Lecture 8: Flow Analysis

Transcription

1 Lecture 8: Flow Analysis Prof. Shervin Shirmohammadi SITE, University of Ottawa Prof. Shervin Shirmohammadi CEG Network Analysis Requirement Analysis Gather Requirements Develop Service Metrics to Measure Performance capacity, delay, RMA Characterizing Behavior Develop Performance Thresholds Distinguishing Between Service Requirements Flow Analysis Establish Flow Boundaries Identify Backbone/Composite Flow Develop Flowspec Capacity Plan Service Plan Prof. Shervin Shirmohammadi CEG

2 Flow Analysis Flow analysis is the process of characterizing traffic flow through the network. The intent is not to show every flow in the network only show those that have the greatest impact on the network architecture and design. Generally these are often a small fraction of the total set of flows for a network. We will look at: Individual, composite, and critical flows. Source and sink models Flow models Flow specifications. Lecture 9 Prof. Shervin Shirmohammadi CEG Background We have established the user, application, host and the network requirements, established requirements specifications Further analyse these requirements based on their end-to-end characteristics We will discuss the concepts of flow and flow specification Use with best effort service for capacity planning Use with specified services for service planning Introduce flow concepts Data sources and sinks Flow models Flow distributions To identify, size, and choose flows Develop cumulative performance specifications for each flow Prof. Shervin Shirmohammadi CEG

3 Definition A Flow is A set of application and protocol information that has some common attributes, such as Source address, Destination address, Information type, Options, Routing, etc. and is transmitted during a single session of an application. Source/Destination Addresses, Port Numbers, Information Type Network User, Server or Other Device Routing through Network QoS Parameters, Directionality Prof. Shervin Shirmohammadi CEG Concepts Flows are: End-to-end, source-to destination (between applications/hosts) They can be directly linked to an application, device, or network Can also be examined on a link-by-link or Network-by-network basis Flow analysis is where performance requirements, services, and service metrics are combined with location information to show where service is needed in the network. Flow Analysis can provide: An end-to-end perspective on requirements Some insight to the degree of hierarchy and redundancy needed Useful information for choosing an interconnection strategy Switching Routing, or Hybrid mechanisms Prof. Shervin Shirmohammadi CEG

4 Representing Flows Flow 1 (Bidirectional) 100 Kb/s Upstream 500 Kb/s Downstream Flow 2 (Unidirectional) 100 Kb/s, 40 ms Upstream Flow Kb/s Flow 3 & 4 (A set of 2 unidirectional flows) Flow 4 1 Mb/s Prof. Shervin Shirmohammadi CEG Types of Flows Individual flow Flow for a single session of an application. When an individual flow has guaranteed requirements it is generally kept with that individual flow. Composite flow Combination of requirements from multiple applications or individual flows. Most flows in a network are composite. Backbone flow Really a composite flow that is defined by its location in the network (i.e. backbone layer). At this stage of our design we should not be considering network structure, so backbone flow should not really exist as such (it should simply be composite flow). Prof. Shervin Shirmohammadi CEG

5 Example Prof. Shervin Shirmohammadi CEG Flow Identification and Development Process Identify Flows, Flow Requirements, and Locations from Requirements Specification Determine where sources and sinks are located Apply flow models where needed Combine performance requirements for flows into flow specification Prof. Shervin Shirmohammadi CEG

6 Critical Flows Critical flows are flows that are more important than others. They are higher in performance or have strict requirements. mission critical, rate-critical, real-time, interactive, high performance. Also, individual flows with guaranteed requirements. More about this in the next lecture. How to identify flows? From an application perspective: Focus on a particular application, application group, device, or function (e.g. video conference, storage). Develop a profile of common or selected applications that can be applied over a user population. Choose the top N (e.g. 3, 5, 10) applications to be applied across the entire network. Prof. Shervin Shirmohammadi CEG Focusing on A Particular App App1: staging data from devices, 100 Kbps, 100 reliability App1: migrating data between servers, 500 Kbps, 100% reliability App2: migrating to remote storage, 10Mbps, 100% reliability Prof. Shervin Shirmohammadi CEG

7 Flow Estimation Determined from requirements For App1: Prof. Shervin Shirmohammadi CEG Flow Requirements Between buildings Between devices Prof. Shervin Shirmohammadi CEG

8 Flow within Building C Prof. Shervin Shirmohammadi CEG Flow Aggregation Prof. Shervin Shirmohammadi CEG

9 Developing a Profile Can use profiles to group flows of common applications. Instead of replicating information, one can use the profile tag. P1: 100 Kbps, 100% reliability. Prof. Shervin Shirmohammadi CEG Data Sources and Sinks A data source is a device or group of devices that primarily produces data that the network will carry A data sink primarily accepts data from the network, acting as a data repository. Most devices on a network will both produce and accept data Data sources: Computing servers, Mainframes, Parallel systems, Computing clusters Data sinks: Groups of disks/tape devices, Video editing or display devices Gives an indication of where flows are consolidated or generated Network Source Sink Prof. Shervin Shirmohammadi CEG

10 Exercise Which of the following devices are data sinks, and which one are data sources? (a) A storage device receiving streaming video from a camera Data Sink (b) A video editing unit, using video from the storage device in (a) Data sink and source (assuming video is written back into (a) (c) A web server Data source, mainly. (d) A storage disk farm Data source and data sink Prof. Shervin Shirmohammadi CEG Data Source and Sink Map (1/3) Prof. Shervin Shirmohammadi CEG

11 Data Source and Sink Map (2/3) Prof. Shervin Shirmohammadi CEG Data Source and Sink Map (3/3) Prof. Shervin Shirmohammadi CEG

12 Choosing the Top N Applications Decision can be based on a number of factors ranging from degrees of usage, number of users, number of devices / servers, or performance requirements. Example: top 5 applications: Web browsing File transfer Word processing Database transactions These top N applications must be the performance drivers fro the network. Always ask: if requirements for Top N are met, are the requirements for the eliminated (from the Top N list) applications met too? Prof. Shervin Shirmohammadi CEG