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Paper review : Analysis and Simulation of a Fair Queueing Algorithm (DKS89)

**Reviewer : Hai Fang** (hfang@acm.org)
**Goal**
To provide a gateway queueing algorithm which can protrect the fair allocation of
network resources from the ill-behaved sources.

**Contribution**
This paper presents a new *practical* fair queueing algorithm, with some rigorous
understanding of the performance of this algorithm.

**Main ideas**

- The old FCFS algoirthm cannot deal with ill-behaved sources effectively, which implies that
it cannot provide genuine fairness among sources.
- The fair queueing algorithm proposed in this paper provides fair allocation of bandwidth,
lower delay for not fully-served resources, and protects from ill-behaved sources.
- This algorithm interacts well with the current flow control algorirhms.

**Evaluation**

*Significance rating*: 4

This paper gives a realistic fair queueing algorithm with careful considerations on
several aspects. This opens the door leading to applying control machanisms to the
gateway in order for the congestion control in datagram networks.
*Convincing rating*

The authors analysis the shortcoming of the primitive FCFS queueing algorithms and
the Nagle's earlier proposal, hence provide a bit-by-bit round robin algorithm with
its improvement which is applied per packet and is more realistic. Then some simulation
results are given where the queueing algorithm was combined with several prominent flow
control algorithms. The results depict that this algorithm provide a fairly good solution
w.r.t. fairness, where especially it prevents ill-behaved sources to grab more resources.
*Limitation*

First, this algorithm requires the gateways to record the states with some computations for each
conversation, and I am wondering the scalability of this algorithm.

The simulation data shows that the Telnet sources are in disadvantage when they coexist with
the FTP conversations. This shows the algorithm give a bias on the bandwidth allocation rather
than the average delay.

**Conclusion**
How to provide the *fairness* among the conversations is an interesting problem.
Control the resources at the gateways seems like a better way than the control machanisms
at end-host. However, it still interacts with the flow control algorirhms, hence the good
behavior when cooperate with the latter is important.

*11/7/01*