DCE vs ONC RPC

DCE vs ONC RPC

Post by Guy Co » Fri, 13 Aug 1993 12:43:37



Could someone describe the migration path (if there is one) from
ONC RPC to DCE RPC?  How compatable are these?  I understand the ONC
paradigm fairly well, but I know next to nothing about DCE.

TIA!
//Guy
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DCE vs ONC RPC

Post by Nathaniel Mishk » Fri, 13 Aug 1993 22:37:00


: Could someone describe the migration path (if there is one) from
: ONC RPC to DCE RPC?  How compatable are these?  I understand the ONC
: paradigm fairly well, but I know next to nothing about DCE.

ONC RPC and DCE RPC are completely incompatible at both the
programming (portability) and protocol (interoperability) level.  Of
course, as representatives of the RPC paradigm, ONC RPC and DCE RPC
have a number of similarities (although DCE RPC has a much larger set
of features).

It should be possible to make a single application (client or server)
that uses both ONC RPC and DCE RPC, if, as a means of migrating an
existing customer base using an application based on ONC RPC, it is
necessary to do so.  For example, supposed you have rev N of a
client/server application that uses only ONC RPC.  In rev N+1, you
might change your clients to use only DCE RPC and your servers to use
both DCE RPC and ONC RPC.  This would allow both rev N and rev N+1
clients to talk to rev N+1 servers.  This approach requires that all
servers be upgraded before any client can be upgraded, but this is
generally an acceptable scheme (esp. since there are usually few
client sites than server sites).
--
                -- Nat Mishkin
                   Atria Software, Inc.


 
 
 

DCE vs ONC RPC

Post by Lee Sail » Sat, 14 Aug 1993 22:30:43



> Could someone describe the migration path (if there is one) from
> ONC RPC to DCE RPC?  How compatable are these?  I understand the ONC
> paradigm fairly well, but I know next to nothing about DCE.

ONC and DCE are conceptually very compatible.  There are some important
differences, of course.  Also, ONC seems to be a medium sized subset of
DCE.  That is, DCE offers a larger set of options.

--
lee

 
 
 

DCE vs ONC RPC

Post by Dave Crock » Sun, 15 Aug 1993 07:01:12



writes:

|> It should be possible to make a single application (client or server)
|> that uses both ONC RPC and DCE RPC, if, as a means of migrating an
|> existing customer base using an application based on ONC RPC, it is
|> necessary to do so.  For example, supposed you have rev N of a
|> client/server application that uses only ONC RPC.  In rev N+1, you
|> might change your clients to use only DCE RPC and your servers to use
|> both DCE RPC and ONC RPC.

Have you tried to do this, yet?  Can you describe the the effort and
difficulties.  How much programming time?  Any operational problems?  Etc.

Thanks.

d/

 
 
 

DCE vs ONC RPC

Post by Nathaniel Mishk » Sun, 15 Aug 1993 08:33:07



Quote:: writes:

: |> It should be possible to make a single application (client or server)
: |> that uses both ONC RPC and DCE RPC,

: Have you tried to do this, yet?  Can you describe the the effort and
: difficulties.  How much programming time?  Any operational problems?  Etc.

Of course not.  Sorry.  I get to be flip now that I'm not officially
associated with the DCE project.  However, I _have_ given the
situation some thought over some period of time and it really _should_
just work.  

The only problems I'd expect would be related to how well DCE Threads
were handled in the DCE product you're using.  For example, if Sun
RPC's call to, say, select() ended up blocking all the threads in your
process (in particular, the ones you're using to process incoming DCE
RPC calls), then clearly you'd have trouble.  DCE Threads has
"wrappers" for select() and the other blocking I/O functions; the
wrappers do a conditional I/O call and if they get EWOULDBLOCK (or the
like) call the Threads scheduler.  This is all well-understood
technology.  Unfortunately, the obvious way to implement the wrappers:

    #define select wrapper_select

doesn't do you much good if you can't or simply don't want to
recompile all the code that calls select(), etc. (e.g., the Sun RPC
library you want to use).  An alternative wrapper scheme is for the
Threads library to define the wrapper with the "real" function name,
and then have the wrapper use syscall() to get at the real system
call.  This scheme works in some cases, but not all (and the rules for
how archives resolve references presents problems).  This is what we
in the DCE project called a "vendor porting issue".  Vendors that have
their act together enough so that the people bringing up DCE know, for
example, the email address of the people who own the C library should
have no problems getting all this right.  (Insert heavy sarcasm here.)

At worst, in the case in question, you'd just have to not use Sun
RPC's svc_run() and do the select() (appropriately wrapped) in some
application thread and then call svc_getreqset().  As befits my
original claim, the details are left as an exercise to the reader.
It's a mere matter of programming.
--
                -- Nat Mishkin
                   Atria Software, Inc.

 
 
 

1. DCE vs ONC RPC...

I have this one paper from some people at the University of Stuttgart
comparing DCE RPC, ONC RPC and some others.  I was wondering if anyone
had any additional papers on different comparisons on these two
beasts.

Thanks
Rich Chung
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