Dropped Connections vs. Dropped Calls?

Tue, 05/15/2007 - 9:19am
Tom Tovar

Wireless operators face a dilemma of their own making as they add new, data-rich services to their service offerings. Over the years, they have worked hard to deliver superior service levels for mobile phone service. Having built their reputations - and advertising campaigns - on this quality of service, they now have to provide the same reliability for wireless data services. This proves to be an entirely different proposition.

Subscribers expect the same reliability and performance across all of the services they receive. They will not differentiate between the CDMA or GSM services and IP-based services. Slow is slow and dropped is dropped, whether for cellular calls, Web page browsing or making VoIP calls on dual-mode phones. Operators have to optimize and protect the entire customer experience, even as that experience expands.

Tom TovarNo matter how much bandwidth you have and how fast/efficient the equipment, core IP services can slow down services in obvious and painful ways.

One potential problem area is the otherwise "invisible" layer that handles naming and addressing in IP networks: DHCP and DNS. DHCP provides devices with IP addresses so they can connect to the Internet and/or IP network. DNS connects users to services by mapping domain names to IP addresses.

These essential functions are often handled by general-purpose open source software designed for much simpler networks. Once these components hit their limits, service levels suffer. And the results are the IP equivalent of dropped calls:

Slow web page downloads. Typical Web pages require tens of separate DNS lookups. Social networking sites like MySpace use profile pages rich in distributed content that may require hundreds of lookups. If the DNS server is overloaded, the page download is slow. The subscriber won't know where the problem lies (the phone, the network), and may switch operators to get better performance.

Inability to connect to wireless IP. Ever been unable to connect in a wireless hotspot? If the DHCP server is overloaded or waiting for responses from external systems, then users cannot connect to IP services.

Dropped data connections. Wireless operators typically use very short lease times, so that mobile users don't reserve an IP address long after they have disconnected. Usually, this is not a problem; leases are renewed in the background before the lease expires. But if the DHCP server is unavailable, a user who has connected may suddenly be disconnected - the equivalent of a dropped call in the data world.

Attacks on the infrastructure: Industry analysts predict that the same attacks that have plagued fixed broadband will soon happen in the wireless world. Operators need a resilient and secure IP naming/addressing infrastructure to protect against these attacks.

Wireless carriers will run into these problems unless they take active steps to prevent them, because the DNS/DHCP servers that most IP networks deploy as a default are not up to carrier standards for reliability and performance.

Many IP networks use open source DNS servers (BIND) for name serving. While great for general-purpose DNS, BIND is inadequate for carrier-grade requirements. It cannot scale to handle large query volumes, and adding more servers leads to server proliferation. It needs frequent restarts to ensure stability, and does not integrate easily into carrier management environments. Wireline carriers already have started major upgrades of DNS infrastructure; wireless providers will have to follow suit as they add IP services.

Likewise, the pervasive ISC-DHCP server struggles under carrier-grade loads. For example, when a large number of devices request leases simultaneously, ISC-DHCP easily becomes overloaded, effectively "hanging" from the subscriber's perspective. A brief, localized power interruption might cause many devices to cycle off the network and cause a longer service outage for the carrier.

How do carriers give subscribers the same quality of experience across all wireless services? The key is to pay the same attention to the IP network infrastructure as to the rest of the network - including the naming/addressing functions. In most cases, this means deploying commercial, carrier-grade infrastructure components.

Here are a few guidelines for wireless IP networks:

  • Maintain adequate DNS capacity to handle up to three times peak capacity.
  • Use highly available DHCP servers with active failover capabilities, and that can handle peaks in lease requests without outages or slowdowns.
  • Make sure all IP naming/addressing components integrate easily into the management environment for monitoring and alerting purposes, and with authentication and billing systems as needed.
  • If you are using DNS/DHCP bundled inside a larger solution, ask your vendor whether the solution uses open source components and can meet the above requirements.

With a reliable, resilient IP infrastructure in place, operators can trust that IP services won't degrade the broader subscriber experience.

Tovar is president and COO with Nominum.


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