CSK / OXFORD ENGINEERING COLLEGEDepartment of Information Technology

CP7101 – DESIGN AND MANAGEMENT OF COMPUTER NETWORKS

Course content Service methodology System description Service description Service characteristics Performance Characteristics Network supportability

Service methodology It is the activity of planning and organizing people, communication and

material components of a service in order to improve its quality and the interaction between service provider and customers.

we can explain our service methodology simply with the steps given below

information gathering : collecting information. problem analysis: finding solutions to problems. planning & designing: network planning(long-term and medium-term

short-term) an iterative process, composing( topological design) defining service level targets(1 year/ 3 year / 5 year) responsibilities and other specific requirements to manage the service. service level requirements(slr) : from a customer to a service provider

describing their service expectations. a service provider prepares a service level agreement (sla) based on

the requirements from the customer. Development & testing. maintenance and modification.

system descriptions

A system is a set of components that work together to provide connectivity, services and communications to users. Components of system includes: Users, hosts (PCs, laptops, handhelds). Devices : routers & switches. Links (wired, wireless). Protocols (IP, TCP,FTP,SNMP). Applications (E-mail, Remote login (Telnet) ,P2P file sharing,

Client/Server.

Service description The organization has been developing service

descriptions for IP networks. IP networks : communication protocol. Encapsulated packet structures.(sends packet) Responsible for addressing hosts(source to destination). Version: (IPv4) – decimal (192.168.2.253) subnet mask: 255 255 255 0(class D) IP ranges: Cla s s A, Cla s s B, Cla s s C, Cla s s D.

Service description

We can look at this from two perspectives: Le ve ls o f p e rfo rm anc e a nd Functions in the network. Levels of performance are described as

RMA (, Reliability, Maintainability, and Availability) s y s te m d e s ig n a ttribute s .Re lia bility : to perform its required functions under stated conditions for

a specified period of time.(work simultaneously)Ma inta ina bility : is us e d to m a inte na nc e the s y s te m s uch a s , repair or

replace faulty, prevent unexpected breakdowns. Ava ila bility : to describe the amount of period that the system

resources is available.

Service description

Functions are described as Accounting: to provide information about users

and their network resource usage(user accounts-login details).

Billing: Creating an invoice related to the use of infrastructure and services(inbound/ outbound).

Scheduling: processes or data flows are given access to system resources (e.g. processor time, communications)

Management: coordinates the efforts of system to accomplish goals and objectives.

Security: give protection.

Service description

Network services in most of today’s networksare based on best-effort (unpredictable) delivery.

Network services are (hierarchical service characteristics, and individual service characteristics) can be grouped together to form higher-level descriptions of a service.

Service characteristics

One of the goals of network analysis is to be able to characterize(give better) services so that they can be designed into the network and purchased from vendors and service providers.

Se rvic e cha ra c te ris tic s a re ind iv idua l network performance and functional parameters that are used to describe services.

Service characteristics Service characteristics contains:

Service levels System Components and Network

Services Service Requests & Requirements Performance Characteristics

Service levels System Components and Network Services. Service Requests & Requirements.(user requirements,

application requirements, device requirements, and network requirements.)

Service offerings(Service offerings map to service requests and thus can also be categorized as best effort, predictable, or guaranteed.)

Service metrics/activities.

Service levels

Service characteristics can be grouped together to form one or more service levels for the network.

There are many ways to describe service levels, including: committed information rates (CIRs); levels of capacity; classes of service (CoSs); delay and capacity characteristics; types of service (ToSs); qualities of service (QoSs);

Service Requests & Requirements

Service requests and requirements are, in part, distinguished by the degree of predictability needed from the service by the user, application, or device making the request.

Based on their predictability, service requests are categorized as best effort, predictable, or guaranteed.

Best-effort service means that there is no control over how the network will satisfy the service request—that there are no guarantees associated with this service.

Service Requests & Requirements Guaranteed service:

provides an assured level of bandwidth, with a firm end-to-end delay bound and no queuing loss for conforming packets of a data flow.

predictable services: can provide services of predictable communication to

applications  makes the development of new ones like an expensive and risky

Service Requests & Requirements For service performance requirements and characteristics to be

useful, they must be configurable, measurable, and verifiable within the system.

Therefore, performance requirements and characteristics were described in terms of service metrics(measurements), which are intended to be:

configurable, set a value for threshold/doorstep and limit measurable, by monitoring current state value.

Performance Characteristics

Services may include one or more of the performance characteristics:

Capacity: is used as a label for the class of characteristics that involves moving information from place to place, including bandwidth, throughput, and so forth.

Delay: is a label for the class of characteristics that includes end-to-end delay, round-trip delay, and delay variation.

RMA: is a label for the class of characteristics that includes reliability, maintainability, and availability

Performance Characteristics Performance requirements can be combinedto describe a performance range for the system. A performance envelope is a combination oftwo or more performance requirements, with thresholds and upper and/or lower limits for each. Availability: Deals with the duration of up-time for operations and is

a measure of how often the system is alive and well. Throughput:

the amount of work that a computer can do in a given time period the amount of processed data in communication networks. throughput is the rate at which a system achieves its goal.

Utilization : Network utilization is the ratio of current network traffic to the maximum traffic that the port can handle.

Delay: the period or amount of time during which something is delayed

Network Supportability

Good network architects/designers take intoaccount the major factors that affect operability and supportability as they make their decisions.

The post-implementation phases of a network’s life cycle can be broken into three elements: operations, maintenance, and human knowledge.

Network Supportability

Key characteristics of a network architecture and design that affect the post-implementation costs include: Network and system reliability Network and system maintainability Training of the operators to stay within operational constraints Quality of the staff required to perform maintenance

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