[HECnet] ANF10 network --> DN200 (RJE, Decnet) --> should be Ddcmp --> MarkP

[Paul Koning]

> On Nov 19, 2021, at 3:52 PM, Mark Pizzolato - Info Comm <Mark at infocomm.com> wrote:
> 
> On Friday, November 19, 2021 at 12:33 PM, Reindert wrote:
>> I updated the remark by Bob with this in my update and could not find that
>> back in your copy of the mail transcript:
>> 
>> Before I get a storm this from Pdp11_dup.c should accompany it:
>> 
>>   The wire protocol implemented is native DDCMP WITHOUT the DDCMP
>> SYNC
>>   characters both initially and between DDCMP packets.
> 
> I still don't understand your problem.  The wire protocol is PACKETS, NOT bytes.  
> The packets are transported over either UDP (as UDP packets) OR via TCP with 
> a 2 byte packet header indicating the data length.  Any packet length is NOT 
> presented across the simulator<->pdp11_dup device, just the data.  On transmit 
> any interpacket bytes that are the DDCMP_SYNC character are stripped BEFORE 
> the packet data is presented to UDP or TCP for outbound delivery.
> 
> - Mark

But how does that process know how to turn a sequence of bytes written to the DUP transmit register into a packet?  To do so, it must know what the particular packet format is.  If a driver is sending BISYNC data, your packet framing algorithm is entirely different from what it is for DDCMP.

	paul