[HECnet] Thousands of DECnet errors on Tops-20

[Peter Lothberg]

Well, MRC was receiving "suggestions" from Stu Grossman on how to do it, but 
if my memory does not fail me the block size was 312, due to lack of buffer space 
in the already crammed single section 512KW 2020. I'm afraid my tape and disk-pack 
are in Seattle. I knew it was not 576 as it had two DUP-11's and using it for transit failed... 

Quiz, do you knew what a DDP is? 

-P 

> From: "tommytimesharing" <tommytimesharing at gmail.com>
> To: "hecnet" <hecnet at Update.UU.SE>
> Sent: Friday, January 15, 2021 3:59:25 PM
> Subject: Re: [HECnet] Thousands of DECnet errors on Tops-20

> Was this maybe that magical version 5 of Tops-20 that MRC put together for the
> 2020? I sure would love to see the sources for that! I'm not sure if this is
> relevant, but the following macro in D36COM is of interest:

>> DEFINE KNMMCS,<
>> ; Symbol,Name,Cost, Maximum receive block size
>> KNMMAC LD.TST,TST, 1, 0 ;TST DEVICE
>> KNMMAC LD.DTE,DTE, 3, <^D576> ;DTE DEVICE
>> KNMMAC LD.KDP,KDP, 4, <^D576> ;KDP DEVICE
>> KNMMAC LD.DDP,DDP, 5, <^D576> ;DDP DEVICE
>> KNMMAC LD.CIP,CI, 2, <^D576> ;CI DEVICE
>> KNMMAC LD.NI ,NI, 1, <^D1504-%RTEHS> ;NI DEVICE
>> KNMMAC LD.DMR,DMR, 2, <^D576> ;DMR DEVICE
>> >;END OF KNMMCS

> What can be seen is that the maximum block size is 576 in all cases except the
> NI, which is 1476 bytes. I don't know if any of these devices are relevant to
> the 2020; one assumes that the DTE, CI and NI are not.

>> On 1/12/21 3:29 PM, Peter Lothberg wrote:

>> The DECnet segment size has to be the same "network wide".

>> If I remember right DECnet looks at the two end nodes and uses the smalles
>> segment size,
>> so if there is any transit node in the path with a small segment size things
>> will not work as
>> it will drop packets bigger than it''s size.

>> The only SW/HW combination I knew of that has other than 576 is MRC/Stu DECnet
>> for
>> Tops20 4.x on DEC2020.

>> -P
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