An ATM WAN/LAN Gateway Architecture

Transcription

1 An ATM WAN/LAN Gateway Architecture Gary J. Minden, Joseph B. Evans, David W. Petr, Victor S. Frost Telecommunications & Information Sciences Laboratory Department of Electrical & Computer Engineering University of Kansas Lawrence, KS Abstract This paper describes a gigabit LAN/WAN gateway being developed for the MAGIC gigabit testbed. The gateway interfaces a gigabit LAN developed by DEC Systems Research Center and the MAGIC SONET/ATM wide area network. The UNI provides 622 Mb/s throughput between the LAN and WAN environments, and supports either a single OC-12c or four OC-3c tributaries. The architecture will initially support IP routing over the B-ISDN backbone, but it is not restricted to the TCP/IP protocol suite. The authors can be contacted via at evans@tisl.ukans.edu. This research is partially supported by DARPA under contract F C-0080, Digital Equipment Corporation, the Kansas Technology Enterprise Corporation, and Sprint.

2 1 Introduction Computer communications networks are reaching transmission capacities exceeding one gigabit per second. Networks are traditionally partitioned into Local Area Networks (LANs) and Wide Area Networks (WANs) for a variety of economic and regulatory reasons. While LANs have been primarily oriented toward data traffic, they are increasingly viewed as the medium for the real-time traffic associated with multimedia applications. On the other hand, WANs have traditionally carried real-time circuit oriented traffic, primarily voice, but data traffic is gaining growing importance. Evolving standards and systems under the label Broadband ISDN (B-ISDN) will integrate data and real-time traffic to provide a variety of services to users. The convergence of integrated traffic and the possibility of new services has lead both exchange carriers and computer network providers to embrace technologies such as SONET (Synchronous Optical NETwork) and particularly ATM (Asynchronous Transfer Mode) for both local and wide area networks. The use of similar technology in the LAN and WAN environments provides the opportunity for geographically distributed high performance networks. A key element in realizing this goal is the development of efficient gateways, or user-network interfaces (UNIs), between the LAN and WAN environments; although the basic technology used on both sides of the gateway may be similar, the operational aspects of LANs and WANs are significantly different. The gateway architecture described in this paper supports communication between LANs and WANs operating at gigabit per second rates. 1.1 Gigabit LAN/WAN Overview The Multidimensional Applications and Gigabit Internetwork Consortium (MAGIC) is a group of industrial, academic, and government organizations participating in gigabit network research. The MAGIC backbone network operates at 2.4 Gb/s and each site on the network includes LANs or 1

3 Minnesota Supercomputer Center Minneapolis, Minnesota EROS Data Center Sioux Falls, South Dakota 2.4 Gb/s SONET/ATM backbone Future Battle Lab Ft. Leavenworth = Campus Network University of Kansas Lawrence, Kansas US Sprint Kansas City Figure 1: MAGIC Network hosts communicating at gigabit per second rates. The MAGIC network is depicted in Figure 1. The University of Kansas (KU) will deploy an experimental gigabit LAN called the AN2, provided by Digital Equipment Corporation and developed by the DEC Systems Research Center [1]. The AN2 is a local area network based on ATM technology [7]. The KU network is shown in Figure 2. The network will consist of several switches (initially two), connected by interswitch links operating at 1 Gb/s. DECStation 5000 hosts equipped with AN2 host adapter boards will be attached to the switches. These hosts will communicate locally via the AN2 switches, and with remote MAGIC sites via a LAN/WAN gateway developed at KU. 1.2 The LAN/WAN Interface The gateway supports B-ISDN ATM traffic between the KU local area network and the MAGIC wide area network at SONET OC-12 or OC-12c rates ( Mb/s) [2, 13]. The architecture of the gateway is based on the existing AN2 gigabit interswitch line card design. The gateway and associated hosts support signaling and connection management procedures for the LAN/WAN 2

4 To MAGIC WAN Learned Hall Ellsworth Hall Switch Switch OC-48 OC-12 possible future expansion Gateway Switch Switch DS3 Ethernet FDDI IP Router Nichols Hall Figure 2: University of Kansas AN2 Configuration interface. A variety of research issues are being addressed through implementation and application of the LAN/WAN interface. A significant issue to be addressed in the testbed is the internetworking of the connection-oriented WAN environment and connectionless LAN environments. Connection setup procedures are being developed to provide virtual circuits for IP datagram traffic traveling from LAN to LAN via the B-ISDN WAN. These procedures will initially focus on permanent virtual circuits (PVCs), but this will later be extended to switched virtual circuits (SVCs). In addition to the issues of simple connection management, more complex network control issues that arise in an ATM network need to be addressed. In particular, dynamic bandwidth allocation mechanisms promise to provide LAN/WAN services more economically. The gateway architecture is designed to allow the testing and evaluation of dynamic bandwidth allocation algorithms. The architecture proposed for B-ISDN is a connection-oriented (CO) transmission service [9]. Most data communications based LANs and common protocols (e.g. IP), however, implement a 3

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6 4.3 Performance Statistics Collection In order to develop fundamental base of knowledge about the nature of LAN/WAN traffic statistics, and to provide a method to evaluate the effectiveness of the dynamic bandwidth allocation and management algorithms just discussed, the gateway supports statistics gathering functions. Statistics are collected on both a per packet and a per cell basis, using the payload type identifier specified in the AAL 5 definition [6]. The statistics that are targeted for collection are: packet interarrival time series packet length distribution over time packet delay statistics, including evolution of statistics over time cell interarrival time series cell delay statistics, including evolution of statistics over time credit queue statistics (length, idle time, time evolution) loss statistics across WAN those due to bit error those due to WAN congestion evolution of statistics over time (loss bursts) The statistics are buffered at the gateway for a short period of time, and then forwarded using a dedicated VCI to a host for bulk collection and analysis. 5 Conclusions This paper has described the gateway architecture for the interconnection of a DEC AN2 gigabit local area network and the 2.4 Gb/s MAGIC gigabit wide area network. The gateway is designed to support the transport of ATM LAN traffic over a B-ISDN wide area network at SONET OC-12 18

7 rates. The gateway can be configured to support a single SONET OC-12c tributary, or four OC-3c tributaries multiplexed into an OC-12 frame. While the MAGIC testbed will use the TCP/IP suite and AAL 5, the gateway architecture is designed to support a variety of higher level protocols and adaptation layers. References [1] T. Anderson, C. Wickey, J. Sax, and C. Thacker. High speed switch scheduling for local area networks. In Proc. ASPLOS, [2] R. Ballart and Y. Ching. SONET: Now it s the standard optical network. IEEE Commun. Mag., 27(3):8 15, Mar [3] J. D. Case, M. S. Fedor, M. L. Schoffstall, and J. R. Davin. Simple Network Management Protocol. Internet Working Group Request for Comments 1157, Network Information Center, SRI International, Menlo Park, California, May [4] D. E. Comer. Internetworking with TCP/IP, Volume I. Prentice-Hall, Englewood Cliffs, New Jersey, [5] P. Crocetti, G. Gallassi, and M. Gerla. Bandwidth advertising for MAN/WAN connectionless internetting. In Proc. IEEE INFOCOM, Bal Harbor, Florida, Apr [6] ATM Forum. Network Compatible ATM for Local Network Applications. Apple Computer, Bellcore, Sun Microsystems, Xerox, Apr [7] 1990 CCITT Study Group XVIII Recommendation I.150. B-ISDN Asynchronous Transfer Mode Functional Characteristics. CCITT, Geneva, [8] L. Mongivoni, M. Farrell, and V. Trecorido. A proposal for the interconnection of FDDI networks through B-ISDN. In Proc. IEEE INFOCOM, Bal Harbor, Florida, Apr [9] M. T. Mullen and V. S. Frost. Dynamic bandwidth allocation for B-ISDN based end-to-end delay estimates. In Proc. IEEE ICC, Chicago, Jun [10] G. M. Parulkar and J. Turner. Towards a framework for high speed connection in heterogeneous networking environments. In Proc. IEEE INFOCOM, Ottawa, Canada, Apr [11] 1989 CCITT Study Group XI Recommendation Q.931. Specifications of Signaling System No. 7. CCITT, Geneva,

8 [12] ANSI Committee T1 Contribution T1S1.5/ AAL 5 A New High Speed Data Transfer AAL. Bellcore Technical Reference Issue 2, IBM et al, Dallas, Texas, Nov [13] Bellcore Technical Reference TR-NWT Synchronous Optical Network (SONET) Transport Systems: Common Generic Criteria. Bellcore Technical Reference Issue 2, Bellcore, Dec