Dirk, Dirk Harms-Merbitz wrote:

Seems to me that a good way of limiting damage from runaway networks/hosts would be a modifaction of RED (Random Early Drop).

RED (in the usage of Floyd and Jacobson) stands for Random Early Detection. There is a similar acronym (ERD) that refers to Early Random Drop. The two algorithms are very different - in RED, you attempt to control the average queue size, but mark (usually drop) new arrivals when necessary. In ERD, you deal explicitly with the instantaneous queue size and you drop all new arrivals until you get your instantaneous queue size below the drop level. Which were you intending to refer to?

Controlled Early Drop (CED? I just made this up, suggestions?) would allow a router to give a preference to connected networks/hosts. Packets from certain networks would have a higher chance of being dropped from a router queue then packets from other networks.

This sounds like weighted RED - normally the probability of being dropped in RED is dependent on the EWMA (exponentially weighted moving average). I think that in weighted RED, the "weight" is used to influence the results of the normal RED algorithm.

CED can be used to price connections! You want 10%, you pay x. You want 50%, you pay y. Everybody gets full speed when the network is empty. When networks get congested everybody gets what they paid for.

These aren't absolute guarantees, however. Remember that in RED there is still the possibility that all new arrivals will be dropped - if the EWMA exceeds the maximum threshold and we are in serious congestion.

Seems like a better way of pricing Internet connections. Right now way too many people are stuck behind small pipes. Most T1 customers use only a small fraction of their circuit. How do you sell Ethernet connections? 100MB Ethernet connections? while still protecting your network. CED looks like a solution on this early Friday morning.

A combination of weighted RED and RSVP might do a mighty fine job. Unless you are using Ethernet for the 10 Mb/s access speed with only one customer per Ethernet, this doesn't really help. CSMA/CD will still take precedence in the face of a really congested link. :-) You can check out a paper that I did with a partner on Floyd and Jacobsen's RED paper. It's at http://pobox.upenn.edu/~tex/red_paper.html. -- ------------------------------------------------------------------------ Jon 'tex' Boone Network Engineer <tex@isc.upenn.edu> ISC Networking (215) 898-2477 University of Pennsylvania