The metropolitan networking space, which has seen more than its share of revolutionary new products in the last two years, may be about to go through its most transforming wave of new network devices. A class of products, called optical access switches or optical WAN platforms, is bringing multiservice capabilities to metropolitan optical networks.
These optical devices sometimes sit in a building or at a customer premises, or replace a SONET add/drop multiplexer (ADM) and aggregate multiple services for SONET muxes or DWDM lambdas (waves). They often support dynamic bandwidth allocation, which allows flexibility in provisioning services that has not been possible in these networks before.
"The impact is going to be significant because the bandwidth demand won't stop," says Frank Dzubeck, president of consulting firm Communications Network Architects. "We are great believers that where the new networks will live is in the wavelength world, and it's coming very shortly."
The new devices, operating on their own, would represent significant change. But their impact is heightened all the more by recent efforts to bring IP-centric protocols to optical switches, specifically multiprotocol label-switching (MPLS). MPLS, a QoS protocol developed initially for IP networks, is used in these optical devices as a way to signal bandwidth requests to optical core networks.
As a result, it is possible that in the future, an optical device sitting at a customer premises could provision bandwidth dynamically on the MAN as well as through core optical networks, and do so on demand.
The Playing Field
The new optical access providers are slotting themselves into various market niches and levels where they can serve a particular kind of need. The new vendors fall roughly into access, metro/PoP and edge categories, depending on the size of their bandwidths, the services they support and whether they groom traffic for waves in the core.
The distinctions are somewhat arbitrary, especially between "access" and "metro/POP," and are based mainly on the bandwidth accommodated by the platform and the range of services that are supported.
* Access devices often sit on a customer premises, in a building or at a SONET ADM, serving an entire building or campus environment. These devices can take in feeds down to the T1 level or from PBXs and LANs. None support DS-0 aggregation, a market that is well served by low-cost IADs. Their output ranges from DS-3 to OC-3, and even OC-12 to gigabit Ethernet at the high end, and are typically multiplexed on a SONET or ATM network. Some do not give a wide choice of services--for example, supporting gigabit Ethernet but not ATM or frame relay. The Appian Communications Inc.'s (www.appiancom.com) Optical Services Activation Platform (OSAP), for instance, is a "last-mile" product using IP over gigabit Ethernet providing "tunable" bandwidth starting at 1.5mbps. It works within an existing SONET infrastructure and can feed the routers, frame relay or ATM switches already in a PoP.
* Metro/PoP devices may replace a SONET ADM or may be located at a service provider's CO or metro PoP. They aggregate a wide range of services--gigabit Ethernet, T1s, ATM--into lambdas or SONET muxes destined for waves. Alidian Networks Inc. (www.alidian.com) uses a feature it calls WavePack technology to flexibly aggregate multiple services into a SONET multiplex.
* Optical edge products, such as Tenor Networks Inc.'s (www.tenornetworks.com) TN250G Optical Service Switch (OSX), reside in the CO or PoP and act as the bond between a carrier's long-haul DWDM network and its metro DWDM (or SONET) access network. The TN250G, for example, connects directly to DWDM equipment and, like others in this class, provides the ability to process IP, TDM, ATM and frame relay on a single port. Both access and metro/PoP devices can act as feeders to optical edge devices.
Some vendors straddle two or more sectors, and Sirocco Systems Inc. (www.siroccosystems.com) claims to play in all three sectors, based mainly on the aggregation level of their product. Sirocco has two Zephyr OAD (optical access device) "access" products. One aggregates bandwidth and services to OC-12s and could replace high-end IADs. The other aggregates to the OC-48 level and could function as a SONET ADM replacement. The company's Typhoon OES (optical edge switch) grooms multiservice streams and feeds traffic onto multiple wavelengths into an optical core.
Some of the vendors include DWDM output while others merely prepare aggregations of traffic for separate DWDM systems to put on lambdas. Sirocco, for instance, has its own built-in DWDM, which will work with other Sirocco devices but not with DWDM of other vendors. The Appian product, while it can be used to migrate a network to DWDM and wave-based services, does not have its own DWDM.
Some, such as Alidian and Sirocco, have the ability to multiplex multiple services onto one lambda, which is sometimes called sub-lambda multiplexing. They also provide the ability to switch sub-lambda streams at each node in the network. Other platforms aggregate traffic into multiplexes of the same service, assigning each service to a different wave.
Such a varied product mix is aiming for an equally varied menu of customers, from CLECs and so-called BLECs (building-centric local exchange carriers) to ISPs and IXCs. "This is a rich space, and optical technology is becoming very popular," says Rashmi Doshi, chief technology officer at Everest Broadband Networks (www.everestbroadband.com), a new BLEC operating in New York and Los Angeles. "There is a need for a bunch of optical products because no one size fits all."
Everest is an example of a company enabled by optical access technology. The company negotiates preferred service provider status with a large building and works with fiber providers, such as Metromedia Fiber Network Inc. (www.mmfn.com), to bring fiber to the building or campus. It may also upgrade the networking within the building to fiber or superior copper.
Optical access products give Everest the "ability to provide services to tenants quickly," Doshi says. "Once we are lit in the building, we can essentially turn up the customer, at least to our PoP, immediately, and if we meet another carrier there, can hand off traffic to that other carrier. We can offer our own IP service if the customer wants to stay on our network."
Everest is considering both Alidian and Appian products. "Alidian offers the ability to take ATM, frame relay and other traffic, and either drop it between buildings or take it back to the PoP on an aggregated basis," Doshi says. "That allows us flexibility, because quite often we don't know the services customers are looking for." Appian is more focused on Ethernet and TDM-based traffic and provides for buildings needing less bandwidth, "such as those starting at the DS-3 level and then going beyond that." Doshi says the advantage of Alidian is that "they can carry different kinds of traffic, and they have technology that can do more dynamic bandwidth allocation because of the protocol they build on the SONET."
The MPLS Effect
The magic in all this is expected to come from MPLS, a protocol that originated in the Internet Engineering Task Force (www.ietf.org) for use in IP networks, but can function across multiple transports, such as optical and ATM.
MPLS is already important in the work of a new industry group--the Optical Domain Service Interconnect (ODSI)--which seeks to give electrical devices, such as large edge routers, the ability to signal bandwidth requests into core optical networks. "These new access companies are going to provide services, but they need access to the core to leverage bandwidth for the services, using ODSI," says Rick Thompson, senior manager of product marketing at Sycamore Networks Inc. (www.sycamorenet.com). "The key is that MPLS is the protocol of choice."
For the first time, the IETF, the important IP standard-setting group, is getting involved in optical networking. Much of the work is focused on how to use MPLS and the open shortest path first (OSPF) protocols from IP networks for signaling in the optical domain.
MPLS and the idea of extending ODSI signaling to access networks is "a very important concept," says Communications Network Architects' Dzubeck, because "the missing element is to extend signaling from the core to customers and to have the ability to do dynamic provisioning to meet customer needs." The capability would also free service providers from having to replace equipment en masse just to deliver a new service.
"This is the latest movement in the optical networking groups, to use the MPLS signaling capability to adapt and get more bandwidth," says Doshi. MPLS brings connection-like capability to connectionless networks, such as IP. For service providers, once a channel has been set up with dynamic bandwidth allocation using MPLS, "the appropriate end points can request more bandwidth." The challenge, Doshi continues, "is that you would need interoperability between different equipment," an issue that is just beginning to be addressed in groups such as the IETF and ODSI.
"Ultimately what customers are looking for is flexibility and delivery," Doshi says. "Everyone is going to have fiber, but service providers are looking for ways to manage that flexibility." It is critical that products be able to do that on an end-to-end basis and talk to other products, he says. "If you have an access device that can grant a gigabit of bandwidth for the next hour, you still need the rest of the network to coordinate with you."
| New Optical Access and Edge Products | ||||
Local Loop | Access | Metro/PoP | Edge | Core |
Passive optical network (PON) companies | Appian Communications Inc. Alidian Networks Inc. Sirocco Systems Inc. Atmosphere Networks Inc. Luminous Networks Extreme Networks Inc. | Chromatis Networks Inc. Alidian Networks Inc. Sirocco Systems Inc. Astral Point Communications Inc. Cyras Systems Inc. Communications Inc. Cisco Systems Inc. Sorrento Networks Inc. Redback Networks Inc. Mayan Networks Corp. | Tenor Networks Inc. Ellacoya Sirocco Systems Inc. Equipe | Avici Systems Inc. Pluris Inc. Sycamore Networks Inc. Tellium Inc. Lucent Technologies Inc. IronBridge Networks Inc. Cisco Systems Inc. Juniper Networks Inc. Vivace Networks Inc. |
