Janet6: From Procurements to Design On-Line Briefing 4th October 2012

I and over 95 members of the Janet community went on-line yesterday to participate in the second of our online briefings on the progress of the Janet6 project. Jeremy Sharp, Head of Strategic Technologies described how Janet6 has come successfully through the requirements gathering and procurement phases and is now in the roll-out phase. Rob Evans, Chief Technical Advisor, described the design and architecture of the new network, and Neil Shewry, Project Manager participated in the Q&A session at the end.  As a non-techie I feared parts of it might be a bit over my head, but it was really interesting. Here are my notes on the nuts and bolts and widgets of the network we're building which is going to provide such a fabulous infrastructure for the research and education community.

Rollout

A 10 year, £30m contract was signed with SSET on 31 July 2012 to supply the network of dark fibre and collocation facilities. A £12.8m contract was then signed with Ciena on 6 September 2012 to provide the optical transmission equipment plus 5 years of maintenance and support services. The roll-out phase has started and the new network will be built by the end of April 2013. This will then be run in parallel with SuperJanet5 until the latter is turned off in October 2013. Janet6 is planned to have a lifetime of 10 years with a possible extension to 15. We have therefore been very careful to design a carrier class network with in-built flexibility, and the ability to respond rapidly to any needed changes, through being directly managed by the Janet Network Operations Centre and our close working relationships with industry partners.

Design and Architecture

Janet6 will consist of nearly 6500 kilometres of fibre. The backbone topology is a “ladder” like SuperJanet5, but with a new cross-link between Birmingham (Erdington) and Nottingham (Lowdham) providing greater resilience and shorter re-route times in the event of failures. The other main change in the core topology is that instead of having two loops in the South, one through Bristol and the other through London, there will be a single loop of fibre through both. Connectivity to the regional networks will be based on the same principle as SuperJanet5, with diverse fibres to two RNEPs per region. However there will be fewer collector arcs picking up multiple regional networks than before, just 1 spanning the Aberdeen and Fife and Tayside regions. All fibre used will be G.652. This is an older specification than G.655 but is preferred due to it working better with modern transmission systems. We have also opted for the one fibre type across the entire network as mixing fibre types causes reflections, losses and other effects which can limit the reach. We are maintaining the current network of Lightpaths (but with the bandwidth between backbone nodes increased to 100GE). This reflects what is currently required. As has been the case up until now, the Lightpath network has evolved to meet customers’ requirements, and this will continue, so if you need Lightpaths elsewhere, please talk to us!

The change in contractor means that we will be vacating the Verizon Points of Presence (PoPs) except for a small presence in Glasgow and Reading due to interconnectivity with the Scottish Schools’ network (in Glasgow) and the TVN regional network (in Reading). We will keep our existing Provider-Neutral PoPs at Telehouse North, Telecity Harbour Exchange, Telecity Manchester and Scolocate in Edinburgh, and are adding new ones at Telecity Powergate (West London), Telehouse West and Leeds (AQL, Salem Church). The latter building has an interesting Grade 2 listed history as a church and in football lore. Telecity Manchester will move from being connected to Warrington and Leeds as an addendum to SuperJANET5, to becoming a Core PoP and an integral part of the backbone. We will not be moving our existing Juniper routers from the PoPs that we are vacating as they need to be upgraded fromT-640s and T-1600s to T-4000s. We will instead be buying and installing new routers for Janet6, which has the additional advantage that we can ensure continuity of service by keeping the old ones in operation until we turn off SuperJanet5.

For the transmission equipment we have purchased Reconfigurable Optical Add/Drop Multiplexers (ROADMs). The fundamental component of this is the wavelength selective switch which makes it reconfigurable. This uses diffraction gratings, lenses and servo-actuated mirrors to redirect mixtures of up to 88 different wavelengths out of different directions. Choices had to be made in the transmission design. One of these was whether to continue to use Dispersion Compensation. The issue is that “coherent” receivers for higher speed circuits are adversely affected by the presence of dispersion compensation, but if omitted it becomes harder to carry lower speed signals. Analysis showed that we didn’t really need it, as although we can’t carry 10G wavelengths, there are few parts of the network where we need to carry a single 10G wavelength. We usually need to carry two or more and so can multiplex them onto a transponder which carries 4 times 10GE circuits over a 40 Gbit/s coherent wavelength, or 10 times 10GE circuits over a 100 Gbit/s coherent wavelength. Similarly we considered the possibility of introducing OTN Switching but this was expensive, not available from a wide range of shortlisted suppliers and difficult to see why we really needed it when we also have the Janet Lightpath layer.

We’re also keeping a close eye on developments in transmission system technologies. Existing transmission systems convert optical signal received from router to electrical, then reconvert it to optical again to transmit. More direct long haul signal transmission systems are starting to arrive for 10G but do not yet exist for 100G. Substantial cost savings should become possible when this technology matures.

Other Lessons Learned During Implementation

We’ve learned some interesting additional things in designing and rolling out the network. Some of our biggest challenges have come not from the network itself but from integrating it with the electricity supplies. The network needs lots of power to keep the UK connected, with each router having two Power Entry Modules (each one requiring 48v DC feeds with 60A breakers) and up to 4 kW more for the transmission equipment. We have been finding that the electrical guys don’t seem to like aggregating capacity as easily as the router guys. We’ve also found out from SSET digging holes in the ground to lay fibre, that local authorities (who can be quite suspicious of telcos wanting to dig up their streets) have reacted very positively when they’ve found out that the holes are being dug for Janet and the research and education community. We have a reputation as a force for good in the UK!

The webpage for the recorded session, and to find further technical information discussed on the day, will be available shortly.