Active Queue Management
Encyclopedia
In Internet routers, active queue management (AQM) is a technique that consists in dropping or ECN
-marking packets before a router's queue is full.
Active queue disciplines drop or mark packets before the queue is full. Typically, they operate by maintaining one or more drop/mark probabilities, and probabilistically dropping or marking packets even when the queue is short.
Recent Publications in Active Queue Management (AQM) schemes
between flows. By dropping packets probabilistically, AQM disciplines typically avoid both of these issues.
By providing endpoints with congestion indication before the queue is full, AQM disciplines are able to maintain a shorter queue length than drop-tail queues, which reduces network latency ("ping time
").
and SRED) require careful tuning of their parameters in order to provide good performance. Modern AQM disciplines (ARED, Blue
, PI) are self-tuning, and can be run with their default parameters in most or all circumstances.
For AQM systems that drop packets (rather than using ECN
marking), the result seems counter-intuitive to many network engineers: "Why should I drop perfectly good packets when I still have free buffer space?"
and Denial-of-Service (AQM&DoS) Simulation Platform is established based on the NS-2 simulation code of the RRED algorithm. The AQM&DoS Simulation Platform can simulate a variety of DoS attacks (Distributed DoS, Spoofing DoS, Low-rate DoS, etc.) and Active Queue Management (AQM) algorithms (RED, RRED, SFB, etc.). It automatically calculate and record the average throughput of normal TCP flows before and after DoS attacks to facilitate the analysis of the impact of DoS attacks on normal TCP flows and AQM algorithms.More Details
Explicit Congestion Notification
Explicit Congestion Notification is an extension to the Internet Protocol and to the Transmission Control Protocol and is defined in RFC 3168 . ECN allows end-to-end notification of network congestion without dropping packets. ECN is an optional feature that is only used when both endpoints...
-marking packets before a router's queue is full.
Queue management
An Internet router typically maintains a set of queues, one per interface, that hold packets scheduled to go out on that interface. Historically, such queues use a drop-tail discipline: a packet is put onto the queue if the queue is shorter than its maximum size (measured in packets or in bytes), and dropped otherwise.Active queue disciplines drop or mark packets before the queue is full. Typically, they operate by maintaining one or more drop/mark probabilities, and probabilistically dropping or marking packets even when the queue is short.
Recent Publications in Active Queue Management (AQM) schemes
Benefits of AQM
Drop-tail queues have a tendency to penalise bursty flows, and to cause global synchronisationTCP global synchronization
TCP global synchronization in Computer networks can happen toTCP/IP flows during periodsof congestion because each sender will reduce their transmission rate at the sametime when packet loss occurs....
between flows. By dropping packets probabilistically, AQM disciplines typically avoid both of these issues.
By providing endpoints with congestion indication before the queue is full, AQM disciplines are able to maintain a shorter queue length than drop-tail queues, which reduces network latency ("ping time
Round-trip delay time
In telecommunications, the round-trip delay time or round-trip time is the length of time it takes for a signal to be sent plus the length of time it takes for an acknowledgment of that signal to be received...
").
Drawbacks of AQM
Early AQM disciplines (notably REDRandom early detection
Random early detection , also known as random early discard or random early drop is an active queue management algorithm. It is also a congestion avoidance algorithm....
and SRED) require careful tuning of their parameters in order to provide good performance. Modern AQM disciplines (ARED, Blue
Blue (queue management algorithm)
Blue is an Active Queue Management algorithm. Like RED, it operates by randomly dropping or ECN-marking packets in a router's queue before it overflows...
, PI) are self-tuning, and can be run with their default parameters in most or all circumstances.
For AQM systems that drop packets (rather than using ECN
Explicit Congestion Notification
Explicit Congestion Notification is an extension to the Internet Protocol and to the Transmission Control Protocol and is defined in RFC 3168 . ECN allows end-to-end notification of network congestion without dropping packets. ECN is an optional feature that is only used when both endpoints...
marking), the result seems counter-intuitive to many network engineers: "Why should I drop perfectly good packets when I still have free buffer space?"
The Simulation and Analysis Platform for AQM algorithms
An Active Queue ManagementActive Queue Management
In Internet routers, active queue management is a technique that consists in dropping or ECN-marking packets before a router's queue is full.-Queue management:...
and Denial-of-Service (AQM&DoS) Simulation Platform is established based on the NS-2 simulation code of the RRED algorithm. The AQM&DoS Simulation Platform can simulate a variety of DoS attacks (Distributed DoS, Spoofing DoS, Low-rate DoS, etc.) and Active Queue Management (AQM) algorithms (RED, RRED, SFB, etc.). It automatically calculate and record the average throughput of normal TCP flows before and after DoS attacks to facilitate the analysis of the impact of DoS attacks on normal TCP flows and AQM algorithms.More Details
AQM algorithms
- Adaptive Virtual Queue (AVQ);
- Random early detectionRandom early detectionRandom early detection , also known as random early discard or random early drop is an active queue management algorithm. It is also a congestion avoidance algorithm....
(RED); - Random Exponential Marking (REM);
- Blue and Stochastic Fair BlueBlue (queue management algorithm)Blue is an Active Queue Management algorithm. Like RED, it operates by randomly dropping or ECN-marking packets in a router's queue before it overflows...
(SFB); - CHOKeChokeChoke may refer to:* Choking, obstruction of airflow into the lungs** Choke , a condition in horses in which the esophagus is blocked** Choking game, a schoolyard game involving deprivation of oxygen to the brain...
; - PI controller.
- Robust random early detectionRobust random early detectionThe existing Random Early Detection algorithm and its variants are found vulnerable to emerging attacks, especially the attacks. Experiments have confirmed that the existing RED-like algorithms are notably vulnerable under LDoS attacks due to the oscillating TCP queue size caused by the...
(RRED) - RSFB: a Resilient Stochastic Fair Blue algorithm against spoofing DDoS attacks
See also
- Network congestion avoidance
- Explicit Congestion NotificationExplicit Congestion NotificationExplicit Congestion Notification is an extension to the Internet Protocol and to the Transmission Control Protocol and is defined in RFC 3168 . ECN allows end-to-end notification of network congestion without dropping packets. ECN is an optional feature that is only used when both endpoints...
(ECN) - BufferbloatBufferbloatBufferbloat is a phenomenon in a packet-switched computer network whereby excess buffering of packets inside the network causes high latency and jitter, as well as reducing the overall network throughput...