15.5. MPLS IN THE DATA COMMUNICATIONS NETWORK (DCN)

Typically, service providers have large internal networks called Data Communications Networks (DCNs). These carry OSS and management traffic for various types of network equipment, including SONET/SDH cross-connects, DWDM equipment and routers. These networks can have a large number of sites – for example in the case of a DWDM transmission system, each amplifier site needs to be hooked into the DCN. In many service providers, several separate DCNs have been built over the course of time, each being used to manage different types of equipment. There is strong interest in merging the separate DCN networks into one network having an MPLS backbone. A popular option is to use VPNs to maintain separation between the different DCNs, as sometimes they are managed by different departments and may have overlapping addresses.

Some of the network equipment being managed via the DCN uses the ISO Connectionless Network Service (CLNS) rather than IP. In order to carry the CLNS traffic across the MPLS backbone, a scheme has been devised which is very similar in concept to a BGP/MPLS IP VPN [BGP-CLNS]. Like the IP VPN scheme, a model in which the PE is a routing peer with the CE is used. Native CLNS routing is used between a PE and locally attached CEs, and the CLNS routes from different VPNs are stored in separate VRFs. CLNS reachability information is communicated between PEs via multiprotocol BGP in the form of labeled routes, using an address ...

Get MPLS-Enabled Applications: Emerging Developments and New Technologies now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.