D-Link DFL-1600 User Manual page 271

23.2. Pipes
separate bandwidth limits may be specified for each of the 4 precedences
with a unit of "kilobits per second". Traffic that exceeds the limit of a
higher precedence will automatically be transferred into the "Low" level for
best effort delivery, as long as there is room in this precedence.
1 byte
Version IP Header Length
Time-to-Live
In addition to the limit per precedence, a limit for the pipe as a whole may
also be specified. When the bandwidth utilization through the pipe reaches
the total limit, traffic will be prioritized depending on what precedence it
belongs to. Higher precedences have a greater chance of making it through
the pipe without queuing.
1. Set a total limit
In order to know how much to limit lower-precedence traffic, the pipe
needs to know the overall capability.
2. Limits cannot be higher than the available connection
bandwidth
If the pipe limits are set higher than the actual available bandwidth,
the pipe will never know that the connection is full, and hence be
unable to throttle the lower-precedence traffic.
3. Bandwidth cannot be guaranteed if available bandwidth is
not known at all times
Identification
Protocol
Source Address
Destination Address
Options(padding)
Data
Table 23.1: IPv4 Packet Format
Note
D-Link Firewalls User's Guide
1 byte
Flags Fragment Offset
Header Checksum
251
2 bytes
Total Length