Bandwidth Allocation - Sagem -LINK F Installation And Operation Manual

SAGEM-LINK F
Installation and Operation Manual
6.3.2 – Bandwidth Allocation
The Bandwidth Allocation is built upon bridge application. The filtering engine can be turned on or off
as required.
Frames received by the Bandwidth Allocator are placed in the appropriate queue :
•
Frames from a source MAC address/VLAN ID that has already been assigned a Private Queue
are stored in that queue until transmitted.
• Frame from a MAC source address/VLAN ID that has not yet been assigned a Private Queue
are stored in the Public Queue until transmitted. If a Private Queue is available, it is assigned to
that Source Address/VLAN ID so that the next time such a frame arrives it will be stored in this
private queue.
Frames in the Private and Public queues are transmitted using the Deficit Round Robin algorithm. This
ensures that each queue receives its fair share (i.e. all active devices receive an equal share) of the
overall bandwidth.
When more than 15 network devices or 15 VLAN IDs are actively transmitting to the service network,
frames from Source Address/VLAN IDs without a designated Private Queue are serviced by the Public
Queue. Thus the 16th, 17th, 18th, ... devices/VLANs all share the Public Queue on a "Best Effort"
basis.
In most cases, LAN bandwidth should
limitation). There is a bottleneck in the LAN to WAN direction.
The SAGEM-LINK F Ethernet option can be configured to allocate bandwidth according to IEEE
802.1Q (without prioritization).
When an Ethernet frame has come from a VLAN, it is recognized by the presence of "0x8100" in the
frame Tag Protocol Identifier field. When processing VLAN frames only the VLAN ID is used, the User
Priority field is ignored.
The system can support up to 1024 VLAN IDs.
6.3.2.1 - Learning process :
The SAGEM-LINK F is able to allocate bandwidth fairly by routing outgoing traffic through a set of
queues and scheduling the release of frames, from each queue, in an equal and fair manner. To do
this the Bandwidth Allocator (BA) must know which network devices on the Subscriber Network are
communicating with the Service Network and it must assign queues to those network devices. A
record of current queue assignments is maintained in a table. The BA Table is created and maintained
in the following way :
1. When a frame arrives at the Bandwidth Allocator, its Source Address /VLAN ID is compared to
the entries in the BA Table.
2a. If a Private Queue has already been assigned to the Source Address /VLAN ID then no
learning is necessary.
2b. If a Private Queue has not yet been assigned to the Source Address /VLAN ID, and one is
available, then a Private Queue is designated for that Source Address /VLAN ID.
2c. If a Private Queue has not been assigned to the Source Address /VLAN ID, and none are
available, then it is assigned the Public Queue.
6.3.2.2 - Bandwidth Allocation Application Queues
Frames forwarded in either direction, are queued while awaiting transmission. The system maintains
15 Private Queues, a Public Queue, and a Subscriber Queue. Private Queues are used to guarantee
a minimum and equal share of the available network bandwidth for up to 15 network devices or
VLANs.
The Public Queue is used to "absorb" the overflow when no Private Queues are available.
Upon startup the 15 Private Queues are assigned to MACs/VLANs flows on a first-come, first-serve
basis. Inactive Private Queues are quickly timed-out and recovered for use by network devices or
VLANs that communicate with the Service Network. Once the system has learned which devices
Reproduction and communication prohibited without the written permission of Sagem Communication
be higher than WAN bandwidth (radio link bandwidth
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Issue 04 : July 2005