Advanced QoS In BreezeACCESS
Ver 4.0 By using CIR/MIR
April 2002
Alvarion Ltd. BreezeCOM and Floware unite
21a HaBarzel St. Tel Aviv, 69710 Israel
Main Line / Fax: 972 3 645 6262 / 6222 www.alvarion.com
Advanced QoS In BreezeACCESS Ver 4.0
By using CIR/MIR
Introduction
Recent development in the Broadband Access market in general and in the Wireless Broadband Access
in particular, raises the need to allow the Service Provider to offer different kinds of Quality of Service
(QoS) to different end users. One QoS parameter is dedicating a bandwidth to an end user over the
shared broadband capacity. In this way the end user is assured that although he is connected to his
Service Provider while sharing the capacity with other users, he “owns” a dedicated bandwidth of his
own whenever he needs it and he is not depended on other end users use of bandwidth. Bandwidth that
is not in use in a specific moment can be offered to other end users on “Best Effort” basis for temporary
use of burst traffic, up to the limit of the available bandwidth or up to some other maximum limitation.
These QoS parameters are referred to as CIR (Committed Information Rate) and MIR (Maximum
Information Rate).
This ability of the Service Provider to sell different QoS to different end users by using CIR and MIR
helps to optimize his business case by allowing to differentiate services and prices to end users. Hence
addressing different market segments like residential, SOHO and medium enterprise by using the same
infrastructure.
Implementation in BreezeACCESS
When using CIR/MIR, each SU (Subscriber Unit) has four different configurable parameters: CIR and
MIR for uplink, and CIR and MIR for downlink. This allows the Service Provider to match the service
to each end user’s exact needs. The AU (Access Point) receives these parameters from all the SUs and
manages the uplink traffic in the entire sector by advertising the actual traffic demand, so the SU knows
if the uplink data rate can exceed the CIR value towards the MIR value by using a leaky bucket
mechanism.
In some business models, the Service Provider can choose to use “Over Subscription” (the total sum of
the configured parameters can exceed the total available capacity of the sector) by assuming that not all
the end users make use of all of their capacity to 100% of the time. In this case, there are two scenarios:
1. The actual momentary demand is less then the AU capacity – In this case each SU will get the
bandwidth it needs according the its CIR and additionally extra available bandwidth will allow
the SU to increase it’s bandwidth up to the MIR value.
2. The actual momentary demand is greater then the AU capacity (over demand) – In this case, the
AU will cause all SUs to decrease their traffic. This degradation will be maintained only for the
duration of the over demand.
Alvarion Ltd. BreezeCOM and Floware unite
21a HaBarzel St. Tel Aviv, 69710 Israel
Main Line / Fax: 972 3 645 6262 / 6222 www.alvarion.com
Advanced Implementation of CIR/MIR in Ver-4.0
•
•
•
Improved MMI
o A new parameter, ‘CIR/MIR Enable’ was added to the AU. This parameter will cause the
AU to support the CIR/MIR mechanism for all the SUs it serves, regardless of the
enable/disable parameter in the SU. This new parameter comes to prevent the situation
that not all the SUs are configured in the same way (all using CIR/MIR or all not using
CIR/MIR) causing the QoS mechanism to miss-behave and simplifies the system
configuration to the administrator.
Performance improvements
o The CIR/MIR implementation in the AU was enhanced in order to optimize performance
in a sector with a large number of SUs.
o Dynamic allocation of the buffers on the AU. The buffers are allocated for downstream
data to the SU according to the sector real traffic. In this way if a SU is not receiving data
its buffers will be freed so other SUs that need more burst bandwidth than their CIR will
get extra bandwidth, up to the MIR. This mechanism was developed to take advantage of
the burst-based nature of IP traffic, creating very dynamic bandwidth allocation for the
SU that matches the actual momentary need of the IP traffic of the SU. This allows each
SU to get burst rates up to the full capacity of the sector.
Graceful degradation – on the rare occasions when over demand appears in a sector, the
transmission rate of all the SUs will be lowered at the same percentage, allowing the unit with
higher CIR value to get more bandwidth than an SU with a lower CIR value, but still allowing
the SU with lower CIR value to get bandwidth.
Alvarion Ltd. BreezeCOM and Floware unite
21a HaBarzel St. Tel Aviv, 69710 Israel
Main Line / Fax: 972 3 645 6262 / 6222 www.alvarion.com
Example of a sector with 3 SUs with no over demand traffic so each SU can transmit the traffic
generated by the computer at the same rate as it is generated.
SU1 CIR
SU1 MIR
SU1 Actual
CIR 64kbps
SU2 CIR
SU2 MIR
SU2 Actual
CIR 512kbps
Total CIR
Actual total
MIR
Total require
Actual total
SU3 CIR
SU3 MIR
SU3 Actual
CIR 512kbps
Figure 1: One sector with no “over demand”
Alvarion Ltd. BreezeCOM and Floware unite
21a HaBarzel St. Tel Aviv, 69710 Israel
Main Line / Fax: 972 3 645 6262 / 6222 www.alvarion.com
Not all
CIR is
needed
Example of a sector with 3 SUs with over demand traffic so each SU transmits the traffic generated
by the computer at a slower rate than it is generated, yet SUs with higher CIR get more capacity then
SUs with low CIR.
SU1 CIR
SU1 MIR
SU1 required
SU1 actual
CIR 64kbps
SU2 CIR
SU2 MIR
SU2 required
SU2 actual
CIR 512kbps
Total CIR
Actual total
MIR
Total required
SU3 CIR
actual total
SU3 MIR
SU3 required
SU3 actual
CIR 512kbps
Figure 1: One sector with “over demand”
Alvarion Ltd. BreezeCOM and Floware unite
21a HaBarzel St. Tel Aviv, 69710 Israel
Main Line / Fax: 972 3 645 6262 / 6222 www.alvarion.com
Not all
CIR is
needed