Evaluation and Comparison of Spanning Tree Protocol and Rapid Spanning Tree Protocol on Cisco switches via OPNET ENSC 427: COMMUNICATION NETWORKS SPRING 2013 FINAL PROJECT Project Group # 2 Joseph Lu 301077704 [email protected] Sen Jiang 301121645 [email protected] Tao Xiong 301129494 [email protected] Table of Contents List of Figures ………………………………………………………………………………..….3 List of Tables …………………………………………………………………………………….4 Abstract .........................................................................................................................................5 1. Ethernet ……………………………………………………………………………………….5 1.1 Ethernet LAN ………………………………………………………………………………..5 1.2 Media Access Control (MAC) addressing ……………………………………………….….5 1.3 Switches ………………………….………………………………………………………….6 1.4 Virtual LANs ...........................................................................................................................6 2. Spanning Tree Protocol (STP) Overview ...............................................................................7 2.1 Spanning Tree Protocol (STP) ………………………………………………………………..7 2.2 Types of STPs ………………………………………………………………………………...9 2.2.1 Rapid Spanning Tree Protocol ……………………………………………………………9 2.2.2 Multiple Spanning Tree Protocol ………………………………………………………..11 2.3 Hypothesis …………………………………………………………………………………...11 3. OPNET Simulations ………………………………………………………………………...12 3.1 Topologies …………………………………………………………………………………..12 3.1.1 Three Layer Topology …………………………………………………………………..12 3.1.2 Ring Backbone Topology ……………………………………………………………….13 3.2 Simulation Setup …………………………………………………………………………….14 3.2.1 Simulation with Ring Backbone Topology ……………………………………………...14 3.2.2 Simulation with Three Layer Topology …………………………………………………19 4. Simulation Results …………………………………………………………………………..20 5. Conclusion and Discussion ………………………………………………………………….21 References ………………………………………………………………………………………23 2 List of Figures Figure.1 MAC Address ………………………………………………………………………….6 Figure.2 Spanning Tree Interface States [4] ...…………………………………………………...8 Figure.3 STP and Redundant Connectivity [4].………………………………………………….8 Figure.4 Root Port [5] …………………………………………………………………………..10 Figure.5 Designated Port [5] ……………………………………………………………………10 Figure.6 Alternate Port [5] ……………………………………………………………………...10 Figure.7 Backup Port [5] ………………………………………………………………………..10 Figure.8 Multiple Spanning Tree Protocol [7] ………………………………………………….11 Figure.9 Three Layer Topology [8] ……………………………………………………………..12 Figure.10 Ring Backbone Topology [8] ………………………………………………………...13 Figure.11 Scenario#1 and #2 ……………………………………………………………………14 Figure.12 Application Definition ………………………………………………………………..15 Figure.13 Profile Definition ……………………………………………………………………..15 Figure.14 Root Bridge Priority ………………………………………………………………….16 Figure.15 Workstation Attributes ……………………………………………………………….16 Figure.16 Server Attributes ……………………………………………………………………..17 Figure.17 Scenario#3 and Scenario#4 …………………………………………………………..17 Figure.18 Scenario#5 and Scenario#6 …………………………………………………………..18 Figure.19 Scenario#7 and Scenario#8 …………………………………………………………..18 Figure.20 Scenario#9 and Scenario#10 …………………………………………………………18 Figure.21 Scenario#11 and Scenario#12 ………………………………………………………..19 Figure.22 Scenario#13 and Scenario#14 ………………………………………………………..19 Figure.23 Results and Protocol Visualization of Scenario#1 and Scenario#2 ………………….20 Figure.24 Results and Protocol Visualization of Scenario#13 and Scenario#14 ……………….20 3 List of Tables Table.1 Port States of STP and RSTP [5] ………………………………………………………...9 Table.2 Project Specification ……………………………………………………………………14 Table.3 Results of All Scenarios ………………………………………………………………...21 4 ABSTRACT Spanning Tree Protocol (STP) was based on the algorithm invented by Radia Perlman to prevent loop forming in networks in 1985. [1] And in 1990, the IEEE published 802.1D as its first standard. It was introduced to any bridged Ethernet local area network. In 2001, the IEEE published Rapid Spanning Tree Protocol as 802.1w which provides significantly faster loop— free paths calculation in response to a topology change. Our project intends to evaluate and compare the performances of STP and RSTP on Cisco switches supported by OPNET. We were planning to do the comparison of STP with more other types such as Multiple Spanning Tree Protocol. However, after searching in OPNET V16.0, we found that in OPNET, Cisco switches only support STP and RSTP. Our project first introduce some background information regarding VLAN, STP, RSTP, Layer Two Switches, Layer Three Switches, Distribution Layer, Access Layer, and so on. Besides the background information, the report discusses some companies that produce switches, especially the one's switches we will be using: Cisco. It then includes our work on OPNET. We build and configure the three layer topology and the ring backbone topology, then analyze and explain some snapshots taken from OPNET. We create STP tree with three layers which totally have approximately ten Cisco switches, and observe the performance of connection coming back up after disconnecting the loop. After finishing the STP evaluation, we run the same procedure for RSTP, and finally compare their results for a conclusion. 1. ETHERNET 1.1. Ethernet LAN Ethernet is the most widely used local area network access model. It is standardized by the Institute of Electrical and Electronics Engineers (IEEE) as 802.3 [2] standard. An Ethernet environment involves various types of devices, such as hubs, bridges, and switches. A switching Ethernet environment is an Ethernet network that consists of switches instead of hubs. A switch is a more intelligent device than hub. It stores Media Access Control address in lookup table and maintain address at its own. There are switches that are used in different layers, such as layer two switches used in the data link layer which learn MAC address automatically, and are cheap and easy to deploy. Ethernet switches are able to link more than one local area network together. 1.2. Media Access Control (MAC) Addressing Media Access Control address [2] is the physical address of the network device found in the data link layer aside from the logical address that is found in the network layer. A MAC address is a hardware identification serial number that uniquely identifies each device in the 5 network. It is manufactured into every network adapter that differentiates network cards. Therefore, the MAC address cannot be modified. A MAC address is 48 bits (6 bytes) in length and usually written as a sequence of twelve hexadecimal digits. The first 24 bits (sixdigits) correspond to the organizational unique identifier (OUI) or the manufacturer’s unique identifier, while the last 24 bits (six digits) correspond to the device serial number that is assigned by the vendor, as illustrated in the figure below: Figure.1 MAC Address The combination of the OUI and the device serial number logically ensures that any of the network adapters have the different MAC address. 1.3. Switches As bridges add Bridges add a level of intelligence to the network by using the MAC address to build a table of hosts, mapping these hosts to a network segment and containing traffic within these network segments. A switch functions the same as a bridge. When a switch receives a frame, it examines the destination and source MAC addresses and compares them to a table of network segments and addresses. The frame is dropped if the segments are the same, whereas forwarded to the proper segment if the segments are different. In Ethernet LAN, switches are able to link several LANs together and forward frames between these LAN segments. They are used as a more intelligent version of hubs in networks. 1.4. Virtual LANs A Virtual Local Area Network (VLAN) is a group of data exchanging ports of every switch that are chosen specifically for putting logic inside the switches correspondingly. Generally speaking, the function of VLANs is assigning tasks to switches through specific ports. VLANs can also be defined as broadcast domains due to the fact that broadcast packets are sent out all ports that are in the same VLAN. VLAN mapping configures layer two switches to provide the logical connectivity among the VLAN members. VLANs are standardized as IEEE 802.1Q. 6 2. SPANNING TREE PROTOCOL (STP) OVERVIEW 2.1. Spanning Tree Protocol (STP) The Spanning Tree Protocol (STP) is a link—management protocol under the Institute of Electrical and Electronics Engineers (IEEE) standard 802.1D for routing bridges and switches. The idea of Spanning Tree Protocol is using the spanning—tree algorithm to provide redundancy to your network without breaking it. When there is one link in the network fails, another way would automatically come up for the traffic to reach its destination. Due to that the network connection forms many loops which make data traffic fails finding the way to its destination, traffic congestion happens as data is transmitted around in circles. By using the STP algorithm, the switches that send bridge protocol data units (BPDUs) are able to identify active redundant links, and block one of these links to prevent any possible network loops. In a network, broadcast storms and constant table changes are created by network loops which bring down the entire network. The spanning tree protocol creates a tree spanning across the entire network and forces redundant paths into a standby or blocking state in establishing path redundancy. In between two network devices such as switches, the spanning tree protocol allows only one active path at one time to prevent network loops.