Amer Networks E5Web GUI - Manual (Page 672)

• Set the pipe limit, as usual, to be 400 Kbps.
• Set the Grouping option for the pipe to have the value Destination IP.
• Set the total for the pipe's Group Limits to be 100 Kbps.
Bandwidth is now allocated on a "first come, first forwarded" basis but no single destination IP
address can ever take more than 100Kbps. No matter how many connections are involved the
combined total bandwidth can still not exceed the pipe limit of 400 Kbps.
Combining Pipe and Group Limit Precedence Values
Let us suppose that grouping is enabled by one of the options such as source IP and some values
for precedences have been specified under Group Limits. How does these combine with values
specified for the corresponding precedences in Pipe Limits?
In this case, the Group Limits precedence value is a guarantee and the Pipe Limits value for the
same precedence is a limit. For example, if traffic is being grouped by source IP and the Group
Limits precedence 5 value is 5 Kbps and the Pipe Limits precedence 5 value is 20 Kbps, then
after the fourth unique source IP (4 x 5 = 20 Kbps) the precedence limit is reached and the
guarantees may no longer be met.
Dynamic Balancing
Instead of specifying a total for Group Limits, the alternative is to enable the Dynamic Balancing
option. This ensures that the available bandwidth is divided equally between all addresses
regardless of how many there are. This is done up to the limit of the pipe.
If a total group limit of 100 Kbps is also specified with dynamic balancing, then this still means
that no single user may take more than that amount of bandwidth.
Precedences and Dynamic Balancing
As discussed, in addition to specifying a total limit for a grouping, limits can be specified for each
precedence within a grouping. If we specify a precedence 2 grouping limit of 30 Kbps then this
means that users assigned a precedence of 2 by a pipe rule will be guaranteed 30 Kbps no matter
how many users are using the pipe. Just as with normal pipe precedences, traffic in excess of 30
Kbps for users at precedence 2 is moved down to the best effort precedence.
Continuing with the previous example, we could limit how much guaranteed bandwidth each
inside user gets for inbound SSH traffic. This prevents a single user from using up all available
high-priority bandwidth.
First we group the users of the ssh-in pipe so limits will apply to each user on the internal
network. Since the packets are inbound, we select the grouping for the ssh-in pipe to be
Destination IP.
Now specify per-user limits by setting the precedence 2 limit to 16 Kbps per user. This means
that each user will get no more than a 16 Kbps guarantee for their SSH traffic. If desired, we could
also limit the group total bandwidth for each user to some value, such as 40 Kbps.
There will be a problem if there are more than 5 users utilizing SSH simultaneously: 16 Kbps
times 5 is more than 64 Kbps. The total limit for the pipe will still be in effect, and each user will
have to compete for the available precedence 2 bandwidth the same way they have to compete
for the lowest precedence bandwidth. Some users will still get their 16 Kbps, some will not.
Dynamic balancing can be enabled to improve this situation by making sure all of the 5 users get
the same amount of limited bandwidth. When the 5th user begins to generate SSH traffic,
Chapter 10: Traffic Management
672