D-Link Xtreme N Gigabit Router Review

Today we are going to check out the D-Link Xtreme N Gigabit router (DIR-655) - a draft 802.11n compliant device that delivers up to 14x faster speeds and 6x farther range than 802.11g. A great choice for a small office due to its network security options, QoS, and remote administration tools. Read more in our review!

by Platon Scheblykin
07/20/2007 | 11:20 AM

Not long ago I reviewed a Linksys WRT300N router that was one of the first to support the draft IEEE 802.11n standard. More devices feature this wireless standard now and I am going to tell you about one of them in this review.


The D-Link DIR-655 router comes from the top-end Xtreme N family that features increased performance. As a matter of fact, the DIR-655 is the senior model in this family and quite deservedly so. Besides supporting a high-speed WLAN, the DIR-655 is equipped with a USB port, wired Gigabit Ethernet interfaces, and advanced QoS setup options.

The manufacturer claims this product to be the best in its class. I will check out this claim right now.

Specifications and Accessories Bundle

I got a model with a hardware version of A2. Here are its specs:



Wireless standard

- IEEE 802.11b/g
- IEEE 802.11n (draft)

Encoding standard

- WEP (64/128bit)


- 3 external dipole antennas

Signal modulation


Operating frequency

- 2.4 - 2.5 GHz

Nominal data transfer rate

- 802.11n (draft): up to 300Mbps
- 802.11g: 6, 9, 12, 18, 24, 36, 48, 54Mbps
- 802.11b: 1, 2, 5.5, 11Mbps

Operating channels

11 for North America, 14 Japan,
13 Europe (ETSI), 3 (non-overlapping)


1 RJ-45 GigabitEthernet 10/100/1000Mb/s port
with auto crossover


4 RJ-45 GigabitEthernet 10/100/1000Mb/s ports
with auto crossover

Other interfaces

1 USB2.0 port (“Windows Connect Now”)


External power supply unit


117 x193 x 30.5 mm

Additional features

- Supports D-Link NetworkMagic
-WiFi certified
- Intelligent QoS Engine

The box contains:

Exterior and Interior Design

D-Link has recently changed the exterior design style of many of its home-targeted products, perhaps deciding that the previous design concept had become out-fashioned. Anyway, the traditional silver-gray case is now a thing of the past. It is replaced with a Mac-like design every respectable manufacturer currently employs. The only problem is that the overall design style doesn’t vary much from model to model. The size and, sometimes, the color scheme are the only things that change. The router I am talking about is not an exception, yet it looks cute despite having nothing original in its appearance. Talking about its physical parameters, the DIR-655 is a very compact device, but feels heavy and solid for its size.

The case is made from white glossy plastic. There is a small manufacturer logo on the top panel. The glossy surface is pretty yet not practical because it gets soiled too easily. Dust and accidental scratches are just too visible on it, too. The side panels are made from a black and rough rubber-like material. The router can be installed in either of three positions: lying on a desk, standing upright, or hanging on a wall. A special stand is included for vertical placement. Fasteners for wall-mounting the router are included as well. As I found out later, the router shouldn’t be placed upright because its antennas would either be oriented horizontally or get in the way of the connected cables. The DIR-655 is ventilated through the slits in its top and bottom cut closer to the rear panel. This seems to be insufficient as the router becomes very hot, especially its bottom panel, even after a short period of operation.

The router’s indicators are located on its front panel, as usual. They are blue LEDs soldered at the edge of the PCB in special holders. Their light can be seen outside through holes in the opaque front panel. The holes are shaped like small icons describing the meaning of each indicator. The descriptions are intuitive and visible on the front panel even without highlighting. The LEDs are bright, even too bright to my taste. They just merge into a solid light spot in semidarkness. There is a total of 9 indicators on the front panel. Here they are (from left to right):

The router’s connectors are all placed on its rear panel. Each connector is labeled and marked with a certain color. Here is what you have here (from left to right):

That’s all about the device’s exterior design. To learn more about the DIR-655, we need to dismantle it.

This procedure isn’t difficult. You unfasten the screws you find under the rubber pieces on the bottom panel. The screws are only hidden under the two front pieces, so you don’t have to remove all of them. You can take off the top panel by applying some effort or pressing on the side panels somewhere near the rear panel. You can use either method because the latches that you unfasten by pressing on the panels don’t hold too tight. But you should begin to take the top panel off from the rear edge because there are latches in the front, too.

The PCB occupies almost all of the internal space. This is the tradeoff for the small dimensions of the device. Considering the small vent slits, it is clear now why the router is so hot at work. The main reason for the high temperature is the heatsinks installed on the processor and switch that get both scorching hot when the router is on. The temperature seems to be near the limit after which a fan would have to be installed. But I have to acknowledge that I noticed no sudden failures in the operation of the router during my tests under an ambient temperature of 22°C.

Having detached the cables that go to the WLAN module and unfastened two more screws, I took the PCB out of the case. Most of the components are located on the top side of the PCB, but the flash chip that stores the router’s firmware is to be found on the reverse side:

The components seem to be placed very densely but you can see a large empty space under the WLAN module if you take the latter out (the module is connected to the main PCB via a miniPCI slot). By the way, the PCB wiring is original if you compare it with the reference PCB for the employed processor.

The board assembly is good, except that the indicator diodes and one choke have too long leads and bend easily even when you touch them but slightly.

The router’s main chips are covered with a metallic screen that has two cut-outs for the heatsinks. Hidden under the screen are the router’s processor, memory, and Gigabit Ethernet switch. As I mentioned above, aluminum heatsinks are glued to the processor and switch. This thermal glue doesn’t ensure proper contact: the middle of the switch doesn’t even touch the heatsink. This is not a big problem, but negligence all the same.

The DIR-655 router belongs to the new Xtreme N family which features the most advanced network processors. Here, the PCB carries a communications and media processor (CMP) from Ubicom’s StreamEngine 5000 series. Featuring a unique architecture, these processors are superior to similar processors with other architectures, at least in their manufacturer’s eyes. The DIR-655 comes with the junior processor model marked as IP5160 which delivers as much performance as modern processors with MIPS and ARM architectures do (according to Ubicom). The manufacturer’s website offers a document that contains a detailed performance analysis of CMPs with different architectures. Here are a couple of tables demonstrating the superiority of StreamEngine 5000 processors:

Overall performance

Routing performance

A key feature of IP51xx processors that gives them the edge in terms of performance is that they have integrated memory besides just cache. Every data packet passes through this integrated memory and is processed much faster.

The exact specifications of the IP5160 are as follows (quoted from the Ubicom website):


StreamEngine 5160

Sustained Performance
(TCP/IP Throughput)

~250+ Mbps

Number of Independent Threads


RAM Type

DDR1/2 16-bit-wide

External RAM

2 Gb

General I/O

PCI, PLIO, USB 2.0 (FS/HS), USB 2.0 (HS)

Ethernet (2 Ports)


Networking I/O

MII (2), RMII (2), RGMII

Hardware Encryption /
Decryption, Key Management & DRM

(RC4, ECC in SW)

Media I/O

IDE, AC97, I2 S, Utopia, MPEG TS, YUV


G.711, G.726, G.729AB,
Line & Echo Cancellation, Multichannel

Audio Processing


The specs are impressive indeed. The DIR-655 doesn’t make use even of half of the processor’s capabilities!

Perhaps relying on the processor’s integrated memory, the manufacturer installed only 16MB of memory into the router. This is the typical amount for a regular SOHO router, yet it seems somewhat small for this particular model. Physically, it is an A2S28D40CTP chip of DDR SDRAM manufactured by PSC.

The router’s OS is stored in a Macronix 25L3205 flash memory chip. This chip has a serial interface and a capacity of 4MB. The firmware image is about 1MB large, so there is an opportunity to make substantial additions to the router’s standard firmware.

The DIR-655 employs a VSC7385 Gigabit Ethernet switch made by VITESSE. This SparX series chip is recommended for use in high-performance SOHO solutions. The chip offers 5 ports, has a 112KB frame buffer, supports IPv4 and IPv6 networks (with Jumbo Frames), and features integrated tools for QoS and other services. Having an integrated processor, it can even work as a router in its own right, but this capability is not utilized in the DIR-655.

The WLAN module resides on a separate card that is attached to the main PCB via a miniPCI bus. Here, we’ve got an AR5008-3NG version of the xspaN AR5008 chipset from Atheros. It employs an AR2133 RF module and an AR5416 MAC controller.


Winding up this section, I want to note two more things in the router’s electronics. First, there is an empty seat for a console connector near the processor. And second, I couldn’t find out the purpose of the button soldered together with an indicator near the right edge of the main PCB. It will probably enable a quick-setup mode or something in future revisions of the router.


Firmware and Web-Interface

To my regret, less can be said about the router’s software than about its hardware. The user of a DIR-655 can use the official firmware only, I couldn’t find alternatives. This is sad because the official firmware doesn’t offer too many options. For example, the router’s USB port is only used to quick-load profiles with WLAN settings from a flash drive. It doesn’t seem right to use the full-featured support of flash drives only for this specific purpose. The DIR-655 would also be much more attractive in the customer’s eyes if it had an integrated FTP server, not to mention more advanced features.

But I quit talking about what this router might be and will instead talk about what it is. Its latest firmware is version 1.03 as of the time of my writing this.

The web-interface for specifying the router’s parameters is designed typically for a home device. Like the exterior design of the DIR-655, the web-interface has been revised and now resembles the D-Link website. Besides the banner that tells you the device model and its hardware and firmware revisions, there are four more frames on the page. The top row stretching the entire screen contains five global groups all the settings are categorized into. The Setup group is for initial setup which you can do either manually or with the help of appropriate Wizards. The Advanced group contains the rest of settings pertaining to the router’s functionality. The Tools group includes options concerning the DIR-655 proper. The pages of the Status group show information about the router and events occurring on it. The Support group contains information that can help you set up various parameters.

The left frame shows a list of pages with settings the current group contains. The selected page from the list is displayed in the middle of the screen. This navigation method is quick and visual but works right only when the whole menu has a logical structure, which is not the case here. Similar settings can sometimes be found on different pages or even in different groups. Well, you get used to this structure eventually.

The right frame contains tips on using the information from the Support section of the current settings page. The router’s help system is excellent, by the way. D-Link has always been good in this respect. You get detailed descriptions even on the settings page itself while the help system offers an in-depth explanation of each parameter with examples and step-by-step instructions.


Let’s see what options are available here. The Setup group comes first. These basic settings are divided into three subgroups: Internet, Wireless and Network. Choosing one subgroup you can then opt to set up the parameters manually or call for a Wizard’s assistance.

On the manual setup page of the first subgroup you can see a list of possible connections to the external network via the WAN port. You can then set up appropriate parameters depending on the selected variant. The DIR-655 supports six most popular connection variants: Static IP, Dynamic IP, PPTP, L2TP, PPPoE, and BigPond. The VPN-server access settings are exhaustive in the case of PPTP and L2TP: the situation when the server resides on a different subnet is supported.

The Wireless Settings page allows to choose the operation mode for the WLAN and to define connection security parameters. The connection channel can be specified explicitly or left for the router to choose. The security parameters comply with the requirements of the second version of the 802.11n draft (WPA2, AES).

The last page in the first group is called Network Settings. Here, you can choose the operation mode for the WAN port: router or bridge. (By the way, this is one of those settings that you expect to find somewhere else). Then, there are fields for entering the router’s internal IP address and the LAN mask. The parameters of the integrated DHCP server are listed below together with fields for reserving certain addresses, a list of reserved addresses and a list of IP-addresses currently assigned by the DHCP server.

Advanced Settings

The next group contains more settings than any other. These settings are related to the functionality most users buy routers for. I mean thorough processing of data traffic.

This group begins with the Virtual Servers page. Here you can specify up to 24 rules for machines on the internal network to run servers of different applications accessible from the external network.

The Port Forwarding page offers 24 rules for specifying ports so that different applications could work in the external network. Ports can be specified in groups, separately, or both. The list of predefined applications is extensive, from popular multiplayer games to peer-to-peer networks. I guess most users are likely to find the applications they need in that list.

You can edit up to 24 rules for port triggering on the Application Rules page. This means dynamic conversion of some ports when they are accessed from the local network.

The QoS page contains options related to the integrated QoS engine including 10 editable rules for traffic prioritization.

The Network Filter page allows to create up to 24 rules for filtering access to the internal network by MAC addresses.

The Access Control page is where you assign rights to use network resources. Particularly, you can restrict access to certain websites or prohibit certain applications (e.g. peer-to-peer networks) to run in the internal network.

The Website Filter page is in fact a list you can use to limit the Internet access for users of the local network. If the appropriate option is activated on the previous page, only the websites from this list will be accessible.

IP-address ranges of the external network whose data will be let through or blocked are specified on the Inbound Filter page.

The Firewall Settings page offers, besides the firewall settings proper, a variegated selection of setup options, including DMZ, a network address spoofing check, operation of some protocols with NAT, etc.

The router’s routing table is filled in on the Routing page. You’ve got a total of 32 editable fields here.

The physical-level parameters of the wireless connection are specified on the Advanced Wireless page.

Traffic prioritization for the wireless connection is set up on the WISH page.

The Wi-Fi Protected Setup page is for quickly adding new devices into the router’s WLAN. It can be done either with a specific PIN code or with a special button on the device being attached. Of course, the device must support the appropriate connection method.

And finally, on the Advanced Network page you can enable/disable the UPnP protocol, to ping the router from the external network, multicast streams. You can also select the speed of the WAN port here.


The Tools group begins with the Administrator Settings.

Here you can set up user and admin accounts as well as remote administration parameters.

The Time page contains all the settings pertaining to the router’s system time and date.

To keep a log on a remote machine, go to the Syslog page.

To enable administrator notifications by email, go to the Email Settings.

The System Settings page is where you can process the router’s settings list: load a list from a disk, save a copy to a disk, reset all settings to the factory defaults. You can also reboot the router from here.

The Firmware page is for updating the router’s firmware.

DDNS related settings can be found on the Dynamic DNS page.

The Ping Test page is where you can ping remote machines from.

On the Schedules page various schedules for the router’s rules can be set up.


I only show you one information page in the Status group. The information is detailed and I liked that the log file could be set up flexibly.


I’ve got two new Wi-Fi adapters from D-Link that are recommended for use with the DIR-655. One is a PCI card (DWA-552) and the other is a PC Card for a notebook (DWA-652). Both are based on an Atheros chipset, the same as is installed in the DIR-655.



I also had a Wi-Fi adapter for notebooks, Linksys WPC300N, based on an Atheros chipset as well. This gave me the opportunity to perform a compatibility check of Wi-Fi equipment from different manufacturers. I didn’t include the Linksys WRT300N router into this review for the reasons that will be explained shortly. I just want to remind you that this router’s ports are Fast Ethernet only.

Here is a list of equipment and software I used for the tests:

I tested the DIR-655’s wired interface first. The router’s speed on the local network is indicative of its peak bandwidth.


Click to enlarge

The three following tests show the bandwidth on the WAN port. The first two tests were performed when the router’s services were disabled, but I enabled QoS, firewall and inbound filter for the third test. The second test was performed with enabled DMZ.


Click to enlarge


Click to enlarge

LAN-WAN (loaded):

Click to enlarge

It’s hard to evaluate the results without having any point of reference, yet the numbers look good to me, especially the small reduction of the channel bandwidth under load.

I performed one more test of the external network to evaluate the router’s ability to work with multiple connections simultaneously. It is important for such applications as p2p networks and, especially, torrent networks. For this test I created a pair in IxChariot using the Throughput scenario in which I changed the file_size parameter from 100000 to 1000000. Then I began to increase the number of pairs by replicating them until there were errors during the test. I stopped at 123 which was quite good for a home router.

The wireless connection in draft 802.11n mode was tested using WPA2 PSK encryption with the AES algorithm. These security settings are the default ones in the draft version of the new standard and are likely to remain such in the final version, too I used the most recent drivers for all the Wi-Fi adapters.

The diagram suggests that the Linksys adapter is an all-around winner. This indicates good compatibility between the equipment and good qualities of the card itself. By the way, as I found out during my tests the positioning of the antenna relative to the router was very important. The results would differ greatly depending on it. So, I oriented the adapters’ antennas towards the router in every WLAN test. And I guess the wrong positioning in space was the main reason for the poor results of the PCI adapter.

Finally I tested the router’s coverage at different distances and with different obstacles. This tested was performed with the different Wi-Fi adapters, excepting the DWA-552. I measured the signal level in five points:

Point 1: Near the DIR-655
Point 2: At a distance of 4 meters without obstacles
Point 3: At a distance of 5 meters + two thin gypsum wallboards
Point 4: At a distance of 6 meters + one brick wall, about 30cm thick
Point 5: At a distance of 17 meters + one thin gypsum wallboard and two 30cm brick walls

Here are the results:

In this test, on the contrary, the card from D-Link is better than the WPC300N. Although it is slower in speed, its graph is smoother which is more important here.

So, the router’s test results are good but I’ll wait for the results of other similar routers to make up my final opinion. Right now I can only say that the router provides enough bandwidth for deploying a small network with all the modern networking features.


The DIR-655 router didn’t prove completely up to my expectations. For a top-end model, it lacks functionality. For devices of this class it is not enough to boast high potential due high-quality onboard controllers: this potential needs to be properly implemented/ In case of D-Link DIR-655 it hasn’t been done fully even on the hardware level.

On the other hand, the router doesn’t look poor against competing products. The very availability of full-featured support of the draft 802.11n standard pushes this device up into the top-end category whereas the Gigabit Ethernet ports complement this positioning. I can’t judge the speed characteristics of the DIR-655 as yet since it is the first Gigabit Ethernet router to visit our test labs, but one thing is certain. The wireless connection of the DIR-655 is comparable in speed to modern wired network, and this is the key point of the 802.11n standard.

An indisputable advantage of the DIR-655 is that it has a Wi-Fi Alliance certification, which means it is an almost 100% compliant IEEE802.11n device.

Although I think the price of $145 is somewhat too high for this model, yet the DIR-655 is a good buy. I would recommend it for a small office due to its network security options, QoS, and remote administration tools. And the exterior design of this device would look better in the office than in the home environment.