Recently, I had
a chance to sit down with Compexs new switch, the PS2216, which is
geared toward SOHO and gamer networks. With a data buffer of 128K, an 8K
address table, and a backplane capacity of 3.2Gps, the switch compares
to some of the higher priced SOHO switches and gives you some
interesting features to boot.
Essentially, switching is the process of transferring data from one
input interface to an output interface. A switch maintains a destination
address and port number in its routing table (this is where that 8K
comes in). When it receives a packet, it pulls in the header and
extracts the source and destination and creates a temporary connection
between the two, passes the packet, and then closes the connection,
instead of repeating the packet to all ports increasing congestion as
would happen on a HUB. The PS2216 uses the standard "store and forward"
switching method, which basically means the switch will wait until it
has the entire packet. Once it does, it will move the packet into its
buffer, calculate its CRC value, and compare that value to the packets
CRC. If the two match, then the packet is passed, if not, it is dropped.
This method ensures packets are reliably transferred, but can increase
latency. Other methods would include "cut-through", which means the
switch will begin to forward the packet once it has the first 6 bytes,
and "fragment-free", which means the switch will begin to forward the
packet once it has received the first 64 bytes, since packet corruption
is usually detected within the first 64 bytes. For all intent and
purposes, the "stop and forward" method is fine for the PS2216 as it is
the safest method and probably the best choice for the home user who
doesnt necessarily need to know much about networking, only that the
device works or doesnt work. And the PS2216 works nicely.
Configuration of the switch was easy, involving some quick
evaluations of which features I would want enabledthose being: port
trunking, port priority, and VLAN (Virtual LAN). Now, depending on how
you look at it, the fact that configuration is done via dip switches
rather than through an OS could be beneficial to the home user. Theres
no need to deal with any on-board OS, like you would with a more
intricate switch. The only downfall is that youre unable to remotely
manage the feature set. But, really, how many times would you be
climbing under your desk to turn on or off a given feature? These
decisions are usually made at the time of install or when you bring in
another workstation.
Since management is done by dip switch, the switch has the hard-coded
values for which ports will be assigned to a given feature and how the
network is laid out. For an example, if you were to enable the VLAN
feature, then all ports would be segmented into their own private VLAN,
meaning one port couldnt communicate with the other, leaving port 1 as
the overlapping port. Theres no way for you to configure VLANs based
upon what ports you would like to have in the VLAN, meaning you couldnt
have two VLANs, one with ports 2 8 and the other with ports 9 16. To
the idle LAN bash, I dont see this feature as being of real use; the
Compex VLAN implementation would work better within a SOHO network. It
would have been useful, if you could configure VLANs and assign ports to
those VLANs instead of a single sweeping configuration.
Just like the VLAN feature, when you enable port trunking it is
enabled for a certain set of ports; however, in this case, you have two
groups, ports 1, 2, 9 and 10 or ports 3, 4, 11, and 12, leaving you
eight additional ports free for other uses, two of which can become
priority ports. Port trunking would come in handy if you had a box on
the network that was pushing excessive amounts of traffic and you needed
to increase its throughput. Essentially, youre taking the ports and
tying them together as a single port. The ports would, with full-duplex
and 100-mbit speeds, give you around 800-mbit in speed. You could also
connect two PS2216s together and use trunking to increase throughput
between the two switches. Out of the entire feature set, this is
probably the most useful, as it allows you to increase the bandwidth of
a given machine on the local network. This would also be useful if you
had some type of media or file server on your network that was pushing
more traffic than other machines. To get this working wasnt too
difficult, and like everything else, it worked without error in my
testing.
Another nice feature included of the PS2216 is the ability to
prioritize ports, in this case 8 and 16. This is a way to assign packets
higher priority over others. The packet with the higher priority is sent
before the ones with lower prioritiesvery useful when you have a gaming
server or another server that could require a higher communication
priority. With this feature enabled, you dont see too much, if any,
degradation in performance.
It seems Compex laid out the features in a nice, easy way, where you
could not only turn on trunking, but port priority. The only downfall
here is you cant combine the two. By this I mean you couldnt trunk
ports together and drop a router on the trunk and then assign a higher
priority to that trunked, logical interface. But, in reality, most home
users wouldnt need this ability.
Overall, the PS2216 is a nice switch to work with. During my entire
testing, I didnt really get hung up with any of the features. The only
downfall is that youre not able to select which ports get what feature:
theyre hard set by the manufacturer. Other than that, the switch
performed under normal usage, as well as during LAN gaming sessions,
without error and no noticeable latency. Combined with the low
price-point of $6065 (the lowest I found on