Service Provider Networks / (none) /

Foundry to make Ethernet MANs more manageable and resilient.

By Phil Hochmuth
The Edge, 09/10/01

ATLANTA - Foundry Networks will announce at NetWorld+Interop 2001 in Atlanta this week a software upgrade that will make its metropolitan-area network core and edge switches easier to manage and bounce back faster from link failures.

One key change is the addition of Rapid Spanning Tree Protocol (RSTP)in Version 7.5 of Foundry's IronWare software for the BigIron MAN backbone and FastIron customer premises equipment switches.

In Ethernet service provider networks based on Layer 2 technology, spanning tree can be used to prevent loops in a network and provide for the rerouting of traffic in the event of a link failure.

Foundry says RSTP, also known as 802.1w, on its switches will let Layer 2 Ethernet MAN services recover from downed backbone links in 2 to 3 seconds, instead of up to 40 seconds as with regular Spanning Tree Protocol.

New features of IronWare 7.5 software include a proprietary method for combining groups of metropolitan service subscribers into what it calls spanning tree domains that are based on virtual LAN (VLAN) tags, which identify each customer.

Called Superspan, this method combines multiple VLANs into groups of RSTP instances - or unique, nonlooping routes - within a MAN.

Foundry, as well as other makers of Ethernet MAN switches, is a proponent of using VLAN tags to divide customers in a service provider network.

Previously, Layer 2 VLAN technology required a separate instance of Spanning Tree Protocol for each VLAN. Superspan lets service providers group VLAN tag numbers into spanning tree domains. Each switch can support between two and 16 such domains, the company says.

The net effect of these domains is to reduce the number of spanning tree maps providers have to manage and increase the number of VLANs that a single switch can handle.

Even though the 802.1Q standard supports a maximum of 4,096 VLANs in a network, most Ethernet switches can only support 64 to 128 spanning tree instances. The company says its switches running Superspan can support the maximum number of VLANS - 4,096 - with up to 256 VLANs in 16 spanning tree domains.

Despite Foundry's position that Ethernet-based MANs based on RSTP and VLANs can provide reliable and secure networks, metropolitan Ethernet vendors and enterprise users have questioned how secure VLANs are in a public network and whether RSTP could support the same level of resiliency as SONET-based networks.

According to market research firm IDC, equipment such as Foundry's, which is based on Layer 2 to 7 Ethernet LAN switch technology, will grow rapidly in service provider networks during the next few years as providers begin rolling out Ethernet WAN services and increase data center and hosting offerings. The research firm expects LAN switch port shipments to service providers to increase from 6 million to almost 40 million between 2000 and 2005.

IronWare 7.5 is available for free to Foundry customers with valid support contracts.

Other recent articles by Hochmuth

Metro vendors question Spanning Tree standard
A look at 802.1w. Network World, 8/6/01.

Questions to ask your MAN service provider
Network World, 7/23/01.

Breaking Foundry news
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