Mạng và viễn thông P43

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Mạng và viễn thông P43 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) 42 Selecting and Procuring Equipment The preceding chapter described the factors in outline equipment design whichare crucial to the success of the network evolution plan. Having a good plan is one thing; executing it is another, andinthisrespecttheorderinganddelivery of theequipmentshouldreceiveconsiderable attention. This is an activity often referred to as ‘procurement’, and it can be carried out very successfullyhighly by 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 productof 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 operatenetworks also manufacture the equipment that goes to make them up; everything from personal computer links upwards needs to be bought from other manufacturers. small pieces For of equipment like modems the purchase may be straightforward, because a range of itemsmeetinga standard specification(say, an ITU-T V-series recommendation) is available from a number of manufacturers. The purchaser then has timeto 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’sown ‘basic’ equipmentdesign.Selectingsuitableequipment is then 763764 SELECTING AND PROCURING EQUIPMENT 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 componentsand 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 oftheirproducts to meettheexternalinterfacerequirements. Forthe purchaser, the larger the number of equipment manufacturers kept in competition and providing ‘standard’ equipment, lower tendered the the prices will be. For the manu ...