WAN Wide area Network

Achievement Standard 91641

Demonstrate understanding of wide area network technologies

·         Clarifies the requirements of the Standard

·         Supports good assessment practice

·         Should be subjected to the school’s usual assessment quality assurance process

·         Should be modified to make the context relevant to students in their school environment and ensure that submitted evidence is authentic

To support internal assessment from 2013

Using this assessment resource without modification may mean that students’ work is not authentic. The teacher may need to change figures, measurements or data sources or set a different context or topic to be investigated or a different text to read or perform.

·         The student describes WAN technologies

Students will usually refer to a WAN they may have at home when they describe technologies.

The description typically covers:

–       a standard definition of a WAN

–       ADSL and Ethernet technologies (what it looks like and what it does)

–       the significant components that allow the WAN to operate (the switch-modem-router-cables)

–       the meaning of the terms ‘full duplex’ and ‘half duplex’ in terms of digital communications technology

–       other features specified in EN 5 of the Standard.

–       The student explains why the components have been used in a WAN to achieve the desired characteristics

The explanation will cover the hardware requirements to establish the WAN (for example, desktop PC, laptop, switch, modem/router, network storage and cables), the specifications of each item, and why the item used is the best fit for the purpose (including budget, speed, band-width and security requirements).

For example:

Analogue transmissions use the same communication lines as telephones and so this service is widely available through the PSTN.

These are dial-up analogue transmissions, which are appropriate for small organisations not requiring higher or more reliable data rates or needing continuous use. Other characteristics of these include:

–       they take advantage of existing lines in telephone networks

–       very accessible

–       voice grade communication

–       slow transmission (56kbps)

–       inconsistent service

–       inexpensive.

The student explains why or why not these characteristics may suit a WAN for a particular purpose.

·         The student describes the use of WAN protocols in a WAN architecture.

The description covers packet switching and circuit switching.

For both types of switching the description typically refers to the frequency of their use in a WAN, movement through the WAN, how the connection is made, and its purpose.

This description relates to only part of what is required, and is indicative only.

·         The student describes WAN technologies.

·         The student explains why the components have been used in a WAN to achieve the desired characteristics.

·         The student describes the use of WAN protocols in a WAN architecture.

·         The student compares and contrasts the characteristics and the purposes of different WAN technologies and components.

The student refers to WANs used in small business settings when comparing and contrasting the purposes of different WAN technologies and components.

The student compares and contrasts the purposes of WAN connection methods, WAN Physical layer connections, and WAN topologies, and contrasts the purposes and characteristics of differing types within these.

For example, (WAN connection methods):

WANs connect LANs in geographically separate areas.

WAN connections typically function at the subnet layer of the TCP/IP reference model (the Physical and Data Link layers of the OSI reference model), and are made over serial connections.

WAN connections operate at a lower speed than LAN connections, and can be made as point-to-point, point-to-multipoint, and switched WAN connections.

The student compares and contrasts the characteristics of connection methods and their purposes, and typically includes SDLC, HDLC, PPP and switched or relayed services including X.25 frame relay, ATM, and ISDN.

The student includes the purpose of the WAN Physical layer (connections).

For example:

The Physical layer WAN connections concern the interface between the DTE and DCE.

The DTE is the endpoint of the user’s network, which connects to the WAN interface.

This is typically a router, computer, or terminal of some type.

The WAN service provider usually provides the DCE, which is often a CSU/DSU, modem, or terminal adapter.

The DCE is then connected to a demarc, which is a communications facility owned by the WAN service provider.

The local loop is the connection (usually copper cable) that links the demarcation to the WAN service provider’s CO switch, which is actually part of the toll network or PSTN.

The student compares and contrasts the characteristics and purposes of WAN topologies. In their discussion, they will refer to peer, star, full mesh, and partial mesh topologies.

They compare and contrast the characteristics and purposes of WAN Data Link Protocols.

For example:

X.25 is the oldest of the switched or relayed services and provides the least efficient service because of its excessive error checking.

Frame Relay is an enhancement over X.25 because it is faster and does not provide redundant error checking.

Other types of WAN datalink protocols the student may include in their discussion are ATM, ISDN, BRI, and PRI.

·         The student explains the layers in the TCP/IP networking model and the role of this model in a WAN architecture.

The student explains the TCP/IP networking model, and the role of this model in a WAN, including the function of each layer in the model.

For example:

The network interface layer specifies details of how data is physically sent through the network, including how bits are electrically signalled by hardware devices that interface directly with a network medium (such as coaxial cable, optical fibre, or twisted-pair copper wire).

The student may also enhance their explanations with diagrams.

·         The student compares and contrasts (IP) addressing with reference to static addresses and dynamically obtained addresses.

The student’s evidence covers:

–       Static IP addresses

–     assigned by administrator

–     procedure varies according to platform

–     reasons for use of a static IP

–       Dynamic IP addresses

–     DHCP servers and other methods

–     address leases

–     reasons for use of a dynamic IP

–       IP

–     IP blocking and firewalls

–     IP address translation (NAT).

The student briefly explains the relevant diagnostic tools available in the operating system being used.

Windows: ping; ipconfig, route; netsh

Linux: ping; ifconfig; netstat; route; ifstat.

This description relates to only part of what is required, and is indicative only.

·         The student describes WAN technologies, and explains why the components have been used in a WAN to achieve the desired characteristics.

·         The student describes the use of WAN protocols in a WAN architecture.

·         The student compares and contrasts the characteristics and the purposes of different WAN technologies and components.

·         The student explains the layers in the TCP/IP networking model and the role of this model in a WAN architecture.

·         The student compares and contrasts  (IP) addressing with reference to static addresses and dynamically obtained addresses.

·         They explain the WAN technologies and components of a WAN.

The student explains how the WAN connection methods work, including dedicated point-to-point, point-to-multi-point, circuit switched and packet switched.

For example, (packet switch):

WANs rely primarily on packet switching, but they also make use of circuit switching.

Switching of any type involves moving something through a series of intermediate steps, or segments, rather than moving it directly from start point to end point.

In packet switching, all transmissions are broken into units called packets, each of which contains addressing information that identifies both the source and destination nodes.

The student will explain how WAN Physical layer connections work, and how WANs are connected at the Subnet layer (TCP/IPmodel) or Physical layer (OSI model), and why this provides a reliable connection. In their explanation they will refer to:

–       connections between two LANs

–       connections between:

–   channels service unit/ data service unit CSU/DSU

–   router

–   routers that now include internal CSU/DSU

–       data terminal equipment (DTE)

–       data-circuit terminating equipment (DCE)

–       demarcation or demarc

–       point of presence (POP)

–       local loop or last mile

–       central office switch (CO)

–       toll network.

The student explains how the WAN topologies work, also referring to cost, configuration, redundancy, design, and fault tolerance.

The student explains how the WAN data link protocols work, including the advantages and disadvantages of each protocol. Students would typically refer to SDLC, HDLC, PPP, ISDN, X.25, Frame Relay, and ATM protocols.

The explanation should also cover the application of Physical WAN Serial interface standards to a WAN connection, such as the advantages of HSSI over TIA-232 in a WAN serial connection.

The student could also refer briefly to recently emerging technologies being used to implement improved WAN access for both the home and small business users, and what advantages these offer the user, and at what cost.

The technologies covered typically include DSL (Digital Subscriber Line), Cable, T(X) lines (Dedicated Telecommunications lines), ATM (Asynchronous Transfer Mode), OC(X) (Optical Carrier WAN access) and any future development.

·         The student explains IP addressing schema.

The student explains how IP addressing schemas operate in a WAN and in designing an appropriate address scheme for a WAN for a particular situation. They include: IP address, subnet mask, default gateway, use of static and dynamic addresses, configuring CHCP, and securing the router with an administrator password.

For example:

The subnet address is allocated to each section of the WAN in such a way that IP addresses are conserved while also allowing for planned expansion. This is achieved using DHCP configuration for dynamic allocation and, where appropriate, static addresses allocated by the administrator.

In the WAN I developed/am familiar with the subnet address was … because….

·         The student explains how NAT (Network Address Translation) provides a form of firewall.

The explanation covers:

–       the size of the network and the requirement for NAT

–       how NAT improves security by translating traffic from an outside subnet to an inside subnet

–       the following terms in the NAT context:

–   inside/outside global addresses

–   inside/outside local addresses.

The student may use clear diagrams to convey their understanding of these terms.

·         The student explains the management procedures for a WAN link.

The explanation covers the features specified in EN 8. Examples include:

–       administration procedures for a chosen router

–       router password security

–       the Admin user

–       router event logging

–       router configuration (editing an existing working config; backing up the working config; firmware upgrades)

–       router diagnostic tools (Ping; Traceroute).

This description relates to only part of what is required, and is indicative only.