FRAME-RELAY TRAFFIC SHAPING

Frame Relay Traffic Shaping

• Allows shaping at PVC level so gets around issue on main interface of dlci eating the bandwidth
• BECN is sent to source to indicate conjestion on the link to slow down transmission rate on reciept of BECN a source will cut it transmission rate down by 3/4
• We can configure on the source  the min-rate command this basically saying we will drop our rate but we will not go below a certain threshold so you might set it to your CIR which is your guranteed amount
• Becn are set by sp routers in the frame-relay header on return traffic to the source
• Issue if the the traffic is unidirectional i.e no reply traffic in this case we use a FECN a fecn is sent to the destination on receipt the destination will create a small qos test frame back to the source so the sp router can mark with becn bit informing source of conjestion
• We can mark frame relay packets as Discard Elegible outbound. This is to say to the service provider if you are experiencing and im over my CIR drop these packets first so we could say drop our non critical tcp traffic which we will know can re trainsmit
• Frame relay provider tend to give a CIR which is guaranteed rate and PIR which is the best effort rate so you can go above your CIR but the traffic is not guaranteed delivery if the sp is experiencing conjestion
• What we tend to do is to shape critical traffic to the CIR and non critical tcp drop capable traffic to the PIR
• We configure frame-relay shaping with the map class command
• There is two ways of configuring shaping in frame-relay either by mqc newer or legacy map class method

Commands

policy-map SHAPE
class TCPTRAFFIC
shape peak 512000
shape adapative 256000 - this is setting the router to accept becn but the min rate set to 256000
set fr-de
Class CriticalTRAFFIC
shape average 256000


To set a router to generate BECN on receipt of fecn from sp

frame-relay fecn-adapt
OK there is two ways of configuring shaping on the command line we have the option the legacy
frame relay or the newer mqc approach.

LAB
----

For the LAB r5 is main point frame relay interface with links to r1 r2 r3 r4
we will configure the modular or new frame-relay shaping on this link. Also we will mark
certain traffic as discard elegible and enable becn and fecn notifications. Then r2 we will
configure the legacy way of doing frame relay traffic shaping

R5
---
Only the class default is support on the pervc shape
Define the policy-map SHAPE
r5(config)#policy-map SHAPE
r5(config-pmap)#class class-default
r5(config-pmap-c)#shape peak 512000
r5(config-pmap-c)#shape adaptive 256000
r5(config-pmap-c)#set fr-de
r5(config-pmap-c)#
So we are shaping to 512000 PIR we will react to becn but we will not drop below minrate of 256000
we are also setting our traffic on this vc as discard elegible

Now we define a map class for applying to DLCI502
r5(config)#map-class frame-relay DLCI502
r5(config-map-class)#service-policy out SHAPE
r5(config-map-class)#

so this is being applied to the vc 502 only
r5(config)#int s0/0/0
r5(config-if)#frame-relay interface-dlci 502
r5(config-fr-dlci)#class DLCI502
r5(config-fr-dlci)#
this is being applied to the vc 503 only
r5(config)#map-class frame-relay DLCI503
r5(config-map-class)#service-policy out SHAPE
r5(config-map-class)#exit
r5(config)#int s0/0/0
r5(config-if)#frame-relay interface-dlci 503
r5(config-fr-dlci)#class DLCI503
r5(config-fr-dlci)#

r5#sh policy-map int s0/0/0
 Serial0/0/0: DLCI 503 -
  Service-policy output: SHAPE
    Class-map: class-default (match-any)
      10 packets, 530 bytes
      5 minute offered rate 0 bps, drop rate 0 bps
      Match: any
      Traffic Shaping
           Target/Average   Byte   Sustain   Excess    Interval  Increment
             Rate           Limit  bits/int  bits/int  (ms)      (bytes)
          1024000/512000    3200   12800     12800     25        3200
        Adapt  Queue     Packets   Bytes     Packets   Bytes     Shaping
        Active Depth                         Delayed   Delayed   Active
        BECN   0         10        530       0         0         no
      QoS Set
        fr-de
          Packets marked 10

R2
---

Legacy Frame-relay
we define the map class with cir
r2(config)#map-class frame-relay DLCI205
r2(config-map-class)#frame-relay cir 512000
r2(config-map-class)#frame-relay fecn-adapt - if it recieves a fecn it will gnerate a qos test frame to sender

r2(config)#int s0/0
r2(config-if)#frame-relay interface-dlci 205
r2(config-fr-dlci)#class DLCI205
r2(config-fr-dlci)#

it is a similar sort of config except you do not use the policy-map initial which gives you more options