1250AP's with 4400 Controllers - LWAPP WAN Bandwidth consumption

Unanswered Question
Nov 15th, 2007
User Badges:

Does anyone know and, preferably, have a link on how much bandwidth a Lightweight AP consumes when deployed across a WAN link? I know Cisco keeps saying no more then 8 across a WAN managed by a centralized controller, but I can't find anything specific. Thanks so much in advance.

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (1 ratings)
Loading.
bbxie Thu, 11/15/2007 - 18:20
User Badges:
  • Silver, 250 points or more

There's a lot of components in LWAPP packets which will vary according to different situation.check this for LWAPP detail: http://tools.ietf.org/html/draft-ohara-capwap-lwapp-02

actually, A discovery request packet is 97 bytes (including the 4 byte FCS),A discovery response packet is 106 bytes (including the 4 byte FCS), Packet sizes for the join request and response messages will vary based on the MTU supported by the transport(1596 or 1596+1500),The initial exchange between the AP and the WLC (ap-manager interface) is approximately 6,000 bytes and a one-time configuration change averages 360 bytes and involves 2 packets each from the AP and the

WLC's ap-manager interface.An RRM-related information exchange takes place once the AP has been provisioned. A typical exchange

between the AP and the WLC (ap-manager interface) is approximately 1400 bytes. In the event of an RRM-related configuration change, there is a four-packet exchange between the AP and the WLC's apmanager

interface. This exchange averages 375 bytes.The system heartbeat, coupled with fallback mechanism, is 4 packets every 30

seconds and comprises of the following packets:

LWAPP ECHO_REQUEST from AP (78 bytes)

LWAPP Echo-Response to AP (64 bytes)

LWAPP PRIMARY_DISCOVERY_REQ from AP (93 bytes)

LWAPP Primary Discovery-Response to AP (97 bytes).

There are two ongoing RRM exchanges. The first one, at every 60-second interval is the load and signal

measurement and consists of 4 packets. This exchange always adds up to 396 bytes, as following:

LWAPP RRM_DATA_REQ from AP (107 bytes)

LWAPP Airewave-Director-Data Response to AP (64 bytes)

LWAPP RRM_DATA_REQ from AP (161 bytes)

LWAPP Airewave-Director-Data Response to AP (64 bytes)

The second sequence of packets is the noise measurement (including a statistics information request and

response sequence) done every 180 seconds. This is a short (0.01 seconds typically) exchange of packets

and averages 2,660 bytes approximately. It consists of the following packets:

LWAPP RRM_DATA_REQ from AP

LWAPP Airewave-Director-Data Response to AP

LWAPP RRM_DATA_REQ from AP

LWAPP Airewave-Director-Data Response to AP

LWAPP RRM_DATA_REQ from AP

LWAPP Airewave-Director-Data Response to AP

LWAPP RRM_DATA_REQ from AP

LWAPP Airewave-Director-Data Response to AP

LWAPP STATISTICS_INFO from AP

LWAPP Statistics-Info Response to AP

LWAPP RRM_DATA_REQ from AP

LWAPP Airewave-Director-Data Response to AP

LWAPP RRM_DATA_REQ from AP

LWAPP Airewave-Director-Data Response to AP

LWAPP RRM_DATA_REQ from AP 00:14:1b:59:41:80

LWAPP Airewave-Director-Data Response to AP

LWAPP RRM_DATA_REQ from AP

LWAPP Airewave-Director-Data Response to AP

LWAPP STATISTICS_INFO from AP

LWAPP Statistics-Info Response to AP.

Rogue measurements are done as a part of the scanning mechanism (for more details, refer to the Auto RF

and Rogue Detection whitepapers) and included in the above RRM exchange every 180 seconds.

The LWAPP data frame header adds 6 bytes to the existing 802.11 packets.

Since LWAPP frames can be fragmented, a Fragment ID field is included and the total packet size can be

determined by adding the original frame and the IP Fragment that follows (It is important to note that the IP

Fragment that follows is not encapsulated in any LWAPP headers).

In conclusion, operation of LWAPP does not introduce heavy bandwidth requirements on the infrastructure and in most typical deployments, there would be no such need to add extra capacity to the infrastructure to accommodate Cisco's Unified Wireless Architecture.

Actions

This Discussion