Broadband Access: Technology, Interfaces, and Management / Edition 1 available in Hardcover
Here's an exciting book that gives you a comprehensive understanding of the emerging and proven technologies that allow high-speed remote access to the Internet and to broadband services such as Video-on-Demand. It shows you how to design the network that provides broadband links between end-users and service providers, and the operations systems that control networks.
About the Author
Alex Gillespie holds a masters in Theoretical Physics from Cambridge University and a Ph.D. in Particle Physics from Durham University. Since 1988, he has been with BT and has edited several international standards. He is the chairman of the Access and Switch Management group in ETSI and has been a guest editor of special issues of major communications magazines.
Read an Excerpt
1: OverviewBroadband access is the link between service providers and the end-users of their broadband services. It is rather like Groucho Marx, who is supposed to have said that he would not join the sort of club that would accept someone like him as a member. Two clubs that might accept broadband access are the Internet club and the not-narrowband club. Unfortunately one of these is too exclusive and the other is not a proper club at all.
The not-narrowband club is not a proper club because it is the world outside of the narrowband club. Narrowband communications are built from 64 Kbps channels. These channels may be combined for higher capacity services. Although there is no hard and fast bit rate that divides broadband from narrowband, there is a practical difference because narrowband services use narrowband switches. These are either analog switches or their digital equivalents that switch 64 Kpbs connections. Unfortunately, there are services, such as broadcast television, that are neither narrowband nor truly broadband.
The Internet club is the club that everyone wants to belong to. The Internet club would like to have broadband access since it is hungry for bandwidth and would like to guarantee quality of service. The need for bandwidth is especially strong in the infrastructure of the Internet to ensure that its rapid growth does not create bottlenecks. Despite the popularity of the Internet club, it is not the club for everyone as there are some things, like Video-on-Demand (VoD), at which its members do not shine.
The first part of this book is an introduction to broadband access, containing an overview and examining the economics and networkarchitecture. The second part gives more detail about mature technologies, in particular the established aspects of SONET/SDH, Asynchronous Transfer Mode (ATM), and the Internet Protocol (IP).
The third part of the book looks at the more recent developments, in particular ADSL and the VB5 interface. The fourth and final part looks at recent developments in optical access, ATM, and IP, concluding with some provoking ideas for the future.
First we take a step back to get a feel for the wider picture.
1.1 Broadband and ATM
Some people find it difficult to think of broadband as anything other than ATM, partly because of the adoption of ATM for broadband ISDN by the ITU-T. Local Area Network (LAN) technologies demonstrate that broadband is not confined to ATM, but they are not appropriate to broadband access because they are used for local communications within organizations, not for connecting end-users to service providers. The difference here is that between connecting to a corporate Ethernet in the office and remote access to an Internet Service Provider (ISP) from home.
The idea that the Internet might supersede ATM will be examined in the final part of this book. For now it is enough to note that the Internet is not in direct conflict with ATM because they each do different things. The Internet provides communications protocols that are not tied to a network technology. ATM is a transport technology that is not tied to a physical transmission.
It is possible for broadband access to use transmission technologies directly without ATM. This can be done both for optical fiber and for copper pair transmission. Likewise IP can be used directly over SONET/SDH, and over optical and electrical media. ATM is also not necessary when cable modems are used for broadband access.
ATM can still be taken as the basis for broadband access so long as the willingness remains to consider alternatives and to adopt them if they are more sensible.
1.2 The Evolution Toward Broadband
Broadband transmission has been easy to justify in the core of the telecommunications network because of the volume of traffic that the core network handles. Broadband transmission for the access is less easy to justify. This is because there needs to be a demand for high capacity communications by end-users to justify having broadband links to them.
The development of ATM has helped to fuel this demand. It has also reversed the historical trend because ATM is more of a revolution than an evolution. Broadband transmission evolved to handle large numbers of narrowband connections between telephone exchanges. ATM was deployed in islands for stand-alone applications.
Both ATM islands and non-ATM LANs exist on the periphery of the telecommunications network. The initial driver for the deployment of ATM in the core network has been the need to interconnect these islands and LANs.
1.3 Access Networks, Core Networks, and Service Providers
Telecommunications operators often view broadband networks as split into two parts, namely an access network and a core network. The end-users of the broadband services are at the far ends of the access network. The core network often includes the link to the service provider because its capacity can be similar to other core links.
The core network directs broadband traffic between its nodes. The access network carries the broadband traffic between end-users and a node of the core network. Unfortunately the boundary between the access network and the core network is not clear-cut because both the access network and the core nodes have used similar technology.
The core network carries the broadband traffic across large geographical areas. It can be connection oriented, connectionless, or a mixture of the two. If it is connection-oriented then connections can be semi-permanent or can be established and released on-demand. Switch nodes join the transmission links to create the end-to-end connections.
Connectionless networks do not create end-to-end connections. Instead they have routers that direct the flow of individual packets of data. The transmission links between switch node and routers are also part of the core network.
1.4 Broadband Technology
The gray area between core networks and access networks has become better defined as the technologies have developed. Both IP routers and ATM switches that handle on-demand connections belong to the core part of public broadband networks. Advanced transmission technologies that connect end-users to the core network belong to the access network.
1.4.1 Access Network Technology
Phase one of the deployment of broadband technology for access networks is the use of legacy transmission media with new transmission technology. Phase two involves the widespread deployment of new transmission media. Between these two phases there can be the deployment of hybrid architectures that compensate for the shortcomings of the legacy media (see Figure 1.1).
188.8.131.52 Phase One: Legacy Media
The first phase of the development of broadband technology for the access network involves using the same physical transmission medium as an existing service, but with a new transmission technology. Asymmetric Digital Subscriber Line (ADSL) transmission is a good example of such a new technology. ADSL operates over the line that carries ordinary telephony. The other common service that demonstrates this is cable television where the new technology is cable modems.
Although coaxial cable is the better physical medium for broadband transmission, it is not possible to take full advantage of this because it is shared between a large number of users (see Figure 1.2). It is the better physical medium because it has a greater bandwidth and more uniform transmission characteristics. It is shared between a large number of cable television users in a tree-and-branch architecture because this is an efficient way to deliver a large number of broadcast television channels.
For telephone lines the situation is reversed. Telephone lines provide a dedicated transmission path to users. The disadvantage of telephone lines is that they have lower bandwidth and more variable transmission characteristics that are suitable for the transmission of analogue voice signals but not good for broadband. It is possible to compensate for the frequency variation of the transmission characteristics by using more sophisticated transmission techniques, but the attenuation at higher frequencies leaves the transmission susceptible to interference.
The cost of a copper pair is much less than the cost of coax because a copper pair is simpler to make and because it takes up less space. The space required is the dominant factor as the dominant cost is that of digging trenches and installing the medium. Copper pairs have an advantage over coax as the same trench can hold many more copper pairs, but this advantage is less than it appears at first because the bandwidth of coax is greater...
Table of Contents
Preface - Conventions. Acknowledgments. Overview - Broadband and ATM. The Evolution Toward Broadband. Access Networks, Core Networks, and Service Providers. Broadband Technology. Network Architecture - Computer Networks. Broadband Access and Service Providers. Broadband Access Architecture. The ATM Core. Economic Considerations - Broadband Service Considerations. Broadband Connection Considerations. SONET/SDH - The Historical Background. Multiplexing and Architecture. The Three Laws. Adaptation Overheads and Synchronization. Layer-Specific Overheads and OAM Flows. The Management Interface and Management Model. ATM Fundamentals and Management Modeling - Paths, Channels, and Cells. ATM Layers and Functions. The Basic Management Model for ATM. ATM Operations, Administration and Maintenance (OAM) Flows - OAM Flow Layers and Ranges. OAM Cell Types and Functions. The Operations System (OS) Interface. The Notification for Defect Reporting. Problems and Deficiencies. ATM Adaptation for Client Services - Introduction. Asynchronous Traffic; Original (AAL3/4). Asynchronous Traffic-Streamlined (AAL5). The Signaling ATM Adaptation Layer (SAAL). Comments on ATM Adaptation. ATM Signaling - Background. Services, Addresses, and Topology. UNI Signaling. NNI Signaling. Management of ATM Switches - Background. ATM Interfaces. Service Profiles. Configuration of the Routing Algorithm. Internet Communication - Introduction. IP Addresses and Address Resolution. IP Over ATM. Internet Control Messages. End-to-End Transport. Routing. Internet Applications - Introduction. User-Friendly Addresses: The Domain Name System. The Internet Trinity. Hypertext and the World Wide Web. Remote Procedure Calls. Management of the Internet (SNMP) - Messages and MIBs. Basic MIB-II Groups and Their Evolution. Additional Groups. The Technology-Specific Groups. Summary. ADSL Transmission - Tones, Modulation, and Coding. Frames, Superframes, and Symbols. Forward Error Correction. Channels, Ports, and Framing. ADSL Management - The ADSL MIB Module. The CMIP Model for the Management of ADSL. VB5 Access Architecture - Service Nodes (SNs) and VB5 Interfaces. Logical Ports and Physical Ports. Signaling and UNI Accesses. Comments on the VB5 Architecture. VB5 Protocols - VB5 Messages and Message Format. Protocol Errors. The Real-Time Management Coordination (RTMC) Protocol. The Broadband Bearer Connection Control (B-BCC) Protocol. VB5 Management - Background. VPs, Logical User Ports, and Logical Service Ports . The Relationship with VB5 Messages. Broadband Access Coordination: X-VB5. Optical Access - Background. ATM PON Architecture. PLOAM Cells on ATM PONs. OLT/ONU Coordination. ATM Enhancements - Background. Enhanced OAM Flows. ATM (Automatic Protection Switching) APS. Paths and Connections. Traffic, Services, and Quality. Optical Technology for IP - Background. IP over Serial Data Links. Optical IP Transmission. Optical IP Networks. The Way Forward - Background. Multiprotocol Label Switching. Internet Protocol Version 6. The Resource Reservation Protocol. Shortcut Routing RSVP for ATM. Acronyms and Abbreviations. About the Author. Index.
The book is concerned with the technology of broadband access, and how this technology is monitored and controlled by operations systems. The book has four parts. It starts with introductory chapters that are followed by an examination of existing ATM, SONET/SDH, and IP technologies. Part Three covers recent developments in ADSL and the VB5 interface, while Part Four looks to the future of optical technology, ATM, and IP, closing with some provocative ideas about future communications protocols.
The division between Internet service providers and other providers with broadband access is not hard and fast. This is because providers of both types of service do not want to limit their options and are prepared to move in or out of Internet-based services. Unlike narrowband access, which can be free, it is likely that no one but a blockhead will ever provide broadband access, except for money.
In various chapters of this book, management models for broadband technologies are described. The diagrams that show the relationships between managed objects use certain conventions (see Figure P.1). Different symbols are used for single objects, multiple objects, and optional objects. Contained objects are shown within the objects that contain them, and arrows are used to represent pointers between objects. The thickness of the heads and tails of the arrows indicate if there are single or multiple objects at either end.