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How to Optimize Intercontinental OWA Network Traffic

Traveling users will sometimes complain about the performance of Outlook Web Access (OWA), especially if they’ve traveled to another continent. This is usually related more to network latency than to network bandwidth issues (Eritrea being a notable exception). For example, N. American users who travel to Europe can expect to see additional quarter- to half-second delays as their HTTP requests and replies travel across the Atlantic in both directions.

Satellite hops make the situation worse. That’s why most transoceanic Internet traffic uses fast cables, but the speed of light is still an absolute upper bound on how fast IP packets can move.

Mysteriously, the situation can often be worse in the case of people who have moved to another country but use OWA while traveling. Take the example of Jane, a U.S. employee who has relocated to Europe. Her IT department moved her mailbox to a European server, so she gets fast performance when she’s in the office. But when she travels within Europe, she uses OWA, which seems to run incredibly slowly.

What’s going on here? The problem is that she’s using the Web address that the U.S. IT department told her to use. It connects to a gateway (e.g., a Microsoft ISA server, reverse proxy, or VPN server) in North America. This was fine when she was based in North America, but now each request causes not two, but four unnecessary transatlantic hops:

  1. Web browser to U.S. gateway
  2. U.S. gateway to European OWA server
  3. European OWA server to U.S. gateway
  4. U.S. gateway to Web browser

One solution is for IT to replace the well-known OWA locations with a standard front page telling people which link to use, encouraging employees to use the gateway closest to them. For example:

Click the location closest to your current location:
N. America west coast
– www.sanfrancisco.example.com/Exchange
N. America east coast
– www.newyork.example.com/Exchange
Western Europe
– www.england.example.com/Exchange
Eastern Europe
– www.russia.example.com/Exchange

Richi Jennings

One Comment

  1. Posted July 10, 2006 at 6:44 PM | Permalink

    Snicker.

    Web mail redirect in Domino v5 solved this. In 2001.

    —* Bill

  2. Posted July 13, 2006 at 3:36 AM | Permalink

    Bill, careful. This isn’t about redirection, which is also supported by ISA+OWA. This is about the corner case where users move but connect to the wrong server.

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