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Conference 7.286::fddi

Title:	FDDI - The Next Generation

Moderator:	NETCAD::STEFANI

Created:	Thu Apr 27 1989
Last Modified:	Thu Jun 05 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	2259
Total number of notes:	8590

815.0. "DEFZA multicast/group addressing?" by GUCCI::DMCCLOUD (Dennis McCloud - SOA ANC) Thu Dec 17 1992 12:33

    I have a few questions concerning address filtering and recognition on
    the DEFZA.  The customer requirement is to be able to support group
    addressing and multicast communications.  The way I understand the
    requirement, the user will be writing multicast applications so for
    the DEFZA/DEFTA how many group addresses are supported?
    
    Customer requirement is for 256.  As best as I can determine the CAM
    chip only supports 64 addresses is this the maximum possible number
    of addresses?
    
    Does the DEFZA/DEFTA support the ALL MULTICAST addresses capability
    similar to the DEMFA as described in note 636.*.
    
    Can the DEFZA/DEFTA dynamically change group addresses without the
    requirement to re-initialize the adapter?

    Has the DEFZA been certified for interoperability with other FDDI
    adapters by American Netional Test Center (ANTC), New Hampshire Test
    Lab (NTHL), or others?
    
    Has GOSIP testing been performed on DEFZA?  Are PICS available?
    
    Lastly,  given that I'm asking all these questions, is there a
    Technical Descripion document available for the DEFZA and/or
    the DEFTA like the one for the DEMFA?  If it is available then
    please point me to where it can be obtained over the net.

T.R	Title	User	Personal Name	Date	Lines
815.1	Some answers	QUIVER::WASHABAUGH	Born to be Mild	`Thu Dec 17 1992 13:43`	21
	The CAM does indeed have 64 entries, however CNS reserves 2 entries, so that leaves the driver 62 to play with. Some drivers also put a broadcast address in the CAM, so that potentially leaves the protocols with 61 to play with. Drivers may choose to support an unlimited amount of multicast addresses or just limit the protocols to what the CAM can support. If the unlimited is supported, it is achieved by enabling reception of all multicasts on the adapter and adding a filtering algorithm (likely to be a binary search for performance considerations). Note that this "unlimited mcast mode" can be slow. I am not familiar with what the VMS and ULTRIX drivers do for the receive filtering. The adapter does NOT have to be reset to change the multicast address filter. It guaretees that no packets are inadvertently dropped during the update. There is a port specification for the DEFZA, but that's not suitable for anyone but driver writers. Doug Washabaugh DEFZA firmware engineer
815.2		NETRIX::thomas	The Code Warrior	`Thu Dec 17 1992 15:17`	1
	Both ULTRIX and OSF/1 limit the addresses to the number in the CAM.
815.3	Thanks!!	GUCCI::DMCCLOUD	Dennis McCloud - SOA ANC	`Thu Dec 17 1992 15:48`	1

815.4	VMS information	STAR::GAGNE	David Gagne - VMS/LAN Development	`Thu Dec 17 1992 22:57`	4
	VMS (on VAX and ALPHA) will enable all multicast once the hardware limit is reached - and it will still only pass packets that match the users' enabled multicast addresses and discard the unwanted packets. This is how all the Ethernet and FDDI drivers on VMS operate.
815.5		ZUR01::HOTZ	Gregor, CS-Support, Switzerland	`Fri Dec 18 1992 09:17`	6
	What's the software limit for Multicasts in the LAN drivers? Same for all drivers? re .0 Is this DECtrade software? I've been asked several times this MC address limit question. Can you explain why you need 256 MCs? greg.
815.6	for VMS	STAR::GAGNE	David Gagne - VMS/LAN Development	`Fri Dec 18 1992 12:00`	10
	On VMS, the limit is based upon the quota of the process and the available pool to store the addresses (say about 10 bytes per address). So you can enable thousands (billions and billions) of multicast addresses. Without looking at the (old) code on VAX/VMS, the only exception may be EX and FX drivers where they may reach a CAM limit. The new EX and FX drivers on probably the next release of ALPHA/VMS and probably the second next release of VAX/VMS will not have the CAM limit - the limit for EX and FX will be the same as the other LAN drivers.