Network

• A virtual private network (VPN) encapsulates data transfers between two or more networked devices not on the same private network so as to keep the transferred data private from other devices on one or more intervening local or wide area networks . Virtual Private Networks reduce network costs because they avoid a need for many leased lines that individually connect to the Internet. Users can exchange private data securely, making the expensive leased lines redundant. 
• VPN technologies have myriad protocols, terminologies and marketing influences that define them. 
• The protocols they use to tunnel the traffic 
• The tunnel's termination point, i.e., customer edge or network provider edge 
• Whether they offer site-to-site or remote access connectivity 
• The levels of security provided 
• The OSI layer they present to the connecting network, such as Layer 2 circuits or Layer 3 network connectivity