MMPLS: Modified Multi Protocol Label Switching

Transcription

1 MMPLS: Modified Multi Protocol Label Switching Kanupriya 1 and Vikas Nandal 2 1 Electronics and Communication Department, U.I.E.T, MDU Rohtak, Haryana (India) priya.kanu846@gmail.com 2 Electronics and Communication Department, U.I.E.T, MDU Rohtak, Haryana (India) Abstract Multi-Protocol Label Switching (MPLS) being one such technology for increasing the efficiency. This technology of forwarding data packets (of a fixed size labels) is based upon a pre-determined path that the data packet needs to traverse, where then coming packet labels are examined to determine the next hop (or the next part of the journey), the old label is then replaced with a new one (label) and once again it is forwarded to the next hop, and the journey continues till it reaches its destination. This dissertation discusses a local and global recovery scheme when the link failure occurs within the backup path as well in the original path. In the existing technique, if any fault occurs at any LSR then detour LSR will compute the protected LSP. This protected LSP will be used as the backup path to transfer the data. But the global path may be more optimized as compared to this protected path. The proposed techniques hybridize the local repair as well as the global recovery schemes to find the optimized recovery path. Whenever any fault occurs at any LSR then the Detour LSR give provides the protected path (local repair) and the global recovery will provide different path (Haskin s model). The total path cost of each is compared and the optimized path is selected in the proposed model. Moreover the original path is recovered after repairing the faulty LSR. Keywords- MPLS, Rerouting, LSR. 1. Introduction Internet has become an integrated carrier gradually, which has multi business such as data, voice, video, multimedia and so on. New multimedia applications require the network to guarantee quality of service. MPLS network has the capability of routing with some specific constraints for supporting desired QOS. Rather than replacing IP routing, MPLS is designed to overlay its functionality on top of existing and future routing technologies and to work across a variety of physical layers to enable efficient data forwarding together with reservation of bandwidth for traffic flows with differing QOS requirements regarding bandwidth, delay, jitter, packet loss and reliability. MPLS is an efficient encapsulation mechanism which uses labels appended to packets for transport of data. A router supporting MPLS is label switched router. [1] An edge node is an LSR connected to a non- LSR. An ingress LSR is the one by which a packet enters the MPLS network, an egress LSR is one by which a packet leaves the MPLS network. Labels are small identifiers placed in the traffic. They are inserted by the ingress LSR, and ultimately removed by the egress LSR. As traffic transits the MPLS network, label tables are consulted in each MPLS device. These are known as the Label Information Base or LIB. By looking up the inbound interface and the label in the LIB, the outbound interface and label are determined. The LSR can then substitute the outbound label for the incoming and forward the frame. The labels are locally significant only, meaning that the label is only useful and relevant on a single link, between adjacent LSRs. The adjacent LSR label tables however should end up forming a path through small or all of the MPLS network, a label switched path (LSP), so that when a label is applied, traffic transits multiple LSRs. If traffic is found to have no label, a routing lookup is done and possibly a new label applied [1] MPLS [2] works by prefixing packets with an MPLS header, containing one or more labels. This is called a label stack. Contains four fields: A 20 bit label value. A 3-bit Traffic class field for QOS priority (experimental) and ECN (Explicit Congestion Notification) 13

2 A 1 bit bottom of stack flag. If this is set, it signifies that the current label is the last in the stack. An 8 bit TTL (Time to Live) field. Figure 1: MPLS Network [1] These MPLS labeled packets are switched after a label lookup/switch instead of a lookup into the IP table. Labels are distributed between LER s and LSR s using the Label Distribution Protocol (LDP). LSR s in an MPLS network regularly exchange label and reach ability information with each other using standardized procedures in order to build a complete picture of the network they can then use to forward packets. When an unlabeled packet enters the ingress router and needs to be passed on to an MPLS tunnel, the router first determines the forwarding equivalence class (FEC) the packet should be in and then inserts one or more labels in the packet s newly created MPLS header [4]. The packet is then passed onto the next hop router for this tunnel. When a labeled packet is received by an MPLS Router, the topmost label is examined.based on the contents of the Label a swap, push or pop operation can be performed on the packet s label stack. Routers can have prebuilt lookup tables that tell them which kind of operation to do based on the topmost label of the incoming packet so they can process the packet very quickly. To ensure end to end QOS guarantees [3] QOS routing protocols usually impose a minimum QOS requirement on the path for data transmission. Restricting the hop count of the path being elected can reduce the resource consumption while selecting the least loaded path can balance the network load. There exist many QOS routing protocols in MPLS networks. All of them can find an optimal path by using their path selection algorithms. Figure 2: MPLS label Stack [1] They mainly focus on both `bandwidth and delay constraints. It means that the delay of the path which is computed by the algorithm is less than or equal to the delay constraint value and the residual bandwidth of all the links along the computed path must be equal to or greater than the bandwidth constraint value. The proposed MPLS Routing algorithm called New QOS Routing Algorithm for MPLS Networks Using Delay and Bandwidth constraints present performance improvement based on CPU Time, path length, call back ratio and maximum flow [5]. 2. Proposed Work In the existing technique, if any link failure occurs then the protected LSP will be used as the backup path to transfer the data. But the global path may be more optimized as compared to this protected path. If before recovery, another link failure occur then no optimization exist in the existing technique. In such situation the existing technique determines the global path and follows the path to transfer the data. The proposed techniques hybridize the local repair as well as the global recovery schemes to find the optimized recovery path. Whenever any fault occurs at any LSR then the Detour LSR give provides the protected path (local repair) and the global recovery will provide different path (Haskin s model). The total path cost of each is compared and the optimized path is selected in the proposed model. If the link failure occurs in selected path then the new path is found by repeating the same process. Original path are 14

3 recovered as the link gets up. The process is optimized as compared to the existing algorithm. 4. Parameter Analyzed Various parameters used for analysis are described below: Packet Delivery Ratio (PDR) The ratio of the number of delivered data packet to the destination. This illustrates the level of delivered data to the destination. Number of packet receive / Number of packet send End-to-end Delay Figure 3: Proposed Diagram. 3. Proposed Algorithm The proposed algorithm explains the process to select the recovery path. 1. Select the S_LER and D_LER 2. Generate Data packet From S_LER say DP and assign label 3. Current_lsr=Next(S_LER) 4. While next(current_lsr)~=d_ler 5. Pop label from DP at current_lsr 6. Assign label to DP having L=next(current_lsr) 7. Move DP to L(extracted from label) 8. Update current_lsr 9. If current_lsr is faulty 10. Select alternate lsr using current_lsr 11. Calculate total cost say t 12. Select global backup path 13. Calculate cost of global backup path say t1 14. If t< t1 15. Select local repair path 16. Else 17. Select global repair path 18. End 19. Update current_lsr 20. end 21. End while 22. Transfer dp from current_lsr to D_LER 23.If any link failure occur then go to step 10. The average time taken by a data packet to arrive at the destination. It also includes the delay caused by route discovery process and the queue in data packet transmission. Only the data packets that successfully delivered to destinations that counted. (arrive time send time ) / Number of connections The throughput of a receiver (per-receiver throughput) is defined as the ratio of the number of bits received over the time difference between the first and the last received packets 5. Results The table 1 shows the comparison of the existing and proposed technique using the parameters discussed in section 5. 15

4 Table 1: Comparison of Results of Proposed Method and Existing Method. Generated Packets Received Packets PDR E2 E Delay Proposed Existing The results shown in the table 1 can also be analyzed graphically as shown in figure 4 and figure E2E delay(existing) E2E Delay(Proposed) The figure 5.1 and figure 5.2, shows the comparison of the e2edelay and the throughput of the existing and the proposed technique. The decrease in the e2edelay is due to the local recovery scheme introduced. The decrease in the recovery time leads to the increase in the throughput that is shown in the figure 5.2. The decrease in the e2edelay and the increase in the throughput show the better performance of the proposed technique as compared to the existing technique. Figure 4: Comparison of E2E Delay between Existing and Proposed Methods (Existing) (proposed) Figure 5: Comparison of between Existing and proposed methods 6. Conclusion This dissertation discusses a local and global recovery scheme when the link failure occurs within the backup path as well in the original path. In the existing technique, if any fault occurs at any LSR then detour LSR will compute the protected LSP. This protected LSP will be used as the backup path to transfer the data. But the global path may be more optimized as compared to this protected path. The proposed techniques hybridize the local repair as well as the global recovery schemes to find the optimized recovery path. Whenever any fault occurs at any LSR then the Detour LSR give provides the protected path (local repair) and the global recovery will provide different path (Haskin s model). The total path cost of each is compared and the optimized path is selected in the proposed model. Moreover the original path is recovered after repairing the faulty LSR. The simulation result shows the comparison of the e2edelay and the throughput of the existing and 16

5 the proposed technique. The decrease in the e2edelay is due to the local recovery scheme introduced. The decrease in the recovery time leads to the increase in the throughput. The decrease in the e2edelay and the increase in the throughput show the better performance of the proposed technique as compared to the existing technique. In future following work can be done: 1. The technique can be extended to use IP with the MPLS for wireless communication. 2. The proposed technique can be extended to used the ATM for the wireless communication. References [1] Mr. Manish G., Sahil S., Indraneel K., Ankitk, JegaPriya J., (2012) Multi-Protocol Label Switching (MPLS), International Journal of Engineering Research and Applications ss(ijera) ISSN: Vol. 2, Issue 3, May-Jun 2012, pp [2] Chen, S., & Nahrsted, K. (1998). An overview of quality of service routing for next-generation high-speed networks: problems and solutions. Network, IEEE, 12(6), [3] Wang, B., Su, X., & Chen, C. P. (2002). A new bandwidth guaranteed routing algorithm for MPLS traffic engineering. In Communications, ICC IEEE International Conference on (Vol. 2, pp ). IEEE. [4] Ravindra Kumar Gupta, Arvind Kumar Singh, Pankaj Singh, Omjeet Singh, (2013),Analyzing Multi Protocol Label Switching Network, International Journal of Advanced Research in Computer Science and Software Engineering, Volume 3, Issue 6, ISSN: X. [5] Qiu, Yimin, Jinguang Gu, Hongbing Zhu, and Yi Zhou. (2009). MPLS-based Network Fault Recovery Research. China, Wuhan, Wuhan University of Science and Technology. 17