A Telephone Connection EXAMPLES OF CONNECTIONS

10 INTRODUCTION Chapter 4: Congestion control in ATM networks Congestion control is a very important component of ATM networks, as it permits an ATM network operator to carry as much traffic as possible so that revenues can be maximized without affecting the QoS offered to the users. Two different classes of congestion control schemes have been developed. These schemes are the preventive congestion control scheme and reactive congestion control scheme. Pre- dictably, the preventive congestion control scheme aims to take a proactive approach to congestion. This is done using the following two procedures: call or connection admission control CAC and bandwidth enforcement. CAC is exercised at the connection level and is used to decide whether to accept or reject a new connection. Once a new connection has been accepted, bandwidth enforcement is exercised at the cell level to assure that the source transmitting on this connection is within its negotiated traffic parameters. Reactive congestion control is based on a totally different philosophy than preventive congestion control. In reactive congestion control, the network uses feedback messages to control the amount of traffic that an end device transmits so that congestion does not arise. In this chapter, we first present the parameters used to characterize ATM traffic, the QoS parameters, and the ATM QoS categories. Then, we describe in detail various preventive and the reactive congestion control schemes. Chapter 5: Signaling in ATM networks In ATM networks, there are two types of connections: permanent virtual connections PVC and switched virtual connections SVC. PVCs are established off-line using net- work management procedures, whereas SVCs are established dynamically in real-time using signaling procedures. In this chapter, we explore the signaling protocol Q.2931 used to set up an SVC. This protocol is used exclusively between a user and the ATM switch to which it is attached. Q.2931 runs on top of a specialized AAL, known as the signaling AAL SAAL. A special sublayer of this AAL is the service-specific connection oriented protocol SSCOP. We first describe the main features of SAAL and SSCOP, and present the various ATM addressing schemes. Then, we discuss the signaling messages and procedures used by Q.2931. Chapter 6: The multi-protocol label switching architecture In this chapter, we describe the basic features of the multi-protocol label switching MPLS architecture. MPLS introduces a connection-oriented structure into the otherwise connec- tionless IP network. MPLS circumvents the CPU-intensive table look-up in the forwarding routing table necessary to determine the next hop router of an IP packet. Also, it can be used to introduce quality of service QoS in the IP network. Interestingly enough, since the introduction of MPLS, several CPU-efficient algorithms for carrying out table look-ups in the forwarding routing table were developed. The importance of MPLS, however, was by no means diminished since it is regarded as a solution to introducing QoS in the IP networks. Chapter 7: Label distribution protocols MPLS requires a signaling protocol for the reliable establishment of a label switched path LSP. MPLS does not require the use of a single signaling protocol, and in view of this, various protocols have been proposed, of which the label distribution protocol LDP ORGANIZATION OF THE BOOK 11 and the resource reser vation protocol – traffic engineering RSVP–TE are the most popular. Typically, an LSR will run both LDP and RSVP-TE. The two label distribution protocols are not compatible, however. In order to establish a label switched path, one of the two protocols has to be used. In this chapter, we describe LDP, its extension constraint-based routing label distribution protocol CR-LDP, RSVP and RSVP-TE. Chapter 8: Optical fibers and components This chapter deals with the physical layer of wavelength division multiplexing WDM optical networks. We first give a general overview of WDM optical networks. We then proceed to describe how light is transmitted through an optical fiber. Specifically, we discuss the index of refraction, step-index and graded-index optical fibers, multi-mode and single mode optical fibers, and various optical effects that occur when light is transmitted through an optical fiber, known as impairments. Finally, we conclude this chapter by describing some of the components used in WDM optical networks, such as lasers, optical amplifiers, 2 × 2 couplers and star couplers, and optical cross-connects OXCs. We note that this chapter is not entirely within the scope of this book, which focuses on layers higher than the physical layer. However, due to the novelty of optical networks, it is important to have some knowledge of the underlying WDM technology. It is not necessary to read this chapter in detail in order to understand the subsequent chapters on optical networks; the key sections to study are the introductory section and the section on components. Chapter 9: Wavelength routing optical networks In this chapter, we explore different aspects of a wavelength routing optical networks. We first start with a description of the main features of a wavelength routing network and introduce the ever important concept of a lightpath and the concept of traffic grooming, which permits multiple users to share the same lightpath. We also present protection and restoration schemes used to provide carrier grade reliability. Information on a lightpath is typically transmitted using SONETSDH framing. Ether- net frames can also be transmitted over an optical network. In the future, it is expected that information will be transmitted over the optical network using the new ITU-T G.709 standard, part of which is described in this chapter. G.709, also known as the digital wrap- per , permits the transmission of IP packets, Ethernet frames, ATM cells, and SONETSDH synchronous data. The rest of the chapter is dedicated to the control plane for wavelength routing networks. We present different types of control plane architectures, and then describe the generalized MPLS GMPLS architecture and the OIF user network interface UNI. GMPLS is an extension of MPLS and it was designed with a view to applying the MPLS label-switching techniques to time-division multiplexing TDM networks and wavelength routing networks in addition to packet-switching networks. The OIF UNI specifies sig- naling procedures for clients to automatically create, delete, and query the status of a connection over a user network interface. Chapter 10: Optical Burst Switching OBS In a wavelength routing optical network, a connection has to be set up before data will be transmitted. The resources remain allocated to this connection even when there is no