WAN Emulation - Testing Network Applications Using WAN Emulators

Newbury Park, CA - A networked application is any application that intrinsically uses a network as part of its operation, e.g. web based applications, networked database access, file transfer programs, mail transfer programs, messaging protocols, streaming voice, video, radio etc. It does not include applications like MS Word, unless of course a file needs to be opened on a remote file share.

These networked applications are now core to many of the things every computer user does every day - simple things like accessing bank accounts online, accessing emails & calendars, booking travel tickets, social networking, (Facebook), and smart phone applications. They also can be found in processes such as controlling traffic lights and operating modern IP based public CCTV.

There is a whole world of difference between how an application runs in the LAN and how it runs in the WAN, Satellite, Mobile 3G/GPRS etc., which cannot be simply resolved by increasing the available bandwidth.

WAN emulation can be accomplished by introducing a device on the LAN that alters packet flow in a way that imitates the behavior of application visitors in the environment being emulated. This device might be either a general-purpose personal computer running software to perform the network emulation or a dedicated emulation device. The device incorporates a variety of network attributes into its emulation model - such as the round-trip time across the network (latency), the quantity of available bandwidth, a given degree of packet loss, duplication of packets, reordering packets, and/or the severity of network jitter. Desktop PCs can be connected to the emulated environment, so that users can encounter the performance and behavior of applications in that environment initial-hand. Similarly, phones can be connected to the emulated environment so that users can directly assess VoIP call quality for themselves.

WAN Emulation differs from simulation in that a network emulator appears to be a network end-systems such as computers can be attached to the emulator and will behave as if they are attached to a network. Network simulators are usually programs which run on a single pc, take an abstract description of the network traffic (such as a flow arrival method) and yield performance statistics (such as buffer occupancy as a function of time).

A network emulator emulates the network which connects end-systems, not the end-systems themselves. Systems which emulate the end-systems are called visitors generators.