[e2e] VJCC vs. Keshav

Detlef Bosau detlef.bosau at web.de
Thu Apr 18 05:06:50 PDT 2013

Am 18.04.2013 11:45, schrieb Jon Crowcroft:
> I think the point i was trying to convey was that
> packet pair (and packet train) and fair queuing (and other more active
> queue management algorithms) have seen evaluation by
> many people using many tools (including measurement as well as

Yes. And being short and frankly: When it comes to mobile networks, I 
don't believe a word of the packet-pair and packet-train stuff.

Even for the radio interface, it simply doesn't make sense to talk about 
an "average bit rate" in this case, when this is associated with both, a 
reasonable hight throughput and a reasonably low block corruption rate.

However, you can well implement packet pair and packet train stuff and 
observe some funny numbers in real networks. That's nice, other people 
collect stamps..... .

But when we put those numbers in c-code and derive "serialization 
delays" from them, the result is simply fictional.

It took me years to learn this lessen and perhaps, it was one of my most 
difficult lessons ever.

So, the question is: What is the reality, which really corresponds to 
our simulators?

When I started my work in a project called COMCAR 13 years ago, and I 
talked about QoS, the EE colleagues ridiculed at me "You dealt with 
wired networks up to now, right?" and a colleague from CE simply 
answered my question concerning bit error rates simply and harsh: "There 
is nothing like bit error rates."

What I learnt meanwhile: Both were right.

And as there is no such thing like a "bit error rate", there is no such 
thing like a (more or less or at least quasi more or less stationary) 
bit rate.

And therefore, all this packet pair stuff and packet train stuff is 
interesting stuff inspired by the behaviour of wired networks, but with 
respect to mobile networks, we talk about pure fiction and artefacts here.

Detlef Bosau
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