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Chapter 7 Queue Management and packet Scheduling

Chapter 7 Queue Management and packet Scheduling. Instructor : Sheau-Ru Tong Presenter : Hao-Hsiang Ku.

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Chapter 7 Queue Management and packet Scheduling

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  1. Chapter 7Queue Management and packet Scheduling Instructor : Sheau-Ru Tong Presenter : Hao-Hsiang Ku From: The ns Manual (formerly ns Notes and Documentation) The VINT Project A collaboratoin between researchers at UC Berkeley, LBL, USC/ISI, and Xerox PARC. Kevin Fall, Editor ,Kannan Varadhan, Editor

  2. Outline • Abstract • 7.1 The C++ Queue Class • 7.2 Drop Tail • 7.3 Different Types of Queue Objects • 7.4 Commands at a Glance

  3. Abstract • Packet scheduling • Buffer management • FIFO • Other kinds of Queues.

  4. 7.1 The C++ Queue Class class Queue : public Connector{ public : virtual void enque(Packet*)=0; virtual Packet* deque()=0; void recv(Packet *,Handler*); void resume(); int blocked(); void unblock(); void block();protected: Queue(); int command(int argc,const char*const* argv) int qlim_; int blocked_; int unblock_on_resume_; QueueHandler qh_; };

  5. 7.1.1 Queue Blocking class QueueHandler : public Handler { public: inline QueueHandler(Queue& q) : queue_(q) {} void handle(Event*); private: Queue& queue_; }; void QueueHandler::handle(Event*) { queue_.resume(); }Queue::Queue() : drop_(0), blocked_(0), qh_(*this) { Tcl& tcl = Tcl::instance(); bind("limit_", &qlim_); }

  6. 7.1.1 Queue Blocking(cont.) void Queue::recv(Packet* p, Handler*) { enque(p); if (!blocked_) { p = deque(); if (p != 0) { blocked_ = 1; target_-\>recv(p, &qh_);}}} void Queue::resume() { Packet* p = deque(); if (p != 0) target_-\>recv(p, &qh_); else { if (unblock_on_resume_) blocked_ = 0; else blocked_ = 1; } }

  7. 7.1.2 PacketQueue Class class PacketQueue { public: PacketQueue(); int length(); void enque(Packet* p); Packet* deque(); Packet* lookup(int n); void remove(Packet*); protected: Packet* head_; Packet** tail_; int len_; };

  8. 7.2 Drop Tail • A bounded, drop-tail queue • class DropTail : public Queue { protected: void enque(Packet*); Packet* deque(); PacketQueue q_; };

  9. 7.2 Drop Tail(cont.) • drop-tail • void DropTail::enque(Packet* p) { q_.enque(p); if (q_.length() \>= qlim_) { q_.remove(p); drop(p); } }Packet* DropTail::deque() { return (q_.deque()); }

  10. 7.3 Different Types of Queue Object • Parameters: • limit_ • blocked_ • unblock_on_resume_ • Other Queue objects • Drop-tail,FQ,SFQ,DRR,RED and CBQ.

  11. 7.3 Different Types of Queue Object(cont.) • Drop-tail objects: simple FIFO queue. • FQ objects:Fair Queue. • SFQ objects : Stochastic Fair queuing. • DRR objects: Deficit round robin scheduling. • RED objects:Random Early-detection Gateway.

  12. 7.3 Different Types of Queue Object(cont.) • CBQ objects:Class-Based Queuing. • CBQ/WRR(Weighted Round-Robin scheduling)

  13. 7.3 Different Types of Queue Object(cont.) • Queue-monitor objects • $queuemonitor • $queuemonitor set-delay-samples <delaySamp_> • $queuemonitor get-bytes-integrator • $queuemonitor get-pkts-integrator • $queuemonitor get-delay-samples

  14. 7.4 Commands at a Glance • $ns_ queue-limit <n1> <n2> <limit> • $ns_ trace-queue <n1> <n2> <optional:file> • $ns_ namtrace-queue <n1> <n2> <optional:file> • $ns_ monitor-queue <n1> <n2> <optional:qtrace> <optional:sampleinterval >

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