Many of today’s networks have implemented technologies such as switching to deal with growth in the network. As networks get bigger using the old-fashioned technologies utilizing bridges and hubs, the networks slow down because of the amount of data traffic and broadcasts. In this section, you’ll learn about how too many devices and broadcasts in a non-switched network can affect how a network performs. A broadcast is a message destined for more than one host on the network. It can be sent to a multicast address for groups, a subnet, or even an entire network.
Critical Information
A flat network topology is a LAN connected by bridges and hubs. Every node in the network sees the data being passed by every other node on the network. This arrangement eats up an incredible amount of processing power and bandwidth, even without collisions forcing data to be re-sent on the physicalwire. A flat network topology begins to slow down due to traffic, collisions, and other bottlenecks.
Of the layer 3 protocols, TCP/IP is the most popular because it is less chatty than the other common layer 3 protocols, Internetwork Packet Exchange (IPX) and AppleTalk. Most network administrators agree that if you have bandwidth to kill, you can add IPX and AppleTalk, which like to scream ¡°I’m here on the network quite frequently thereby eating up bandwidth. A few devices on the network don’tuse too much bandwidth; but as the number of network nodes increases, so does the number of broadcasts required to identify the nodes running those protocols on the network.
The processors in each node handle the task of reading each packet to determine if the packet received is for itself or some other device. This takes away from the processing power needed for other tasks and applications, causing a slowdown that the users discover and complain about. Many network
administrators pass off this slowness as a problem with the PCs, and the most vital PCs are rebuilt, upgraded or replaced. Of course, upgrading or replacing PCs with faster processors can alleviate the slowness; however, the administrators have no idea that there are other solutions to this problem.Administrators can upgrade to Fast Ethernet, Gigabit Ethernet, or a switched network instead of hubs. Many administrators who don’t know about switching and its benefits implement different wiring solutions such as fiber optic with its high costs of cabling and installation labor. This is usually because of a salesman who convinced them that fiber is better. And it is in some situations, such as in large factories that deal with electrical equipment, but fiber is very expensive and usually unjustified.
The most cost-effective solution is to upgrade to switches. Doing so confines your collision domains so only the interfaces are attached to the switches ports, and you can segment your broadcast domains to as many as you would like by implementing VLANs. When companies finally decide to upgrade to a switched network, they can typically do so over a weekend by simply replacing the hubs they have.
Sometimes, if you have a 10BaseT network with Category 3 or 4 cabling, the best solution is to fix the immediate problems by upgrading to Category 5 or 6 cabling and implementing a Fast Ethernet network in conjunction with installing switches. However, most network users do not need more than true 10Mbps from the Access-layer switches to their desktops even if they are using high-bandwidth applications. After all, before they had switches, the users were getting along with only 3 or 4Mbps on their 10Mbps link, due to broadcasts, collisions, and network utilization.
Exam Essentials
Remember the causes of congestion.
The main problem of congestion is too much traffic, caused by too much data being transmitted, too many broadcasts, and too many collisions.
Remember the benefits of switches and VLANs
Hubs can use only half-duplex on each attached interface, making way for multiple collisions. Switches allow for full-duplex between the transmitter of the sending interfaces. This is because it uses two cables one to send and one to receive so there should never be data collisions. A switch makes each port its own collision domain. VLANs allow you to segregate certain ports into their own broadcast domains.
Key Term and Concept
broadcast
A frame or packet destined for all hosts on a group, segment, or network.
Related posts:
- Advantages of LAN Segmentation
- LAN segmentation using bridges and switches
- Full and Half-Duplex Ethernet Operation
- Layered Model Exam Points
- Benefits of Network Segmentation With Routers
- Virtual LANs
- Distance Limitations of Fast Ethernet
- Network Addressing Exams Points
- Features and Benefits of Fast Ethernet
- Full and Half-Duplex Ethernet
