In order to achieve this on their NGN, termed 21CN, BT plan to consolidate several separate networks onto one converged IP network. Convergence has been a buzzword in the industry for a number of years, but in terms of scale and ambition 21CN is unique.
Paul Indoo, Product Marketing at Nortel, a key supplier to BT’s 21CN project, believes IP is increasingly used to support more than just data applications, as seen by the success of VoIP and IPTV.
"As a result it’s natural that convergence at the services and application layer has been achieved over an IP network. In the LAN, Ethernet is well established as the transport layer for IP and so there is an opportunity to re-use Ethernet as the transport layer in the WAN for large national IP networks.”
The benefits to the enterprise
Nortel believes that this results in a number of benefits for the enterprise. First of all because of its success Ethernet has benefited from decades of successful deployments and has undergone rigorous standardisation. This means that not only does Ethernet provide the most cost-effective network interface, but it is also well-understood within the industry. By extending the use of Ethernet through the WAN enterprises can reduce both their capital and operational expenditure.
”The benefits are not only limited to an enterprise’s bottom line” says Indoo. “The flexibility of Ethernet allows bandwidth to be increased quickly and easily in increments of 1 Mbps up to 10 Gbps. This means that a service provider can be more responsive to their customer’s changing bandwidth requirements. From a customer perspective there is no need to buy additional bandwidth to provide spare capacity, as additional bandwidth can be purchased easily, which means customers only need to pay for the bandwidth they need.
Using Ethernet in the WAN also removes the requirement to translate from Ethernet into a WAN protocol (e.g. ATM, FR) and so Ethernet frames are subject to less delay and jitter. By improving network performance, Ethernet makes the WAN more suitable to support real-time applications like VoIP and IPTV that enterprises are looking for.
Ethernet networks that service providers are building must be both scalable and reliable. The services provided over these networks must be standardised and offer guaranteed performance with Quality of Service (QoS). Furthermore the service provider must have access to mature network management tools, in order to manage customer expectations through an agreed Service Level Agreement (SLA).
The industry has developed a number of enhancements to Ethernet to add these capabilities including IEEE 802.1ah Provider Backbone Bridges, which adds massive service scalability. The development of Provider Backbone Transport (also known as PBB-TE by the standards bodies), allows Ethernet tunnels to be created that support guaranteed performance levels, comparable to those achievable with SONET/SDH. Finally comprehensive OAM tools are achievable through implementation of IEEE 802.1ag (Connectivity Fault Management) and ITU-T Y.1731 (Fault and Performance Monitoring).”