1 / 33

Business Data Communications

Business Data Communications. Chapter Six Backbone and Metropolitan Area Network Fundamentals. Primary Learning Objectives. Define backbone and metropolitan area networks Differentiate between horizontal and vertical network segments Recognize the function of a backbone network protocol

duncan
Download Presentation

Business Data Communications

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Business Data Communications Chapter Six Backbone and Metropolitan Area Network Fundamentals

  2. Primary Learning Objectives • Define backbone and metropolitan area networks • Differentiate between horizontal and vertical network segments • Recognize the function of a backbone network protocol • Understand the advantages and disadvantages of distributed and collapsed backbones • Explain the concept of backbone fault tolerance • List examples of backbone design considerations • Identify common backbone problems • Describe Switched Multimegabit Data Services

  3. Backbone and Metropolitan Area Networks • A backbone network (BN): • Connects other networks of an organization • Networks connected are typically LANs • Generally spans a building or campus • Has its own address • A metropolitan area network (MAN): • Is often used to connects BNs • Generally spans a city • Is sometimes viewed as a citywide backbone • Has its own address • The distinction between BNs and MANs is blurring

  4. Horizontal and Vertical Networks • Each individual LAN is called a network segment • A network segment may be horizontal or vertical • Horizontal networks are configured on a single floor • Vertical networks are configured on multiple floors • Whether horizontal or vertical, network segments are usually connected to each other by means of a backbone network

  5. A Horizontal Network

  6. A Vertical Network

  7. Connecting to a backbone

  8. Backbone Network Protocols • BNs most often support high traffic demand for connected LANs • Therefore a BN generally uses a protocol that provides higher throughput than the protocol used by the connected LANs • Gigabit Ethernet: • Is a common protocol choice for BNs • In its initial form was labeled 802.3z by the IEEE • Supports 1 Gbps (billion bits per second) • Does not change the underlying Ethernet format • Is both half- and full-duplex capable • ATM and Frame Relay are also possible BN protocols

  9. Distributed and Collapsed Backbones • In addition to having a protocol, BNs have an architecture • Two common types of BN architecture are: • Distributed • Collapsed • Factors that influence the BN architecture choice include: • Business need • Condition of the facility or physical plant • The way that users need to communicate • Budget • Placement of networked devices

  10. Distributed Backbones • “Distributed” implies “in more than one location” • A Distributed Backbone: • Runs throughout the entire facility • Uses a central cable • Requires its own protocol • Is its own network • Is usually connected to network segments, LANs, by switches and/or routers • Can have directly connected devices that are part of the BN

  11. Distributed Backbones Each router will have two network addresses

  12. Distributed Backbones • When configured with multiple routers, may need to pass traffic through several routers for that traffic to reach its final destination • Going through several routers can result in traffic delay • Internetwork traffic can be expected to increase when more routers are used • Require that each network segment have its own cabling and connecting device to the distributed backbone, adding to expense

  13. Distributed Backbones • Are generally more complex than collapsed backbones, resulting in more complicated: • Security • Maintenance • Monitoring • Allow the placing of commonly needed networked devices or resources directly onto the backbone • May be the only viable solution for a business, depending on the facility and layout of network segments

  14. Distributed Backbone with a Directly Connected DB Server

  15. Collapsed Backbones • Use a single central device, namely a router or switch, to which network segments are connected • This central router or switch is in essence the backbone • Connect network segments to the collapsed backbone, using other hubs, switches, or routers • Generally reduce cabling needs, however: • Connected devices must be able to support cable segment lengths that span the distance to the collapsed backbone • Legacy networks using lower grade UTP may not be collapsed-backbone compatible

  16. Collapsed Backbones • Do not require a protocol different from that of connected network segments • Having one protocol can make network administration easier • However, depending on how the backbone needs to be used relative to traffic demands, having one protocol may not be an advantage • Utilize a “backplane”--a high-speed communications bus--in the switch or router

  17. Collapsed Backbones • Use fiber optic cabling to connect network segments to a collapsed backbone’s backplane • Fiber allows network segments to be widely scattered across a building or campus • Might not allow legacy Ethernet networks to utilize the collapsed backbone architecture • Pass internetwork traffic through only one device • Centralize security, monitoring, and maintenance • Can achieve significant cost savings

  18. Collapsed Backbones Internetwork traffic passes through only one connecting device, in this example a switch, to its ultimate destination

  19. Distributed versus Collapsed

  20. Backbone Fault Tolerance • “Fault tolerance” is the capability of a technology to recover in the event of an error, failure, or some other unexpected event • Backbones, because they connect and provide communication to various segments of an enterprise, must be fault tolerant • Resource redundancy is a common means of providing fault tolerance

  21. A Simplified Redundant Backbone

  22. Backbone Fault Tolerance • Redundant backbones also allow for traffic load balancing • By permitting placement of half of all network segments onto one or the other backbone, duplicate backbones allow internetworking traffic to be shared or balanced • Duplicating the backbone can be done in whole or in part, based on cost and need • Documentation is also part of recovery procedures

  23. Backbone Design Considerations • Internal versus external wiring • Identification and labeling of all backbone networks, devices, wiring • Knowledge of collision domain boundaries • An enterprise with a mix of Ethernet networks (such as Standard, Fast, Gigabit) might have a mix of collision domains • Wiring closets • Data centers

  24. Backbone Design Considerations

  25. Backbone Design Considerations

  26. Wiring Closet Design

  27. A few Good Tools

  28. Common Gigabit Backbone Problems • Packet errors • Early collision • Late collision • Runts • Giants and jabbering • Broadcast storms

  29. Common Gigabit Backbone Problems • Cable errors: • Near-end cross talk • Attenuation • Impedance • Attenuation to cross talk • Capacitance • Cable length

  30. Common Gigabit Backbone Problems • Network Interface Card errors: • Improper configuration – diagnostic software • Physical failure • Connectivity testing with ping: • Based on ICMP • Various vendor implementations • Echo_Request • Echo_Reply • Time-to-live

  31. Common Gigabit Backbone Problems

  32. Switched Multimegabit Data Services - SMDS • Were designed specifically for MANs • Support exchanging data between: • LANs in different parts of a city • Network segments over a large campus • Provide packet-switched datagram delivery • Are associated with a common carrier’s SMDS network • Require subscribers to pay only when they use the common carrier’s network

  33. In Summary • The distinction between BNs and MANs is blurring • BNs are critical in connecting the various network segments of an organization • BNs have both a protocol and architecture: • Gigabit Ethernet is a popular BN protocol • Two BN architectures are distributed or collapsed • Fault tolerance is important for the backbone • Common Gigabit backbone problems include packet, cable, and NIC errors • SMDS is associated particularly with MANs

More Related