Download (direct link):
This chapter is organized as follows. We first present the main features of the ATM architecture, such as the structure of the header of the ATM cell, the ATM protocol stack, and the physical layer. Then we briefly describe the ATM shared memory switch architecture, which is the dominant switch architecture, and various scheduling algorithms used to determine the order in which ATM cells are transmitted out. Subsequently, we describe the three ATM adaptation layers (AAL): AAL 1, AAL 2, and AAL 5. We conclude the chapter with a description of classical IP and ARP over ATM, a technique standardized by IETF to transport IP over ATM.
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. Predictably, 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 network 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 connectionless 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 ofservice (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
and the resource reservation 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 x 2 couplers and star couplers, and optical cross-connects (OXCs).