Optical core switching tops 4 Terabit-per-second.

After the launch of Alcatel-Lucent's 1870 TTS optical core switch, three experts comment.

Event:

Alcatel-Lucent has launched its 1870 Transport Tera Switch (TTS) that has a switch capacity of 4 Terabits-per-second (Tbps). The platform switches and grooms traffic at 1Gbps granularity while supporting lightpaths up to 100Gbps.

“It is designed to address the explosion of traffic in core networks, driven by video and the move to cloud computing among others,” says Alberto Valsecchi, vice president of marketing, optics activities at Alcatel-Lucent.

The 1870 TTS supports next-generation Optical Transport Network (OTN), carrier Ethernet and SONET/SDH protocols, as well as generalized multiprotocol label switching/ automatically switched optical network(GMPLS/ ASON) control plane technology to enable network management and traffic off-load between the IP core and optical layers.

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It [the 1870 TTS]  is designed to address the explosion of traffic in core networks"

Alberto Valsecchi, Alcatel-Lucent

Central to the 1870 TTS is an in-house-designed 1Tbps switch integrated circuit (IC). The switch chip is non-blocking and by switching at the OTN level supports all traffic types. The device is designed to limit power consumption and is claimed to consume 0.04 Watts per Gbps. Four such ICs are required to achieve the 4Tbps switch capacity.

 Each platform line card has a 120Gbps capacity and supports 1, 2.5, 10 and 40Gbps interfaces with a 100Gbps interface planned. The line card’s optical transceiver interfaces include 12 XFPs or two CFP modules. Three 40Gbps interfaces will be supported in future and a 240Gbps line card is already being mentioned (Alcatel-Lucent describes the platform as ‘8Tbps hardware ready’).

The cards also use tunable XFP modules. The 1870 TTS can thus be used alongside existing optical platforms for long-haul dense wavelength division multiplexing (DWDM) transport or support its own links. “There is urgency for this [platform] to manage bandwidth in the central office,” says Michael Sedlick, head of cross-connect product line management at Alcatel-Lucent. “It can solve both requirements: working with installed based WDM platforms and enabling a more integrated implementation [using tunable XFPs].”

 “It is already in trials and is selected by tier one service providers,” says Valsecchi.

Why is it important:

Gazettabyte asked three experts to give their views on the announcement. In particular, to position the 1870 TTS platform, discuss its significance, and the importance of GMPLS/ ASON support.

Ron Kline, principal analyst, network infrastructure at Ovum

The platform announcement is essentially about solving three key [service provider] dilemmas: scaling to meet the huge growth in traffic, working through the transition from SONET/SDH to Ethernet and driving efficiencies in the network through automation that helps reduce capital expenditure and operational expenditure.

 The 1870 TTS is not a new class of platform but rather the next generation of bandwidth management systems that is using electrical OTN switching rather than STS-1 [SONET frame] switching.  

Alcatel-Lucent’s existing 1850 packet optical transport system is really the next generation of aggregation (optical edge device/ multi-service provisioning platform) equipment. The difference is where the device goes in the network and the granularity of the switching.

For the 1870, you are switching bandwidth at wavelength rates (2.5G, 10G, 40G, etc.) There is also some sub-wavelength granularity as well. The device is protocol independent because client signals (SONET/SDH, Ethernet, video, etc) are all encapsulated in the OTN wrapper.  

The most similar platforms are the Ciena 5400 introduced in September ’09 and Huawei’s OSN 8800. Tellabs also introduced a high-speed shelf for the 7100 that has a 1.2Tbps OTN matrix and ZTE has the ZXONE 8600 that it introduced in March ’09.

Momentum has been building for several years now. The current generation of optical core switches (Ciena's CoreDirector, Alcatel-Lucent's 1678 MCC, the Sycamore 16000) cannot scale large enough and are SONET/SDH based. The need is to be able to groom at the wavelength level. Current switch sizes (640Gbps, 1.2 Tbps for Sycamore) can’t scale so you have to place another switch and also use capacity to tie the switches together.  The larger you grow the bigger the problem—you use 10% of capacity to tie two machines together, 20% to tie 3 together, etc.

In addition, older generation optical core switches are SONET/SDH-based and have trouble with Ethernet so they have to use the generic framing procedure/ virtual concatenation (GFP/VCAT) to manipulate the signal. When you move to OTN switching you don’t have to convert between protocols to switch through the matrix.  

And yes, so far 4Tbps is the highest switch capacity per chassis.

As for the control plane, ASON automates configuration so it is more applicable for turning up and down bandwidth. In Alcatel-Lucent’s case, it is integrating the control planes across its product portfolio which gives visibility across the entire network. Although router offload is a key application for the device, you don’t necessarily need a control plane to do it.  

IP routing is much more expensive (per bit) then wavelength switching. The idea is to switch at the lowest network layer possible. People have been using an inverted triangle with 4 layers to illustrate. IP routing is at the top followed by layer-2 switching, TDM/OTN switching and then wavelength switching.

Eve Griliches, managing partner, ACG Research

The 1870 TTS isn’t a new platform class but the platforms in general are new. Huawei, Fujitsu, Tellabs, Cisco and various others have platforms all geared towards this but most are missing some element today.  In this case, Alacatel-Lucent is still missing the optical portion of the product [DWDM and ROADM].

The platform is starting out as a large OTN and packet switch which will eventually turn into a full packet optical transport product - that is my estimate.  Each vendor is approaching this area differently, suffice to say, I think this is an OK and decent approach.

The GMPLS/ ASON control plane technology means the 1870 TTS can manage the optical and IP layers together.  Some providers want that, some don't.

Andrew Schmitt, directing analyst, optical, Infonetics Research

The 1870 TTS is a lot like the 1850, just bigger. I suspect much of the new functionality in the 1870 will migrate down to the 1850.

It is significant as there are not that many boxes - none, really - that can do converged SDH/OTN/layer-2 switching all on one backplane. Several other vendors such as Ciena with its 5400, Cyan and Tellabs are going in this direction but Alcatel-Lucent has some legitimacy since it already was out with the 1850. Only the Fujitsu 9500 is in this class.

GMPLS/ ASON allow routers to communicate with the layer one infrastructure and set up and tear down paths as needed. It gives the router visibility into the lower layers of the OSI stack.

I think the key point is really the 1870 TTS’s 4Tbps switch capacity. This box represents the cutting edge of converged layer-1 plus layer-2 packet optical transport system technology.

Now we will see whether carriers adopt this architecture or whether they use IP over WDM or OTN switching only.

The Alcatel-Lucent 1870 TSS: the two central cards, larger than a shelf, each contain four 1Tbps universal switch ICs. There are two cards per platform as one is used for redundancy.