Comparison of MSTP and GELS Benchmarking Carrier Ethernet

Comparison of MSTP and (G)ELS Benchmarking Carrier Ethernet Technologies Workshop Session AI. 1: Scientific and Technical Results Krakow, Poland April 30, 2008 Luis Fernando Caro, Jose Luis Marzo University of Girona Dimitri Papadimitriou Alcatel-Lucent Bell

Presentation Outline § Comparison of MSTP with constraint-based routing algorithms § Objective § MSTP scheme § Simulations § Comparison of RSTP with constraint-based routing recovery techniques § Objective § Recovery schemes

Comparison of MSTP with constraint-based routing algorithms: Objective § Objective: compare Multiple Spanning Tree Protocol (MSTP) with provisioning techniques that rely on constraint-based routing Ethernet VLAN-Label Switching (ELS) § For the MSTP in order to enable it to satisfy specific bandwidth request like its done on ELS, a scheme that uses the MST of the topology and the trees given by MSTP is implemented Note: constraint-based routing algorithms select a routing path satisfying constraints (like hop count, delay) in order to reduce costs, balance network load, or increase throughput

Comparison of MSTP with constraint-based routing algorithms: MSTP scheme § The minimum spanning tree (MST) is calculated for the network topology, this tree serves as the base for all the information sent between all the nodes in order to establish connection request and discover the network topology § For the scheme, an offline tool is implemented with the following objectives: § Guaranty that the data sent to satisfy each connection request does not exceed the requested bandwidth § Calculate and monitor the available bandwidth on each link § Ensure that when the multiple spanning tree protocol calculates the tree (corresponding to a given VLAN ID), the links that do not have enough unused bandwidth for the assigned connection request are not considered § Create new MSTP tree (if VLAN available) and add edge nodes to an already established tree. This is performed based on a given tree creating strategy. § Manage if the MST or any created MSTP tree is used for establishing the path so as to satisfy incoming bandwidth request

Comparison of MSTP constraint-based routing algorithms: MSTP scheme § A given tree, can be used to route any bandwidth request that has as source and destination any of the nodes of the trees Example tree Set of data paths that can be routed using the tree

Comparison of MSTP with constraint-based routing algorithms: MSTP scheme § As the MST serves as the base for all the information sent between all the nodes, it is initially used for satisfying any incoming bandwidth request § When the MST fails to give a route (because of bandwidth exhaustion), two tree creating strategies are implemented: § Maximum VLAN reutilization strategy: It only creates a new tree if none of the existing trees can be used (by adding the sources and destination nodes to the tree) for satisfying the given bandwidth request § Greedy VLAN strategy: Creates a new tree for the given bandwidth request as long as there is a VLAN Ids available § When the maximum number of trees (4096) are created both strategies try to use the existing trees

Comparison of MSTP with constraint-based routing algorithms: Simulations § Cost 266 (37), Germany 50 (50) and Exodus (79) topologies with 37, 50 and 79 nodes, respectively, are considered § For all the topologies the link capacity is set to 10 Gb/s and link cost was assigned in terms of the capacity § Delay was assigned based on the geographical distance of the nodes § The implemented algorithm for ELS is the SPF(cost, hop count) and the CSPF (available capacity, delay, hop count) § Bandwidth requests are generated until the network its completely overloaded. Two sets of bandwidth request were generated: § Request from 10 to 100 Mb § Request of 100 Mb

Comparison of MSTP with constraint-based routing algorithms: Simulations Cost 266 topology

Comparison of MSTP with constraint-based routing algorithms: Simulation The CSPF had the best performance in terms of accommodated bandwidth Accommodated bandwidth results were similar for both request lists Max Reut uses 78%-80% less trees than New tree and 31%53% less when compared to CSPF labels Its important to note that CSPF accommodates more bandwidth

Comparison of MSTP with constraint-based routing algorithms: Simulation The major difference in Avg Delay and Avg Hop count was of 7% between the CSPF and Max. Reut

Comparison of RSTP with constraint-based routing recovery techniques: Objective, Methodology, and Comparisons § Objective: make a comparison between Rapid Spanning Tree Protocol (RSTP) and recovery techniques (dynamic restoration and shared bandwidth preplanned protection) enabled by constraint-based routing (ELS) § Methodology: as in the previous study, an offline tool will be associated to RSTP so as to satisfy i) specific bandwidth request and ii) provide for restoration and protection capabilities § Comparisons: will be performed based on estimated recovery time and amount of resources required for the different recovery schemes under investigation

Comparison of RSTP with constraint-based routing recovery techniques: Recovery schemes Bandwidth provisioning coupled with the following recovery schemes § Dynamic (restoration): § no prior resource reservation or path protection before failure occurrence § when a component fails, a new route for the affected paths or segments (depending on the scheme used) must be calculated and established Comparison: between RSTP + offline tool (used previously) against the restoration schemes against mechanism proposed in RFC 4872/RFC 4873 § Pre-planned (protection): § Path Protection only (no bandwidth reservation after path failure occurrence) § Path + Shared Bandwidth Protection over common segments (soft bandwidth reservation before failure occurrence -> commitment of bandwidth after failure occurrence) § Path + Shared Bandwidth Protection over common segments (full bandwidth reservation before failure occurrence, max of protected data paths) Comparison: between RSTP + offline tool (enhanced to support the specific protection types) against mechanism proposed in RFC 4872/RFC 4873 Note: recovery time will be estimated analytically

THANK YOU QUESTIONS? Luis Fernando Caro, Jose Luis Marzo University of Girona Dimitri Papadimitriou Alcatel-Lucent Bell