The IP over ATM Mailing List Archive by date

[onvural@vnet.ibm.com]

*** Resending note of 03/28/96 15:38                                           
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 Subject:                                                                      
Subject: Re: EE Times on IP over ATM                                           
All these issues have been investigated in detail and the literature           
is full of various conclusions under different assumptions. One                
result of interest to the enclosed arguments is that upto 60-70%               
link utilization, reassemble process introduces additional work                
with NO recognizable benefit. Beyond 70%, checking corrupted SDUs              
is beneficial. These conclusions did not consider early packet                 
discard/partial packet discard. I would think                                  
reassemble process inside the network may not buy much if EPD/                 
PPD is implemented. Nevertheless, I agree this is an implementation            
issue. Raif                                                                    
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On Thu, 28 Mar 96 14:15:00 EST Hiroshi Esaki Wrote:                            
                                                                               
> I guess it depends on the implementation.                                    
>  Whether really re-assemble AAL5 SDU (i.e., CRC-32 check) and assemble       
>  again in MCS or not (just scheduling the cell departure) seems to be        
>  implementation issue for each MSC vendor.                                   
                                                                               
Quite true.All you really need to do is to collect all the cells together      
and then send them all out after all cells composing an SDU have been          
collected.  Of course, re-assembling the packet does have the advantage        
of being able to detect SDU corruption so as not to relay a bunch of           
cells for a corrupt packets.  On the other hand just collecting cells and      
being aware of SDU boundaries is probably more efficient in terms of both      
memory usage and throughput.  But as you point out, this is entirely           
an implementation decision.                                                    
                                                                               
 --- pete