Actively Reserved Bandwidth Architecture

The MPLS architecture has some shortcomings. First, it will lead to the heavy load of edge-LSRs due to calculating the path of traffic in the MPLS domain, when traffic is increasing considerably. Second, it spends time to establish a path. When network resource is insufficient, it will cost more time to re-establish a path. Therefore, proposed a new architecture, called Actively Reserved Bandwidth Architecture, to improve the original MPLS architecture.

In the Actively Reserved Bandwidth Architecture, each core-LSR reserves some bandwidth for every edge-LSR. These core-LSRs construct a path that occupies the bandwidth for the edge-LSR. While a traffic flow requests an edge-LSR for transmission, the edge-LSR can quickly find a path with sufficient bandwidth to transmit it without calculating and establishing the path in the MPLS domain. This reduces the chance of failure in establishing a path and decreases the load in edge-LSR. Therefore, this approach is good for transmitting multimedia traffic due to the serious delay limitation. Sometimes, an edge-LSR requests the bandwidth exceeding the reserved capacity. The edge-LSR uses the original architecture in calculating and establishing a path to transmit the traffic flow in the MPLS domain. This may use other edge-LSR's reserved bandwidth in some core-LSRs. When the situation occurs, these core-LSRs signal the edge-LSR whose reserved bandwidth is occupied. And, the core-LSRs cut down the reserved bandwidth for the edge-LSR.

Advantages
The advantages of Actively Reserved Bandwidth Architecture are pointed out as follows:

• To reduce the need of establishing a path. If the reserved bandwidth is sufficient, the edge-LSR has no need to establish a path.
• To decrease the probability of failure in establishing a path. When the reserved bandwidth is occupied by other edge-LSR, the core-LSRs will actively notify the edge-LSR.
• To be suitable for real-time multimedia traffic. Establishing paths results in time delay.

According to the feature of MPEG-4 video, treating one VOP as a unit of transmission is more efficient than treating one packet as a unit of transmission. Actively Reserved BandwidthArchitecture improves CR-LDP in the MPLS domain. This architecture achieves better results and is more suitable for multimedia traffic, such as MPEG-4 video. The future research on Actively Reserved BandwidthArchitecture is expected. Due to dynamic network traffic on Internet, the core-LSR hardly reserves definite bandwidth for the edge-LSR to handle all cases. Many studiesemphasized the traffic engineering of MPLS, which is an important topic for further research. Besides, there is a trend in internet router for differentiating the type of incoming network traffic. This makes flow-orientedcontrol easier in LSR, and also supports QoS mechanisms. It is necessary to have an optimal design of bandwidth reservation in core-LSRs for the edge-LSR.