YOU DECIDE
LLOYD BARTSHE
NETW 208

Scenario Summary
Over the past several weeks, you have carefully considered the devices and media that will be used to communicate between the Pittsburgh and Cleveland offices. You must now move your attention to moving data between the two networks. Kim has recently bought a networking book and began reading up on Frame Relay, but was confused by all of the new terminology. Perhaps with your networking knowledge, you can help Kim in this area.

First I think Kim has some serious control issues that at some point should be addressed. The writers of this scenario mustn’t realize that at the understanding that a non-tech person is beginning to read a tech book to help make important tech decisions is equal to an NFL team whose looking for a new coach and gets a resume from someone whose accomplishments only include how many Madden championships he’s won. While on the surface it looks similar, but in reality it’s just scary.

I would first explain to Kim that Frame Relay is a WAN implementation methodology which uses virtual circuits to insure an end to end data transmission rate at a guaranteed level of service with additional bandwidth made available if it is not being utilized, but that is not guaranteed. So when considering price, you should only consider the guaranteed rate as opposed to the theoretical additional bandwidth as it is not guaranteed and in a major metropolitan area you might not ever see this extra bandwidth. As it is expressed in the scenario summary Kim is going to see a lot of terminology that she might not understand so I would prepare a short description of all the most common terms she might come across.
DLCI— Data-link connection identifier is a number that identifies the logical local circuit between the router and the frame switch. My discussion of DLCIs assumes local significance, which is the norm in practical application. Think of these as circuit identifiers that are provided by the service provider.
PVC— Permanent virtual circuit is a virtual circuit that corresponds to an end-to-end path going through a Frame Relay cloud. It is permanently established compared to a switched virtual circuit (SVC), which is established on demand.
LMI— Local Management Interface is the signaling between the local router and the local Frame Relay switch. The three types include Cisco (LMI), ANSI (Annex D), and Q933A (Annex A).
CIR— Committed Information Rate is the delivery during normal conditions—minimum acceptable throughput.
Committed burst— Guaranteed delivery under normal conditions.
Excess burst— Bytes outside the CIR accepted by the frame switch and marked as DE eligible.
DE— Discard Eligible is really a priority discard bit in case the network becomes short of resources.
BECN— Backward explicit congestion notification is set in frames traveling in the opposite direction of the congested path.
FECN— Forward explicit congestion notification informs the DTE device receiving the frame that congestion was experienced in the path between the source and destination.
SLA— You have a service level agreement with your service provider, which includes such things as response time, availability, restoration of service, throughput, and SLA reporting. For example, physically you may have a T1 or T3 but you only pay for the subscription you need, yet you can burst to the maximum burst rate within your physical capacity if available. On the other hand, frames flagged as DE are dropped when congestion occurs. The ingress frame switch optionally performs the policing. It can drop all frames in excess of CIR plus burst or it can just mark them DE and let them proceed. This is a service provider policy choice.
CPE— Customer premises equipment.
(Informit, 2014)
I would try to explain to Kim that Frame Relay gets its speed from a simplistic method of sending Frames without all the overhead of higher level protocols. But also this means that it does no error checking, letting the end points worry about error checking and retransmission requests. Frame Relay will try to account for congestion on the network and uses methods to prevent congestion.

Frame Relay, would not really provide us with the type of bandwidth, we might expect from today’s more modern WAN solutions. However Frame Relay does have a few advantages. Its protocol independent, cheaper to upgrade and maintain, Frame Relay is ideal for unpredictable, high-volume, and bursty traffic. And in the past you needed dedicated lines, where with Frame Relay you do not, making it cheaper to implement.

Informit. (2014, 9 21). Retrieved 9 21, 2014, from Pearson: http://www.informit.com/library/content.aspx?b=CCNP_Studies_Troubleshooting&seqNum=87