Improved VC-merging method in MPLS networks

VC-merging allows VCs to be mapped onto the same VC label. In the multiprotocol label switching (MPLS) domain, an ATM-LSR (label switch router) needs a VC-merging method because of network scalability problems. VC-merging also plays an important role in providing multipoint-to-multipoint multicast and share-tree multicasting paradigms. When VC-merging is applied to multiple streams of incoming packets, all the VC-merged cells have the same label at the output port of the ingress node. If those VC-merged cells are transmitted using AAL5, cell interleaving occurs. Thus, at the egress node of VC-merging, an identification process is required in order to distinguish cells belonging to a packet from other cells. Various approaches have been proposed to help this identification process. In this paper, we propose improvements to the traditional VC technique to minimize the need for additional buffers at intermediate merge points to decrease end-to-end delay. This improved VC-merging mechanism requires receiving nodes to have a queue corresponding to each queue of the sender node, such that cells from a particular queue of the sender node are queued in a corresponding queue of the receiving node. In order to distinguish VC-merged cells from non VC-merged cells, an information cell is used. Upon the arrival of a cell at the sender node, the scheduler of the sender node transmits the cell immediately based on a round-robin algorithm. Simple equations in this paper show that the improved VC-merging method has advantages against the traditional methods in terms of buffer size and end-to-end delay time. Furthermore, if we change the scheme of queue searching (e.g. weighted fair queueing), QoS can also be supported