An MPLS Connection EXAMPLES OF CONNECTIONS

ORGANIZATION OF THE BOOK 9 Below, we briefly examine the content of each chapter. Chapter 2: SONETSDH and the Generic Frame Procedure GFP In this chapter, we focus on the SONETSDH transport technology. We first start with a description of T1 and E1, and then we present in detail the SONETSDH hierar- chy, the SONET STS-1 frame structure, overheads, payload, and the SONET STS-3 frame structure. Subsequently, we describe the SONETSDH devices and SONETSDH rings. One of the main features of a SONETSDH rings is that they are self-healing. That is, a SONETSDH ring can automatically recover when a fiber link fails. Link failure can result from a fiber being accidentally cut, or the optical components that are used to transmit on a fiber fail, or the SONETSDH switch fails. We describe various architectures for self-healing rings, such as two-fiber and four-fiber protection schemes. We conclude this chapter with a description of the generic framing procedure GFP and data over SONETSDH DoS. GFP is a lightweight adaptation scheme that permits the transmission of different types of traffic over SONETSDH and, in the future, over G.709. DoS is a network architecture that uses GFP together with two other mechanisms to provide an efficient transport of integrated data services over SONETSDH. Chapter 3: ATM networks The asynchronous transfer mode ATM architecture was standardized in 1987 by ITU-T as the preferred architecture for the broadband integrated services data network B-ISDN. ATM is a mature technology that is primarily used in the backbone. For instance, it is widely used in the backbone of internet service providers ISPs and it has been deployed to provide point-to-point and point-to-multipoint video connections. It is also used in cellular telephony to carry multiple voice connections using the ATM adaptation layer 2 AAL 2. It is also used for circuit emulation, a service that emulates a point-to-point T1E1 circuit over an ATM network. ATM is also used in access networks such as ADSL-based residential access networks and ATM passive optical networks. ATM is not visible to the networking users, as is the IPTCP protocol, and because of this, it is often mistaken as a network that it is no longer in use The ATM architecture was a novel departure from previous networking architectures; it has built-in mechanisms that permit the transport of different types of traffic with different QoS. Until the advent of multi-protocol label switching MPLS architecture in the late 1990s, ATM was the only networking technology that provided QoS. From the educational point of view, it is a good idea to develop a working knowledge of ATM and its congestion control schemes before proceeding to MPLS in Chapter 6. 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. 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