🚀 go-pugleaf

In article <CMM.0.88.655642509.jon@gode.ifi.uio.no> jon@ifi.uio.no (Jon Oelnes) writes:
>In the ISO connection-less network protocol (ISO8473) one function is
>Route Recording. I have only an old copy (DIS version) at hand, and my
>question is if the following text is still valid, and if my interpretation
>is correct:

 [ valid text Deleted ]

>Now, reassembly is normally performed in the final _end system_, not in the
>ISes. My interpretation of the text is that no restriction is posed on
>reassembly in the _end systems_. An ES may perfectly well reassemble
>fragments which have followed different routes.
>Also, the point of discarding (in an IS) fragments which followed different
>routes, is only valid if the IS really does reassembly. If it just passes
>the fragments on, no error occures.

Unfortunatly fragements which follow different routes and which have
the Compelete Route Recording selected will never reach an ES.
Lost fragements will also cause the PDU to never reach an ES.
It is mandatory for IS's to be able to reaseemble.
Although it is never mentioned in the standard, IS's should foward
all PDU fragments through the same route if Complete Route Recording or
Security is set. Both these functions require 
the PDU to be dropped if the PDU cannot be reassembled.
If the users does not want to lose PDU's due to the fragements
travelling different paths the Partial Route Recording should
be used. 
Complete Route Record gives the user the actual path that the PDU
traversed. It is interesting to note that if there is not enough
room in the head to add the Network Entity Title, conformant 
systems MAY still attempt to reassemble the PDU and drop 
it if it cannot be reassembled.
However if it can reassemble the PDU, the PDU is forwarded without
the addition of the NET.
>
>Thanks in advance.
>Jon Oelnes, Norwegian Computing Center, Oslo
>E-mail: Jon.Olnes@nr.no    or    jon@ifi.uio.no


Brad Kemp
Locus Computing Corp
bhk@locus.com			uunet!lcc!bhk