Fiber Optic Technology

OPTICAL TECHNOLGY Developed by By Taiwo-Jalupon Iman

Introduction Name:Field Taiwo-Jalupon Iman of Education Field of Health Care Field of Business Conclusion

Reg. No.:R073004500609

NIIT 1

Table of Contents OPTICAL TECHNOLOGY………………………………………1 Table of Contents………………………………………………….2 Introduction……………………………………………………4 Chapter 1 Fiber Optic Networking……………………………………….5 Chapter 2………………………………………………………6 Optical Networking Hardware…………………………………6 Optical Cable…………………………………………6 Fiber Buffers………………………………………..6 Fiber Optic Splices………………………………….7 Fiber Optic Connectors……………………………..8 Fiber Optic Couplers………………………………..9 Fiber Optic Transmitter…………………………….10 Fiber Optic Receivers ………………………………10 Chapter 3 Interoperability………………………………………………..12 Synchronous Communication………………………12 Digital Circuits and DSU/CSUs……………………….12 Telephone Standards…………………………………..13 Optical Carrier Standards……………………………14

2

The Local Subscriber Loop ………………………15 Cable Modem Technology………………………..18 Chapter 4 Multiprotocol Label Switching…………………………….19 Requirement and objective……………………….20 Common Misconception about MPLS……………21 Promise of MPLS…………………………………22 Chapter 5 Network Management………………………………………24 What is Network Management? …………………24 A Historical Perspective………………………….24 Network management Architecture………………25 ISO Network Management Model……………….26 Performance Management……………......26 Configuration Management………………27 Accounting Management………………….27 Fault Management…………………………28 Security Management………………………28 Conclusion References

3

Introduction An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length. Fiber optics is the overlap of applied science and engineering concerned with the design and application of optical fibers. Optical fibers are widely used in fiber-optic communication, which permits transmission over longer distances and at higher data rates than other forms of communications. Fibers are used instead of metal wires because signals travel along them with less loss, and they are immune to electromagnetic interference. Optical fibers are also used to form sensors, and in a variety of other applications. Optical fiber consists of a core, cladding, and a protective outer coating, which guides light along the core by total internal reflection. The cores, and the lower-refractive-index cladding, are typically made of high-quality silica glass, though they can both be made of plastic as well. An optical fiber can break if bent too sharply. Due to the microscopic precision required to align the fiber cores, connecting two optical fibers, whether done by fusion splicing or mechanical splicing, requires special skills and interconnection technology. Two main categories of optical fiber used in fiber optic communications are multi-mode optical fiber and single-mode optical fiber. Multimode fiber has a larger core (≥ 50 micrometres), allowing less precise, cheaper transmitters and receivers to connect to it as well as cheaper connectors. However, multimode fiber introduces multimode distortion which often limits the bandwidth and length of the link. Furthermore, because of its higher dopant content, multimode fiber is usually more expensive and exhibits higher attenuation. Single-mode fiber’s smaller core (<10 micrometres) necessitates more expensive components and interconnection methods, but allows much longer, higher-performance links. In order to package fiber into a commercially-viable product, it is protectively-coated, typically by using ultraviolet (UV) light-cured acrylate polymers, terminated with optical fiber connectors, and assembled into a cable. It can then be laid in the ground, run through a building or deployed aerially in a manner similar to copper cable. Once deployed, such cables require substantially less maintenance than copper cable.

4

Chapter 1

Fiber Optic Networking Optical fiber can be used as a medium for telecommunication and networking because it is flexible and can be bundled as cables. It is especially advantageous for long-distance communications, because light propagates through the fiber with little attenuation compared to electrical cables. This allows long distances to be spanned with few repeaters. Additionally, the light signals propagating in the fiber can be modulated at rates as high as 40 Gb/s [3], and each fiber can carry many independent channels, each by a different wavelength of light (wavelength-division multiplexing). Over short distances, such as networking within a building, fiber saves space in cable ducts because a single fiber can carry much more data than a single electrical cable. Fiber is also immune to electrical interference, which prevents cross-talk between signals in different cables and pickup of environmental noise. Also, wiretapping is more difficult compared to electrical connections, and there are concentric dual core fibers that are said to be tap-proof. Because they are non-electrical, fiber cables can bridge very high electrical potential differences and can be used in environments where explosive fumes are present, without danger of ignition. Although fibers can be made out of transparent plastic, glass, or a combination of the two, the fibers used in long-distance telecommunications applications are always glass, because of the lower optical attenuation. Both multi-mode and single-mode fibers are used in communications, with multimode fiber used mostly for short distances (up to 500 m), and single-mode fiber used for longer distance links. Because of the tighter tolerances required to couple light into and between single-mode fibers (core diameter about 10 micrometers), single-mode transmitters, receivers, amplifiers and other components are generally more expensive than multi-mode components.

5

Chapter 2 Optical Networking Hardware

Optical Cables Optical fibers have small cross sectional areas. Without protection, optical fibers are fragile and can be broken. The optical cable structure protects optical fibers from environmental damage. Cable structure includes buffers, strength members, and jackets. Many factors influence the design of fiber optic cables. The cable design relates to the cable's intended application. Properly designed optical cables perform the following functions: Protect optical fibers from damage and breakage during installation and over the fiber's lifetime. Provide stable fiber transmission characteristics compared with uncabled fibers. Stable transmission includes stable operation in extreme climate conditions. Maintain the physical integrity of the optical fiber by reducing the mechanical stresses placed on the fiber during installation and use. Static fatigue caused by tension, torsion, compression, and bending can reduce the lifetime of an optical fiber. Fiber Buffers Coatings and buffers protect the optical fiber from breakage and loss caused by microbends. During the fiber drawing process, the addition of a primary coating protects the bare glass from abrasions and other surface contaminants. For additional protection, manufacturers add a layer of buffer material. The buffer material provides additional mechanical protection for the fiber and helps preserve the fiber's inherent strength. Manufacturers use a variety of techniques to buffer optical fibers.

6

The types of fiber buffers include tight-buffered, loose-tube, and gel-filled loose-tube. Figure 3-13 shows each type of fiber buffer. The choice of buffering techniques depends on the intended application. Figure 3-13. - Tight-buffered, loose-tube, and gel-filled loose-tube buffer techniques.

Fiber Optic Splices A fiber optic splice is a permanent fiber joint whose purpose is to establish an optical connection between two individual optical fibers. System design may require that fiber connections have specific optical properties (low loss) that are met only by fiber-splicing. Fiber optic splices also permit repair of optical fibers damaged during installation, accident, or stress. System designers generally require fiber splicing whenever repeated connection or disconnection is unnecessary or unwanted. 7

Mechanical and fusion splicing are two broad categories that describe the techniques used for fiber splicing. A mechanical splice is a fiber splice where mechanical fixtures and materials perform fiber alignment and connection. A fusion splice is a fiber splice where localized heat fuses or melts the ends of two optical fibers together. Each splicing technique seeks to optimize splice performance and reduce splice loss. Low-loss fiber splicing results from proper fiber end preparation and alignment. Fiber Optic Connectors A fiber optic connector is a demateable device that permits the coupling of optical power between two optical fibers or two groups of fibers. Designing a device that allows for repeated fiber coupling without significant loss of light is difficult. Fiber optic connectors must maintain fiber alignment and provide repeatable loss measurements during numerous connections. Fiber optic connectors should be easy to assemble (in a laboratory or field environment) and should be cost effective. They should also be reliable. Fiber optic connections using connectors should be insensitive to environmental conditions, such as temperature, dust, and moisture. Fiber optic connector designs attempt to optimize connector performance by meeting each of these conditions. Fiber optic connectors can also reduce system performance by introducing modal and reflection noise. The cause of modal noise in fiber optic connectors is the interfering of the different wavefronts of different modes within the fiber at the connector interface. Modal noise is eliminated by using only single mode fiber with laser sources and only low-coherence sources such as light-emitting diodes with multimode fiber. Fiber optic connectors can introduce reflection noise by reflecting light back into the optical source. Reflection noise is reduced by index matching gels, physical contact polishes, or antireflection coatings. Generally, reflection noise is only a problem in high data rate single mode systems using lasers. Butt-jointed connectors and expanded-beam connectors are the two basic types of fiber optic connectors. Fiber optic butt-jointed connectors align and bring the prepared ends of two fibers into close contact. The end-faces of some butt-jointed connectors touch, but others do not depending upon the connector design. Types of butt-jointed connectors include cylindrical ferrule and biconical connectors. Fiber optic expanded-beam connectors use two lenses to first expand and then refocus the light from the

8

transmitting fiber into the receiving fiber. Single fiber butt-jointed and expanded beam connectors normally consist of two plugs and an adapter (coupling device). Fiber Optic Couplers Some fiber optic data links require more than simple point-to-point connections. These data links may be of a much more complex design that requires multi-port or other types of connections. Figure 4-23 shows some example system architectures that use more complex link designs. In many cases these types of systems require fiber optic components that can redistribute (combine or split) optical signals throughout the system. Figure 4-23. - Examples of complex system architectures.

One type of fiber optic component that allows for the redistribution of optical signals is a fiber optic coupler. A fiber optic coupler is a device that can distribute the optical signal (power) from one fiber among two or more fibers. A fiber optic coupler can also combine the optical signal from two or more fibers into a single fiber. Fiber optic couplers attenuate the signal much more than a connector or splice because the input signal is divided among 9

the output ports. For example, with a 1 X 2 fiber optic coupler, each output is less than one-half the power of the input signal (over a 3 dB loss). Fiber optic couplers can be either active or passive devices. The difference between active and passive couplers is that a passive coupler redistributes the optical signal without optical-to-electrical conversion. Active couplers are electronic devices that split or combine the signal electrically and use fiber optic detectors and sources for input and output. Fiber Optic Transmitters A fiber optic transmitter is a hybrid electro-optic device. It converts electrical signals into optical signals and launches the optical signals into an optical fiber. A fiber optic transmitter consists of an interface circuit, a source drive circuit, and an optical source. The interface circuit accepts the incoming electrical signal and processes it to make it compatible with the source drive circuit. The source drive circuit intensity modulates the optical source by varying the current through it. Fiber Optic Receives In fiber optic communications systems, optical signals that reach fiber optic receivers are generally attenuated and distorted (see figure 7-5). The fiber optic receiver must convert the input and amplify the resulting electrical signal without distorting it to a point that other circuitry cannot use it. Figure 7-5. - Attenuated and distorted optical signals.

As stated previously, a fiber optic receiver consists of an optical detector, an amplifier, and other circuitry. In most fiber optic systems, the optical detector is a PIN photodiode or APD. Receiver performance varies depending on the type of detector used. The amplifier is generally described as having two stages: the preamplifier and the postamplifier. The preamplifier is defined as the first stage of amplification following the optical detector. The postamplifier is defined as the remaining stages of 10

amplification required to raise the detector's electrical signal to a level suitable for further signal processing. The preamplifier is the dominant contributor of electrical noise in the receiver. Because of this, its design has a significant influence in determining the sensitivity of the receiver. The output circuitry processes the amplified signal into a form suitable for the interfacing circuitry. For digital receivers, this circuitry may include lowpass filters and comparators. For analog receivers, this circuitry may also include low-pass filters. Receiver sensitivity, bandwidth, and dynamic range are key operational parameters used to define receiver performance

11

Chapter 3 Interoperability

Synchronous Communication Most voice systems use synchronous (or clocked) technology, while most data networks use asynchronous technology.

In a synchronous network (also called a synchronized network or isochronous network): • Data is moved at a precise rate • The network does not slow down as the traffic increases • Data emerges from the network at exactly the same rate it enters

In voice systems, clocked transmission is important for maintain low delay, low loss, and low variance of delay.Digital Circuits and DSU/CSUs It is possible to lease digital point-to-point circuits from common carriers for use in long-distance computer networks. The fee depends on the circuit capacity and distance. A specialized piece of hardware called a Data Service Unit/Channel Service Unit (DSU/CSU) is needed to interface a computer to one of the telephone companies digital circuits.

The CSU portion of the DSU/CSU device handles line termination and diagnostics. For example: 12

• Surges generated by lightning or other interference • Whether the line is disconnected • Prohibits excessive 1 bits (preventing excessive current on the line) The DSU portion of the DSU/CSU device handles the data. For example: • Translates between data formats of the carrier and the customer Telephone Standards U.S. Standards for digital telephone circuits are called the T-series standards. (Japan has a modified T-series, Europe has the E-series)

DS Terminology and Data Rates T1 rate = 24 voice calls (24 * 64 Kbps) A device is used at each end of the T1 to mux/demux the voice calls. T3 rate = 28 T1 circuits. We distinguish between the T-standards (which define the underlying carrier system) and the DS standards or Digital Signal Level standards (which specify how to multiplex multiple phone calls onto a single connection). For example: T1 denotes a standard for a carrier operating at 1.544 Mbps. DS1 denotes a service that can multiplex 24 phone calls onto a single circuit. Lower Capacity Circuits Because leasing a T1 circuit is very expensive it is possible to lease a lowercapacity circuit, called fractional T1. Fractional T1 are available in (56 Kbps, 64 Kbps, 128 Kbps, 9.6 Kbps, 4.8 Kbps, etc.) The phone company uses Time Division Multiplexing (TDM) to subdivide the T1 circuits. Intermediate Capacity Digital Circuits

13

Technology called inverse multiplexing can provide intermediate capacity circuits (e.g. greater than T1 and less than T3). A device known as an inverse multiplexor (inverse mux) is needed at each end of the lines.

Highest Capacity Circuits A trunk is a high-capacity circuit. The international Synchronous Transport Signal (STS) standards specify the details of high speed connections.

Optical Carrier Standards The STS standards refer to the electrical standards in the digital circuit interface over copper. The OC standards refer to the optical signals that propagate across optical fiber. The C Suffix The optional suffix of C is used to designate a concatenated circuit. For example, • An OC-3 circuit consists of three OC-1 circuits operating at 51.840 Mbps each • An OC-3C circuit is a single circuit operating at 155.520 Mbps 14

Synchronous Optical NETwork (SONET) In addition to STS and OC standards, SONET (Synchronous Optical NETwork) standards define a broad set of digital transmission standards. In Europe these standards are known as SDH (Synchronous Digital Hierarchy).

If you lease an STS-1 circuit, you will probably be required to use SONET encoding on the circuit. Each STS-1 frame is 810 octets (9 “rows” with 90 “columns”). SONET uses time to determine frame size, so higher rate circuits will have larger frames. SONET is primarily used on single point-to-point circuits, but it also has additional possibilities for other high-speed configurations. The Local Subscriber Loop The terms local loop or local subscriber line are used to refer to the connection between the phone company Central Office (CO) and an individual subscriber’s residence or business. Currently most subscribers obtain access to networks by using analog signals on a conventional analog telephone service. ISDN ISDN (Integrated Services Digital Network) • One of the first attempts to provide subscribers with high-speed digital services • Provides digitized voice and data over conventional (twisted-pair copper) wiring The ISDN Basic Rate Interface (BRI) is (2B + D) channels

15

B channels: operate at 64 Kbps, intended for digitized voice, data or compressed video • D channel: operate at 16 Kbps, intended as a control channel Note: Both B channels can be bonded to form a single 128 Kbps channel •

Note: ISDN sounded promising when it was proposed, but is now an expensive option that offers moderate thoughput.Digital Subscriber Line Technology

DSL (Digital Subscriber Line) is also a technology for providing digital services across the local loop. There are several variants of DSL which differ by the first word in their title, so they are collectively, xDSL. Defn: Downstream service refers to data flowing out to the user. Defn: Upstream service refers to data flowing from the user. ADSL (Asymmetric Digital Subscriber Line) • Most popular xDSL technology • Asymmetric service (downstream service higher bit rate than upstream service) • Maximum downstream rate is 6.144 Mbps • Maximum upstream rate is 576 Kbps (640 Kbps – 64 Kbps control channel) • Does not require any changes in local loop wiring • Can run simultaneously with standard phone service

ADSL’s High Speed

16

Researchers noticed that many local loops can support frequencies higher than those used by the telephone system. Difficulty: No two local loops have identical electrical characteristics--the ability to carry signals depends on the distance, gauge of wiring used, and level of electrical interference. Designers were unable to pick a particular set of carrier frequencies or modulation techniques that would work in all cases. Thus, ADSL is adaptive. • ADSL modems are powered on. • They probe the line to find its characteristics. • They agree to communicate using techniques that are optimal for the line. ADSL uses a scheme known as DMT (Discrete Multi Tone modulation) that combines frequency division multiplexing and inverse multiplexing. DMT is implemented by Dividing the bandwidth into 286 separate frequencies or subchannels. • 255 frequencies used for downstream data • 31 frequencies used for upstream data • Conceptually there is a separate “modem” running on each subchannel which has its own modulated carrier. •

Bandwidth below 4KHz is not used (to avoid interference with analog phone signals)

Other DSL Technologies

Symmetric Digital Subscriber Line (SDSL) provides symmetric bit rates in both directions. High-Rate Digital Subscriber Line (HDSL) provides a DS1 bit rates of 1.544 Mbps in two directions. • It has a short distance limitation on local loops. • Requires two independent twisted pairs. • HDSL2 is a proposal that runs over two wires. • Moving between a T1 circuit and HDSL is straightforward. • Tolerates failure gracefully. Very-high bit rate Digital Subscriber Line (VDSL) can provide a bit rates of 52 Mbps. • Cannot be used on existing wiring between the Central Office and subscribers.

17

Cable Modem Technology Cable modem do not use the telephone local loop, but the CATV (cable television network), with speeds up to 36 Mbps. • Uses coaxial cable (immune to electromagnetic interference) • Broadband signaling (frequency division multiplexing) In theory, a pair of cable modems (using frequency division multiplexing) could be used for each subscriber. One at the customer, one at the CATV center. Unfortunately, the bandwidth is not high enough. Instead, the cable company uses one frequency for a set of customers, and time divison multiplexing between the users. Cable Modem Upstream Communication Traditional CATV systems do not have a mechanism for upstream communication. Two approaches for adding upstream traffic: 1. Dual path approach—uses a second standard dial-up modem for upstream traffic. Downstream traffic comes from the cable modem connection.

2. Modifying the cable infrastructure—Requires significant changes and cost to the cable system. Could support video on demand and interactive TV. Examples: • Using Hybrid Fiber Coax (which combines optical fiber for trunks and coaxial cable for the feeder circuits) is a promising approach, but much of the existing cable infrastructure will need to be replaced. • Using Fiber To The Curb (FTTC) is also being proposed. Using fiber close to the subscriber, and then copper for the feeder circuits to the subscribers. Broadcast Satellite Systems Uses asymmetric delivery: • Broadcast satellite for downstream traffic. • Lower-capacity network (e.g. dial-up) for upstream.

18

Chapter 4 Multiprotocol Label Switching

Multiprotocol Label Switching MPLS is the latest step in the evolution of multilayer switching in the Internet. It is an IETF standards-based approach built on the efforts of the various proprietary multilayer switching solutions. MPLS uses the control-driven model to initiate the assignment and distribution of label bindings for the establishment of label-switched paths (LSPs). LSPs are simplex in nature (traffic flows in one direction from the head-end toward the tail-end), duplex traffic requires two LSPs, one LSP to carry traffic in each direction. An LSP is created by concatenating one or more label switched hops, allowing a packet to be forwarded from one label-switching router (LSR) to another LSR across the MPLS domain. An LSR is a router that supports MPLS-based forwarding. The MPLS control component centers around IP functionality, which is similar to proprietary multilayer switching solutions (see Figure 6). However, MPLS defines new standard-based IP signaling and label distribution protocols, as well as extensions to existing protocols, to support multivendor interoperability. MPLS does not implement any of the ATM Forum signaling or routing protocols so the complexity of coordinating two different protocol architectures is eliminated. In this way, MPLS brings significant benefits to a packet-oriented Internet. Figure 6: Multiprotocol Label Switching

19

The MPLS forwarding component is based on the label-swapping algorithm. If the Layer 2 technology supports a label field (such as the ATM VPI/VCI or the Frame Relay DLCI fields), the native label field encapsulates the MPLS label. However, if the Layer 2 technology does not support a label field, the MPLS label is encapsulated in a standardized MPLS header that is inserted between the Layer 2 and IP headers (see Figure 7). The MPLS header permits any link layer technology to carry an MPLS label so it can benefit from label-swapping across an LSP.

Figure 7: MPLS Header

The 32-bit MPLS header contains the following fields: _ The label field (20-bits) carries the actual value of the MPLS label. _ The CoS field (3-bits) can affect the queuing and discard algorithms applied to the packet as it is transmitted through the network. _ The Stack (S) field (1-bit) supports a hierarchical label stack. _ The TTL (time-to-live) field (8-bits) provides conventional IP TTL functionality. Requirements and Objectives The charter of the MPLS working group is to standardize a base technology that combines the use of label swapping in the forwarding component with network layer routing in the control component. To achieve its objectives, the MPLS working group has to deliver a solution that satisfies a number of requirements, including: _ MPLS must run over any link layer technology, and just ATM. _ MPLS core technologies must support the forwarding of both unicast and multicast traffic flows.

20

_ MPLS must be compatible with the IETF Integrated Services Model, including RSVP. _ MPLS must scale to support constant Internet growth. _ MPLS must support operations, administration, and maintenance facilities at least as extensive as those supported in current IP networks. Common Misconceptions about MPLS There are a number of misconceptions concerning the role of MPLS in the core of the Internet. Some in the Internet community believe that MPLS was developed to provide a standard that allowed vendors to transform ATM switches into high-performance Internet backbone routers. While this might have been one of the original goals of proprietary multilayer switching solutions in the mid-1990s, recent advances in silicon technology allow ASIC-based IP route lookup engines to run just as fast as MPLS or ATM VPI/VCI lookup engines. Although MPLS can enhance the forwarding performance of processor-based systems, accelerating packet forwarding performance was not the primary force behind the creation of the MPLS working group. Others in the Internet community believe that MPLS was designed to completely eliminate the need for conventional, longest-match IP routing. This never was an objective of the MPLS working group because its members understood that traditional Layer 3 routing would always be required in the Internet. _ Packet filtering at firewalls and ISP boundaries is a fundamental component of supporting security and enforcing administrative policy. Because packet filtering requires a detailed examination of packet headers, conventional Layer 3 forwarding is still required for these applications. _ It is unlikely that a large number of host systems will implement MPLS. This means that each packet transmitted by a host still needs to be forwarded to a first-hop Layer 3 device where the packet header can be examined prior to forwarding it towards its ultimate destination. The first-hop router can then either forward the packet using conventional longest-match routing or assign a label and forward the packet over an LSP. _ If a Layer 3 device along the path examines the IP header and assigns a label, the label represents an aggregate route because it is impossible to maintain label bindings for every host on the global Internet. This means that, at some point along the delivery path, the IP header must be examined by another Layer 3 device to determine a finer granularity to continue forwarding the packet. This router can elect to either forward the packet 21

using conventional routing or assign a label and forward the packet over a new label switched path. _ At the last hop before the destination host, the packet must be forwarded using conventional Layer 3 routing because it is not practical to assign a separate label to every host on the destination subnetwork. The Promise of MPLS The question remains, “Why should an ISP consider deploying MPLS in the core of its network?” The most important benefit of MPLS is that it provides a foundation that permits ISPs to deliver new services that cannot be readily supported by conventional IP routing techniques. ISPs face the challenge of not only delivering superior baseline service, but also providing new services that distinguish them from their competition. MPLS allows service providers to control costs, provide better levels of base service, and offer new revenue-generating customer services. Figure 8 illustrates how MPLS provides enhanced routing capabilities by supporting applications that require more than just destination-based forwarding. Assume that the routers in the core of the network perform conventional, longest-match IP forwarding. If either Host A or Host B transmits a packet to Host C, the packet follows Path 1 across the core of the network because this is the shortest path computed by the IGP. Figure 8: MPLS Enhances Routing Functionality

Suppose that the network administrator has been monitoring traffic statistics and needs to implement a policy to control congestion at Router B. The policy would reduce congestion at Router B by distributing the traffic load along different paths across the network. Traffic sourced by Host A and destined for Host C would follow the IGP shortest path, Path 1. Traffic sourced by Host B and destined for Host C would follow another path, Path 2. Using conventional IP routing, this policy cannot be implemented because all forwarding at Router A is based on the packet’s 22

destination address. Now, if the routers in the core of the network function as LSRs, it is easy to implement a policy to reduce congestion at LSR B. The network administer configures LSP 1 to follow Path 1. The network administer configures LSP 2 to follow Path 2. Finally, the network administer configures LSR A to put all traffic received from Host A and destined for Host C into LSP 1. Likewise, LSR A is configured to place all traffic received from Host B and destined for Host C into LSP 2. The ability to assign any FEC to a customtailored LSP gives the network administrator precise control of traffic as it flows through the provider’s network. With careful planning, MPLS provides ISPs an unprecedented level of control over traffic, resulting in a network that is more efficiently operated, supports more predictable service, and can offer the flexibility required to meet constantly changing customer expectations. You should note that the remainder of this section describes the potential for MPLS to assign traffic to FECs based on an extremely rich set of packet classification capabilities. Initial MPLS implementations will provide a more restricted set of packet classification capabilities which should be expected to evolve as the software implementing the control component matures. As ISPs are required to roll out new customer services, the MPLS forwarding infrastructure can remain in place. New services can be deployed by simply modifying the control component that assigns packets to an FEC and then maps each FEC to a custom-built LSP (see Figure 9). For example, packets can be assigned to an FEC based on a combination of the destination subnetwork and application type, a combination of the source and destination subnetworks, a specific QoS requirement, an IP multicast group, or a Virtual Private Network (VPN) identifier. Similarly, network administrators can provision LSPs to satisfy specific FEC requirements— minimize the number of hops, meet specific bandwidth requirements, force traffic across certain links in the network, and so forth. The final step in evolving routing functionality is to configure the head-end LSR to place packets assigned to a particular FEC into an LSP that has been customized to support the FEC’s requirements. Figure 9: How MPLS Enhances Routing Functionality

23

Chapter 5 Network Management

What Is Network Management? Network management means different things to different people. In some cases, it involves a solitary network consultant monitoring network activity with an outdated protocol analyzer. In other cases, network management involves a distributed database, autopolling of network devices, and highend workstations generating real-time graphical views of network topology changes and traffic. In general, network management is a service that employs a variety of tools, applications, and devices to assist human network managers in monitoring and maintaining networks. A Historical Perspective The early 1980s saw tremendous expansion in the area of network deployment. As companies realized the cost benefits and productivity gains created by network technology, they began to add networks and expand existing networks almost as rapidly as new network technologies and products were introduced. By the mid-1980s, certain companies were experiencing growing pains from deploying many different (and sometimes incompatible) network technologies. The problems associated with network expansion affect both day-to-day network operation management and strategic network growth planning. Each new network technology requires its own set of experts. In the early 1980s, the staffing requirements alone for managing large, heterogeneous networks 24

created a crisis for many organizations. An urgent need arose for automated network management (including what is typically called network capacity planning) integrated across diverse environments. 6-2 Network Management Architecture Most network management architectures use the same basic structure and set of relationships. End stations (managed devices), such as computer systems and other network devices, run software that enables them to send alerts when they recognize problems (for example, when one or more userdetermined thresholds are exceeded). Upon receiving these alerts, management entities are programmed to react by executing one, several, or a group of actions, including operator notification, event logging, system shutdown, and automatic attempts at system repair. Management entities also can poll end stations to check the values of certain variables. Polling can be automatic or user-initiated, but agents in the managed devices respond to all polls. Agents are software modules that first compile information about the managed devices in which they reside, then store this information in a management database, and finally provide it (proactively or reactively) to management entities within network management systems (NMSs) via a network management protocol. Wellknown network management protocols include the Simple Network Management Protocol (SNMP) and Common Management Information Protocol (CMIP). Management proxies are entities that provide management information on behalf of other entities. Figure 6-1 depicts a typical network management architecture.

Figure 6-1 A Typical Network Management Architecture Maintains Many Relationships 25

Network management system

ISO Network Management Model The ISO has contributed a great deal to network standardization. Its network management model is the primary means for understanding the major functions of network management systems. This model consists of five conceptual areas, as discussed in the next sections. 6-3 Performance Management The goal of performance management is to measure and make available various aspects of network performance so that internetwork performance can be maintained at an acceptable level. Examples of performance variables that might be provided include network throughput, user response times, and line utilization. Performance management involves three main steps. First, performance data is gathered on variables of interest to network administrators. Second, the data is analyzed to determine normal (baseline) levels. Finally, appropriate performance thresholds are determined for each important variable so that exceeding these thresholds indicates a network problem worthy of attention.

26

Management entities continually monitor performance variables. When a performance threshold is exceeded, an alert is generated and sent to the network management system. Each of the steps just described is part of the process to set up a reactive system. When performance becomes unacceptable because of an exceeded user-defined threshold, the system reacts by sending a message. Performance management also permits proactive methods: For example, network simulation can be used to project how network growth will affect performance metrics. Such simulation can alert administrators to impending problems so that counteractive measures can be taken. Configuration Management The goal of configuration management is to monitor network and system configuration information so that the effects on network operation of various versions of hardware and software elements can be tracked and managed. Each network device has a variety of version information associated with it. An engineering workstation, for example, may be configured as follows: • Operating system, Version 3.2 • Ethernet interface, Version 5.4 • TCP/IP software, Version 2.0 • NetWare software, Version 4.1 • NFS software, Version 5.1 • Serial communications controller, Version 1.1 • X.25 software, Version 1.0 • SNMP software, Version 3.1 Configuration management subsystems store this information in a database for easy access. When a problem occurs, this database can be searched for clues that may help solve the problem. Accounting Management The goal of accounting management is to measure network utilization parameters so that individual or group uses on the network can be regulated appropriately. Such regulation minimizes network problems (because network resources can be apportioned based on resource capacities) and maximizes the fairness of network access across all users. As with performance management, the first step toward appropriate accounting management is to measure utilization of all important network resources. Analysis of the results provides insight into current usage patterns, and usage quotas can be set at this point. Some correction, of course, will be required to reach optimal access practices. From this point, ongoing measurement of resource use can

27

yield billing information as well as information used to assess continued fair and optimal resource utilization. Fault Management The goal of fault management is to detect, log, notify users of, and (to the extent possible) automatically fix network problems to keep the network running effectively. Because faults can cause downtime or unacceptable network degradation, fault management is perhaps the most widely implemented of the ISO network management elements. Fault management involves first determining symptoms and isolating the problem. Then the problem is fixed and the solution is tested on allimportant subsystems. Finally, the detection and resolution of the problem is recorded. Security Management The goal of security management is to control access to network resources according to local guidelines so that the network cannot be sabotaged (intentionally or unintentionally) and sensitive information cannot be accessed by those without appropriate authorization. A security management subsystem, for example, can monitor users logging on to a network resource and can refuse access to those who enter inappropriate access codes. Security management subsystems work by partitioning network resources into authorized and unauthorized areas. For some users, access to any network resource is inappropriate, mostly because such users are usually company outsiders. For other (internal) network users, access to information originating from a particular department is inappropriate. Access to Human Resource files, for example, is inappropriate for most users outside the Human Resources department. Security management subsystems perform several functions. They identify sensitive network resources (including systems, files, and other entities) and determine mappings between sensitive network resources and user sets. They also monitor access points to sensitive network resources and log inappropriate access to sensitive network resources.

Conclusion

28

Modern fiber cables can contain up to a thousand fibers in a single cable, so the performance of optical networks easily accommodates even today's demands for bandwidth on a point-to-point basis. However, unused point-topoint potential bandwidth does not translate to operating profits, and it is estimated that no more than 1% of the optical fiber buried in recent years is actually 'lit'. Modern cables come in a wide variety of sheathings and armor, designed for applications such as direct burial in trenches, dual use as power lines [3], installation in conduit, lashing to aerial telephone poles, submarine installation, or insertion in paved streets. In recent years the cost of small fiber-count pole-mounted cables has greatly decreased due to the high Japanese and South Korean demand for fiber to the home (FTTH) installations. Telecommunications companies developing FTTH technology plan to support 100+ Mbps bandwidth per home. They view fiber optic cabling as the best technology for high-speed, high-quality residential area networking, eventually replacing both telephone and cable TV lines. Costs to get FTTH services off the ground are high, but fiber to the home installations are steadily increasing around the world.

Referencecs Textbooks Davie, B., P. Doolan, and Y. Rekhter, Switching in IP Networks: IP Switching, Tag Switching, and Related Technologies, Morgan Kaufmann, 1998, ISBN 1-55860-505-3. Metz, Christopher, IP Switching: Protocols and Architectures, McGraw-Hill, New York, 1999, ISBN 0-07-041953-1.

URLs 1. Alberto Bononi, Optical Networking (Springer, 1999). 2. B Thomas, RFC 3037: LDP Applicability, http://www.ietf.org/rfc/rfc3037.txt. 3. http://www.tpub.com/neets/book24/index.htm

29