Inside a hub, all ports are connected to each other. A hub provides a network, which connects all stations together, shares the same path and operation mode. For example, when five PCs connected to a 100Mbps hub, these 5 PC will share the 100Mbps and each PC can only obtain 20Mbps bandwidth. Also, when one port in a hub receives a data frame, the hub will copy this frame to all ports in that hub. The features will not only expose all data to public but also cause serious collision when the traffic increases.

On the other hand, inside a switch, all the ports are connected to each other only when addressed. A switch provides a network, which connects stations only when they access each other. Each port on a 100Mbps switch has independent 100Mbps bandwidth. A switch will learn the attached PC's MAC address automatically. When receiving a data frame, it will check MAC table. If the switch finds the MAC address in the table, it will transfer the data directly to that port and reduce the traffic rather than copy to all ports. As a result, collision seldom happens in a switch.

Deployment steps might include replacing 10/100 Mbps adapters with auto-negotiating 10/100/1000 adapters. Of course, these servers would need to be connected to a Gigabit-enabled switch. With the 1000BASE-T standard, Gigabit Network Cards and switches can support both 100/1000 and 10/100/1000 auto-negotiation between Fast Ethernet and Gigabit Ethernet. This allows network professionals to deploy 1000BASE-T incrementally into the network. For instance, a 100/1000 server Network Card may be installed into a new server while the server switch remains 100BASE-TX, or vice versa..

One of these differences in the algorithms between a switch and a router is how broadcasts are handled. On any network, the concept of a broadcast packet is vital to the operability of a network. Whenever a device needs to send out information but doesn't know whom to send, it sends out a broadcast. For example, every time a new computer or other device comes on to the network, it sends out a broadcast packet to announce its presence. The other nodes (such as a domain server) can add the computer to their browser list (kind of like an address directory) and communicate directly with that computer from that point on. Broadcasts are used any time a device needs to make an announcement to the rest of the network or is unsure of who the recipient of the information should be.

A hub or a switch will pass along any broadcast packets they receive to all the other segments in the broadcast domain, but a router will not. Think about a four-way intersection: All of the traffic passed through the intersection no matter where it was going. Now imagine that this intersection is at an international border. To pass through the intersection, you must provide the border guard with the specific address that you are going to. If you don't have a specific destination, then the guard will not let you pass. A router works like this. Without the specific address of another device, it will not let the data packet through. This is good to keep networks separate from each other, but not so good when you want to talk between different parts of the same network. This is where switches come in.

A broadcast domain is a network (or portion of a network) that will receive a broadcast packet from any node located within that network. In a typical network, everything on the same side of the router is all part of the same broadcast domain. A switch that you have implemented VLANs on has multiple broadcast domains, similar to a router. But you still need a router (or Layer 3 routing engine) to route from one VLAN to another -- the switch can't do this by itself. You can create a VLAN using most switches simply by logging into the switch via Telnet and entering the parameters for the VLAN (name, domain and port assignments). After you have created the VLAN, any network segments connected to the assigned ports will become part of that VLAN.

While you can have more than one VLAN on a switch, they cannot communicate directly with one another on that switch. If they could, it would defeat the purpose of having a VLAN, which is to isolate a part of the network. Communication between VLANs requires the use of a router. Here are some common reasons why a company might have VLANs:

5.1 Security
VLAN can separate systems that have sensitive data from the rest of the network so that the network security is enhanced. This is because VLAN will decrease the chances for people who are not authorized to access some certain information.
5.2 Projects/Special applications
Managing a project or working with a specialized application can be simplified by the use of a VLAN that brings all of the required nodes together.
5.3 Performance/Bandwidth
Careful monitoring of network use allows the network administrator to create VLANs that reduce the number of router hops and increase the apparent bandwidth for network users.
5.4 Broadcasts/Traffic flow
Since a principle element of a VLAN is the fact that it does not pass broadcast traffic to nodes that are not part of the VLAN, it automatically reduces broadcasts. Access lists provide the network administrator with a way to control who sees what network traffic. An access list is a table the network administrator creates that lists which addresses have access to that network.
5.5 Departments/Specific job types
Companies may want VLANs set up for departments that are heavy network users (such as multimedia or engineering), or a VLAN across departments that is dedicated to specific types of employees (such as managers or sales people).

On the other hand, Solid Category 5 cables have their advantages, too. Theoretically speaking, due to its superior electrical properties, solid Category 5 supports a higher level of performance than stranded cables, though the benefit can be negligible in practice. Businesses that are accustomed to wiring inside office walls or under floors to fixed locations, and are willing to pay more for the possibility of improved network performance, often prefer solid cabling.

Finally, when working with Category 5 cable, it's important to know that several different types of RJ-45 connectors exist. One type, designed for use with stranded cables, generally is incompatible with solid cable. Other types of RJ-45 connectors may work with both stranded and solid Category 5.

Using the Internet's Resource Reservation Protocol (RSVP), packets passing through a gateway host can be expedited based on policy and reservation criteria arranged in advance. Using ATM, which also lets a company or user pre-select a level of quality in terms of service, QoS can be measured and guaranteed in terms of the average delay at a gateway, the variation in delay in a group of cells (cells are 53-byte transmission units), cell losses, and the transmission error rate.

The Common Open Policy Service (COPS) is a relatively new protocol that allows router and layer 3 switches to get QoS policy information from the network policy server.

In contrast, Class of Service (CoS) is a way of managing traffic in a network by grouping similar types of traffic (for example, e-mail, streaming video, voice, large document file transfer) together and treating each type as a class with its own level of service priority. Unlike Quality of Service (QoS) traffic management, CoS technologies do not guarantee a level of service in terms of bandwidth and delivery time; they offer a "best-effort." On the other hand, CoS technology is simpler to manage and more scalable as a network grows in structure and traffic volume. You can take CoS as advanced traffic control, and QoS as professional traffic control.

There are three main CoS technologies: 802.1p Layer 2 Tagging, Type of Service (ToS), and Differentiated Services (DiffServ).

802.1p Layer 2 Tagging and ToS make use of three bits in the layer 2 packet header that can be used to specify priority. Since three bits does not allow for much sophistication in managing traffic, a new protocol, Differentiated Services (DS or DiffServ), has been developed in draft form by an IETF Working Group. Differentiated Services uses a different approach to managing packets than simple priority labeling. It uses an indication of how a given packet is to be forwarded, known as the Per Hop Behavior (PHB). The PHB describes a particular service level in terms of bandwidth, queuing theory, and dropping (discarding the packet) decisions.

In bridging networks, computer or node addresses have no specific relationship to location. For this reason, messages are sent out to every address on the network and accepted only by the intended destination node. Bridges learn which addresses are on which network and develop a learning table so that subsequent messages can be forwarded to the right network.
Bridging networks are generally always interconnected local area networks since broadcasting every message to all possible destinations would flood a larger network with unnecessary traffic. For this reason, router networks such as the Internet use a scheme that assigns addresses to nodes so that a message or packet can be forwarded only in one general direction rather than forwarded in all directions.

A bridge works at the data-link (physical network) level of a network, copying a data frame from one network to the next network along the communications path. A bridge is sometimes combined with a router in a product called a router.

A1: How to reset the ˇ§IP addressˇ¨, ˇ§User Nameˇ¨ and ˇ§Passwordˇ¨ to default value?
Step 1: Unplug the switch from power.
Step 2: Press and hold down the Reset Button.
Step 3: Power up the switch, keep holding down the Reset button for a few (between 15 to 25 seconds.
Step 4: Release the Reset Button.

A2: How to reset the all parameters to default value?
Step 1: Unplug the switch from power.
Step 2: Press and hold down the Reset Button.
Step 3:.Power up the switch, keep holding down the Reset Button for a few (between 50 to 70) seconds.
Step 4: Release the Reset Button.