Aggressiveness Protective Fair Queuing for Bursty Applications Nir

Background: Network planning • Network Designers use the traffic properties to plan the capacity of the network. Link Capacity APFQ - Nir Halachmi (IDC)

Background: Exploiters • Exploiters – Malicious: Denial of Service (DDOS) – Innocent: pre-fetching, massive users Drop Link Capacity Exploiter APFQ - Nir Halachmi (IDC)

Background: Solution- Fair Scheduling protection against Exploiters • Weighted Fair Queuing (WFQ) mechanisms provides that the resource is fairly (typically equally) divided among all Drop 1 Link Capacity 1 Exploiter Drop APFQ - Nir Halachmi (IDC)

Our main contribution • The user traffic is bursty. • WFQ cannot provide fair service to bursty applications in the presence of aggressive users • We propose WFQ-like mechanism called Aggressiveness Protective Fair Queuing (APFQ) that solves this problem. APFQ - Nir Halachmi (IDC)

Bursty Application • Many application are bursty (model on/off ~ active/idle) – Http on off Time APFQ - Nir Halachmi (IDC)

Bursty Traffic • Network Designers use the traffic burstiness property to plan the capacity of the network. Drop Link Capacity Drop APFQ - Nir Halachmi (IDC)

Aggressive Users • Aggressive user use the idle time to get more BW Drop Link Capacity Drop APFQ - Nir Halachmi (IDC)

WFQ defensives • WFQ cannot provide good fairness in the presence of such aggressive users. Drop Link Capacity Drop APFQ - Nir Halachmi (IDC)

The effect of aggressive user on (polite users (WFQ APFQ - Nir Halachmi (IDC)

Aggressiveness Protective Fair (Queuing (APFQ We propose a new WFQ-like mechanism called Aggressiveness Protective Fair Queuing (APFQ) that solves this problem by dynamically decreasing the weight of the aggressive users. APFQ - Nir Halachmi (IDC)

Agenda • • • Related Work. Solution Requirements. APFQ algorithm. APFQ analysis Simulation. APFQ - Nir Halachmi (IDC)

Related Work • Dynamic WFQ was proposed to handle the fact that it is hard to assign static weight accurately [Shin and el. 2001][Makrakis and el. 2001]. – Fix the weight according to arrival rate or the queue length. – Does not address bursty traffic problem. • Dynamic WFQ was proposed as part of a mechanism to handle DDOS [Thomas and el. 2003] – Penalty mechanism to flows – Does not deal with traffic burstiness and does not suggest or analyze the weight function mechanism APFQ - Nir Halachmi (IDC)

Solution Requirements • Provide fairness to polite users. • The limitation imposed on the users is a function of the system load. – Protect innocent users by negatively discriminating aggressive users on an overloaded Network. Drop Link Capacity Drop APFQ - Nir Halachmi (IDC)

APFQ • Dynamic weight function that reduces the weight assigned to aggressive users • For every flow (user) the mechanism counts the amount of traffic that a source has generated in the near history • It uses this amount to affect the weight given to the user. APFQ - Nir Halachmi (IDC)

Weight function • BS – the assigned quota. • SM(t) – offered traffic during the last sliding. window in time t. • wo original fix weight. • α – punishment factor – configure by the system. APFQ - Nir Halachmi (IDC)

APFQ Illustrated • Polite user transmit data: Time • Aggressive User Transmitted data under WFQ • Aggressive User Transmitted data under APFQ - Nir Halachmi (IDC)

APFQ algorithm KBytes 1 7 Time W(0) Weight Time APFQ - Nir Halachmi (IDC)

Analysis pre conditions • • • Polite user transmits at rate R for Ton and idle for Toff. Aggressive user transmits at constant peak rate R. N concurrently active users. K aggressive users , N-K polite users. For each user original fix weight wo = 1 Packets that are not transmitted within a period of ∆ from their arrival time are dropped. • B is the output link capacity. • ∆ = Ton + Toff = sliding window size. • ƒ = burst factor = APFQ - Nir Halachmi (IDC)

Polite User • Offered Data • Transmitted Data WFQ • Transmitted Data APFQ - Nir Halachmi (IDC)

Naive Aggressive User • Offered Data • Total offered Data • Transmitted Data WFQ APFQ - Nir Halachmi (IDC)

Naive Aggressive User • Transmitted Data APFQ • For α =1 • For α=2 APFQ - Nir Halachmi (IDC)

Continuous Naive Aggressive • Continuous Naive Aggressive - an aggressive user that was active in the previous window size. • I. e. , offered traffic during the last sliding • Hence the assigned weight is fixed APFQ - Nir Halachmi (IDC)

Continuous Naive Aggressive • Transmitted Data APFQ • For α =1 Exactly as polite use under APFQ • For α=2 Exactly as polite use under APFQ - Nir Halachmi (IDC)

t s o f f e • Sophisticated Aggressive ruser is assumed to know the function used by APFQe and optimizes its offered d traffic in order to maximizet the traffic APFQ will transmit for him. r a f f • An approach for the sophisticated aggressive user is to offer the same amount ofi traffic as the mechanism c allow her to transmit. i APFQ - Nir Halachmi (IDC) n Sophisticated Aggressive

Sophisticated User Upper Bound • Lemma: Under APFQ a sophisticated aggressive user cannot transmit in a period of duration ∆ more than (m+2)·BS traffic where m is derived from equation APFQ - Nir Halachmi (IDC)

Sketch of proof APFQ - Nir Halachmi (IDC)

Sophisticated User Lower Bound • Lemma: There is a strategy where the sophisticated aggressive user can transmit during an interval of length ∆ under APFQ with α at least (m+1)·BS traffic where m is derived from equation. APFQ - Nir Halachmi (IDC)

Optimal Strategy for sophisticated aggressive APFQ - Nir Halachmi (IDC)

Analysis Summery User Type WFQ transmitted traffic APFQ transmitted (α=1) traffic (α=2) Polite user 1 1 1 Naïve aggressive user ƒ 1 + log ƒ 2 Continuous naïve aggressive user ƒ 1 Sophisticated user ƒ APFQ - Nir Halachmi (IDC)

Simulation • Simulated APFQ on NS 2 • NS 2 code implementing WFQ contributed by Paulo Losi • APFQ was implemented as a software wrapper around WFQ. APFQ - Nir Halachmi (IDC)

Tests Set-up APFQ - Nir Halachmi (IDC)

Experiment 1 • Examine the percentage of packets transmitted per flow as a function of the link capacity. • Scenario 1: 12 polite users • Scenario 2: 10 polite users and 2 aggressive users. APFQ - Nir Halachmi (IDC)

Experiment 1 Results APFQ - Nir Halachmi (IDC)

Experiment 2 • Examine how many aggressive users a given network can handle without negatively affecting the polite users. • Test APFQ robustness to large networks. APFQ - Nir Halachmi (IDC)

Experiment 2 • 300 users with a variable number of aggressive users out of them. • The number of aggressive users was increased in each round. • The Link-capacity was set to 9000 Kb/sec. APFQ - Nir Halachmi (IDC)

Experiment 2 Results APFQ - Nir Halachmi (IDC)

Implementation consideration • APFQ can use a regular WFQ. • Experiments revealed that Dynamic WFQ, in some scenarios, can causes disorder. • The cause of the problem is that the WFQ implementation implicitly assumed the weight of the queues is constant (i. e. static weight). APFQ - Nir Halachmi (IDC)

Conclusion • Aggressive users use the idle time to get more bandwidth. • WFQ has a fairness problems in the presence of aggressive users. • APFQ is a mechanism that provide fairness in such cases, using a dynamic weight function. APFQ - Nir Halachmi (IDC)

? Questions Thank You APFQ - Nir Halachmi (IDC)

Problem demonstration V_t =0 6 5 4 3 2 1 0 Time 1 P 4 F=4 P 3 F=3 P 2 F=2 P 1 F=1 1 V_t =1 6 6 5 4 3 2 1 Time P 1 F=1 1 P 5 F=5 P 4 F=4 P 3 F=3 P 2 F=2 1 V_t =2 8 7 6 5 4 3 2 Time P 2 F=2 1 P 6 F=9 P 5 F=5 P 4 F=4 P 3 F=3 0. 25 APFQ - Nir Halachmi (IDC) P 1 F=1

Problem demonstration V_t =8. 4 8 7 6 5 4 3 2 Time P 7 F=6 P 5 F=5 P 4 F=4 P 3 F=3 P 2 F=2 P 1 F=1 p 6 F=9 P 7 F=6 P 5 F=5 P 4 F=4 P 3 F=3 1 P 8 F=13 p 6 F=9 0. 25 V_t =9. 2 8 7 6 5 4 3 2 Time 1 P 8 F=13 0. 25 V_t =10 8 7 6 5 4 3 2 Time 1 0. 25 P 8 F=13 P 2 F=2 APFQ - Nir Halachmi (IDC) P 1 F=1

Problem demonstration V_t =6 Time P 7 F=6 P 8 F=13 p 6 F=9 P 5 F=5 The new flow arrive and it’s finish time is set by the virtual time and not by the real round time (it finish time should have been 3) 1 P 4 F=4 P 3 F=3 P 2 F=2 P 1 F=1 0. 25 V_t =6. 8 8 7 6 5 4 3 2 Time P 7 F=6 P 8 F=13 p 6 F=9 P 4 F=4 1 P 5 F=5 0. 25 The new flow packet should have been transmitted by now V_t =7. 6 8 7 6 5 4 3 2 Time P 7 F=6 P 8 F=13 p 6 F=9 1 0. 25 P 5 F=5 P 4 F=4 P 3 F=3 P 2 F=2 APFQ - Nir Halachmi (IDC) P 1 F=1

Sketch of proof APFQ - Nir Halachmi (IDC)