27 Jun
2023
27 Jun
'23
2:21 a.m.
Since there has been a bunch of work done to revive what is supposedly a DECnet Phase I
implementation (DECnet/8 for RTS/8) I realized I could perhaps get some more information
going back that far. Some months ago Nathan Brookwood (formerly known as Nathan
Teichholz) gave a talk about the beginning of RSTS-11, and in that he mentioned as an
aside that he subsequently served as program manager for the initial development of
DECnet.
So I asked him if DECnet/8 sounded familiar and if he could tell me anything further about
that time. His reply:
----------
I was responsible for coordinating all the versions of DECnet for the initial "Phase
I" releases, but developers in each operating system were responsible for the
implementations. Each group was building from the definitions of DDCMP and NSP that were
extant in the 1973-75 period. There was also a testing and communications protocol called
"NICE" (don't ask me what that stood for) and a file transfer utility.
The Phase I versions did not include routing, and when the developers tried to add routing
capabilities to those first versions, they discovered that there was a need to make
significant changes to NSP that would preclude backwards compatibility with the Phase I
versions. The implementation of DDCMP survived intact, since physical link protocols are
below the routing protocols level.
----------
That ties into the statement in the Phase III General Description document which says that
Phase I nodes can't coexist with later versions in the same network, and it also
matches what the DECnet/8 manual makes quite clear in its chapter discussing the protocol
details: Phase I NSP is conceptually pretty similar to Phase II NSP, but the packets are
100% incompatible. So the "significant changes" Nathan mentioned are what
happened in DECnet Phase II -- which modifies NSP to include sequence numbers and ACKs and
in the process also changes lots of other details in the protocol encoding. That still
wasn't quite enough, and Phase III filled in some missing details in an upward
compatible fashion (the Connect Ack and Retransmitted Connect Initiate message, as well as
timeout and retransmit algorithms).
paul
27 Jun
27 Jun
5:19 a.m.
Hi Paul,
I had been following that discussion on DECnet/8, although pretty silently
as I don't have much useful information to add. It is interesting to
understand the impetus for the enhancements to the protocol.
Also of interest is this talk about the origins of RSTS-11. Where was this
and was it recorded (posted to YouTube, etc.)?
Regards, Tim.
On Tue, 27 Jun 2023 at 08:22, Paul Koning <paulkoning(a)comcast.net> wrote:
Since there has been a bunch of work done to revive
what is supposedly a
DECnet Phase I implementation (DECnet/8 for RTS/8) I realized I could
perhaps get some more information going back that far. Some months ago
Nathan Brookwood (formerly known as Nathan Teichholz) gave a talk about the
beginning of RSTS-11, and in that he mentioned as an aside that he
subsequently served as program manager for the initial development of
DECnet.
So I asked him if DECnet/8 sounded familiar and if he could tell me
anything further about that time. His reply:
----------
I was responsible for coordinating all the versions of DECnet for the
initial "Phase I" releases, but developers in each operating system were
responsible for the implementations. Each group was building from the
definitions of DDCMP and NSP that were extant in the 1973-75 period. There
was also a testing and communications protocol called "NICE" (don't ask me
what that stood for) and a file transfer utility.
The Phase I versions did not include routing, and when the developers
tried to add routing capabilities to those first versions, they discovered
that there was a need to make significant changes to NSP that would
preclude backwards compatibility with the Phase I versions. The
implementation of DDCMP survived intact, since physical link protocols are
below the routing protocols level.
----------
That ties into the statement in the Phase III General Description document
which says that Phase I nodes can't coexist with later versions in the same
network, and it also matches what the DECnet/8 manual makes quite clear in
its chapter discussing the protocol details: Phase I NSP is conceptually
pretty similar to Phase II NSP, but the packets are 100% incompatible. So
the "significant changes" Nathan mentioned are what happened in DECnet
Phase II -- which modifies NSP to include sequence numbers and ACKs and in
the process also changes lots of other details in the protocol encoding.
That still wasn't quite enough, and Phase III filled in some missing
details in an upward compatible fashion (the Connect Ack and Retransmitted
Connect Initiate message, as well as timeout and retransmit algorithms).
paul
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12:48 p.m.
On Tue, Jun 27, 2023 at 1:20 PM Tim Sneddon <tim(a)sneddon.id.au> wrote:
Also of interest is this talk about the origins of
RSTS-11. Where was this and was it recorded (posted to YouTube, etc.)?
I had the same thought, it was news to me too that there had been a
talk about the origins of RSTS-11, very interested to hear from the
people involved.
Found it here, scroll to the bottom of the page for Nathan's talk, but
there are many other interesting topics there too.
https://www.decconnection.org/techtalks.htm
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2 comments
3 participants
participants (3)
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Nigel Williams -
Paul Koning -
Tim Sneddon