Cisco Certified Expert

Critical Goals for the WAN Technology

capabilities to support video training without disrupting

performance

Must use currently available technologies from WAN service providers in the region

Response time must be 1/10 of a second or less for interactive applications

Availability must be 99.98 percent or higher

The short-and long-term costs for operating the WAN must be contained

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64-Kbps leased lines

X

X

X

SONET

X

X

X

ISDN

X

X

Frame Relay

X

X

ATM

X

X

X

X

X

ATM

X

X

X

X

If all options had met all critical goals, then other goals could have been listed also to further the decision-making process. Options could have been evaluated on how well they met noncritical goals on a scale from 1 to 10, as shown in Table 7-1, "Example Decision Table." However, in the case of Klamath, it was not necessary to go beyond evaluating how well options met critical goals.

After analyzing business and technical goals, characterizing the existing core WAN, and analyzing the options available from the WAN service providers in the area, it was decided to update the core WAN architecture from 64-Kbps lines to Ethernet over ATM. This choice will keep costs low and benefit from the QoS features of ATM.

The three main contenders, besides Ethernet over ATM, were ATM, ISDN, and Frame Relay. ATM was ruled out because ATM router interfaces are too expensive. ISDN was ruled out because it cannot scale to the extent that Ethernet over ATM can. Frame Relay was seriously considered, but Ethernet over ATM was selected instead of Frame Relay because ATM was specifically designed to handle environments with diverse applications, such as the delay-sensitive videoconferencing and interactive manufacturing-support and financial-modeling applications at Klamath.

In the new design, the delay-sensitive traffic will be carried on ATM virtual circuits that are distinct from the circuits that carry other data. Traffic management parameters will be specified and implemented so that the ATM network accepts and carries traffic according to the QoS needs of the different applications.

NOTE

With such optimization techniques as those covered in Chapter 13, Frame Relay could probably meet Klamath's QoS goals. However, Ethernet over ATM was selected because ATM was designed to meet the requirements associated with networks that run both video and mission-critical data applications.

The current WAN service provider that leases the existing 64-Kbps circuits was selected as the service provider for the new Ethernet over ATM WAN. The current provider was selected because it offers the following advantages over other providers:

• A proven history of supplying highly reliable ATM services to customers

• Excellent pricing for Ethernet over ATM that was comparable in price to the cost of adding numerous 64-Kbps circuits to meet capacity requirements

• The ability to allow Klamath to keep their current IP addressing scheme

• 24-hour support, 7-days a week, with a guaranteed MTTR of 1 hour

• A single point of contact who is responsible for Klamath's service

Each site in the core of the network will connect to the ATM network via a 10/100 Ethernet interface in a router. For now, 10-Mbps Ethernet will be used. Upgrading to 100 Mbps or 1000 Mbps will be possible in the future, but for now, 10-Mbps Ethernet was chosen because the service provider offers attractive pricing for 10-Mbps Ethernet over ATM and because 10 Mbps is sufficient capacity for the current network applications.

Klamath will replace the existing routers in the core of the network with new highend routers that provide superior packets-per-second throughput, high-availability features, and support for optimization features. Klamath also considered future support for voice traffic in their router selection. In the future, the PBXs at each site will be connected to the router and Klamath's separate voice network will be dismantled. All voice, data, and video traffic will traverse the Ethernet over ATM network. This will simplify the topology of the current voice/data network and facilitate manageability. It will also allow Klamath to reduce the costs of operating separate data and voice networks and realize a quick return on the investment for the new equipment. Figure 11-9 shows the new design for Klamath's core network.

Figure 11-9. The New Core WAN at Klamath

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