Date: Wed, 26 Jun 1996 11:50:19 -0400 From: dennis@etinc.com (Dennis) To: "Ron G. Minnich" <rminnich@Sarnoff.COM> Cc: hackers@freebsd.org Subject: Re: Frame relay and ATM support: virtual interface per vpi? Message-ID: <199606261550.LAA21205@etinc.com>
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>> what do you mean "at the hardware"? >MINI is an interface which has 4096 virtual atm interfaces, i.e. 4096 >independent sets of control/status registers, memory buffers, and >whatever else it takes to support this, at the hardware level. These >resources are addressed on page boundaries. User programs can map in an >individual interface and control it directly. There's a one-to-one >correspondance between VCIs and virtual interfaces. VCI multiplexing is >done in hardware, not in software, which is a fundamental difference from >other atm interfaces. > >There's reasons for doing this outside the scope of this discussion, but >let's just say it makes cluster computing a whole lot easier. You can get >data from app-to-app in a few microseconds, a definite win as compared to >the typical O(500 microseconds) you get from existing atm interfaces. > >The only nice way i've found to do this is to make each hardware mini >interface have a corresponding 'if' structure. in practice i doubt very >much to see more than a fraction of the virtual interfaces used, but you >never know. I'm planning to allocate these structures dynamically. You dont want to do this for frame (or anything else) if you dont have to, as it talks up way too much memory and makes buffering and queuing a nightmare. Since most FR locations have 1 or 2 VCs, its also a real waste. Dennis ---------------------------------------------------------------------------- Emerging Technologies, Inc. http://www.etinc.com Synchronous Communications Cards and Routers For Discriminating Tastes. 56k to T1 and beyond. Frame Relay, PPP, HDLC, and X.25 for BSD/OS, FreeBSD and LINUX
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