[Sis-SCPS-INTEREST] Latest Version of the SCPS RI

[Feighery, Patrick D.]

For those of you that have a copy of the SCPS RI, please read on.

During the last couple of days, we have found and corrected a bug in
the SCPS RI gateway which you should be aware of.  Under certain
conditions it will stop traffic from traversing the gateway.

Here is a quick synopsis

The problem only occurs when you are running the gateway under linux
via the TAP interface and you configure the gateway to not pass non-IP
based traffic (e.g., IPX, appletalk, etc.)  In our case the problem
reared its head when the gateway received CISCO's Cisco Discovery
Protocol (CDP) which operates directly over ethernet. If the gateway
receives a packet/frame that is not IP based and the gateway is
configured to not pass it we simply drop it on the floor.  So far so
good.  Unfortunately we do not free up the memory by placing it back in
the memory pool.  Bad programmer.  In our case we see a CDP packet
every 30 seconds or so.  So after about 8 hours or so we have no more
buffers to receive the packets.  Thus the packets will starting filling
up the receive queue for the tap interface. After the tap interface is
full, the ethernet frames can no longer be bridged.  A simple two line
fix corrects this problem.  For those of you that may be unaware, the
gateway does have the ability to either allow or deny non-IP based
traffic from traversing the RF side and thus consuming its resources.
 
The newest release of the SCPS RI is version 1.1.119.

Besides the change listed above, following are some even shorter
synopses of some changes from the 1.1.113 release - which we have been
sending out for about a year now.

  o  Updated some of the existing documentation which was pointed
     out by some of you to be well.. Antiquated to put it nicely.

  o  Added some additional documents
	o  The SCPS gateway user's guide - which I have been including
	   in recent requests.
      o  A Frequently Asked Questions (FAQ) about the SCPS gateway.
         If there are additional questions/answers please send them
         to me and I will include them in future versions of this
         document.
      o  Some of you have brought up performance issues with SCPS
         and Microsoft's file sharing.  This mini-white paper
	   discusses the interaction issues with Microsoft's
         Server Message Block (SMB) protocol used to implement
	   their File Sharing over the net, how it performs over
         large bandwidth*delay paths, and its interaction with SCPS. 

  O  Fixed some compilation issues with newer versions of gcc.
     Unfortunately, I am an old K&R C programmer and well.. ensuring
     correct typing of variables has never been a strong point.
     Thanks to those who have pointed this out and sent in diffs.

  O  Fixed minor rate control bug when emitting non TCP based IP
     traffic.

  O  Corrected some bookkeeping issues concerning lower level buffer
     utilization and added some stats which can be log to
     /var/log/messages. This is how I tracked down the bug mentioned
     in the first part of the e-mail.
 
  O  Changed the default behavior to keep the transport layer source
     port constant as the gateway creates the two peer transport
     layer connections.  I originally kept the transport layer source
     ports different to assist in the debugging of various things.
     However it was brought to my attention that some testing tools
     assume the source port received by the test sink apps must be
     the same as the source port sent the test source app.  To
     revert to the previous behaving you need to
     #define CHANGE_SRC_PORT.  This may be significant to some...

If you already have a copy of the SCPS RI, send me an e-mail and I will
be happy to reply with the latest release.

Best Regards

	Pat