10-11 Generic Traffic Shaping (GTS) | Cisco Field Manual[c] Router Configuration

GTS buffers outbound traffic and then transmits it in a regulated fashion, within the bandwidth constraints of a network.
GTS tends to prevent the effects of traffic surges or bursts from propagating through a network.
GTS can be used to match the transmission rate to a remote device with a differing access rate.

NOTE

GTS can be used on a Frame Relay interface to shape traffic for all VCs on an interface or subinterface. To shape traffic on a per-DLCI basis, you can configure one DLCI per subinterface and use GTS, or you can use Frame Relay Traffic Shaping (FRTS). See Section 10-12 for more information.

Configuration

Enable GTS for outbound traffic on an interface:
```
 (interface)  traffic-shape  {  rate   group   access-list  }  bit-rate  [  burst-size  [  excess-burst-size  ]] 
```
Outbound traffic is held to the bit-rate (bits per second), with an allowed burst-size (in bits) of traffic over the bit-rate within a time interval. An excess-burst-size (in bits) can also be specified to allow an amount of traffic over the burst size in an interval. The time interval is burst-size / bit-rate (if burst-size > 0) or excess-burst-size / bit-rate (if burst-size = 0).

If the rate keyword is used, all outbound traffic is shaped. Otherwise, the group keyword can be used to shape only traffic matched by the access-list (any access list numbered 1 to 2699).

For Frame Relay, the bit-rate corresponds to the Committed Information Rate (CIR) that is contracted with the service provider. In addition, burst-size corresponds to the Bc parameter, and excess-burst-size corresponds to the Be parameter.
(Optional) Use GTS for Frame Relay.
1. Adjust the bandwidth when BECNs are received:
```
 (interface)  traffic-shape adaptive   bit-rate  
```
  When BECN signaling is received from the Frame Relay switch, indicating switch congestion, GTS uses the bit-rate (bits per second; the default is 0) as the lower bandwidth limit. Traffic is then shaped to within this lower bit-rate and the normal committed bit rate.
2. Respond to FECNs:
```
 (interface)  traffic-shape fecn-adapt  
```
  The router reflects any FECNs received from the Frame Relay switch in the reverse direction as BECNs. This informs the far-end router of a congestion situation and tells it that the local router is adapting its traffic shaping. If used, the fecn-adapt keyword should be configured on both ends of a Frame Relay VC so that both routers can inform each other of changes in traffic shaping.

Generic Traffic Shaping Example

GTS is configured on interface serial 2/4 to shape traffic to a 128 kbps rate. The traffic is allowed to burst 16 kb over the normal rate. Serial interface 2/5 uses GTS to shape SMTP traffic to host 10.5.17.10 to within 64 kbps. All other traffic on the interface is shaped to 128 kbps.

Interface serial 2/6 is one end of a Frame Relay PVC. The PVC has a CIR of 128 kbps but is allowed to burst to 256000. If congestion is signaled by a BECN, GTS shapes the outbound traffic to within 128 kbps and 256 kbps. FECNs is reflected as BECNs.

  interface serial 2/4   traffic-shape rate 128000 16000 16000   access-list 101 permit tcp any host 10.5.17.10 eq smtp   access-list 102 permit ip any any   interface serial 2/5   traffic-shape group 101 64000   traffic-shape group 102 128000   interface 2/6   encapsulation frame-relay   traffic-shape rate 256000   traffic-shape adaptive 128000   traffic-shape fecn-adapt