ZyXEL VMG4380 User Guide - Page 176
Token Bucket, Single Rate Three Color Marker
![]() |
View all ZyXEL VMG4380 manuals
Add to My Manuals
Save this manual to your list of manuals |
Page 176 highlights
Chapter 10 Quality of Service (QoS) Table 53 Internal Layer2 and Layer3 QoS Mapping LAYER 2 LAYER 3 PRIORITY QUEUE 6 IEEE 802.1P USER PRIORITY (ETHERNET PRIORITY) 6 TOS (IP PRECEDENCE) 4 5 7 7 6 7 DSCP 100110 100100 100010 100000 101110 101000 110000 111000 IP PACKET LENGTH (BYTE) 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. Configure the bucket size to be equal to or less than the amount of the bandwidth that the interface can support. It does not help if you set it to a bucket size over the interface's capability. The smaller the bucket size, the lower the data transmission rate and that may cause outgoing packets to be dropped. A larger transmission rate requires a big bucket size. For example, use a bucket size of 10 kbytes to get the transmission rate up to 10 Mbps. Single Rate Three Color Marker The Single Rate Three Color Marker (srTCM, defined in RFC 2697) is a type of traffic policing that identifies packets by comparing them to one user-defined rate, the Committed Information Rate (CIR), and two burst sizes: the Committed Burst Size (CBS) and Excess Burst Size (EBS). 176 VMG4380-B10A / VMG4325-B10A User's Guide
![](/manual_guide/products/zyxel-vmg4380-user-guide-04fa459/176.png)