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Glossary of important WAN terms

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PCQ Bureau
New Update

We all know what a WAN is, or what a router is used for. So we don't want to

unnecessarily fill up pages telling you all about them all over again. Instead,

we'll focus on terms that you must be aware of and why they're important in

today's trying times.

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Active/Active Connection: A mode where two devices are working

together in a load-balancing fashion. In case one fails, the other one

automatically takes over. In the WAN world, it is common for enterprises to have

Active/Active links between locations. This way, both links will do load

balancing while transferring data from one destination to another. In case one

link fails, the other one automatically takes over. The other type of connection

is called Active/Passive, wherein there's a second connection that's in hot

standby. It doesn't do load balancing, but becomes alive if the primary link

fails.

Caching: This is again, not a new term, but is very much relevant for

WANs today. Caching basically refers to storing duplicate values of data in

places where the original data is very expensive to get. For instance, it's

widely used in proxy servers, wherein the proxy server stores copies of

frequently accessed web pages. This way, when clients request for a web page,

the request is fulfilled from the local proxy cache instead of downloading the

web page again from the Internet. Similarly, various caching techniques are

being used in modern day WAN accelerators. This allows faster access to data

between two WAN accelerators.

Hub and Spoke Model: Think of a chariot or bicycle wheel when you

think of this model. Basically, data travels across the different spokes from

one end to the central hub. Many enterprises who use MPLS based connectivity for

instance, follow this model. In this, the various branch offices would be at one

end of the spoke, and the other end would terminate in a network aggregation

point or on the network operator's MPLS ring. This ring would in turn connect to

the enterprise's central hub. This allows for point-to-point connectivity

between an organization's branch offices and the central head quarter, or the

data center.

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ISDN BRI: The term ISDN doesn't need any explanation. It's an old and

well-known method of digital communication. BRI stands for Basic Rate Interface.

It's one type of ISDN connection, which supports 128 Kbps transmission rate,

using two B-channels of 64 Kbps each, and one D-channel for sending control

information. The other kind of ISDN is PRI. This comprises of 23-B Channels (for

US) and 30-B channels (for Europe). Both support a D-Channel. Usually, most

enterprises tend to use an ISDN BRI connection as a backup link, which becomes

active if the primary link fails.

MPLS: Short for Multi-Protocol Label Switching. It's basically an IETF

standard for data transmission in packet-switched networks. The technology works

between the data link and transport layer, and is therefore also known as a

Layer 2.5 protocol. The big benefit of a MPLS network is that it allows one to

move information around more efficiently, by providing traffic prioritization

and class of service tagging. Given that the traffic on most networks today

comprises of voice, video, and data, such a service proves very beneficial.

That's why a lot of enterprises prefer to go to a network operator who provides

MPLS for their branch office connectivity.

PE/CE: Providers' Edge/Customer's Edge. These terms are used to

determine where the WAN equipment is located.

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QoS: Short for Quality of Service, which comprises of different kinds

of techniques used to prioritize different kinds of traffic flowing over WAN

links. This is to ensure that high-priority, or time-sensitive traffic like

voice and video gets higher precedence over low-priority data traffic. QoS is

increasingly becoming important, thanks to the plethora of applications that

have hopped onto the WAN links. We have devoted a separate article in this story

to explain QoS in more detail.

SaaS: Software as a Service, which is a relatively new phenomenon when

we compare it against some of the other terms we've defined in this glossary.

Software as a Service essentially implies providing software applications over

the web as a service to customers. This is basically a re-avataar of the older

Application Service Provider model, in which the service provider would host

applications in his premise and offer it on 'rent' to different customers. Types

of services include email and messaging, and business applications like ERP and

CRM. It finds relevance in this glossary because SaaS is delivered over a WAN.

So whether it's an enterprise that's web-enabled its applications and provides

them to its various branch offices, or a service provider who sells applications

as a service, both have to ensure that their WAN links are optimized to provide

this service.

VDI: Short for Virtual Desktop Infrastructure. This is a hot new

buzzword, which unlike thin clients, hosts the entire desktop of a client on a

central server. The logic behind VDI is the same as thin clients. You don't have

to manage a large and spread out desktop workforce. Instead, everything is

hosted centrally in the data center and accessed remotely over LAN or WAN links.

VPN: Virtual Private Network. Though this has been around for quite a

long time, today there are several different ways of deploying it. You could

deploy it over the Internet or an MPLS cloud. You could use it for connecting

branch offices to HO or for allowing mobile users to connect to the central

network. We've devoted a separate article on different kinds of VPNs.

WAN Accelerator: This is a device that can be used to get better

performance from a WAN link. These devices use various techniques such as

caching, compression, QoS, etc to speed up data transmission over WAN links.

Increasingly, enterprise WANs have started going beyond carrying basic data to

voice and video as well. Under such cases, having a WAN accelerator that can do

all these things definitely helps.

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