Back Bone Design & Local Access Network Design:- Back Bone Design:- In computer networking, a backbone is a central conduit designed to transfer network traffic at high speeds. Network backbones are designed to maximize the reliability and performance of large-scale, long-distance data communications. The best known network backbones have been those used on the Internet. Backbones typically consist of network routers and switches connected by fiber optic or Ethernet cables. Computers normally do not connect to a backbone directly. Instead, the networks of Internet service providers or large organizations connect to these backbones and computers access the backbone indirectly.
A backbone network or network backbone is a part of computer network infrastructure that interconnects various pieces of network, providing a path for the exchange of information between different LANs or sub networks. A backbone can tie together diverse networks in the same building, in different buildings in a campus environment, or over wide areas. Normally, the backbone's capacity is greater than the networks connected to it.
Types of backbone network:-
Serial Backbone:- Serial backbone is formed of two or more devices that are connected in a daisy chain (linked series). It is a simplest kind of backbone. As the one can see from Figure, serial backbone can be made not only from switches, but also from gateways and routers.
While designing the backbone, the one should consider the limit of the devices that can be connected to the backbone in the repeating fashion. Exceeding the limit would result in the unexpected errors and data loss in the network. Serial backbone networks are not very fault tolerant and not very scalable, that make them less commonly used that the distributed backbone.
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Computer Network
Distributed backbone:- A distributed backbone is a backbone network that consists of a number of connectivity devices connected to a series of central connectivity devices, such as hubs, switches, or routers, in a hierarchy. This kind of topology allows for simple expansion and limited capital outlay for growth, because more layers of devices can be added to existing layers. In a distributed backbone network, all of the devices that access the backbone share the transmission media, as every device connected to this network is sent all transmissions placed on that network.
Distributed backbones, in all practicality, are in use by all large-scale networks. Applications in enterprise-wide scenarios confined to a single building are also practical, as certain connectivity devices can be assigned to certain floors or departments. Each floor or department possesses a LAN and a wiring closet with that workgroup's main hub or router connected to a bus-style network using backbone cabling .Another advantage of using a distributed backbone is the ability for network administrator to segregate workgroups for ease of management.
Collapsed backbone:- This type of backbone uses single, powerful router as the central connection point for multiple sub networks. As Figure shows, the central device is the highest level of the backbone. It should have powerful computational power in order to manage big traffic coming in. This is highly risky, since if the central device fails, the whole network would be down. However, this type of backbone is useful for the one who wants to interconnect two types of sub networks, with ability to manage and troubleshoot them.
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Parallel backbone:- Parallel backbone is a variation of the collapsed backbone, where devices are having more than one connection between them. As Figure shows, there are multiple connections between the high level routers and the network segments. Duplicate connections ensure networks availability at anytime, higher speeds, and high fault tolerance. Logical drawback of this solutions is the increased price, since amount of required cabling is highly increased. It is not obligatory to have duplicate connections between all the devices, selective implementation of parallel structure would significantly lower the overall price and make additional ports of the devices available.
Figure. Parallel backbone
Local Access Network Design :- Basically network design is one of the four phases of PDIOO (Plan Design Implement Operate Optimize) life cycle. In this phase of the network life cycle, the designer’s task will be to develop the physical and logical design of the network project. The physical design of the network is concerned with the identification of LAN and WAN technologies and network devices that are supposed to realize the performance of the logical design at large. During this phase, the network designer is responsible for selecting devices such as cabling wires, switches, bridges, routers, wireless access point and others. As we can see the logical design phase is a foundation for the physical network design, and it is where the designer develops a hierarchical and modular network. This phase includes designing of network layer addressing, selection of switching and routing protocols, security planning and network management design.
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Computer Network
Hierarchical network design involves dividing the network into discrete layers. Each layer provides specific functions that define its role within the overall network. By separating the various functions that exist on a network, the network design becomes modular, which facilitates scalability and performance. The typical hierarchical design model is broken into three layers: ■ Access ■ Distribution ■ Core Access Layer:-
The access layer interfaces with end devices, such as PCs, printers, and IP phones, to provide access to the rest of the network. The access layer can include routers, switches, bridges, hubs, and wireless access points. The main purpose of the access layer is to provide a means of connecting devices to the network and controlling which devices are allowed to communicate on the network.
Distribution Layer The distribution layer aggregates the data received from the access layer switches before it is transmitted to the core layer for routing to its final destination. The distribution layer controls the
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Computer Network flow of network traffic using policies and delineates broadcast domains by performing routing functions between virtual LANs (VLANs) defined at the access layer. VLANs allow you to segment the traffic on a switch into separate sub networks. For example, in a university you might separate traffic according to faculty, students, and guests. Distribution layer switches are typically high-performance devices that have high availability and redundancy to ensure reliability. Core Layer The core layer of the hierarchical design is the high-speed backbone of the internetwork. The core layer is critical for interconnectivity between distribution layer devices, so it is important for the core to be highly available and redundant. The core area can also connect to Internet resources. The core aggregates the traffic from all the distribution layer devices, so it must be capable of forwarding large amounts of data quickly.
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