How Frts Works - HP FlexNetwork MSR Series Configuration Manuals

64 kbps when no congestion occurs. Even if congestion occurs in the network, Router B can still
transmit packets at the rate of 32 kbps.
Figure 36 FRTS implementation
Router B
DTE
FRTS uses the parameters CIR ALLOW, CIR, CBS, and EBS for traffic shaping. FR PVCs can
transmit packets at the rate of CIR ALLOW when no congestion occurs. In the case of bursty
packets, FRTS allows an FR PVC to transmit packets at a rate exceeding the CIR ALLOW.
When congestion occurs, the DCE sends FR packets with the BECN bit set to 1 to the DTE. Then,
the DTE reduces its transmission rate from CIR ALLOW to CIR. If the DTE does not receive an FR
packet with the BECN bit set to 1 within 125 milliseconds, it increases its transmission rate back to
CIR ALLOW.

How FRTS works

FRTS is implemented by using token buckets. The meanings of the related parameters in the
protocol are modified as required by the actual algorithm and principles.
token bucket works.
Figure 37 How a token bucket works
Packets to be sent
through this interface
Classification
In the token bucket method, packets requiring traffic control are processed in the token bucket as
follows before transmission:
•
If the token bucket has enough tokens (in bits) for sending these packets, the packets are
allowed to pass.
•
If the token bucket does not have enough tokens for sending these packets, these packets are
put into the FR class queue.
•
Once the token bucket has enough tokens, the packets are taken out of the FR class queue for
transmission.
In this way, you can control the rate of a class of packets. .
The FR protocol-provisioned parameters correspond to the FRTS parameters as follows:
•
The sum of CBS and EBS equals the token bucket size.
•
The CIR ALLOW defines the number of tokens put into the token bucket per second.
Data flow direction
128 kbps
Ser2/1/1
Frame Relay
network
CIR ALLOW = 64 kbps
CIR = 32 kbps
Tokens are put
into the bucket at
the set rate
FRTS queue
64 kbps
Ser2/1/1
Tokens
Packets sent
Token bucket
125
Router A
DTE
Figure 37 shows how a