Network Hubs and Switches
Hubs and switches function as a common connection
point for the workstations, printers, file servers and other devices that make
up a network. The main difference between hubs and switches is the way in which
they communicate with the network.
What is a Hub?
A hub functions as the central connection point of a network. It joins together
the workstations, printers, and servers on a network, so they can communicate
with each other. Each hub has a number of ports that connect it to the other
devices via a network cable.
How does a Hub work?
A hub is an inexpensive way to connect devices on a network. Data travels around
a network in ‘packets’ and a hub forwards these data packets out to all the
devices connected to its ports.
As a hub distributes packets to every device on the network, when a packet is
destined for only one device, every other device connected to the hub receives
that packet. Because all the devices connected to the hub are contending for
transmission of data the individual members of a shared network will only get a
percentage of the available network bandwidth. This process can slow down a busy
network.
A 10Base-T hub Ethernet Hub provides a total of 10
Mbit/sec of bandwidth, which all users share. If one person on the network is
downloading a very large file, for example, little or no bandwidth is available
for other users. These users will experience very slow network performance.
What is a Switch?
A switch is more sophisticated than a hub, giving you more options for network
management, as well as greater potential to expand. A switch filters the data
packets, and only sends the packet to the port which is connected to the
destination address of that packet. It does this by keeping a table of each
destination address and its port. When the switch receives a packet, it reads
the destination address and then establishes a connection between the source
port and the destination port. After the packet is sent, the connection is
terminated.
What are the advantages of a Switch?
A switch provides higher total throughput than a hub because it can support
multiple simultaneous conversations. For example, when a 100Mbit/sec hub has
five workstations, each receives only 20Mbit/sec of the available bandwidth.
When a 10/100Mbit/sec switch is used every port on the switch represents a
dedicated 100Mbit/sec path, so each workstation receives 100Mbit/sec of
bandwidth.
Switches also run in full duplex mode, which allows data to be sent and received
across the network at the same time. Switches can effectively double the speed
of the network when compared to a hub which only supports half duplex mode.
Managed Switches
A managed switch allows the ports on the switch to be configured, monitored,
enabled and disabled. Switch management can also gather information on a variety
of network parameters, such as:
The number of packets that pass through each of
its ports
What types of packets they are
Whether the packets contain errors
The number of collisions that have occurred
You should look for the following features on a
managed switch:
Gigabit Ethernet support
SNMP management and remote control capabilities
A management interface that can be accessed
through an internet browser
Auto-negotiation support which auto-senses the
speed and duplex capabilities of connected devices
Built-in expansion capability
Using a managed switch can reduce hidden costs by
using:
Switch and traffic monitoring to help head off
problems before they occur, reducing user downtime
Management tools that offer an intuitive graphical
user interface (GUI) that simplifies configuration and monitoring tasks
Management functions can be performed remotely
using a web browser or directly via a console connected to the switch.
