16 Jul
2024
16 Jul
'24
4:09 a.m.
Yes, that's the other thing that bothered me, that NML was not reporting
what is in the config file.
The BUFFER-SIZE parameter uses the NODE% JSYS .NDBSZ function to set the
IBBSIZ variable in the monitor. When I checked that, i found that it
was properly set to the specified value of 1476.
I did not see any corresponding NODE% function to read IBBSIZ, however,
so the question really is where the Tops-20 NICE process (NMLT20) might
be finding that out.
There is a function (.NDRDB) to return DECnet data blocks, but that
doesn't seem to return an obvious table. Similarly, one can determine
the segment size (.NDCIN), but apparently only for active connections.
Since DEC never released the source for Tops-20 NMLT20 (and believe me,
we asked for it!), that's about as far as I can go without some reverse
engineering to see what JSYI it's using and what these might be returning.
On 7/15/24 9:20 PM, Johnny Billquist wrote:
My question wasn't about the exact number, but the
fact that it was
not the number shown by NCP.
There is control over both in RSX as well, but there NICE isn't
reporting the buffer size in that parameter, but you can see it in
another place, and yes, it's the value used in the routing
advertising, which makes sense, since that is what you announce you
will accept as size for routing packets. And yes, it's (completely)
unrelated to the segment buffer size, which is what NSP cares about.
And as long as the buffer size is atleast large enough to hold the
maximum segment size, everything will be happy.
I also haven't checked any code, but for ethernet, I would think that
routers will either send out 1500 byte packets, or send out the packet
the size of the smallest announced accepted size. Now I'm sortof
curious which. Maybe the DECnet routing spec already would tell me...
I know that for point-to-point links, RSX sends packets larger than
the segment size if routing init says it can accept that, as long as
the sending side can build that size.
And that is also where VMS had the bug that I mentioned before.
Johnny
On 2024-07-16 03:12, Thomas DeBellis wrote:
Yes, 1746 has always struck me as an odd number,
but the macro
definitions which calculate it were puzzling enough that I didn't
want to assume. As I recall, there was commentary about fidgeting
withthe number which I also didn't think I understood at the time.
But this was over three years ago, so I could certainly be
misremembering.
Just as a reminder for any Tops-20 user: your ERROR.SYS file */will/*
fill up with class 5 events (buffer not large enough) if you don't
condition NTMAC to ignore this. At NMXFIL+1, you need to change
three lines, viz:
NMXFIL: $SFIL
$FIL(2,4) ;[T152] ;Event classes 2 through 4 known by
monitor
$NOFIL(5,5) ;[T152] ;HECnet overflows us with packet too
long
$FIL(6,6) ;[T152] ;Event class 6 known by monitor
$NOFIL(^D96,^D96) ;LCG specific events - turned off
IFN FTDEBUG <
$FIL(^D480,^D480) ;Accept event class 480 while debugging
$EFIL
On 7/15/24 9:04 PM, Paul Koning wrote:
I think that 1476 is a TOPS-20 private thing, the
data link buffer
sized used by the Ethernet driver. The NCP parameters control what
routing advertises (buffer size) and what NSP asks for as connection
segment size(segment buffer size).
paul
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To unsubscribe send an email to hecnet-leave(a)lists.dfupdate.se On Jul 15, 2024, at 8:49 PM, Johnny
Billquist<bqt(a)softjar.se> wrote:
Maybe someone can explain to me why it looks like the buffer size
reported by NCP is 576 when it sounds like you are both setting it
to 1476?
Johnny
On 2024-07-15 22:48, Thomas DeBellis wrote:
> These are the relevant lines from my SYSTEM:7-1-CONFIG.CMD:
> DECNET BUFFER-SIZE 1476
> DECNET MAXIMUM-ADDRESS 1023
> NODE VENTI2 2.522
> DECNET ROUTER-LEVEL-1
> ETHERNET 0 DECNET
> The maximum buffer size of 1476 is what I determined from a review
> of the relevant code in the monitor, which I commented about, some
> months back (but see below).
> This is the response from my local excutor (VENTI2::)
> OPR>ncp shOW exECUTOR chaRACTERISTICS
> Request # 280; Show Executor Node Characteristics Completed
> Executor Node = 2.522 (VENTI2)
> Identification = Venti Due Test System
> Management Version = 4.0.0
> CPU = DECSYSTEM1020
> Software Identification = Tops-20 7.1 PANDA II
> Loop Count = 1
> Loop Length = 127
> Loop With = Mixed
> Incoming Timer = 30
> Outgoing Timer = 60
> NSP Version = 4.0.0
> Maximum Links = 65535
> Delay Factor = 48
> Delay Weight = 10
> Inactivity Timer = 120
> Retransmit Factor = 10
> Routing Version = 2.0.0
> Type = Routing IV
> Routing Timer = 600
> Broadcast Routing Timer = 40
> Maximum Address = 1023
> Maximum Circuits = 20
> Maximum Cost = 100
> Maximum Hops = 16
> Maximum Visits = 20
> Maximum Broadcast Nonrouters = 64
> Maximum Broadcast Routers = 32
> Maximum Buffers = 80
> Buffer Size = 576
> Segment Buffer Size = 576
> The buffer size of 576 is what I remember being for non-Ethernet
> packets going over an IMP (which I'm sure is irrelevant because
> this was IP only). 1500 is the maximum for non-jumbo sized
> Ethernet frames, the 1476length being 24 bytes less. I plan to
> investigate that when I finally get into the guts of why ERROR.SYS
> fills up with class 5 errors from NTMANfor packets being too long.
> ------------------------------------------------------------------------
>
> On 7/14/24 5:04 AM, Johnny Billquist wrote:
>> Anders...
>>
>> On 2024-07-14 10:20, Anders Andersson wrote:
>>> "merlyn drforbin"<kropotkin(a)gmx.com> wrote:
>>>
>>>> Any way to set endpoint buffer size on panda decnet phase IV
>>> Could some of this (in SYSTEM:7-CONFIG.CMD) be what you are
>>> looking for?
>>> This is from RARITY (not PANDA, but DEC vanilla
>>> distribution,kind of), I'm
>>> not sure I have the correct values myself, been experimenting.
>>> ; DECnet parameters:
>>> ;default is DECNET BUFFER-SIZE 576
>>> decnet buffer-size 1476
>>> ;default is DECNET MAXIMUM-BUFFERS 80
>>> ;decnet maximum-buffers 40
>> Hmm. That do not seem to be the values currently used:
>>
>> .ncp tell rarity sho exec cha
>>
>> Node characteristics as of 14-JUL-24 10:58:22
>>
>> Executor node = 1.802 (RARITY)
>>
>> Identification = Rarity of Maneframe Six
>> Management version = 4.0.0
>> Software identification = DECnet-20 Version 4.0
>> Loop count = 1, Loop length = 127
>> Loop with = Mixed
>> Incoming timer = 30, Outgoing timer = 60
>> NSP version = 4.0.0
>> Maximum links = 65535, Delay factor = 48
>> Delay weight = 10, Inactivity timer = 120
>> Retransmit factor = 10, Routing version = 2.0.0
>> Type = Routing IV, Routing timer = 600
>> Broadcast routing timer = 40
>> Maximum address = 1023, Maximum circuits = 20
>> Maximum cost = 100, Maximum hops = 16
>> Maximum visits = 20, Maximum broadcast endnodes = 64
>> Maximum broadcast routers = 32, Maximum buffers = 80
>> Buffer size = 576, Segment buffer size = 576
>>
>> .
>>
>>
>> However, also to clarify some things. The segment buffer size
>> should probably stay at 576. This is basically the size of
>> packets used at theDECnet level, and I have some vague
>> recollection that nodes should use the same size, or DECnet might
>> fail. DECnet is not that clever about different sizes there.
>> The buffer size on the other hand can be larger (modulo VMS bug
>> that I mentioned a few days ago), but that would only be used by
>> link layer protocols, like the routing information packets that
>> are sent, for example.
>>
>> But if you are experimenting, please let me know if you figure
>> something out. Positive or negative. Always good with more
>> information.
>>
>> Johnny
>>
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--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email:bqt@softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
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