Converged Packet Transport

CM-4000

CM-100

CM-21

CM-View NMS

Network Services

PTS for Data Services

PTS for TDM Services

Building Blocks


Packet Transport Building Blocks

Packet transport represents the point of convergence between transport and carrier Ethernet. The building blocks that make up packet transport technology are illustrated in the figure below, where these are divided into forwarding and control plane building blocks.

Forwarding plane building blocks

  • Service awareness - Corrigent's packet transport solution introduces the concept of service awareness into the transport network. It enables service providers to provide the class of service guarantees according to the performance, availability and security requirements stipulated in customer's SLAs. Specifically, service awareness allows operators to provide finer-granularity traffic classification and real-time performance monitoring at the service level, as well as flexible protection according to the service characteristics such as delay sensitive voice and packet-loss sensitive video.

  • MPLS - In the forwarding plane, MPLS provides a universal encapsulation layer and a convergence layer for all services including Ethernet, TDM, Fibre Channel, ATM and Frame Relay. All services are mapped into MPLS packets and transported over the packet transport infrastructure as virtual circuits or pseudo-wires.

  • RPR - RPR enables a loss-less shared media over the SONET/SDH layer, for the statistical multiplexing of data and TDM services. It complements MPLS by providing a MAC/traffic management layer, which guarantees service performance and class of service differentiation and which also guarantees high-service availability through standard sub-50ms protection switching mechanisms. Corrigent's CM-100 PTS provides an integrated 10 Gbits/s RPR solution, supporting four classes of service, dual-transit buffer, standard fairness and multiple RPR protection options including steer, wrap and SWIS protection.

  • Ethernet - Ethernet has become the de facto standard way of delivering data services over a transport infrastructure. For example, looking at the way service providers deliver multicast and point to point services over the transport network, we observe that while multicast services such as IPTV are delivered using an Ethernet LAN (E-LAN) or Virtual Private LAN Service (VPLS) infrastructure, point to point services such as VoIP are delivered over an Ethernet Line (E-Line) infrastructure. Packet transport provides carrier-class Ethernet services, taking advantage of reduced-cost Ethernet interfaces as well as the high levels of reliability and availability associated with packet transport. The CM-100 PTS is an MEF certified carrier Ethernet device. It enables the establishment of point to point (E-Line) and multipoint (E-LAN) Ethernet services, providing simple native Ethernet connectivity to end users, or creating a service infrastructure for the delivery of advanced IP services such as IPTV).

  • TDM over packets - Packet transport enables the statistical multiplexing of data and TDM services over the same infrastructure. TDM traffic can transported as TDM over packets (TOP), in which case the benefits of packet transport can be realized through the convergence of TDM and packet infrastructure. Corrigent's TOP implementation is according to the IETF draft-ietf-pwe3-sonet-11.txt for Circuit Emulation over Packet (CEP). In this scheme, the payload is broken into 783-byte packets, which corresponds to the size of the SPE. A 4-byte CEP label is then appended to each packet, including indications for AIS, UNEQ, pointer adjustment and sequence number. An MPLS header and VC label are used to identify the virtual circuit and forward the packet to the proper destination. TOP enables important bandwidth optimization and a reduction in operational costs associated with separate TDM and packet networks.

Control plane building blocks

  • OAM - In migrating towards packet transport, it is important to provide effective methods for monitoring the performance of the network and services, as well as for managing the network. Ethernet, MPLS and RPR OAM combine to provide multi-layer network fault indications, performance monitoring, diagnostic and testing functions, which guarantee the proper functioning of the network at the service, MAC and physical layers. Corrigent's OAM implementation including Ethernet OAM, making it the first packet transport device to offer standard Ethernet OAM capabilities.

  • Fault management - Fault management in packet transport networks provides fault detection mechanisms beyond those typically found in transport equipment and/or carrier Ethernet switches. Corrigent relies on multiple indications to detect a failure and determine signal integrity. Corrigent's PTS relies on physical layer indications, which in combination with RPR, MPLS and Ethernet specific tools such as keepalive, autonegotiation failure or RSVP-TE Path Error messages, provide robust fault management tools for network operators.

  • Connection setup - The CM-100 PTS makes use of standard MPLS control plane technology to reserve the path over which MPLS PWE3 virtual circuits and MPLS LSP tunnels are established. RSVP-TE signaling is used for this purpose, providing a standard method for resource reservation, within and between administrative domains, which results in faster and simplified service provisioning.

  • Interworking - Service interworking is a fundamental building block in packet transport networks. It facilitates the migration from the legacy PPP/MLPPP connectivity model over TDM interfaces (Packets over TDM - TOP) to a DHCP connectivity model over Ethernet interfaces towards the IP edge.