Andrew Malis (malis@bbnccs.ARPA)
Wed, 19 Mar 86 6:50:40 EST
Boy, I wrote the thing, and I didn't even receive the
distribution notice! I wonder how many others I've missed ...
I initially (some time ago) resisted some of terminology changes
that you mentioned, but was overruled by many others that prefer
the new terminology (including DCA, by the way). Some of these
changes go back several years now in BBN and DCA literature, but
are just making their way out to the rest of the world. By the
way, the software that runs on the PSN is referred to as PSN
Release x, with the End-to-End being one module of the PSN.
Other modules include, for example, Store-and-Forward, Routing,
and X.25 L3.
VDHs, as you mention, are mostly extinct animals these days.
The story on uncontrolled messages is a bit more complicated. Up
to now, the EE's flow control has been (in the absence of subnet
congestion control) the only governor of the amount of traffic a
host can submit to the network. When you take that away by using
uncontrolled messages, you are really introducing the possibility
of debilitating congestion on the network.
As a result, the use of uncontrolled messages has been, shall we
say, controlled (administratively). There are, I believe, no
hosts on the MILNET that have permission to send them, and only a
small number on the ARPANET (mostly associated with packet
speech). I know of no TOPS-20s that are currently allowed to
submit uncontrolled messages. As an example, neither of the
hosts at SUMEX are enabled, and at the ISI complex, the only
enabled host is ISI-SPEECH11 (I just checked these).
After we decided to upgrade the uncontrolled messages into the
new datagram service, we also found that because of scheduling
constraints, we wouldn't be able to include it in PSN 7.0 (the
first new EE release). Even if we had, its use would (due to the
absence of congestion control) have to be limited to the same
small set of hosts.
The good news is that subnet congestion control is actively under
development, and both it and datagrams are scheduled for PSN
Release 8.0. At that time, we can experiment (on the ARPANET
first, of course) with always using datagrams for TCP/IP traffic.
That was one of the reasons why we decided to upgrade to the new
datagrams - the old uncontrolled messages just weren't useful
enough to support this.
By the way - the datagrams, when included, will be accessed by
good old subtype 3.
This archive was generated by hypermail 2.0b3 on Thu Mar 09 2000 - 14:36:04 GMT