1 / 11

Role and Mechanism of Queue

Role and Mechanism of Queue. Internet Engineering. What is Queue ( buffer ). Packet exchange = Store – and – forward Router temporary stores packet in buffer Packet is queued and then stored ( In Drop Tail ) earlier income packet will transmit soon, what comes in first is handled

peoplesm
Download Presentation

Role and Mechanism of Queue

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Role and Mechanism of Queue Internet Engineering

  2. What is Queue (buffer) • Packet exchange= Store – and – forward • Router temporary storespacket in buffer • Packet is queued and then stored • (In Drop Tail)earlier income packet will transmit soon, what comes in first is handled • If the queue overflows, packets will be dropped Router Queue (buffer)

  3. Relationship between Node, Queue, Link • In NS2, each link has a queue • Packets go through queue before sent out to the link • If input rate is larger than output rate, overflow packets will be accumulated in queue • It can response to temporary traffic increase • Packet are dropped if queue length exceeds its capacity Queue (Buffer) Packet Link Node Bandwidth Node 2 Node 3 Node 4 Node 0

  4. Packet flow 4Mbps 20ms 40Mbps 6ms 40Mbps 6ms Node 0 Node 2 Node 3 Node 4 + 0.062 0 2 cbr 1000 ------- 0 0.0 4.0 62 62 - 0.062 0 2 cbr 1000 ------- 0 0.0 4.0 62 62 r 0.0682 0 2 cbr 1000 ------- 0 0.0 4.0 62 62 + 0.0682 2 3 cbr 1000 ------- 0 0.0 4.0 62 62 - 0.1302 2 3 cbr 1000 ------- 0 0.0 4.0 62 62 r 0.1522 2 3 cbr 1000 ------- 0 0.0 4.0 62 62 + 0.1522 3 4 cbr 1000 ------- 0 0.0 4.0 62 62 - 0.1522 3 4 cbr 1000 ------- 0 0.0 4.0 62 62 r 0.1584 3 4 cbr 1000 ------- 0 0.0 4.0 62 62 Why? 62ms 84ms 22ms Observe the packet (ID=62) (% awk ‘$12==62’ out.tr) ※experiment 1-1-(b): bandwidth 4Mbps

  5. Time for forwarding packet Time for sending packet from node 2 to node 3 4Mbps 20ms 40Mbps 6ms 40Mbps 6ms Node 0 Node 2 Node 3 Node 4 Queuing time in queue + Forwarding time + Time for transmission between links 62ms → (Queue length)×(Time for sending packet out) ※Queue length: the number of packet kept in queue, 31 in this ex 2ms → (Packet size [bytes])÷(Bandwidth of Link [Mbps]) 1000[bytes] 4[Mbps] 20ms → (Link delay) Total 84ms

  6. Packet flow(Dropped packet) Drop 40Mbps 6ms 4Mbps 20ms 40Mbps 6ms Node 0 Node 2 Node 3 Node 4 Dropped after join a queue + 0.063 0 2 cbr 1000 ------- 0 0.0 4.0 63 63 - 0.063 0 2 cbr 1000 ------- 0 0.0 4.0 63 63 r 0.0692 0 2 cbr 1000 ------- 0 0.0 4.0 63 63 + 0.0692 2 3 cbr 1000 ------- 0 0.0 4.0 63 63 d 0.0692 2 3 cbr 1000 ------- 0 0.0 4.0 63 63 Observe packet(ID=63)by (% awk ‘$12==63’ out.tr) ※In experiment 1-1-(b), bandwidth is 4Mbps

  7. Experiment 2 • Consider following relationship • Sending traffic rate • Bandwidth of bottleneck link • Queue length • Number of bytes discarded from queue 0 4 CBR/UDP 40Mbps 40Mbps Queue Size: B 2 3 Bandwidth: Bw (Bottleneck link) 5 1

  8. 【Supplement】 Execution of Experiment 2 % ns problem2.tcl 1.0Mb32 • out.tr out.nam out.queue out.udp are created % gnuplot gnuplot> l “problem2.gp” gnuplot> … gnuplot> set term post color gnuplot> set output “graph.ps” gnuplot> rep gnuplot> q • If you don’t like the format, you can modify kadai1-2.gp (Bw) (B)

  9. 【Supplement】 out.queue content • out.queue (Trace file of queue) • $1 : time • $2, $3 : position of queue(link) • $4 : accumulated data in queue (queue length) [bytes] • $5 : accumulated packet number in queue [packets] • $6 : number of packets arrived to queue [packets] • $7 : number of packets sent out from queue [packets] • $8 : number of packets dropped by queue [packets] • $9 : amount of data arrived to queue [bytes] • $10 : amount of data send out from queue [bytes] • $11 : amount of data dropped by queue [bytes] ※ $5~$11 is cumulative value from start of simulation

  10. 【 Supplement 】 out.udp content • out.udp (Trace file of UDP) • $1 : time • $2 : send traffic rate [Mbps] • $3 : bandwidth of bottleneck link [Mbps]

  11. Example of graph(attention point) 31 ※In experiment 2 when Bw is 1.0Mbps and B is 32kbytes

More Related