Switches, Bridges, Hubs, DSL Modem, DSLAMS, ISDN, Switch, DSL Splitters

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Switches and Bridges

Another piece of network hardware related to the switch is the Bridge. A Bridge is effectively a two-port switch.

Because there is not much market for a two-port switch, bridges are no longer manufactured.

Switches and Hubs

Before switches became available, devices called hubs were common.

Hubs were less intelligent network devices that always copied all frames to all ports.

By only copying frames to the destination ports, switches utilize network bandwidth much more effectively than hubs did.

DSL Modems and DSLAMS

A DSL circuit exists between the DSL modem on the customer premisis and a DSLAM (Digital Subscriber Line Access Multiplier). The DSLAM is usually located in the telco Central Office (CO).

One DSLAM can terminate several hundred DSL connections.

ISDN

ISDN (Integrated Services Digital Network) is a system of digital phone connections that has been designed for sending voice, video, and data simultaneously over digital or ordinary phone lines, with a much faster speed and higher quality than an analog system can provide. ISDN is basically a set of protocol for making and breaking circuit switched connections as well as for advanced call features for the customers. ISDN is the international communication standard for data transmission along telephone lines and has transmission speeds up to 64 Kbps per channel.

Switch

A switch is a network device with multiple ports in one network whose task is to copy frames from one port to another.

Switches operate at Layer 2 of the OSI Model, the Data-Link Layer. This is in contrast to routers, which operate at Layer 3 of the OSI Model, the Network Layer.

A switch stores the MAC Address of every device which is connected to it.

The switch will then evaluate every frame that passes through it. The switch will examine the destination MAC Address in each frame.

Based upon the destination MAC Address, the switch will then decide which port to copy the frame to.

If the switch does not recognize the MAC Address, it will not know which port to copy the frame to. When that happens, the switch will broadcast the frame to all of its ports.

DSL Splitters

Some DSL implementations move data traffic over the same pair of wires which carry voice telephone traffic.

Other DSL implementations move date traffic over a dedicated wire pair.

Most American homes have two pairs of wires from the local telephone company. If the home has only one telephone line in use, DSL can be installed on the second pair.

If the home has both telephone lines in use, DSL must share one wire pair with voice traffic. This is done using a DSL splitter.

A DSL splitter is a small box which attaches to the wire pair and splits it into two separate wire pairs, one for voice traffic and the other for DSL traffic.