Browse Prior Art Database

Integration of Metering and Marking with Flow Control

IP.com Disclosure Number: IPCOM000016026D
Original Publication Date: 2002-Jun-26
Included in the Prior Art Database: 2003-Jun-21
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Abstract

A flow control scheme might use the offered load of a Pipe i, namely Oi, in which the packet belongs, and the maximum and minimum desired rates for this pipe, namely Hi and Li, to determine the transmit probability of the packet. The basic idea is to use the same parameters, that is, Oi, Hi, and Li, to meter and mark a packet. Thus each Flow i 1, 2, ..., M, has two

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 2

Integration of Metering and Marking with Flow Control

A flow control scheme might use the offered load of a Pipe i, namely Oi, in which the packet

belongs, and the maximum and minimum desired rates for this pipe, namely Hi and Li, to

determine the transmit probability of the packet. The basic idea is to use the same parameters,

that is, Oi, Hi, and Li, to meter and mark a packet. Thus each Flow i = 1, 2, ..., M, has two

performance parameters called Li (a low value of bandwidth, a guaranteed level) and Hi (a

high value of bandwidth, a maximum total bandwidth, an upper limit on allowed bandwidth

that must be reached before marking some packets Red). Again, the Offered traffic rate Oi

for Flow number i is compared to Li and Hi. Offered rate Oi values for Flow number i might

also be subjected to averaging to obtain a time-weighted average such as Exponentially

Weighted Moving Average (EWMA). In present invention, an offered rate for Flow i,

averaged or not, is simply designated Oi. The marking scheme defined as such, is called

Proportional Marking.

"Proportional Marking" is defined as follows. This is eventual, average marking behavior. Short-term effects are not considered. (1) If the Offered traffic in Flow i is constant and at or below CIR = Li, then the bandwidth of Green output is the same as the Offered. No Yellow packets are sent, and no Red packets are sent. (2) If the Offered traffic in Flow i is constant and between CIR = Li and CIR+PIR = Hi, then the bandwidth of Green output is CIR = Li and the rest is Yellow. No Red packets are sent. (3) If the Offered traffic in Flow i is constant and at or above CIR+PIR = Hi, then the bandwidth of Green output is CIR= Li, the bandwidth of Yellow output is PIR = Hi - Li, and the rest of the sent packets are Red.

The outcome of the Proportional Marking is now a number of pipes, each one of them having their own Hi and Li thresholds. A Flow Control mechanism measures the offered load of a pipe i against the Hi and Li thresholds and determines the transmit probabilities for the packets in the pipe.

For Flow i with offered rate Oi(t) at time t, let three Color Marking Probabilities Pigreen(t), Piyellow(t), Pired(t) be the three probabilities that a packet arriving during time interval [t, t+Dt) is marked Green (Priority 0), Yellow (Priority 1), or Red (Priority 2). These probabilities are held constant over [t, t+Dt) and are actually determined by events in the previous epoch [t-Dt, t). On average, the bps of the three colors of packets in Flow i over [t, t+Dt) are Oi(t+Dt)*Pigreen(t), Oi(t+Dt)*Piyellow(t), and Oi(t+Dt)*Pired(t).

Furthermore, for each Flow i define two one-bit functions called Excess Bandwidth Signals as follows:
Bigreen(t) := if Oi(t)*Pigreen(t) <= Li, then 1; else 0 Biyellow(t) := if Oi(t)*P...