Scalable Internet Backbone Using Multi-Gigabit ATM-Based Connectionless Switching

Shigehiko USHIJIMA
Katsunori NORITAKE

IEICE TRANSACTIONS on Communications   Vol.E81-B    No.2    pp.324-332
Publication Date: 1998/02/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on ATM Switching Systems for future B-ISDN)
Category: ATM switch interworking
connectionless,  Internet,  router,  ATM,  gigabit,  IP,  

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We propose a hardware-based packet forwarder for multi-gigabit IP backbone networks. The conventional Internet deploys routers as a key block, but its software-controlled architecture makes it hard to scale up the packet forwarders, especially for table-lookup processes. We propose introducing a pure connectionless (CL) switching approach with a hardware-based forwarder to construct the core part of a scalable IP multi-gigabit backbone. Compared to a software-based forwarder, the table-lookup time is reduced to 100 ns by using content-addressable memory. This hardware-based pipeline implementation easily achieves a maximum forwarding performance of up to 9. 6-Gbps, or 23 million packets per second, for applications ranging from traditional best-effort IP applications to newly emerging time-critical ones. We also consider additional processing when transferring IP packets to enhance best-effort quality. This is done using selective packet-level discarding, including early packet discard and its enhancement, to achieve minimum bandwidth guaranteed service at the packet level. We discuss the IP backbone scalability issue from the viewpoint of new IP-forwarder technologies, paying special attention to connection-oriented (CO) vs. CL switching and hardware vs. software implementation. A pure CL switching solution consisting of a CL server (CLS) and a CL client (CLC) is proposed to balance the hardware- and software-based CL transport functions. As a first step to this solution, a compact CLS has been developed. It supports 600-Mbps throughput and up to 9. 6-Gbps forwarding power using a modular architecture. It was evaluated in an ATM field trial using an experimental network. The results show the effectiveness of our approach to providing enhanced best effort services.