When the wire lets you down: Using 3G and 4G for wireless WAN backup

Wireless WAN backup solutions using 3G networks and 4G networks are quickly becoming a viable alternative to slower ISDN or DSL connections. Whether in the middle of downtown or on the other side of the world, going with a WWAN connection might be a better choice than relying on ancient copper for your WAN backup.

Wide area network (WAN) outages are simply a fact of life for many enterprises, whether they are caused by natural disasters or ancient and unreliable copper networks. A WAN backup plan is critical for many industries.

Enterprises have traditionally used WAN backup solutions like analog lines and ISDN connections for failover in branch offices, but wireless WAN backup options like cellular 3G networks and nascent 4G networks have surpassed these older wired technologies.

The best approach to incorporating wireless in your overall WAN backup plan will largely depend on both the hardware options available for your WAN routers as well as the services available in your organization’s remote sites.

“We experience outages in our stores two to four times a week,” said Shawn Winters, IT Infrastructure Manager for Gristedes, a Manhattan-based grocery chain. “Usually when one of the wired connections in a store goes down, they all do, leaving us dead in the water without credit card processing. Our wireless backup keeps us running without relying solely on Manhattan’s century old copper.”

Hardware options for wireless WAN backup links

Wireless WAN backup offerings are generally available in three forms. Some vendors offer custom-built modular radios designed to be installed within a branch router, such as the 3G and 4G Wireless WAN eHWIC cards available for Cisco’s Integrated Services Router (ISR).

Other branch office products rely on USB ports to interface with 3G or 4G wireless USB dongles available from wireless carriers. Aruba Networks takes this approach with its Virtual Branch Networking family of WLAN access points and controllers. An Ethernet gateway, which is basically a WWAN modem that connects through an Ethernet interface on a router, is a third option.

Despite the varying form factors, all three options offer the same functionality: a secondary network interface for remote routers to access when the primary link is unavailable. The router perceives the wireless WAN backup link as just another connection available to it. The network administrator must configure the branch router for exactly when it should use that wireless connection, and he should set policies specifically for it. In most routers, administrators can define the Quality of Service (QoS) and port policies per interface. For example, a branch router can shut down external Web access when it is in 3G backup mode, to conserve the bandwidth of the wireless WAN backup interface for mission-critical applications. Likewise, an administrator can also configure a remote router to monitor the primary WAN connection and shut down the wireless interface when the primary is back online.

When do you need a wireless WAN backup solution?

MPLS failover is the most common use case for utilizing 3G networks or 4G networks as a wireless WAN backup.

A wireless WAN backup is not only a lower-cost alternative to ISDN or DSL circuits, but it could actually be more effective in maintaining uptime at remote sites than wired options.

Enterprises also rely on 3G and 4G networks for wireless LAN backup or primary links in ATM machines, retail kiosks and digital signage solutions. Wireless WAN solutions are especially appealing in these cases because enterprises can avoid negotiating with a third-party property owner over pulling cables for backup links through shopping malls and other multitenant spaces.

Finally, 3G networks and 4G networks can also serve as a quick and easy stopgap measure to get new remote sites up and running while waiting for primary WAN links to be installed and provisioned. In some areas, enterprises can wait months to get wired circuits brought into a location.

“We switched a store location over to the wireless link during a remodel and my users didn’t even notice the difference for the several days they were on it.” Winters said.

Carriers put up roadblocks to wireless WAN backup

Although 3G networks offer enterprises a good wireless WAN backup solution, many wireless carriers can make it difficult for enterprises to execute such a strategy.

“Our wireless links are faster and more reliable than the primary T1 WAN connections in our stores, but the current five gigabyte monthly cap the carrier has on it keeps us from using it as the primary link into our stores,” Winters said.

Wireless carriers vary wildly with the wireless WAN data plans they offer enterprises. The offerings depend on the number of sites covered under the backup plan, how many other phones and services the enterprise uses from the carrier, and the length of contract the organization is willing to commit to with the carrier. 

Winters is facing high prices and bandwidth caps on Gristedes’ current HSPA+ service because the company declined to sign a long-term contract with its carrier. It is holding out for a 4G LTE-based service.

WAN engineers should have a good understanding of their bandwidth and performance needs before evaluating wireless WAN backup solutions. Likewise, engineers should get demonstration units and test them at each of an organization’s remote sites to ensure that a vendor’s service works where you need it to and avoid any sticker shock when a wireless carrier's first invoice arrives.

This was first published in February 2011

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