AlcaLu Tunes Up Redundancy
High availability generally involves having backups available -- a second switch fabric that can take over after the primary fails, for instance. Alcatel's announcements today for the 7450 Ethernet Service Switch, 7710 Service Router (SR), and 7750 SR lines expand that idea to create redundant relationships between boxes in a network.
"There have been people who maintain state across two processes in a box, but this is the first time I can recall anybody doing it across two boxes," says Mark Seery, an analyst with Ovum RHK Inc.
It's esoteric stuff, but high availability has helped Alcatel-Lucent get its routers -- created by startup TiMetra Networks, an Alcatel acquisition -- noticed by carriers. "It's something tangible they can test in the labs," says Lindsay Newell, director of marketing for AlcaLu's IP group.
That's led to a rapid rise in market share for Alcatel-Lucent, challenging Juniper for second place behind Cisco. AlcaLu has gotten a reputation for routing and Ethernet aggregation in IPTV networks, particularly. (See Routers, Switches Surge and Juniper Gives Static to IPTV Critics.)
Every router vendor has some interest in high availability, but a key for Alcatel-Lucent was to diverge from the approach favored by Cisco, called graceful restart. Instead, Alcatel-Lucent favored a method called stateful failover. "For many years the conventional wisdom was that it wouldn't scale, but so far it hasn't proved to be an insurmountable challenge," Seery says.
Alcatel-Lucent is releasing a handful of new high-availability features today, all of which are meant to work together to keep video streams, or any other traffic, delivered intact.
Take the case when the link goes down between an Ethernet aggregation box (like the 7450) and an access device (such as a DSLAM). Ethernet's standard means of finding a backup link takes too long for broadcast video purposes, so AlcaLu says its new approach is to allow the DSLAM to stay connected to two aggregation points, treating them as a single aggregation node.
That trick, known as Multichassis Link Aggregation, is coupled with a new, proprietary feature AlcaLu calls the Multichassis Sync Protocol, which lets the two aggregation boxes share information on each subscriber session in process. That way, in case of a failure, the backup connection can be activated immediately without losing information about any broadcast streams in progress. The whole idea is to minimize the time it takes for the network to recover from a failure.
Alcatel-Lucent routers can apply these features to any DSLAM supporting the IEEE 802.3ag standard for link aggregation. In other words, this isn't necessarily a bid to force carriers into all-AlcaLu networks. "For service providers who have other vendors' DSLAMs, this can drop in behind it," Newell says.
Alcatel-Lucent is also announcing high availability for virtual private LAN services (VPLS) and pseudowires. The pseudowire case is particularly important because redundancy has to be factored in for every new traffic type that hits the network. "Every time we have a new one, we have to deal with HA," Seery says.
Separately, Alcatel-Lucent has a few hardware announcements coming out today, including a six-slot version of the 7450 with 80-Gbit/s capacity.
— Craig Matsumoto, West Coast Editor, Light Reading