Building a network that can be shared across public sector organisations brings cost savings and is necessary to deliver other shared services, but it also brings its own challenges. This paper looks at the top ten vital ingredients used to build and run these networks based on the experience of MLL Telecom, a specialist public sector network operator.

1) A High Speed Fibre Core – where you need it

Predicting the future in technology is a risky business, but if your shared network is successful then one thing you can be certain about is that it will carry ever increasing amounts of traffic. A high speed core is a given, but how fast is fast enough and where should you get it from?

Whilst 1Gbit/s may be enough for now, make sure your provider and the rest of the equipment in your network can support a 10Gbit/s core. In most cases this will mean sourcing services from the major UK operators such as BT, Cable &Wireless Worldwide or Virgin Media, and the most cost effective way to buy this bandwidth is as an Ethernet service. The alternates to BT can offer competitive pricing but don’t usually have full network coverage everywhere you need it. Ask your operator to integrate BT Openreach services (which they will have access to) to extend their existing high speed core exactly where you need it.

2) MPLS for Privacy

The entire premise of a shared network is that all the traffic will be running over the same infrastructure. But to make that work from a security perspective you will need to segment each user group so they can’t see each others traffic. These are usually known as VPNs (Virtual Private Networks). Some physical locations may need several VPNs delivered to the same site to segment different internal user groups, such as public and staff users in a library.

There are a number of ways of providing this privacy, all going under the name of VPNs. One way is to encrypt the traffic using a technology such as IPSec. An alternative is to create logically separate Ethernet (or Layer 2) networks. The third approach, and the one we’d recommend, is to use a technology called MPLS (Multi Protocol

Label Switching) which is implemented on certain types of routers. All the major telecoms operators use MPLS to deliver their commercial VPN services and it is the technology of choice for the latest shared public sector networks. It is extremely scalable, supporting a massive number of separate closed networks, and relatively easy to administer. As you’ll see in other sections it also offers advantages in delivering Quality of Service and resilience too. Up until recently MPLS was the preserve of the telecoms operator because it was only available on very high-end routing systems, but now you can ask your
integrator or operator to design it into your own dedicated shared network. The design and operational experience required for MPLS or Ethernet VPN’s is not trivial, so whichever one you select, we’d recommend you work with someone experienced in these technologies.

3) Quality of Service

Privacy for the different users of the network is only half the problem. The other part of the challenge is how to allocate each organisation their fair share of capacity. Ideally you want any of the users to have access to the entire capacity of the network if it is available, but also to ensure that they don’t hog bandwidth in the event of congestion or partial network failure. You may also want certain applications, such as voice or real-time video, to be given priority over others. Collectively these features are known as Quality of Service (QoS).

QoS comes into play during the periods when the network is congested. QoS can prioritise the delivery of specific users, locations or applications. Different QoS mechanisms deliver a range of certainty about the amount of capacity reserved for any particular usage. The most robust QoS mechanism available on an IP network is MPLS. It might not be practical to deploy MPLS across an entire network but it can be mapped into other IP (Internet protocol) QoS mechanisms where necessary.

4) Ethernet First Mile Technology

EFM (Ethernet First Mile) or SDSL (Synchronous Digital Subscriber Loop) provides a symmetric Ethernet service across the copper telephone pairs that are usually already available to reach your premises. Unlike residential ADSL, which typically has fast download but slow upload speeds, the same bandwidth can be delivered in both directions. Another key difference to residential broadband is that EFM services can be delivered without any contention. Consumer broadband usually shares the amount of access bandwidth provided across many users, working on the basis that most users won’t be using the service at the same time. When they do, performance drops due to contention. Specialist operators, such as MLL Telecom, can provide EFM services with no contention at all.

Consequently, EFM is an extremely cost effective way of delivering connections at speeds up to 40Mbit/s.
In order to deliver you your own EFM network the operator will need to take rack space for you inside your local telephone exchanges using LLU (Local Loop Unbundling.) LLU allows operators to deliver services directly to the end-user without being restricted by the incumbent telephone company\’s portfolio. Only Ofcom licensed operators, such as MLL Telecom, have approval to do this.

EFM is ideally suited to communities of users that are concentrated in one area, such as a county or town. This allows several sites to be connected from each telephone exchange, delivering significant cost savings over fibrebased services. Examples of organisations that are taking advantage of EFM services include Local Authorities, schools, healthcare networks and CCTV connections.

5) Use BT\’s exchanges for your own dedicated network

Whilst your operator is taking rack space in BT exchanges to deliver you low cost EFM connectivity they can also put a layer of switching (or routing) in for you. Moving some of your routing capacity from your own buildings to the inside of the network has several key benefits when delivering a shared network:

Additional cost of routers is more than offset by lower transmission costs as no site needs more than a single circuit to connect to the core, rather than being connected to several other buildings.

Traffic is routed optimally around the network rather than ‘tromboning’ in and out of HQ locations. Routers in public sector buildings are simpler, lower cost devices.

Author Bio: Daniel Kidd writes about a wide range of technology, mobile and telecoms issues. For more information please visit Public Sector and Shared Networks

Category: Computers and Technology
Keywords: public secor networs, menaged, shared