[e2e] random early time-to-die
S.Zimmermann at tu-harburg.de
Fri Jun 15 09:00:42 PDT 2001
Murat Yuksel wrote:
>>This is a form of congestion pricing using the TTL as a purse?
> I think it is not "pricing". You are decreasing TTL for the purpose of
> defining when to kill the packet. Congestion based pricing would be to
> increase the price of that packet rather than killing it.
View it the other way around:
Each packet has a "budget". It doesn't matter whether it is encoded in
the TTL field or in another yet-to-be field. Each router decreases the
budget by an amount proportional to the "congestion charge". When the
budget is zero, the packet is dropped.
But what can we gain from that? One of the ideas behind congestion
pricing strategies is that sources adjust their rates without packet
loss. This scheme still uses packet loss. So the known congestion
pricing strategies seem to be superior to this proposal. Dropping the
packets might provide an incentive, but then the sender should not be
able to freely set its budget.
However, could we use this as admission control? Let's assume, the total
cost for end-to-end delivery is roughly constant for short time periods.
If the budget is lower than the cost, all packets are dropped = the
connection is refused. If the budget is greater than the cost, all
packets are delivered = the connection is accepted.
By setting a budget field in the packet header, a sender could choose
the importance of the connection. Of course, the budget should somehow
correspond to real money, otherwise everybody would choose the maximum
amount. But one could implement service classes that way.
The questions remains, however, if we want admission control at this layer.
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