ZyXEL SBG3300-N Series User Guide - Page 146
Token Bucket
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Chapter 9 Quality of Service (QoS) Table 53 Internal Layer2 and Layer3 QoS Mapping LAYER 2 LAYER 3 PRIORITY QUEUE 4 IEEE 802.1P USER PRIORITY (ETHERNET PRIORITY) 4 TOS (IP PRECEDENCE) 2 5 5 3 6 6 4 5 7 7 6 7 DSCP 010110 010100 010010 010000 011110 011100 011010 011000 100110 100100 100010 100000 101110 101000 110000 111000 IP PACKET LENGTH (BYTE)
Chapter 9 Quality of Service (QoS)
SBG3300-N Series User’s Guide
146
Token Bucket
The token bucket algorithm uses tokens in a bucket to control when traffic can be transmitted. The
bucket stores tokens, each of which represents one byte. The algorithm allows bursts of up to
b
bytes which is also the bucket size, so the bucket can hold up to
b
tokens. Tokens are generated
and added into the bucket at a constant rate. The following shows how tokens work with packets:
•
A packet can be transmitted if the number of tokens in the bucket is equal to or greater than the
size of the packet (in bytes).
•
After a packet is transmitted, a number of tokens corresponding to the packet size is removed
from the bucket.
•
If there are no tokens in the bucket, the Device stops transmitting until enough tokens are
generated.
•
If not enough tokens are available, the Device treats the packet in either one of the following
ways:
In traffic shaping:
•
Holds it in the queue until enough tokens are available in the bucket.
In traffic policing:
•
Drops it.
•
Transmits it but adds a DSCP mark. The Device may drop these marked packets if the network
is overloaded.
4
4
2
010110
010100
010010
010000
5
5
3
011110
011100
011010
011000
<250
6
6
4
100110
100100
100010
100000
5
101110
101000
7
7
6
110000
111000
7
Table 53
Internal Layer2 and Layer3 QoS Mapping
PRIORITY
QUEUE
LAYER 2
LAYER 3
IEEE 802.1P USER
PRIORITY
(ETHERNET
PRIORITY)
TOS (IP
PRECEDENCE)
DSCP
IP PACKET
LENGTH (BYTE)