Re: UDP checksum calculation - uses lenght twice ?

Hi, Alexander , just a little correction :
TCP headers have no relation with Unix(BSD) stack because TCPIP stack was
invented by Vint Serf and Bob Kahn in 1973-1974 ( even RFC973 appeared in
1981 due to http://www.faqs.org/rfcs/rfc793.html ) and first Berkley socket
subsystem appeared in 1983 only. Unix long time was single computer Os
opposite to other minicomputer ( the first computer for Unix was PDP-7 and
shortly moved to PDP-11 ) Oses called RT ( search for DECNet e.g. which was
develop in parallel with TCP/IP so DEC didn't want TCP long period :)
opposite to HP and other minicomputer's ( for RT ) OEMs.
That just part of my life in computers : ) both on DEC and HP RT computers.
My first network experience was on HP21xx serie ( mini with microcomputers
net ) the same time Berkley sockets first issued. That was so long ago that
you can't to find any data about RTE Os
( RT Executer of HP ) in the web, DEC is something different , but that due
to Dave Catler and his team moved from DEC to MSFT and created all modern
Windows ( not a lot but that is its history :
http://research.microsoft.com/~gbell/Digital/timeline/1957.htm )

Arkady


"Alexander Nickolov" <agnickolov@xxxxxxxx> wrote in message
news:O6ZT7JF9FHA.2676@xxxxxxxxxxxxxxxxxxxxxxx
> I'm not exactly sure, but I believe the reason is due to an
> implementation detail of the BSD network stack. The
> pseudo-header corresponds to the last 12 bytes of the
> original IP packet header, but modified after processing
> at the IP layer. These contain the source and destination
> addresses, the TTL (which is now zero), the protocol (17
> for UDP), and the IP header checksum, which is apparently
> replaced with the packet length before the packet is passed
> to the UDP layer for processing. Notice it is _not_ in network
> byte order :)...
>
> I hope this is the answer you were looking for all along...
>
> --
> =====================================
> Alexander Nickolov
> Microsoft MVP [VC], MCSD
> email: agnickolov@xxxxxxxx
> MVP VC FAQ: http://www.mvps.org/vcfaq
> =====================================
>
> "R.Wieser" <address@xxxxxxxxxxxxx> wrote in message
> news:ux58gzC9FHA.3876@xxxxxxxxxxxxxxxxxxxxxxx
>> Arkady Frenkel <arkadyf@xxxxxxxxxxxxxxxx> schreef in berichtnieuws
>> #WLcVnC9FHA.2264@xxxxxxxxxxxxxxxxxxxxxxx
>>
>> Hello Arkady,
>>
>>> P.S. BTW Police officer ( in this case RFC sure not me :) describe
>>> that maybe not clearly enough but "This gives the TCP protection
>>> against misrouted segments" ( RFC ) is the explanation.
>>
>> I'm sorry, but no ammount of effort on my part in trying to explain what
>> I
>> want does seem to help ....
>>
>> Your above answer is as correct as the "because otherwise it does not
>> function" one, but allso does *not* answer my question.
>>
>> I'm asking why the calculation has been designed as it curently is,
>> nothing
>> more, nothing less.
>>
>> Regards,
>> Rudy Wieser
>>
>>
>>
>
>


.

Relevant Pages

  • Re: Alpha remembrance day
    ... DEC's disk drive business, they were starting to catch on, but since ... to integrate a TCP/IP stack into on OS? ... UNIX Server/Workstation. ... IBM courted him for a long while ...
    (comp.os.vms)
  • Re: Signs of Maccie desperation!
    ... they cannot be implemented in UNIX? ... Network mapping magically detects what your ... Same with the new stack. ... interface, and a ton load of new technologies in the file system, kernel, ...
    (comp.sys.mac.advocacy)
  • Re: COM/EXE header problem
    ... some header for example. ... mov ax,0x4c00 ... I would expect a linker to warn about "no stack" and "no entrypoint". ... The first "stack" is just a name - could be "segment frank stack" just as easily - but the second "stack" is a segment "attribute", ...
    (alt.lang.asm)
  • Re: How can I detect a carriage return using java.net
    ... The stack used by DEC Unix on the alphaserver did the same - and that was a Mach based implementation. ... If you got an error you can report it, but this doesn't affect the logic unless it was EAGAIN or EINTR, which both indicate that the recv() returned without reading any valid data but the connection is still intact. ...
    (comp.lang.java.programmer)
  • Re: How to avoid stack overflow in C????
    ... Your question would be better answered in comp.sys.sun (or another newsgroup dedicated to your platform or perhaps a Unix specific newsgroup such as comp.os.unix.programming) as it is venturing on the OT line here. ... working fine without crashing down. ... There are very large differences between a segmentation fault, stack fault,. ... If so, your operating system may have a way to increase the stack size, however on unix you may need to recompile the kernel. ...
    (comp.lang.c)