ATL Telecom R1-SW Ethernet Switch - Manual (Page 176)

R1-SW24L2B User’s Manual
9-8
If tokens are full in the token bucket, no token is provided. When packets are received, the same
amount of token are removed. If the number of tokens is less than size of a packet, the packet is
specified as non-conforming packet. And, if the number of tokens is more than size of a packet
or is the same as the size of packet, the packet is specified as conforming packet. The packet
specified as non-conforming packet is processed by QoS profile of the packet.
There are two method of token bucket - single token bucket, dual token bucket. Single token
method uses only one bucket, and dual token method uses two bucket.
In dual token bucket method (RFC 2698 tr-TCM algorithm), the first bucket receives tokens at PIR
rate and the second bucket receives tokens at CIR rate. The first bucket size also is PBS and the
second bucket size is CIR. A packet that is specified as non-conforming in the first bucket finally
becomes the non-conforming packet. If a packet that is specified as conforming in the first bucket
becomes non-conforming in the second bucket, the packet is specified as loosely non-conforming
packet.
Dual token bucket method can control the packet with detailed classification above.
The following graph shows the dual token bucket method.
Bucket Size
= PBS
Token Rate
= PIR
Bucket Size
= CBS
Token Rate
= CIR P