Jan 16, 2003 Week 2: Day 2
Active hubs regenerate the signal, whereas passive hubs do not. Passive hubs
do not require power. Check this link out for more information about hubs.
Just kidding. Try this one: Top
5 Dual-Speed (10/100) Ethernet Hubs for Home
Hubs remain a very popular device for small networks because of their low cost. A good five-port Ethernet hub can be purchased for less than $50 USD. So-called home networking kits package together one of these hubs and two matching Ethernet adapters for approximately $50 USD. For many home networks, a four-port hub will be sufficient to build a LAN. An eight-port hub can cost twice as much as the four-port, but if room for future growth is a consideration, the extra cost may be a worthwhile investment. The five-port hub, with its "uplink" capability, offers a good compromise between up-front cost and future extensibility.
The least expensive four-port hubs support only traditional (10 Mbps) Ethernet. 10 Mbps will adequately support Internet connection sharing of today's traditional dial-up, cable modem, and DSL services. A 10/100 hub supports both 10 Mbps and 100 Mbps (Fast Ethernet) connections. These higher-performance hubs can prove very useful in some situations. For example, online gamers who enjoy "LAN parties" and network game play at home will almost certainly notice a significant performance increase when running at 100 Mbps. Note that to run at this speed, both the hub and the network interface card (NIC) on the computer must be rated at 10/100 or 100 Mbps.
When acquiring a hub, many people
fail to consider the noise a hub can generate. Older hubs contain fans used
to keep the unit cool, and the noise from these can range from barely perceptible
to quite annoying depending on the quality of the manufacturing. The situation
has improved in recent years: hubs used to sound something like a jet engine
when powered on in a quiet room. Nowadays, some manufacturers have successfully
eliminated the need for a fan in their hubs, and these are almost completely
silent.
A switch is a small device that joins multiple computers together at a low-level
network protocol layer. Technically, switches operate at layer two (Data Link
Layer) of the OSI model.
Switches look nearly identical to hubs, but a switch generally contains more "intelligence" (and a slightly higher price tag) than a hub. Unlike hubs, switches are capable of inspecting the data packets as they are received, determining the source and destination device of that packet, and forwarding that packet appropriately. By delivering messages only to the connected device that it was intended for, switches conserve network bandwidth and offer generally better performance than hubs.
Like hubs, switches primarily are available for Ethernet, come in a range of port configurations starting with the four- and five-port models, and support 10 Mbps Ethernet, 100 Mbps Ethernet, or both.
Computer
Networking FAQ #11
What is the difference between a hub and a switch?
Some switches support two modes of operation: half-duplex communication and full-duplex communication. Half-duplex communication allows transmission on the link in only one direction, either sending or receiving. While full-duplex communication allows devices to send and receive data simultaneously.
Because large switches could have as many as 1024 devices attached, they can be configured to route transmissions among one or more groups of selected devices as if the devices were connected in a bus or ring. For example, if a switch’s first four ports are configured as a single VLAN, traffic is limited to these four ports and is not transmitted to other devices attached to the switch.
1. What is the term used to refer to the single cable segment to which all devices
on a bus network are attached?
Think about it, then click HERE
to see the answer.
2. What is attenuation?
Think about it, then click HERE
to see the answer.
3. In addition to a physical ring,
what other configuration can be used to connect devices on a ring topology network?
Think about it, then click HERE
to see the answer.
4. What is full-duplex communication?
Think about it, then click HERE
to see the answer.
Check out the mini-lecture on Variations of the Major Toplogies
VLANs support logical grouping of network nodes to reduce broadcast traffic
and allow more control in implementing security policies. A VLAN is a group
of PCs, servers and other network resources that are on physically different
segments but communicate as though they were on the same wire. For example,
your marketing personnel may be spread throughout a building, yet if they are
all assigned to a single VLAN, they can share resources and bandwidth as if
they were connected to the same segment. Such a logical grouping helps free
IT managers from the restrictions of their existing network design and cabling
infrastructure and offers a fundamental improvement in the ease with which LANs
can be designed, administered and managed.
Performance: Reduces network through the segmentation of the network which more effectively restricts the dissemination of node-to-node traffic throughout the network. Users and resources that communicate most frequently with each other can be grouped in common VLANs so that their traffic is contained.
Manageability: Software-based VLANs mean changes do not require a visit to the wiring closet. Logical groupings allow network structure to quickly and easily adapt to an addition, relocation or reorganization of nodes through a management console.
Switched networks are generally
wired as physical star topologies. The type and number of interfaces on the
network devices and switches determine the VLAN configuration that can be used
on the switch. The same considerations apply to choosing a VLAN as to the three
standard topologies.
Quick Quiz
1. Which topology variation provides complete fault tolerance?
Think about it, then click HERE
to see the answer.
2. Through what configuration method are switches able to operate as routers?
Think about it, then click HERE
to see the answer.
3. Which topology requires the most expensive of the networking devices discussed?
Think about it, then click HERE
to see the answer.
Here is today's case analysis. What do you think?
A set of five shared database servers is being developed by your software department. These systems rely on each other for redundancy and are fault-tolerant of each other. Design a network which will provide these computers full redundancy, no matter the cost.
OK, that does it for today. The quiz is available! Don't get behind.