1. RSTP vsSTP Instructors : Assoc ’ Prof ’ Reuven Cohen Mr. Itay Dabran Mr. Mordo Shalom Submitting : Danny Kalmar 01702821-8 Gilad Wallach 03279719-3 Omer Sharabi 03385662-6

2. Agenda  Project Definition  Implementation  Test Plan  Results  Main Conclusions  General Observations

4. Introduction  Why do we need spanning tree bridges?  At the beginning : 802.1d  But : the rules were changed  RSTP as an evolution of STP.

5. Goals  Implementing STP and RSTP  Comparing between the performances of the protocols  Results ’ discussion.

7. S/W Modules General:  We implemented a simulation which runs both protocols over a variety of randomized nets  It can run several tests in a single execution and collect statistics about the building and recovery abilities of each protocol  Simulation ’ s parameters : num ’ of bridges and lans, num ’ of tests and failures within each test, bridge ’ s configuration and packet ’ s lost probability.

8. The Net Manager Module  Simulation ’ s main loop  Main features :  Creation and initialization of new a randomized net  Running the bridges protocols using the net ’ s members ’ interfaces and the given parameters  Detection of the tree ’ s : building, failing and recovering  The ability to run multiple tests and failures on a given configuration  Statistics collecting.

9. The Bridge Module  Supports both protocols due to the mode of operation  Main features for the 802.1W:  RSTP ’ s BPDUs mechanism  Rapid Transition to Forwarding State  Proposal / Agreement mechanism  Sync Mechanism  Uplink Fast  RSTP ’ s Topology Change Detection and Propagation

10.  Main features for the 802.1D:  STP ’ s BPDUs mechanism  STP ’ s Topology Change Detection and Propagation

11. The LAN Module  Main features :  Distribution of BPDUs from the previous cycle to their destinations  The LAN receives all messages and prepare them to be sent out the next cycle.

12. The Testing Module  Main features :  Generation of failures on demand : disconnection of a forwarding port or connection of a disabled port while keeping the net with connectivity  Maintenance of failures ’ list in order to support running the same tests for both protocols.

13. System Arch Bridge.Tick() Lan.Tick() TestCreateFailure() send_bpdu received_bpdu Net Manager Testing LAN Bridge

14. Main Loop (1) Case: - Packets ’ lost probability != 0  For all tests : Set a randomized net Run each protocol till its tree become stable Collect test ’ s results.  Print statistics.

15. Main Loop (2) Case: - Packets ’ lost probability = 0  For all tests : Set a randomized net Run each protocol till its tree become stable Collect initialization ’ s results For all failures :  Activate the failure  Run each protocol till its tree recover  Collect recovery ’ s results.  Print statistics.

17. Test ’ s Parameters  All the net ’ s member possibilities are represented as a pair of (Bridge_Num, LAN_Num ) : Dense networks : { (2,6), (5,10), (8,15),(10,17), (12,25), (15,30) } Sparse networks : { (2,2), (5,5), (8,8),(10,10), (12,12), (15,15)}  Bridge ’ s parameters (following the Cisco configuration) : Forward delay = 15000 ticks Max age = 20000 ticks Hello time = 2000 ticks.

18. Performance's Criteria Case: - Packets ’ lost probability = 0 : Average Initialization time Average number of BPDUs ’ that were sent during initialization Average recovery time Average number of BPDUs ’ that were sent during recovery Case: - Packets ’ lost probability =! 0 : The same without the recovery information

21. Recover Time in Sparse Networks Immediate conclusions:  RSTP recovers much faster than STP

23. Recover Time in Dense Networks Immediate conclusions:  RSTP recovers much faster than STP  Recover time is similar to that in sparse networks.

25. BPDUs Num sent during Recovery Time in Sparse Networks Immediate conclusions:  RSTP requires less BPDU to achieve stability  This is caused mainly because the recovery time is much faster.

27. BPDUs Num sent during Recovery Time in Dense Networks Graph Explanation:  RSTP requires less BPDU to achieve stability  Dense network requires much more BPDUs to stabilize.

29. Conclusions  Recovery – RSTP recovers significantly faster than STP, less significantly better in BPDUs count  Dense and Sparse networks – We did not find any critical differences except the expected gap between BPDUs count  Packet Lost Probability – both protocols act as usual as long as the the probability is less than 10%. Both protocols stability is not guaranteed over ~60%.

31. Observations  The uplink fast feature in the RSTP can improve if it will use the “ Back Up ” port feature in addition to the “ Alternate ” port feature  RSTP ’ s initialization ’ s performances can be increased significantly through appropriate configuration ( “ slow ” transition avoidance)  Attention to the fact that RSTP recovers faster than STP which is a very important thing in today networks. RSTP “ pays ” in increased BPDUs count which is less important due to today possible band width.  Additional tests could explore more deeply the affects and the exact legal range of values of Packet Lost Probability for each protocol.

32. Old Foils

34. Initialization Time in not busy Networks Graph Explanation:  Similar initialization times in medium and large size Networks,with slight advantage to the RSTP protocol  In small Networks RSTP builds the tree much faster  As expected, a long Forward Delay lengthens the initialization time.

36. Initialization Time in busy Networks Graph Explanation:  Similar initialization times in medium and large size Networks,with slight advantage to the RSTP protocol  In small Networks RSTP builds the tree much faster  As expected, a long Forward Delay lengthens the initialization time.  Initialization time is similar to that in not busy networks.

40. BPDUs Num sent during Initialization Time in not busy Networks Graph Explanation:  Linear growth in bpdu sent during initialization in relation to the network size in both protocols  RSTP sends much more BPDUs because of levels of distribution.

42. Bpdus Num sent during Initialization Time in busy Networks Graph Explanation:  Linear growth in bpdu sent during initialization in relation to the network size in both protocols  the gap between the number of BPDUs in RSTP and STP is not as big in busy networks.