Global Network System Large-Scale, Guaranteed, Carrier-Grade 192 Global Network System Large-Scale, Guaranteed, Carrier-Grade Takanori Miyamoto Shiro Tanabe Osamu Takada Shinobu Gohara OVERVIEW: traffic drives acceleration in public data, and, responding to the exponential growth of the traffic, new infrastructures are being constructed globally. In this paper, the system requirement for the next-generation (Internet Protocol) is discussed, and large-scale, guaranteed and carrier-grade are three major concepts that are the basis of the architecture design. We especially focus on the three architectural issues for the next-generation : centralized control architecture, hierarchical and encapsulated intra- addresses, and high-speed hardware switching. And the configuration, based on the developed architecture, of the and the management, which are the main components of the backbone, are presented. INTRODUCTION THE 21st century is positioning itself as a new century of s. Networks will change radically as we move from the telephone era to the era. So far, the telephone and the data have evolved individually for different purposes. Now, the explosive increase of traffic is triggering a drastic change in the structure, where the telephone and data coexist. The traffic which flows into the backbone has doubled every three months (this equals an increase of ten times in a year). This increase far exceeds Moore s Law, when assuming that the CPU (central processing unit) performance of personal computers doubles every 18 months. In a few years, traffic will occupy more than 90% of all global traffic. And services will take the leading role of communication services and will become the base of the s. While maintaining its usefulness, the data must take the role of communication infrastructure, a role which the telephone has filled so far. The present, in which routers are deployed at random cannot attain the performance, reliability and operability required for a communication infrastructure. We must now construct an based on new concepts, where a new architecture has been proposed so far. 1 2) This paper proposes the architecture of the global featuring a large-scale, guaranteed, and carrier-grade, and clarifies both the technical issues and the approaches to resolve them. And this architecture provides an and a management. SYSTEM REQUIREMENTS FOR A LARGE- SCALE NETWORK The next-generation will be Largescale, Guaranteed, and Carrier-grade. Largescale means that the number of subscribers will be similar to that of current telephone s and that the has to support a high-speed interface while maintaining architectural ungrammatical scalability. Guaranteed means that the reachability of an packet is certified by improving the reliability of routing and forwarding functions within the. This causes, as a result, the service of bit-based charging. Furthermore, the should support a QoS (quality of service) control scheme which assures the predetermined bandwidth and latency needed for real-time application using video and voice as well as a mission critical application. And Carrier-grade means that s are being outsourced by professional carriers. Thus, a virtual private (VPN) function covering wide area, and a security function are needed both with highly reliable and easy-to-use performance. Supposing the above requirements, Fig. 1 summarizes the issues in conventional and its approaches of the architecture. To increase the scale of the, we must improve switching throughput of a router, reduce address search time within a router as the speed of the interface increases, reduce the traffic for routing between routers. Furthermore, a more sophisticated mechanism
Hitachi Review Vol. 48 (1999), No. 4 193 Issues in conventional Large scale (Forwarding capability) Switching throughput Interface speed Routing control Guaranteed QoS control Application/Service (Best effort type) Approaches Centralized routing control Unified management of routing Cooperation with SS7 and IN Policy-based control Hardware switching High speed switching by hardware forwarding Quality monitor and QoS control Performance measurement Carrier-grade (Distributed management) Intelligent service with Vo Mobile Charging Internal addressing Hierarchical addressing (Compression of address size) Encapsulation Optimized routing Fig. 1 Approach to Next Generation Network. of quality monitoring and control will be required to realize the real-time communications for the conventional supporting best-effort type of service. As the current does not support total management of resources, the reliability and operationality are not necessarily satisfactory as services. For example, it is very difficult for the current distributed to realize IN services, such as free dial with Vo (Voice over ) application, and a mobility service for mobile hosts. The should also support bits-based charging and OAM (operation, administration, and maintenance) that will provide intelligent services. The next chapter shows three approaches to resolve the above problems from the viewpoint of architecture. TECHNOLOGIES Centralized Control Architecture The present uses a dynamic routing scheme applying the open shortest path first (OSPF) protocol or the border gateway protocol (BGP), which exchanges routing information among neighboring routers. Dynamic routing is based on a distributed control scheme, which guarantees the arrival of user information without depending on the topology. However, in this scheme, the amount of routing information increases as the itself grows. By transferring route information to all adjoining routers periodically, each router can calculate the route based on the recent route information. Here, the amount of route information transferred increases to the order of n 2 if the number of router (n) increases. The processing load of other routers also increases to the order of n 2, because each router receives the router information and calculates the route in the similar way. The increase in the amount of route information can degrade the high-speed transfer of user information. As a result, the throughput cannot be increased even if many routers are installed. On the contrary, a conventional telephone uses centralized control, which manages the topology, and fixed routing to notify each only when the configuration has changed. If centralized control is applied to an in which s are deployed hierarchically, the increase in the amount of routing information caused by dynamic routing can be suppressed. The administrator can engineer the according to the amount of traffic. Because the uses a conventional dynamic routing protocol to send routing information and to receive from other s, a route control is provided to control the routing information transmission and reception with other s. The route control calculates the route according to the routing information and disseminates the calculated route to all routers only when the route is changed. Centralized control eliminates additional route calculations from each router and reduces the amount of traffic required for routing information throughout the entire from the order of n 2 in distributed control to the order of n. Fig. 2 compares centralized
Global Network System Large-Scale, Guaranteed, Carrier-Grade 194 Distributed (conventional) Routing information Centralized control with route Processing load, Traffic volume: n 2 order n order Processing load (Relative value) 10,000 1,000 100 Centralized (proposed) Route Routing information Distributed Centralized 10 10 20 30 40 50 60 70 80 90 100 (n: Number of s) Add Hierarchical Optimize routing Economical Decrease retrieval time High speed interface See graph Routing with Hierarchical Encapsulation Interface throughput (Gbit/s) 100 10 Internal addressing (Classified) 1 1996 1998 2000 2002 2004 (Year) Delete internal address Current mechanism (Flat address) Fig. 2 Centralized Routing Control. Fig. 3 Encapsulation with Hierarchical Addressing. control with distributed control. Hierarchical and Encapsulated Intra-Network Addresses Hierarchical deployment of edge s and core s and introduction of intra- addresses assigned to each play a major role in both easing the management and high speed switching. Assigning to each a simple for routing within the instead of the conventional address, the edge encapsulates the for routing through the core s in the same. Fig. 3 illustrates the effect of introducing intra- hierarchical addresses. It has two major effects: effect by a hierarchical and effect by introducing simple es. A hierarchical configuration reduces the number of intermediate core s between the originating edge and the terminating edge, and it shortens the transmission delay compared with a in which routers are deployed at random. And it allows carrier-grade management since the route is determined and facilities can be provided according to the amount of traffic. Compressed address bits further allow fast retrieval of addresses in the core. This scheme supports the 10-Gbit/s or faster interface even when in the era of the upcoming version 6 (v6). Encapsulation is an essential function not only for intra- routing but also for advanced services. The private addresses of VPN and mobile addresses are assigned irrespective of the actual accommodation location in the, and then the encapsulation is mandatory for routing within the. Encapsulation applies to various services: VPN, mobile, -based IN, and it supports high-speed transmission [such as multi-protocol label switching (MPLS)]. A flexible encapsulation structure is needed so that an edge can support multi-service s. High-Speed Hardware Switching Hardware forwarding Very high switching can be achieved by using the hardware technologies for forwarding, route retrieval, and filtering, which are implemented by software in conventional routers. The original retrieval algorithm is applied to the advanced application specific IC (ASIC), and it provides high-speed retrieval processing independently of the number of entries. QoS function Real-time traffic including voice and video is very sensitive to delay and its jitter. It is very important to provide high QoS function when handling multimedia traffic. Hardware implementation of QoS function achieves high performance and high reliability. Fig. 4 summarizes the architecture of a large-scale using these technologies.
Hitachi Review Vol. 48 (1999), No. 4 195 SS7 layer Signaling GW Network management system signaling Route Other Management RM PS RM : routing manager RP : routing processer NIF : interface PS : power supply Access STM ATM Mobile Edge Core transport layer Edge Access STM ATM Mobile Access Crossbar switch RP RP RP RP NIF NIF NIF NIF NIF NIF Backbone Fig. 4 Network Architecture. Fig. 5 Node Architecture. APPROACH Node Architecture 3) Fig. 5 shows an example of the configuration of the. The consists of a interface (NIF), a routing processor (RP), crossbar switch, and a routing manager (RM). The NIF supports a variety of lines from low to high speed. The RP is the heart of the and controls everything from forwarding to route search, QoS, filtering, etc. all by hardware. The crossbar switch is a high-speed switch which connects RPs. The RM manages the route information and distributes it among RPs. High-speed transfer is implemented by non-cache, full-hardware transfer scheme. The RP implements large-capacity search processing independent of the number of entries by using a proprietary search algorithm which is implemented by advanced ASICs. The QoS functions, including priority control and bandwidth control, are also implemented by hardware that supports differentiated services (Diff-Serv) of the Internet Engineering Task Force (IETF). Management Server signaling s, which are applied for a variety of intelligent services, as well as the transport are introduced, in the developed architecture. Depending on the services, many kinds of management s, such as the route (routing control ), the authentication, the policy, and the signaling gateway are introduced. In this chapter, briefly introduced is the basic function of the route, which plays a role of controlling route of each packet in a centralized manner. The route is introduced to improve the reliability and operability of the by managing all the routing data between the neighboring routers, and to improve the throughput within the by functional division with. The route exchanges the routing information between the neighboring routers, and it delivers and informs the updated information to all the s. As routers exchange the routing information autonomously using OSPF (open shortest path first) protocol in the current, the route exchanges between only the exterior router while the static routing is applied between the interior s in this architecture. The route is implemented as middleware and application software on a general-purpose platform. CONCLUSIONS In this paper, the system requirements and the corresponding concepts, Large-scale, Guaranteed, Carrier-grade, for the next-generation global are presented. And three architectural issues are shown, which are centralized routing control, hardware switching, and internal hierarchical addressing schemes. In addition, functions for both the, and the management are shown. Some technical issues must be resolved in order to proceed to the global : (1) How to apply the architecture to a variety of backbone s such as WDM (wavelength division multiplexing), SONET (synchronous
Global Network System Large-Scale, Guaranteed, Carrier-Grade 196 optical )/SDH (synchronous optical /synchronous digital hierarchy) and ATM (asynchronous transfer mode). (2) How to accommodate the versatile access including mobile. (3)How to translate SLA (service level agreement) between the users and carriers who have some contract on the service level, into actual engineering parameters. REFERENCES (1) N. Watanabe et al., A Backbone Network Architecture of the Next-Generation Computer Network, NTT R&D 47, No.4 (1998), pp. 435-444. (2) H. Hara et al., Access Network Systems and Edge Nodes Systems for the Next-Generation Computer Network, NTT R&D 47, No. 4 (1998), pp. 425-434. (3) K. Sugai et al., GR2000: a Gigabit Router for a Guaranteed Network, Hitachi Review 48, No. 4 (1999), pp.203-207 (this issue). ABOUT THE AUTHORS Takanori Miyamoto Joined Hitachi, Ltd. in 1980, and now works at the Network Systems Development Operation of the Enterprise Server Division. He is currently engaged in the development of systems for carriers. Mr. Miyamoto is a member of Institute of tmiyamoto@ebina.hitachi.co.jp Shiro Tanabe Joined Hitachi, Ltd. in 1978, and now works at the Network System Research Laboratory of the Central Research Laboratory. He is currently engaged in the research and development of systems. Mr. Tanabe is a member of the IEEE, and the Institute of tanabe@crl.hitachi.co.jp Osamu Takada Joined Hitachi, Ltd. in 1979, and now works at the 4th Department of the Systems Development Laboratory. He is currently engaged in the research and development of QoS and routing technique of Internet. Mr. Takada is a member of the IEEE, and the Information Processing Society of Japan, and can be reached by e-mail at takada@sdl.hitachi.co.jp Shinobu Gohara Joined Hitachi, Ltd. in 1977, and now works at the Network Systems Development Operation of the Enterprise Server Division. He is currently engaged in the development of systems. Mr. Gohara is a member of the IEEE, and the Institute of gohara@ebina.hitachi.co.jp