Cisco Cisco 4G LTE Enhanced High-Speed WAN Interface Cards for Europe

Page 58 of 63

11. WAN Optimization over 4G LTE

Cellular WAN connections such as 4G LTE or 3G are shared medium. Many users contend for the same maximum

bandwidth that is offered by the service cell tower. The ability to efficiently transmit data depends heavily on the

radio conditions. These radio conditions are affected by the signal strength, surrounding objects that block the

signal, and other nearby radio sources that cause interference. The packet loss is quite normal over a radio link.

The recovery mechanism for such bits and bytes puts further strain on useful data throughput for end users. These

conditions significantly affect the end-user experience for the cellular as a WAN connection.

As a result, enterprise deployments face these challenges:

●

Varying latency: Latency for a packet varies by the packet size as well as signal conditions.

●

Varying bandwidth: The shared medium, unpredictable interference, and radio-link retransmissions cause

significant fluctuation in meaningful bandwidth.

●

Cost: Unlike wired WAN such as DSL/Cable/T1s, cellular WAN have higher per-usage charges beyond a

included monthly data-caps. This could prove costly depending on the service contract with the SP.

To overcome these challenges, Cisco has designed Cisco Wide Area Application Services (WAAS). These

services improve the application experience by optimizing the existing WAN link. The Cisco WAAS techniques

follow:

●

TCP flow optimization: This technique improves the overall TCP transactions by eliminating the inherent

efficiencies around TCP window, back-off mechanism, etc.

●

Data redundancy elimination (DRE): DRE allows the routers to avoid repeating certain traffic by using

caching and forwarding the pointers to cached data instead of the data itself. It reduces the sheer number of

bits sent over the WAN while achieving the same goal of information exchanged.