The authors in the paper argue that fair allocation mechanisms require complex operations to be implemented at the router level. These operations include maintenance of state per flow and performing operations on a per flow basis which are not suited for high speed network routers. The authors propose a technique called core-stateless fair queueing where the edge routers maintain per flow state and insert labels into the packets. These labels convey the estimated flow rate and are used by core routers. The core routers perform FIFO scheduling with probabilistic dropping of packets based on the packet labels.
Edge routers compute flow arrival rate using exponential averaging. The estimated rate of arrival of each new packet is computed from the inter arrival time, the length of the packet and the previous rate. At the core router fair rate is estimated from the algorithm of aggregated arrival rate and aggregated accepted rate which are updated on each packet arrival. In case of congestion at a router the packet labels are not correct and they need to be updated as minimum of old label and fair rate. The paper also discusses weighted CSFQ which supports flows with different weights. The authors show simulations comparing CSFQ with FIFO, RED, FRED and DRR.
The argument that laid the basis of the research involved reducing the complex operations performed by routers in order to achieve fairness. I am curious what is the current trend, do we use CSFQ type implementation or is DRR used these days. Also, are there scenarios where the estimations used in CSFQ do not work well in complex scenarios where flows come and go simultaneously and their life span is too short. The simulations show that CSFQ performs better with TCP burstiness but how long does it take to stabilize when multiple new connections are started.
I would recommend having this paper in the syllabus because it ties very well with the other reading for fair queuing lecture.
Edge routers compute flow arrival rate using exponential averaging. The estimated rate of arrival of each new packet is computed from the inter arrival time, the length of the packet and the previous rate. At the core router fair rate is estimated from the algorithm of aggregated arrival rate and aggregated accepted rate which are updated on each packet arrival. In case of congestion at a router the packet labels are not correct and they need to be updated as minimum of old label and fair rate. The paper also discusses weighted CSFQ which supports flows with different weights. The authors show simulations comparing CSFQ with FIFO, RED, FRED and DRR.
The argument that laid the basis of the research involved reducing the complex operations performed by routers in order to achieve fairness. I am curious what is the current trend, do we use CSFQ type implementation or is DRR used these days. Also, are there scenarios where the estimations used in CSFQ do not work well in complex scenarios where flows come and go simultaneously and their life span is too short. The simulations show that CSFQ performs better with TCP burstiness but how long does it take to stabilize when multiple new connections are started.
I would recommend having this paper in the syllabus because it ties very well with the other reading for fair queuing lecture.
No comments:
Post a Comment