[c-nsp] Packet Latency Calculator

[Eric Helm]

Matthew Crocker wrote:
> Hello,
> 
>    Every once and a while I have a customer complain about latency  
> through our network.  Normally it is on the initial hop (DSL).  Does  
> anyone know of a calculator I can use to figure the theoretical  
> minimum latency for a circuit?
> 
> For example:
> 
> Customer traceroutes through to their gaming server (15 hops away).   
> They see 30ms ping times on the first hop (DSL Line).  The DSL line  
> is IP over PPP over Ethernet over ATM over DSL.  With all the extra  
> encapsulation and the ATM cell tax how big is the new packet?  How  
> long would it take to send/recieve this packet over a 768kbps DSL link?
> 
> Anyone know a good place to look?
> 
> -Matt
> 
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Matt,
This cisco link has a nice table of serialization delay values:
http://www.cisco.com/warp/public/788/voip/delay-details.html#serializationdelay

And here is discussion of Protocol Overhead for Ethernet and ATM:
http://sd.wareonearth.com/~phil/net/overhead/

I belive PPPoE adds 8 bytes of overhead.

/Eric