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S6C8 – Frame-Relay Traffic

S6C8 – Frame-Relay Traffic. Controlling Frame-Relay Taffic. Packet Switched Networks. Use Frame-Relay Switches Curriculum emulates with Router programmed to act like a switch Switches can drop traffic Switches can prioritize traffic

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S6C8 – Frame-Relay Traffic

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  1. S6C8 – Frame-Relay Traffic Controlling Frame-Relay Taffic

  2. Packet Switched Networks • Use Frame-Relay Switches • Curriculum emulates with Router programmed to act like a switch • Switches can drop traffic • Switches can prioritize traffic • Can control, or "shape", traffic so that certain protocols and VCs conform to specified transmission rates. • Switches can control flow of traffic • Keeps high bandwidth switch from overpowering a slow router • Can provide multiple levels of bandwidth and service

  3. Traffic Shaping Terminology • Local Access Rate - clock speed (port speed) of the connection (local loop) to the Frame-Relay cloud. • Committed Information Rate – bps rate which the Frame Relay switch agrees to transfer data. • Over-subscription - sum of the CIRs on all the VCs exceeds the access line speed • Committed Burst -- maximum number of bits that the switch agrees to transfer during any Tc =Bc/CIR

  4. Traffic Shaping Terminology 2 • Excess Burst (Be) - maximum number of uncommitted bits that the Frame Relay switch attempts to transfer beyond the CIR • Excess Information Rate (EIR) - maximum bandwidth available to the customer Be+CIR • Forward Explicit Congestion Notification (FECN) - switch recognizes congestion in the network and sends an FECN packet to destination device to note congestion has occurred. • Backward Explicit Congestion Notification (BECN) - switch recognizes congestion in the network, sends BECN packet to the source router to reduce the rate at which it is sending packets. • Discard Eligibility (DE) bit – marks packet for possible drop if line is congested

  5. Rate Determination Factors • Capacity of the local loop • speed of the local loop is called the local access rate • CIR – higher rates require more money • if a customer's CIR is less than the local access rate, the customer and provider agree on whether bursting above the CIR is allowed • CIR can be 0 – recommended you monitor closely • Provider does not guarantee burst traffic will be delivered • DE bit identifies which frames will be discarded

  6. Traffic Shaping • Rate enforcement on a per-virtual-circuit basis - configure a peak rate to limit outbound traffic to CIR, EIR or some other defined value • Generalized BECN support on a per-VC basis -The router monitors BECNs and throttle traffic based on packet feedback • Priority/Custom/Weighted Fair Queuing (PQ/CQ/ WFQ) support at the VC level - allows for finer granularity in the prioritization and queuing of traffic, gives more control on an individual VC.

  7. Use Traffic Shaping • Topology consists of a high-speed (T1 line speed or greater) connection at central site and low-speed (56 kbps or less) at branch • Rate enforcement can also be used in conjunction with dlci • Network constructed with many VCs to different locations on a single physical line into the network • can pre-allocate the bandwidth that each VC receives on the physical line • Different types of traffic (IP, Systems Network Architecture [SNA], or Internetwork packet Exchange [IPX]) to transmit on the same Frame Relay VC • Prior to Cisco IOS Release 11.2, Custom Queuing was defined only at the interface level. Now it can be defined at the VC level

  8. Configuring Traffic Shaping • Specify a map class. • map-class frame-relay map-class-name • Configure the map class. • Define the average and peak rates • Specify that the router dynamically fluctuates the rate at which it sends packets • Enable Frame Relay on an interface • Enable Frame Relay traffic shaping on interface. • frame-relay traffic-shaping • Add the map class to VCs on the interface • Router(config-if)#frame-relay class map-class-name

  9. Rate Enforcement • Define a map class • Router(config)#map-class frame-relay map-class-name • Define the rate enforcement parameters • Router(config-map-class)#frame-relay traffic-rate average [peak] • Enable both traffic shaping and per-VC queuing for all VCs • Router(config-if)#frame-relay Traffic-shaping • Associate a map class with an interface • Router(config-if)#frame-relay class name

  10. Traffic Shaping - Dynamic • Perform the following steps to configure traffic • Shaping-over-Frame Relay BECN support: • define a map class and enter map class configuration mode • use the following command to enable BECN support: • Router(config-map-class)#frame-relay adaptive-shaping becn

  11. Dynamic Shaping - 2 • Enable both traffic shaping and per-VC queuing for all VCs • Router(config-if)#frame-relay traffic-shaping • Associate a map class with an interface or subinterface • Router(config-if)#frame-relay class name

  12. Queuing • Queue lists prioritize traffic based on protocol type • Queue lists can even prioritize traffic based on the source and/or destination address • Configure the router to prioritize certain traffic over other traffic • Packets cut in front of the line • delay-sensitive application traffic, such as voice or Telnet, will be as unaffected as possible by the shaping process • Add Frame Relay map class to a VC, and you can specify different peak and average rates on a per-VC basis

  13. Traffic Mapping Show Commands • show frame-relay pvc dlci • show traffic-shape • show traffic-shape statistics

  14. ODR • Is not a true routing protocol • Presents a more scalable solution than static routes • Transport mechanism for ODR routes is the Cisco Discovery Protocol (CDP) • CDP runs on any media that supports the Subnetwork Access Protocol (SNAP) • Hub router can automatically discover stub networks while the stub routers still use a default route to the hub • network portion does not have to be strictly classful. • VLSM is supported

  15. Configuring ODR • ODR is enabled with a single command, router odr • Turn off any dynamic routing protocols in the spoke routers. • ODR and a dynamic routing protocol can be run on a hub router • RTA(config)#router odr • RTA(config)#router ospf 1 • RTA(config-router)#redistribute • odr metric 100 subnets • RTA(config-router)#network • 10.2.0.0 0.0.255.255 area 1

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