LISTSERV mailing list manager LISTSERV 15.5

Help for EVN-NREN Archives

EVN-NREN Archives

EVN-NREN Archives


Next Message | Previous Message
Next in Topic | Previous in Topic
Next by Same Author | Previous by Same Author
Chronologically | Most Recent First
Proportional Font | Monospaced Font


Join or Leave EVN-NREN
Reply | Post New Message
Search Archives


Re: Overview of eVLBI paths through GEANT (fwd)


Jouko Ritakari <[log in to unmask]>


European VLBI Network discussion.


Mon, 18 Apr 2005 15:52:15 +0300





TEXT/PLAIN (1 lines)

Hi Julianne & others,

On Mon, 18 Apr 2005, J. Sansa wrote:

> i have looked at the tsunami protocol, aparent results are sure
> aggressive, am afraid too aggressive and unfair to anyother traffic on
> the link. would this do for evlbi, isnt there other traffic using the
> same link???

Well, you have to think things through.
The TCP congestion control algorithm is trying to be fair to oother users.
The critical fault there is that the algorithm tries to measure network
congestion by measuring packet loss. This was a valid approach twenty
years ago, when the links were slow and congested.

However, in modern networks there rarely is congestion or packet loss.
Almost all the packet loss is caused by the slowness of the receiving
computer. The TCP congestion algorithm wrongly interpretes this to be
congestion and slows dowm. This is the main reason why most of the eVLBI
tests have been spectacular failures.

If we use the best available microcomputers, we see almost no packet loss
below 400 Mbit/s speed, about 2.6% packet loss at 512 Mbit/s and 7% at 640
Mbit/s speed. Packet loss in backbone networks (Nordunet, GEANT, SURFnet,
Abilene) has always been below 0.05%.

For nice load graphs see


Back to: Top of Message | Previous Page | Main EVN-NREN Page



CataList Email List Search Powered by the LISTSERV Email List Manager