Advanced ATM Switching in Xylan's Multi-Layer Switch.

CALABASAS, Calif.--(BUSINESS WIRE)--March 17, 1997--Xylan Corp. (NASDAQ:XYLN) today announced a major extension of its OmniSwitch campus switch -- a 13.2 Gbps ATM cell switching fabric completely integrated with LAN switching, routing, virtual LANs, wide area access, and security.

The chip technology which Xylan developed to implement cell switching is called X-Cell.

Why Multi-Layer Switching?

Campus networking has consolidated on a new model -- Ethernet, Fast Ethernet, and Token Ring at the desk, and ATM in the backbone. This provides more bandwidth at the desk and more bandwidth in the backbone. And -- importantly -- it can increase network reliability.

Some vendors want to push all of the intelligence in the network into the center, using simple LAN switches, with ATM uplinks, in the wiring closets. But a better alternative is now available. Multi-layer switches in the wiring closets deliver Ethernet, Fast Ethernet, and Token Ring to the desktop, and high-speed ATM for the backbone and servers. Why is this better?

-- With multi-layer switches, the network can be meshed together with PNNI, ensuring rapid recover from link or node failure. Simple access switches can only use UNI. -- A high-speed switching fabric in the wiring closet can support Fast Ethernet to every desk. Simple access switches don't have the bandwidth to do this. In many cases they'll need to be completely replaced in one or two years. -- With multi-layer switches, ATM-attached servers can be placed anywhere in the campus switch network. With simple access switches, they must be centralized.

What's Needed in a Multi-Layer Switch?

A true multi-layer switch should combine:

-- LAN (MAC-layer) switching for fast switching among LAN-based workstations, with virtual LANs to allow network-wide workgroups -- ATM switching for high-speed backbones and WAN access -- high-speed routing to move data between virtual workgroups

In a true multi-layer switch, frames and cells must be linked together with a high-speed SAR (segmentation-and-reassembly) process. The OmniSwitch's FCSM (frame-to-cell switching module) provides both a 622 Mbps SAR function and multiple LANE clients.

A true multi-layer switch should support multiple classes of service. The OmniSwitch simultaneously and optimally supports:

-- CBR (constant bit rate) -- rt-VBR (real-time variable bit rate, such as MPEG video) -- nrt-VBR (non-real-time variable bit rate, such as frame relay) -- ABR (available bit rate, such as PCs and other workstations with ATM interface cards) -- UBR (unspecified bit rate, such as LAN switches)

Revolutionary Buffer Management

The OmniSwitch ATM cell switching pioneers the use of DIBOC (Dynamic Input Buffering with Output Control). Xylan is patenting this technique, which makes optimal use of buffers, and allows the fabric to support large loads without cell loss, even in bursty, mixed-traffic applications. DIBOC also makes large cell buffers economically feasible. The OmniSwitch supports:

-- 1,365 cell buffers per 25M port (expandable to 4,096) -- 8,192 cell buffers per OC-3c/STM-1 port (expandable to 32,768) -- 131,072 cell buffers per OC-12c/STM-4c port -- over 2,000,000 cell buffers per OmniSwitch

Older ATM switch designs assume that end stations will support ABR (available bit rate) congestion control. A true multi-layer switch can't make that assumption; the real world is populated with Ethernet, Token Ring, and Fast Ethernet stations, which will continue to transmit until a layer-four protocol like TCP throttles them. Unfortunately, by that time older ATM switches will have long since started to drop cells. In contrast, the OmniSwitch can use DIBOC, plus huge cell buffers, to sustain the load. And when even those are not enough, it will still outperform other switches due to intelligent cell discard mechanisms:

-- With EPD (early packet discard) the OmniSwitch will wait until it sees the first cell of a packet, and then discard the entire packet. -- With PPD (partial packet discard) the OmniSwitch will, if necessary, start to discard in the middle of a packet, but will discard all of the remaining cells from that packet. -- With RED (random early discard) the OmniSwitch will ensure that discards are done fairly, taking one packet from each of various connections as needed.

The network manager can even prioritize specific connections, with 16 levels of priority, so that in the event that cells must be lost, high-priority channels are protected.

Failure Resistance

Networks have become critical to the functioning of the organizations they serve. And the ATM backbone is the most critical part of the network. Xylan has made the OmniSwitch one of the most failure-resistant ATM switches available.

-- Each cell switching module is a separate switch. A full-mesh passive backplane interconnects the modules at wire speed, so that failure of any one module affects only its connections. -- Because OmniSwitches can be meshed together as peers using PNNI, convergence after link failure is typically less than one second. Access switches using redundant UNI uplinks can easily take 10 to 30 seconds to converge after link failure. In fact, PNNI even provides load balancing across multiple links, so that failure of a single link impacts less traffic. And this is truly dynamic PNNI. CDV (cell delay variation) and maxCTD (maximum cell transit delay) are measured continually, and the PNNI routes are updated as needed. -- The OmniSwitch supports "soft PVCs (permanent virtual circuits)"; there's no need to configure the intervening path. And if there's a failure in the network the end switches will automatically reroute the connection. -- Obviously, recovery from a network failure can only occur as rapidly as a switch can set up virtual circuit connections. The fast call setup time of the OmniSwitch minimizes cell loss during a recovery period.

Standards

It's a multi-vendor world, and ATM products must be based on standards.

-- ATM Forum UNI 3.0 & 3.1 -- ATM Forum PNNI 1.0 -- ATM Forum IISP (for interoperability with older ATM switches) -- LAN Emulation 1.0, client and server, Ethernet and Token Ring -- Traffic Management 4.0 -- IAB RFC 1483 (ATM LAN Encapsulation) -- IAB RFC 1577 (Classical IP over ATM) -- SVCC (switched virtual channel connections), both point-to-point

and multipoint

SVPC (switched virtual path connections), both point-to-point

and multipoint

PVCC (permanent virtual channel connections), both point-to-point

and multipoint

PVPC (permanent virtual path connections), both point-to-point

and multipoint

Dynamic LAN Emulation

OmniMSS is a high-speed, flexible layer-three protocol engine for ATM networks. Through a combination of internal OmniSwitch capabilities and those of OmniMSS, Xylan is able to offer an industry-leading LAN Emulation service. Capabilities include:

-- redundant LANE services: one OmniMSS units can back up another, in the event that the first fails -- scalable LANE services: per OmniMSS, up to 5,000 LANE clients distributed across any number of emulated LANs (for example, 100 ELANs with 50 clients each) -- intelligent broadcast management: the OmniMSS Broadcast Manager scans broadcast frames, such as IP ARP requests and replies, and transforms broadcast frames to unicast frames, dramatically reducing broadcasts on the backbone

Lots of Ports

Coupled with the OmniSwitch's cost-effective support for large numbers of Ethernet, Fast Ethernet, Token Ring, FDDI, and frame relay ports, the ATM density allows it to serve as an effective wiring closet alternative to "Superhubs." At the same time, the OmniSwitch X-Cell serves as a powerful backbone switch for a campus network.

The OmniSwitch with X-Cell has very high port capacity:

-- 16 OC-12 ports, multimode and single mode fiber -- 64 OC-3 ports, multimode and single mode fiber -- 16 DS-3/E3 ports -- 168 25M ports, UTP3 and UTP5 -- 32 DS-1/E1 ports

OC-3 ports will ship in March; other port types are scheduled to ship within the second quarter of 1997.

Network Management

All of the power in X-Cell would be useless without the ability to easily administer it. The OmniSwitch is graphically managed through Xylan's network management tools. Extensive port and virtual circuit statistics deliver a detailed view of traffic volumes and cell errors.

And this switch is designed to be managed in the real world. Some ATM switches use 32-bit counters; that's enough to count cells for three minutes on an OC-3 link. The OmniSwitch uses 40-bit counters -- enough for 35 days.

New Generation of Chip Technology

X-Cell is based on a new generation of ATM switching chips developed by Xylan in partnership with LSI Logic. Each switching module uses the new Fabric and IOP ASICs. These move far beyond the capabilities of off-the-shelf chip sets. Advanced buffer management, intelligent cell discard, extensive virtual circuit statistics, fabric multicast replication -- all of these are built into the X-Cell hardware.

X-Cell also includes new chip technology from Sun Microsystems, a Xylan technology partner. The ATM/622s chip is an OC-12 rate SAR (segmentation and reassembly) chip; it converts between cells and frames at 622 Mbps. This is critical for effectively supporting the emerging model of multi-layer switching.

About Xylan

In less than four years since its founding, Xylan Corp. has introduced a complete set of technologies for high-bandwidth campus switching systems. Each is powerful, and all are integrated into a single set of product platforms. Capabilities available now and in the next six months include:

-- LAN switching for Ethernet, Token Ring, Fast Ethernet, and FDDI, including ATM uplinks and any-to-any translation -- 13.2 Gbps ATM switching, with OC-3, OC-12, DS-3, E3, DS-1, E1, and 25M ports, using advanced buffer management -- hardware-based IP and IPX routing, including RIP, OSPF, RIPII, BGP4, and IP multicast -- advanced upper-layer switching protocols, including PNNI, LAN Emulation, NHRP, and MPOA  -- policy-based virtual LANs -- the broadest in the networking industry -- IP security firewall software, tightly coupled with the switching fabric -- compressed, high-speed frame relay for wide area access -- graphical network management, with unique tools for managing VLAN policies and members, ATM virtual circuits, network-wide traffic patterns, and hardware/software configuration

Many of the capabilities described in this release are available in OmniSwitch release 3.0, shipping in March. Some capabilities will become available in the second quarter of 1997. This news release includes forward-looking statements that involve risks and uncertainties, including the timely availability of new products and other risks detailed in the company's prospectus and report Form 10-Q for the quarter ending September 30, 1996.

CONTACT: Xylan Corp.

John Mazzaferro, 818/878-4714

[e-mail]

Douglas Hill, 818/878-4518

[e-mail]

http://www.xylan.com

or

Tony Fisch Consulting

Tony Fisch, 818/501-6608