Case Study
MPC Installs 10-Gigabit Ethernet Infrastructure
Phil Crawley, head of the Systems Integration arm of root6, considers the implications as film and television production moves to 10 Gigabit Ethernet networking with reference to the recent 10GigE installation at The Moving Picture Company.
While ‘convergence’ is a term that has been used in broadcast engineering for the last couple of decades, it finally seems that the workflow of acquisition, post-production and delivery as well as the technology used to create content are becoming entirely digital. 2007 saw something of a sea-change as film students abandoned their DV equipment for HDV, broadcasters (eventually!) all bought into HD and film post houses started to create effects in 4K resolution. The trend is unceasingly upwards and since Moore’s Law hasn’t yet run out of steam, both storage and bandwidth continue to shift up the gears. To this end, the kind of machine rooms we’re all familiar with are starting to look more like data centres – increasingly systems integrators are planning the Ethernet and fibre first while the video and audio are becoming afterthoughts.
In the midst of all of this we are seeing the redefinition of storage for film and TV. The large, often proprietary Storage Area Networks (SAN) are giving way to commodity hardware based on more open standards – it’s not uncommon for an editing workstation to be hanging off a storage system based on the same TCP/IP standard that the internet-connected PC uses. That same network topology might also encompass the connection to the transmission server and, if you subscribe to one of the increasing number of cable Video On Demand (VOD) services, your set-top box will receive the programme in the same way. Video Podcasting is another story but confirms this observation.
With all this in mind it isn’t surprising that post houses are looking at their network infrastructures and seeing how they can best leverage this essential part of their facility to improve business. Flexibility and agility are the name of the game. Where fibre was previously an exotic extra to connect a small number of workstations to a SAN it is now essential to flood a building. The new emerging 10 Gigabit Ethernet (10GigE) standards for copper networking are well worth investigating because, for a lot less than a step-change in cost, you achieve an order of magnitude improvement in network performance and although details are sketchy, all the research currently being done by the IEEE indicates that category 7 cable will be good for up to 100-Gigabit Ethernet.
Last year The Moving Picture Company (MPC) approached root6 to update its entire production network to 10GigE. The project was in two phases – in traditional networking terms they could be regarded as the horizontal and the vertical segments – the departmental networking and the campus back-bone. We had to train our engineering staff and wiremen to the new standards and invest in tooling and test equipment. MPC have a commitment to Tyco’s product range and so with the help of distributors Wadsworth we embarked on what was our biggest data-only project.
10 Gigabits over copper – cat7/6a
Since there is no ratified standard for Ethernet at this data rate (even though both Intel and Cisco have products) everyone is referring to it with different terminology. The Germans refer to the cable as cat7, the Americans as cat6a (the 'a' is augmented) and Tyco (who seem to have the biggest portfolio so far) as XG-10Gig cable. The new cable is a 600Mhz channel and by QAM64 and OFDM signal processing techniques they can get 10 Gigabits per second down one hundred metres of cable. If you use earlier cat5e or cat6 cable you are pretty much limited to sub-30 metre lengths.
The differences in cable and termination are sufficiently marked with respect to traditional cat6 as to require different tools and techniques and everything is specified (even down to the sub-50N of force you can apply when pulling it into ducts!). Manufacturers seem to have woken up to the fact that relying on common-mode rejection as the only means of noise reduction is flawed and consequently this new cable is double-screened - the pairs are individually shielded and there is an overall screen. This is why the cable is also referred to as PIMF (Pairs In Metal Foil).
Reasons for differences:
- Near-end cross talk is dramatically reduced by virtue of the new ends and termination tool. When properly terminated the twisted pair and shield is maintained to within a couple of millimetres of the pin on the connector. You could never achieve this with traditional punch-down methods.
- Alien cross-talk is minimised by the over-shield - cat5e and cat6 never really enjoyed this advantage.
- Inter-pair cross-talk is minimised by the foil shield around each of the pairs.
There is no RJ45 plug that can be crimped on - you can only buy pre-made patch cords and panel to panel wiring is the only termination type permitted on site.
Testing for 10GigE over copper isn't yet ratified so we use a slightly ad-hoc method; the tests are performed to ISO11801 ClassEA Channel (not permanent link) standards using PIMF 600 patch cables. Tyco recommend using a set of 2M patch leads for 500 tests and keeping them referenced to the tested ports.
On the DTX setup it will be ISO ClassEA Channel 25N1255. This is the latest draft standard for 10GigE cabling system performance. There is currently no permanent link standard to work to as the permanent link requires component performance parameters which have not yet been defined.
10 Gigabits over fibre – OM3
The Systems arm of root6 has been installing bespoke fibre for the last three years. We have invested in training, the equipment for fusion splicing and the necessary test and measurement gear. One of the reasons for entering this area of the market is because as a major reseller of various SAN systems we considered that the general use of tight-buffered cable by some integrators provided a less than perfect solution.
In the case of tight-buffered fibre the glass fibres are lined in a nylon jacket which is coated in a plastic sheath. These cables are cheap to manufacture and are flexible enough for dressing within equipment bays. The problem with tight-buffered cable occurs when you try to run long lengths of it through voids and dry-risers (between the machine room and the edit suite, for example) – it isn’t really man enough for the job and will often fail. Traditional cable-working techniques tend to compromise it, which is expensive if you have to hire wiring staff or worse still, lose the edit because the cable has just given up the ghost. The attraction to most in-house engineering departments is that they can buy the cables ready-made and not concern themselves with manufacturing leads with which they have little familiarity.
By far the better way of providing a fibre infrastructure is to run in a loose-buffered cable. The construction of this differs in that the fibres float in a mineral oil that is contained within a plastic hose. This is wound in a Kevlar mesh (the same material from which bullet-proof vests are made from!) which is all covered in a plastic sheath. The cable scores over tight-buffered cable, in that the fibres can slide within the oil as the cable is pulled around bends and the Kevlar means you can step on the cable and abuse it a lot more than patch cord cable. The bulk of the cost of the cable is in the protective construction and not in the glass fibres themselves and so it becomes very economical to run in a four-core where you might only need two (a transmit-receive pair) or a twenty-four core where you only need eight (for example). This price scalability means you can future proof yourself (you always end up building more edit suites!) and guard against possible damage (despite the glowing account above it does occasionally get damaged). Neither of these advantages can be ascribed to tight-buffered cable. Although the initial installation cost is marginally higher the total cost of ownership and reliability/flexibility is considerably improved.
A recent development in fibre is a move to a 50 micron standard called OM3 – this uses a higher quality of ‘laser-optimised’ glass and being a skinnier fibre contains the beam better allowing for 10 Gigabit performance. Given how much further OM1 (which, by comparison uses a 62.5 micron fibre) cable has come from its original 1 Gigabit standard it seems probable that 10 Gigabits is merely the starting point for OM3 cable. This is the grade of cable we used to wire MPC’s vertical network, getting through many kilometres of fibre as we flooded their Wardour Street premises over last summer.
Once completed the installation was inspected by Tyco and our test results submitted – they have warranted the installation for the next 25 years. Based on that time-span, by the time we come to rip it out and re-install we’ll be looking at 50-Terrabit networks!