Tài liệu Mạng và viễn thông P42 ppt

As well as a technical specification, an invitation to tender includes a number of commercial and other contract conditions.. Even if none of the tenders meet the specifications and com

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Procuring Equipment

The preceding chapter described the factors in outline equipment design which are crucial to the success of the network evolution plan Having a good plan is one thing; executing it is another, and in this respect the ordering and delivery of the equipment should receive considerable

attention This is an activity often referred to as ‘procurement’, and it can be carried out very successfully by highly mechanistic management methods Various ‘project management’

techniques are available which tackle network design as if it were the input of a procurement

‘process’, much as ‘raw material’ is the input to a manufacturing ‘process’ In production-line fashion, project management techniques lead the project through its design and checking stages, and on to ordering, installation, and testing However, in the same way as a poor raw material has an effect right through to the end product of a manufacturing chain, so the defects of a poor network design cannot be made good during implementation This chapter describes a typical methodology for selecting and procuring equipment, starting from the outline equipment design

42.1 TENDERING FOR EQUIPMENT

Except for some of the largest corporations, very few companies that operate networks also manufacture the equipment that goes to make them up; everything from personal computer links upwards needs to be bought from other manufacturers For small pieces

of equipment like modems the purchase may be straightforward, because a range of items meeting a standard specification (say, an ITU-T V-series recommendation) is available from a number of manufacturers The purchaser then has time to concentrate

on the finer differences (size, price, reliability, ease of maintenance, etc.) of the various equipments, and to choose what suits them best More costly equipment, like major transmission systems or large exchanges, can seldom be bought ‘off-the-shelf Instead, the differing circumstance of each network and application means that a considerable amount of ‘adaptive engineering’ is required in each case, to modify or upgrade the manufacturer’s own ‘basic’ equipment design Selecting suitable equipment is then

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Networks and Telecommunications: Design and Operation, Second Edition.

Martin P Clark Copyright © 1991, 1997 John Wiley & Sons Ltd ISBNs: 0-471-97346-7 (Hardback); 0-470-84158-3 (Electronic)

much more difficult, because at the time of order it may be that none has yet been developed Under these circumstances, the normal method of equipment selection is by

an invitation to tender ( I T T ) , request f o r proposal ( R F P ) or request f o r quotation ( R F Q )

and procurement follows after a contract has been placed with the manufacturer who has tendered a price and a technical conformance nearest to the specification

As well as a technical specification, an invitation to tender includes a number of commercial and other contract conditions The specification itself either lays out in precise detail the individual electrical components and connections to be made, or it is a

functional specijication which lays out only which general functions must be performed and which external interfaces are required Functional speclJications are preferred by tenderers and manufacturers alike because they place fewer constraints on the internal design of the equipment They permit a wider range of manufacturers to consider adaptation of their products to meet the external interface requirements For the purchaser, the larger the number of equipment manufacturers kept in competition and providing ‘standard’ equipment, the lower the tendered prices will be For the manufacturer the benefit is the larger market

Each tender sets out the degree to which the equipment can be adapted to conform

with the specification, the degree to which the commercial conditions are considered acceptable, and the quoted price Even if none of the tenders meet the specifications and commercial conditions in every respect, purchasers can at least gain an understanding

of each piece of equipment and decide on their own trade-offs between various factors, which are

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price and conditions for payment

amount of further technical development required by an existing product, and how much confidence there is that it can be achieved

ease of equipment maintenance

time required for installation, and whether the in-service date is early enough

quality of product and installation

modularity of kit; the ease of with which parts may be replaced or with which a subsequent equipment extension may be carried out

warranty and after-sales service

the area and standard of accommodation required

robustness and reliability of equipment

political factors (nationality and financial liquidity of manufacturer, etc.)

software licence and conditions

The process of invitation-to-tender and response is illustrated in Figure 42.1 and is much the same, no matter what type of equipment is being purchased The length of each of the working documents (specification, tender, etc.) depends on the complexity

of the requirement and the confidence gained from previous experience, but the

contract itself needs only to be a short document committing the manufacturer to

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Figure 42.1 Procuring equipment

conform with the tender response In the event of a failure to conform with the requirements of the contract, a number of penal clauses usually cover each of the possible eventualities For example, failure on the part of the manufacturer to develop a given function may result in no payment, while failure on the part of the purchaser to pay a given instalment, or to provide some detailed information on a given date may nullify the contractual obligation placed on the supplier

42.2 PROJECT MANAGEMENT

Even before the equipment goes out to tender, the job of project management must have commenced, to coordinate all the separate aspects associated with the provision Equipment room accommodation will be needed (some to a clinical standard) - built or refurbished by a separately contracted company; power and standby generator

equipment may need to be purchased and installed; and all sorts of changes in the network may need to be undertaken

During tendering, a sound project management keeps each task on schedule,

extracting prompt replies from manufacturers, insisting on rigorous evaluation and

timely contract placement At the next stage the job becomes one of overseeing the manufacturer’s work and quality, and of coordinating the supporting in-house or other contractors’ activities

Later on in the process, prior to the contract completion date (CCD), the purchaser should test the equipment, especially any new developments, to check conformance

with the specification before final acceptance and payment

The key to successful project management is early project planning This must be thorough and realistic Forgetting some activities, or programming too much or too little time for other activities, can seriously upset the smooth running of the entire project

It is valuable during the project planning stage to undertake a critical path analysis

This sets out the relationship between each of the sub-projects, laying out the full

sequence of events (or sub-projects) and the dependency of any individual event start

date on the completion of an earlier event For example, it would not be possible to fit-

out a building before it had been built, but it might not matter whether the electrical wiring or the plumbing were to be carried out first This consecutive sequence of interdependent sub-projects determines the earliest date at which the project could be completed If any of the sub-projects were to take longer than scheduled, then the

earliest possible project completion date would slip by at least the same number of days Figure 42.2 illustrates a simple critical path analysis project schedule A number of

computer software packages are available for this purpose (e.g Microsoft Project)

The exchange installation project depicted in Figure 42.2 comprises ten sub-projects

or events Four of these events make up the critical path of the project These are the

building and fitting out of the accommodation, followed by the exchange installation, the exchange testing, and the wiring-up of the network None of these activities can commence before the previous one has been completed, so that the consecutive time period required for their completion determines the minimum overall project length Slippage in any of these four sub-projects delays the project’s earliest completion date (i.e the exchange opening)

In contrast, the other six events do not lie on the critical path This means that a degree of slack time is available For example, a total of 29 months is available to recruit and train maintenance staff, but only 10 months are required These tasks could therefore be delayed for 19 months after the project start date without affecting the project end date In fact, the only constraint in this case is that the training of staff cannot commence before January 1991, after the exchange installation, otherwise there

is no equipment to be trained on This relationship is shown by the dotted line arrow on

Figure 42.2, indicating a dependent event The use of a dotted line arrow indicates that

it is only a one-way dependency, rather than two-way In other words, the exchange

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must be installed before training can commence, but in our example it is not the case that the maintenance staff need to have been recruited before exchange testing can commence

Other events which are not time-critical are the ordering of circuits and the

installation of transmission equipment The ordering must precede the installation, but the ten months needed for the work are far less than the 26 months available The transmission equipment installation cannot commence until July 1990 at the earliest, after the accommodation has been prepared

Not only does a critical path analysis provide a checklist of all the tasks to be undertaken, it provides a straightforward and mechanistic method for marshalling

resources and ensuring the timely completion of critical path events Furthermore, it allows the scheduling of non-critical events in the most efficient and convenient manner possible within the timescale For example, staff training in Figure 42.2 could start at any time between January and February 1991, according to convenience

42.3 PROCUREMENT POLICY

Before purchasing items of equipment, it is prudent for any company to determine a proper procurement policy A procurement policy protects the interests of the purchaser It is no good always buying the cheapest equipment if this means the eventual acquisition of a diverse range of slightly incompatible equipment, each piece

requiring different spares and differently trained maintenance staff, and with insoluble compatibility problems should the equipments ever need to be integrated On the other hand, if a company always purchases equipment from a single supplier, then dependency creeps in; the supplier’s prices may escalate to give a better profit

margin; worse still, the supplier may go out of business or become unreliable or un- cooperative Using even a small range of different suppliers helps to maintain competition between them An example of a complete equipment purchasing policy might be that ‘new equipment purchased should be compatible with an IBM

equipment’

At the time of tendering for equipment, due account should be taken of the company procurement policy It makes poor sense to write a specification which precludes all but one supplier, when the company procurement policy is to promote competitive tendering, with a long term objective of maintaining at least two suppliers Over-

worded and complicated specifications tend to have the effect of precluding suppliers, so that in general it is best to try to keep conditions of tender and contract

as simple as possible

42.4 PLANNING DOCUMENTATION

Before commencing any major project, whether it involves procurement or not, the network operator must determine the long term network strategy or ‘vision’ of which the project forms a part The strategy should set out the long term objectives for network development, and against the backdrop of short term constraints, it should

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map out a series of projects to achieve the long term goal Typically, the strategic goal

may be reached in a number of different ways, and the analysis leading up to a

recommendation of a particular plan should consider and reject a number of alternative

options

Having laid out the long term strategy and mapped it into a series of component

projects, the planning, coordination, and documentation of each individual project

must commence Any project is best documented in a controlled and layered structure

to ensure easy reference to detailed information while retaining consistency and

oversight across the whole job

Figure 42.3 shows a schematic documentation structure of three layers, oriented in a

triangular fashion At the top or ‘strategy’ layer the documentation is light, laying out

the overall objectives, the end goal, the resources to be used, and in outline the major

component projects of the strategy At the second or ‘plan’ layer a number of separate

planning documents exist, each comprehensively describing an individual project The

plan needs to cover everything: service and project timescales, staff responsibilities,

network topology, maintenance procedures, customer service arrangements, accom-

modation requirements, sales, procurement, customer billing, training and all other

conceivable aspects Ideally, the document refers to the strategy that it supports, and

also explains the existence and inter-relationship of any more detailed specifications

which exist to support it The third and last layer of documents, ‘specifications’, covers

the detailed technical definitions and procedures

Specification documents are the meat of the project It is documents at this level of

detail that are tendered to prospective manufacturers and are subsequently used for

definitive reference That is not to say that layer 1 and 2 documents are any less

important, because they hold the entire project and strategy together

Given a proper document structure, a document registration procedure should be set

up to ensure proper quality inspection of documents Documents should be checked for

L a y e r 1

L a y e r 2

L a y e r 3

Figure 42.3 A layered documentation structure

accuracy, comprehensiveness, and clarity by persons other than their original authors

T o ensure that there is no confusion over discrepancies between differently updated or amended versions of the same document, a proper re-issuing and change-control procedure should be adopted

42.5 THE TENDER DOCUMENT

The tender document or invitation to tender describes the equipment to be supplied It is

prepared by the network-operator whenever a major item of equipment is to be procured It describes which technical functions the equipment is expected to perform and it includes any commercial conditions which apply to the supply contract Once prepared, the tender document is sent to one or more prospective suppliers, who consider the requirements and send back formal replies, stating what they are able to offer and the price to be charged if their offer is taken up

The tender document and the chosen manufacturer’s response to it form the documentation of contract Any subsequent contractual dispute between the network operator and the supplier is resolved by reference to this documentation From the network operator’s point of view, it is important to ensure that the tender document makes the obligations on any contracted supplier absolutely clear The supplier on his side aims to make it clear in the response, which of the specified items can be supplied and which are not included in the offer The most harmonious business relationships and the most successful projects are based on accurate understanding In the remainder

of the chapter we describe items that should to be included in the tender document

42.5.1 Commercial Conditions of Contract

In the opening section of the tender document a general introduction should be given, explaining briefly the type of equipment required and in what timescales This prevents any ‘no-hope’ supplier from wasting further time by analysing all the detail The

commercial conditions of contract should go on to explain in detail what items of work are the obligation of the supplier, the timescales for delivery of each item, and the terms

on which payment is to be made (for example, installments as each part is delivered, or

‘only when the whole job is done’) The commercial conditions also need to lay out the penalties for failure to conform with the requirements of contract These penalties sometimes include an obligation on the supplier to correct errors and may call for a sum

of money to be paid to the network operator as compensation for liquidated damage

42.5.2 Other General Conditions of Contract

The general conditions of contract may clarify any other legal or general constraints which the network operator might wish to impose This section might cover the ownership of any document copyright, the ownership of patent rights and intellectual

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property rights (IPRs) of any new items that may be developed, and may cover general conditions pertaining to the disclosure of information The section may constrain the supplier not to make press releases and should cover the procedure for resolution of contract disputes It could cover both parties’ rights to terminate the contract, and (if relevant) the privilege of one party in the event of the other’s bankruptcy Finally, the section may clarify how particular legal constraints on one of the parties affects the contract For example, let us imagine that the network operator is obliged by law not to release information to a particular third party This information may, however, be required by the supplier in order that the contract can be fulfilled In such an instance the supplier should be obliged by contract not to release the information to the third party This type of situation can easily arise Imagine a telephone company A buying an

exchange from company B, where company B is both a telephone network operating company and an exchange supplier Now company A may need to reveal to its exchange supplier details of its network configuration, and this may include details

pertinent to network business held jointly with one of company B’s network operating competitors In this instance company A needs to release details to the exchange

supplier part of company B, but with the proviso that this information is not passed back to company B’s network administrators, who might gain unfair competitive

advantage from it

42.5.3 Technical Conditions

The technical part of the specification sets out the type of equipment required and its detailed functions Once upon a time, many of the large public telecommunications operators (PTOs) had a hand in designing the equipment In those days the specifica-

tion was at a level of detail of an actual equipment design, almost a detailed circuit and component design, so that contracts were principally for manufacture Nowadays,

however, it is more common for purchasers (including PTOs) to provide a functional

speczjication, laying out no more than the broad functions the equipment is expected to perform, together with the details of any external interfaces enabling the new device to interwork correctly with other network components As we have already noted, the use

of a functional specification as opposed to an equipment design speclJication promotes

competition among prospective suppliers, with a long term benefit of lower costs and higher quality Items which may be pertinent in the specification are explained below

0 accommodation and environment

0 network configuration and topology

0 operation and maintenance

0 equipment size and performance

0 functions

0 control interfaces

0 power supply

Figure 42.4 A modern ISDN exchange (Courtesy of Siemens A G )

The accommodation and environment in which the equipment is to be installed: any

constraining floor layouts, temperature considerations or other adverse conditions (e.g siting of equipment in a manhole)

The network configuration and topology in which the equipment is to work, include

the specification of any interfaces to other network components

The operation and maintenance requirements: whether remote control or monitoring

of equipment is required; which test points and test equipment is required; whether internal diagnostic programmes are required; what failure alarms are required

The equipment size and expected performance; for an exchange, the total daily traffic throughput in calls, and the peak hour traffic intensity (number of simultaneous calls) should be quoted, together with performance expectations under overload The

number of busy hour call attempts (BHCA for circuit switched networks) or packets

(packet switched) may be important to the dimensioning of the exchange processing capacity, and the total number of daily call attempts may govern how much storage capacity is required for any statistical information which may be required from the exchange For a transmission system, the bandwidth of the system or the bit rate needs

to be quoted, along with its jitter performance, sensitivity to noise, and other relevant information

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