Real World Computing

I've got a couple of test accounts with Sipgate (www.sipgate.co.uk), which is neither the cheapest nor the most reliable of VoIP providers - I've known it to go down on Friday evening and not be fixed until the following Monday morning - but it does allow you to set up an incoming number for free, and that's useful when testing new devices. I went through various option screens on the E61 and set up my Sipgate account details, but I kept seeing "unable to register" messages. After ages trying different usernames and passwords, finally the penny dropped - I hadn't seen any STUN setup screen on the Nokia. Simple Traversal of User Datagram Protocol Through Network Address Translators, or STUN, is a mechanism that allows VoIP and other services to work behind a NATed connection, as found in pretty much all wireless routers. Most VoIP software and hardware includes support for STUN, but it's nowhere to be found on the E61 - a surprising omission given its otherwise excellent facilities. For the VoIP client to work, the Nokia would

need a fixed IP address, and even in most corporate environments that's a pipe dream. So does that mean the E61's internet telephony client is useless? It certainly isn't as usable as it would be with STUN support, but there are a couple of workarounds.

First, if you're in charge of your own wireless network, you should be able to set up port forwarding: force the E61's Wi-Fi connection to always have the same IP address, either by choosing one outside of the scope of your DHCP range, or else by using address reservation to always give a particular MAC address the same IP address. Once that's set up and tested, forward UDP ports 5004 (Real-time Transport Protocol) and 5060 (the main SIP port) to the device. If possible, you should also lock down your firewall rules so they only do this port forwarding for incoming traffic from your VoIP provider - for Sipgate, I normally set up the range 217.10.79.1-217.10.79.254. Once you've done this, your E61 should work fine with your VoIP provider, but be aware that some providers run the SIP traffic across some other UDP port than 5060, so you may need to alter this.

What if you want to use public Wi-Fi hotspots? Try asking the barista at Starbucks to set up port forwarding on their Wi-Fi router? Perhaps not. That's where the second workaround comes into play. UK-based VoIP provider VoIPtalk (www.voiptalk.org) has set up a NAT traversal proxy that allows anyone to access their VoIP service, even if they're sitting behind a NAT-based router. To get it working on your E61, sign up at www.voiptalk.org, where not only will you get the account for free but they'll also give you an initial £2 of credit - again, useful for testing. It's probably best to follow the instructions, including downloading their soft-phone, as at least that way you can check the account is working properly from your PC.

Next, you'll need to configure the E61. From the main menu, go to Tools | Settings | Connections, then click on SIP settings. From the Options menu, select Add new and choose Use default profile. Then set up the SIP account as follows:

Profile name: VoIPtalk

Service profile: IETF

Default access point: <a Wi-Fi access point you've previously configured>

Public user name: <mysipname>@voiptalk.org (where <mysipname> is your VoIPtalk SIP username)

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