A backbone network can be constructed as a switched backbone, a route.docx
- 1. A backbone network can be constructed as a switched backbone, a routed backbone or a VLAN backbone. Each of these approaches has its advantages and disadvantages. Discuss the advantages and disadvantages of each approach. Describe an example of a situation where a switched backbone would be preferred. Describe an example of a situation where a VLAN backbone would be preferred. Solution Answer a) Switched Backbones: most common type of backbone, used in distribution layer, used in new buildings, sometimes in core layer, can be rack or chassis based. Advantages of switched backbone 1. It propagates color information across entire network. 2. It allows greater scalability by extending bridge domains. 3. It has improved performance due to simultaneous access of switched operations. 4. It is a simpler more easily managed network and less devices are required. Disadvantages of switched backbone 1. The Backbone is running bridging.
- 2. 2. The Broadcast traffic increases drastically on the backbone. Routed Backbones: move packets along backbone on basis of network layer address, typically using bus, Ethernet 100Base-T, sometimes called subnetted backbone. Advantages of Routed Backbone 1. There is no bridging in backbone. 2. It is easy to integrate into existing internetwork. 3. It can run native protocols in the backbone. 4. In this Each message stays in one LAN unless addressed outside the LAN. 5. Routed backbone is Easier to manage. 6. Clear segmentation of parts of the network connected to the backbone as each network has a subnet address and can be managed separately. Disadvantages of Routed Backbone 1. The Color information is not propagated across backbone and must be configured manually. 2. If subnets are split, a bridged path has to be set up between switches. 3. It's Tend to impose time delays. 4. Slower performance as routing takes more time than
- 3. bridgine or switching. 5. Management and software overhead costs due to need to establish subnet addressing and provide reconfiguration when computers are moved. Virtual LANS: networks in which computers are assigned into LAN segments by software rather than by hardware. It can be single switch or multiswitch VLANS. Very popular technology. Advantages of VLAN Backbone 1.Faster performance: Allow precise management of traffic flow and ability to allocate resources to different type of applications. 2.Traffic Prioritization 1. Include in the tag: a priority code based on 802.1q 2. Can have QoS capability at MAC level 3. Similar to RSVP and QoS capabilities at network and transport layers. Disadvantages of VLAN Backbone 1.It's Cost is high. 2.There is a Management complexity in the VLAN Backbone. 3.Some "bleeding edge" technology issues to consider. Answer b) We use the switched backbone in ATM switching
- 4. technologies ATM switching offers high-speed switching technology for voice, video, and data. Its operation is similar to LAN switching technologies for data operations. ATM, however, offers superior voice, video, and data integration today. We also used it in Routing technologies Routing is a key technology for connecting LANs in a campus network. It can be either Layer 3 switching or more traditional routing with Layer 3 switching features and enhanced Layer 3 software features. Switched backbone are also used in campus. A true switched internetwork, therefore, is more than a collection of boxes. Rather, it consists of a system of devices integrated and supported by an intelligent internetworking software infrastructure. Presently, this network intelligence is centralized within routers. However, with the advent of switched internetworks, the intelligence will often be dispersed throughout the network, reflecting the decentralized nature of switching systems. Answer C) VLANs can be used to group a set of related users, regardless of their physical connectivity. They can be located across a campus environment or even across geographically dispersed locations. The users might be assigned to a VLAN because they belong to the same department or functional team,
- 5. or because data flow patterns among them is such that it makes sense to group them together. Note, however, that without a router, hosts in one VLAN cannot communicate with hosts in another VLAN. In a network based on broadcasts to all listeners to find peers, as the number of peers on a network grows, the frequency of broadcasts also increases, potentially to a point that much of the network time and capacity is occupied with only sending broadcasts between all members. VLANs can help reduce network traffic by forming multiple broadcast domains, to break up a large network into smaller independe nt segments with fewer broadcasts being sent to every device on the overall network.