Subject: Re: best server option

From: James Kempf <[email-masked]>
Date: Thu, 6 Jul 2000 08:57:29 -0700 (PDT)

>> 
>> The problem is what a particular service means by "best".
>
>Suppose you just use a really naive approach - like the max or min of
>an attribute?  This is *really useful* and easy to implement interoperably
>if we allow only one attribute, and either MAXIMUM or MINIMUM as the mode.
>
>That doesn't help you when your max function depends on two attributes -
>like the proxy with the lightest load *and* the fastest processor, where 
>load is twice as important as processor speed.  That is a pretty complex
>function though and best handled, as you indicated, by getting all the
>attributes and doin a client side computation.
>

Exactly. I think there may be lots of cases that a single attribute "best"
won't cover. It's a slippery slope, and one that is therefore best
confined to an extension, IMHO.

		jak

---

From: Erik Guttman <[email-masked]>
Date: Thu, 6 Jul 2000 18:13:35 +0200 (MET DST)

> confined to an extension, IMHO.

Let me know what you think about the attached proposal for a SLP Extension.

Thanks,

Erik
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =

BEST SERVER SEARCH EXTENSION

This extension is used with a SrvRqst or SrvRply.

When used with a SrvRqst, either Mode = 1 or Mode = 2.  The Criteria-
Attribute-Tag to use is specified.

When used with a SrvRply, Mode = 4 and the Criteria-Attribute-Tag
is returned.  If no Best Server Search Extension is present in the
reply, then a reply of one service means there *is only one service.*
If the Best Server Search Extension is present, then one service
means the 'best' one was returned.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      Extension ID = TBD       |     Next Extension Offset     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Offset, contd.|     Mode      | Criteria-Attribute-Tag Length |    
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    Criteria-Attribute-Tag                     /
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Mode = 1 means MINIMUM
       2 means MAXIMUM
       4 means BEST

The Criteria-Attribute-Tag is an attribute tag, which is an attribute
of services advertised with the service type present in the SrvRqst
message.