MadgeOne Multilayer IP/IPX Switching Technical Backgrounder -- January 1997.

SAN JOSE, Calif.--(BUSINESS WIRE)--Jan. 20, 1997--LAN switching today does a great job of addressing some of the most pressing issues facing network planners -- particularly, how to increase the amount of bandwidth available to LAN users cost-effectively, while preserving investment in the existing LAN infrastructure. In most real networks, conventional LAN switches cannot provide all the answers. Routers are still needed in the LAN because:

-- The existing IP addressing scheme divides the LAN into multiple

subnets, and routers are needed to forward packets between subnets. -- The filtering of IP packets provided by routers is an important

element of security policy within the LAN. -- The risk of excessive broadcast traffic in the LAN demands the

broadcast containment capabilities of routers.

Routers create a number of problems for network planners and administrators. The relatively poor performance of routers compared with LAN switches restricts the flexibility of the network: for example, it is often impractical to move servers to a central location, because users accessing servers across a router-based backbone will suffer from a serious performance hit. Routers also create work for network administrators in handling moves and changes: when PCs are moved from one part of the network to another, it is usually necessary to configure a new IP address into each PC that is moved. The need for two different types of equipment in the LAN infrastructure - switches and routers - also adds to the complexity of both the cabling plant and the network management task.

Madge's solution - multilayer IP/IPX switching - combines the functionality of LAN switches (Layer 2 switching) with that of routers (Layer 3 switching) in one integrated system. This has the immediate benefit of reducing box count and simplifying the network design.

The excellent price/performance characteristics of most LAN switches is achieved by implementing the Layer 2 data forwarding path through the switch in hardware, using Application Specific Integrated Circuits (ASICs). There have been many attempts to apply this approach to Layer 3 switching, although Madge is the first to succeed in implementing Layer 3 switching entirely in hardware. This breakthrough enables Madge to deliver multilayer IP/IPX switching solutions with far higher performance at far lower cost than conventional routers, without sacrificing any of the security or management controls traditionally provided by routers. Price/performance is not the only advantage: with multilayer switching and advanced VLAN management tools, moves and changes can be accomplished without needing to assign new IP addresses. Multilayer IP/IPX Switching for Ethernet and Token Ring Madge is integrating Layer 3 switching functionality into both LANswitch (1Q97) and Ringswitch (2H97) LAN backbone switches to create multilayer IP/IPX switching solutions supporting Ethernet, Fast Ethernet, Token Ring, FDDI and ATM connectivity.

The LANswitch solution is based on the 3LS IP/IPX switching module. This device installs in the LANswitch chassis and connects to the 1.28 Gbps Cellenium Bus backplane. With the 3LS installed, the LANswitch becomes a multilayer IP/IPX switch capable of connecting up to 128 Ethernet segments, including up to 250 IP or IPX subnets, at full wire speed. The 3LS module can perform Layer 3 forwarding of Internet Protocol (IP) and Internetwork Packet eXchange (IPX) packets between subnets at greater than 400 thousand packets per second. The 3LS is compatible with all switched media types supported in the LANswitch, including Ethernet, Fast Ethernet, FDDI and ATM.

The 3LS module supports the standard routing protocols for IP, Routing Information Protocol (RIP) and Open Shortest Path First (OSPF). The RIP protocol for IPX is also supported. LANswitch with 3LS can therefore be installed alongside routers in existing LAN infrastructures, and it will participate fully in routing protocol exchanges with conventional routers in both LAN and WAN. The 3LS module handles legacy protocols such as DECnet, Appletalk and LAT by means of a selective bridging function.

Packet filtering capability for security and access control is embedded in the frame forwarding hardware of the 3LS IP/IPX switching module. Filtering criteria include source/destination IP or IPX address, address prefix, and application/service type. The configuration of multiple filtering criteria has no measurable impact on forwarding performance.

Multilayer IP/IPX Switching for ATM

Madge will provide distributed multilayer IP/IPX switching solutions (2H97) based on ATM backbones by integrating support for the emerging ATM Forum standard MultiProtocol Over ATM (MPOA) in ATM switches, ATM adapter cards and ATM edge switches for Ethernet and Token Ring.

Madge took a pioneering role in the development of the ATM Forum standard for LAN Emulation (LANE), and led the market with the first full implementation of standards-compliant LANE incorporating both Ethernet and Token Ring support. MPOA builds upon LANE by adding a distributed Layer 3 switching function, allowing ATM edge switches and ATM-attached end stations that belong to different subnets to intercommunicate on direct switched connections, bypassing routers.

MPOA offers a superior solution for enterprise ATM LAN backbones by comparison with proprietary cell-switched routing technologies such as IP Switching. MPOA is a true multilayer switching solution that provides direct support for routable protocols such as IP and IPX, as well as routable and non-routable legacy protocols including DECnet, Appletalk, NetBIOS and SNA/DLC, without needing to encapsulate them in IP. MPOA also allows subnets to extend across the ATM backbone, enabling moves and changes to be carried out without the need for new IP addresses to be assigned. By contrast, IP Switching is a pure Layer 3 solution which imposes the same subnet limitations as conventional routers.

MPOA is also a better match for enterprise LAN backbones than topology-based solutions for IP over ATM such as Tag Switching. Like IP Switching, Tag Switching is a pure Layer 3 approach for IP only. Tag Switching surrounds the ATM backbone with full-featured routers as edge devices, which places this solution at a serious cost disadvantage by comparison with MPOA. The major benefit of Tag Switching, its immense scalability, is important in the Internet but does not offer any advantage over MPOA in enterprise network applications.

CONTACT: Madge Networks

Bill Jeppesen, 408/952-9014

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