[fa.telecom] Hunt Group Information

kester@houxq.UUCP (09/22/83)

       About one or two	months ago, I posted an	article	requesting
       information about Central Office	Hunt Group Architecture.
       This article is to repay	those who had helped me. I can not
       gurantee	the accuracy of	the following information.

       There is	really no limit	to the number of local loops a
       regular hunt group can support.	There is probably a limit
       of one thousand lines to	start, but you can always call-
       forward the last	line to	another	one thousand line hunt
       group.  In this way, a hunt group of a size of 10,000 lines
       can be constructed.  However, a regular hunting size of more
       than one	hundred	is not recommended.  You can easily subject
       your services to	a killer trunk problem -- For example, if a
       bad trunk is the	number 2 loop in the hunting table, then
       you will	only have 1 loop available for all users.

       Uniform Call Distribution service is probably the best
       hunting service one would want.	The service gurantee even
       traffic load on all idle	loops in a hunt	group.	The largest
       size of such a service is said to be 1024 loops.	 This
       number was quoted to me by Southern Bell	folks at Atlanta
       and a person who	knows about NJ Bell.  The service is
       available with additional charges if you	subscribe to ESSX
       or CENTREX automatic call distribution services.	 It is
       obviously a ESS service and is not available on a cross bar
       switch.	I have seen the	UCD offered by C&P as a	stand alone
       service to National Institute of	Health in Washinton D.C.
       They have roughly 800 lines under one rotary.

       Busy Out	key does knock out a local loop.  However, it is
       not guranteed to	work every time.  The way each operating
       company reponds to busy out varies.  Usually a trouble card
       is dropped whenever a busy out loop is detected.

       Lead time to a large (hundreds of lines)	hunt group can be
       as much as 12 to	14 months depending on the site	location,
       the availability	of local loops and the availability of
       inter-central office trunk lines.  The way telephone company
       bring their local loops to your site is their business. They
       are obligated to	provide	you the	service	under a	pre-set
       tariff.	Of course you can negotiate a transmission
       methodology that	fits you best, but then	you will have to
       negotiate the cost with the phone company.

       The problems of managing a large number of dial-in lines
       usually include the following.

	 1.  Finding out just which line is giving you trouble.
	     This requires some	sort of	real-time monitoring
	     capabilities.

	 2.  After a trouble line has been located, one	would like
	     to	isolate	the probleem to	device level.  That is to
	     find out wheter the local loop, the modem,	or the
	     frontend port is giving you hell.	You can	then call
	     up	the responsible	maintenance personnel to fix the
	     bug.

	 3.  Switching a subset	of your	modems to some other
	     frontend because of routine maintenance of	your
	     frontends or because of a failure condition.
	     Obviously you will	have to	have extra frontend ports
	     available for this	kind of	operation.

       The above functions can be fulfilled by some of the modern
       electronic matrix switches available in the market.  But
       they do cost money.

       Special thanks to Norm Thompson at ATT-BTL who has given	me
       a great deal of good information.


       Kester Fong
       ATT Information Systems Labs
       !houxq!kester