[e2e] How shall we deal with servers with different bandwidths and a common bottleneck to the client?

Detlef Bosau detlef.bosau at web.de
Sat Dec 23 13:45:36 PST 2006

I apologize if this is a stupid question.

However, I would like to know how we shall deal with this scenario.

Consider a client maintaing TCP sessions to different servers. (My PC is 
actually doing so, so there is at least one specimen.)

Consider the following topology

               ---------------(FE)--------------- Server 1 
Client  ----- (E)------router ------------(FE)----------router
----------------(E)------------------Server 2

E = Ethernet (10 Mbit/s)
FE = Fast Ethernt (100 MBit/s)

The link in the middle represents some transport network / path, e.g. 
the Internet. The common bottleneck is actually the link between client 
and router.
Consider there were two greedy TCP flows to the client, one originates 
from server 1 and the other from server 2.

My feeling is that the flow server 1 - client should achieve more 
throughput than the other. From what I see in a simulation, the ratio in 
the secnario above is roughly 2:1. (I did this simulation this evening, 
so admittedly there might be errors.)

Is there a general opinion how the throughput ratio should be in a 
scenario like this?



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