The network topology is in the attachment. Topology (Alcatel NMS-Cisco 6513-Cisco 6513-MA5200G BRAS-Alcatel DSLAM), NMS wants to manage DSLAM through MPLS VPN (vpn-instance) but was not able to communciate with it.
In the whole network from Cisco 6513 to MA5200G we configured the mpls mtu size as 1532(1524 bytes because of NMS and 8 bytes more for two mpls labels), in MA5200G since it does not support mpls mtu command, we configured mtu 1532 in the interface, after this configuration in the network, the NMS was able to manage DSLAM successfully.
NMS was not able to manage DSLAM because the packet was getting fragmented in the network, the mpls mtu size in the network from Cisco 6513 to MA5200G BRAS was by default configured as 1500, the Alcatel NMS was sending MTU as 1524 and with a "dont fragment" flag bit set. So all the packets above 1500 were getting lost in the network. The ethreal trace captured in the NMS when the packets were getting fragemented is in the attachment which can be opened by Ethreal packet analyser.
When using mutli vendor equipment in the network, make sure that the mtu size is the same in the network and make sure what mtu size the NMS is sending since it can vary for different application and also check if the NMS is sending the packet with "dont fragment" flag bit set because if this is the case the packets will not get fragmented if the mtu size defined in the network is less than the size what the NMS is sending.