Time was when your modem, ethernet router and wireless base station may have been residing in separate boxes. Nowadays, wireless tech is almost always wrapped up together with your broadband modem and ethernet router, into a single box that’s casually called ‘the router’.
There’s still a good case for breaking up that converged hub into its components, for some people anyway. Your ISP will almost certainly offer you an all-in-one router, but it’s likely to have old wireless tech on board, selected for cheapness and reliability rather than bleeding-edge performance.
By keeping your broadband modem and wireless/ethernet router in two boxes, and you can optimise the modem to your ISP’s network, and the wireless router to your home network.
It’s not necessarily the most straightforward solution though. Even if you can find specialist standalone modems, there will be more manual configuration required; but network professionals and power users will enjoy the useful benefits.
Fortunately D-Link is one of few companies to keep the useful technology of dedicated modems alive.
The D-Link DSL-320B is a one-trick pony, a tried-and-tested ADSL modem, also specified for us with all current ADSL2+ services. The D-Link DSL-320B was launched late 2007, making it pensionable by IT standards. But after two years of subsequent firmware development it’s a dependable device, using the current v1.22 firmware signed off in October 2009.
This D-Link DSL-320B standalone modem is a compact plastic box, just 120 x 105mm, and standing 32mm high. Cooling vents run along the top, and the unit can get a touch warm in normal use when the broadband link is in steady use.
On the back of the D-Link DSL-320B is a RJ11 socket to link to your telephone line, and a single RJ45 that makes an ethernet connection to your computer or router. A press-button switch lets you easily power the modem down, rather than pull out the plug to its 5V power adaptor.
Across the front of the D-Link DSL-320B are four green LEDs, for Power, Status, LAN and DSL. In normal operation, Power is continuously lit, the Status light pulses regularly, LAN flashes on network activity, while DSL is constant green to indicate showtime.
Modes of operation
There are three main modes of operation, configured via web browser. PPPoE/PPPoA and Static IP are two options if you want to connect the modem directly to a PC. Both these setups mean the D-Link DSL-320B serves as a basic router, able to perform network address translation (NAT) and issue your computer a new IP address, for example by DHCP.
But if you’re using another router after this modem, such as an 802.11n wireless router, you should select Bridge mode. This ensures only one level of NAT is being undertaken – essential for clear two-way comms with the outside world – with the data signal from your ISP passed transparently to the wireless router through the D-Link DSL-320B modem.
A wizard in the D-Link DSL-320B's interface page helps with basic setup, although Bridged mode requires most of the setup to be carried out on the following router.
This router will then require the relevant network settings provided by your ISP, with key details such as VPI, VCI, the ISP's static or DHCP settings, and DNS addresses.
For normal non-bridged use, it’s possible to make use of other built-in services, such as parental control time filters and operation logs. In bridged mode, you need to temporarily disconnect from your router first and plug a PC straight into the D-Link DSL-320B to inspect or adjust its extra non-modem functions.
We tested the D-Link DSL-320B on a home Be Unlimited line, a nominal 24Mbps down/1.3Mbps up ADSL2+ service.
Our local exchange and its DSLAMs (digital subscriber line amplitude multiplexers) are around 1km distant. With this D-Link DSL-320B unit using the same Broadcom chipset technology as Be’s own DSLAMs, we saw good optimisation of the connection, resulting in excellent sync speeds and data throughput.
The modem’s status page reported 21Mbps/1.3Mbps initial sync speeds, while real-world broadband measurement with speedtest.net showed consistent results of 18Mbps down and 1.2Mbps up.
The D-Link DSL-320B is specified for Annex M as well as standard ADSL2+ Annex A operation. Annex M allows some download speed to be traded for upload performance.
Be offers its Be Pro subscription to capitalise on Annex M and provide ‘up to 2.5Mps’ uploads. That kind of increased upload speed is invaluable for businesses offering VPN to its staff, or for high-definition Skype video chats, website hosting, Torrent sharing and online gaming.
We weren’t able to test Annex M on the D-Link DSL-320B but have had limited experience of the protocol’s capabilities before on our Be connection.
In extended testing of the D-Link DSL-320B, with a Cisco E4200 serving as wireless gigabit router, it did not falter or suffer any known line outages whatsoever. Throughput was also consistently excellent, and no issues were found in its operation – a sadly unusual state for much modern networking hardware.