C-M-G
Series
Manual
© TDT GmbH
Chapter 5: Network Configuration
Seite 76 von 136
5.13 Postfix Configuration (M3000, G5000 only)
Postfix is an open source Mail Transfer Agent. This service is only included in M- and G-Series devices.
Please load the description from the official Postfix website under
5.14 QoS Control
Using Quality of Service (QoS) it is possible, to regulate the available bandwith of a connection and for
example to distribute it across different ports or IPs.
During a normal internet connection via modem each packet is stored sequentially in the so-called packet
queue. The size of the packet queue exceeds the bandwith of the internet connection. All stored packets
are processed sequentially. Likewise, QoS only administers a packet queue within a router. Thereby you
have the possibility, using the QoS rules, to decide which packets have priority and which ones must wait.
If these rules are correctly configured, the router sends the packets from its packetqueue to the modem at
such a speed, that they don’t have to wait in line of the modem’s packetqueue. In this case, it is as if the
queue has been fetched from the modem to the router.
5.14.1 Outgoing Interfaces
5.14.1.1 Interface parameters
Command
Description
Interface
Selects the incoming interfaces
Enable Interface
Interface will be activated/deactivated
5.14.1.2 Root Qdisc Parameters
Note
All QoS rules will be carried out as user
root
.
5.14.1.2.1 TBF (Token Bucket Filter)
Because of this functionality, there are three scenarios:
If the network packets for retransmission arrive at the same rate as the TBF can create new
tokens, the Qdisc can immediately transmit them.
If the network packets arrive at a faster rate, then they must wait until enough tokens are
available. This reduces the transmission rate to the token rate.
If the packets arrive at the TBF with a lower rate or no packets arrive at all, the surplus tokens
trickle back into the bucket. If it is at any time full, all following tokens flow into an electronic gully.
When packets come again with a high rate, they use the collected tokens. This means that the
Qdisc is permitted to send a higher rate as the TBF is really allowed. This excess rate is called
burst.
Command
Description
Rate
(kbit/s)
Gives the maximum delay, which the packets are delayed
(resident in the queue)
