CAPWAP Issues: QoS

1
CAPWAP Issues QoS

• Mahalingam Mani
• IETF 676 Nov 2006, San Diego

2
QoS Issues Outline

• Besides the list of issues 196, 212 214
  (discussed subsequent slides) which are primarily
  related to control, configuration (and text
  clarification) of QoS policies and parameters
  related to STA-WTP mobile traffic we have
• The issue (not on tracker?) related to
• Should QoS enforcement be extended to WTP-AC data
  traffic path DTLS encrypted or not?
• The question (of applying a QoS priority to) to
  control path as well.
• Discussion
• 2.1.1 specifies QoS division of labor as follows,
  in split-MAC
• Classifying _at_ AC
• scheduling _at_ WTP/AC
• Queuing _at_ WTP
• Are there any control message elements sensitive
  to ordering or latency
• Between themselves?
• Between themselves and data-frame dispatches?
• Regardless of both we have a replay-prevention
  problem to solve (Puneet et al)
• DTLS in the control path (when management frames
  to AC may have to be colored)
• DTLS in the data-path
• Intermediaries end up reordering packets by
  priority

3
Issue 196

• Issue
• IEEE 802.11 Update Mobile QoS. Is this for data
  traffic to the AC? If so, then why is this an
  802.11 message element
• Initial Response
• ltPRCgt Intended to be a way to push policies to
  the WTP to prioritize mobile traffic.
• further comment
• The question appears to wrongly map Update Mobile
  QoS command (which is intended to QoS
  parameters/config. for WTP-client traffic)
• Status Open as of -03
• Proposed resolution clarify the usage scope and
  close it as editorial fix schedule for -04?

4
Issue 212

• Issue
• Section 11.9.9 "If the QoS field is set," -
  which field gt (where) are you checking for the
  presence or absence of the QoS Field?
• Initial Response
• Another good catch of a change that is missing as
  a result of splitting up message elements.
• Status Open as of -03
• Followup
• This is 6.14 in the 11bindings draft now
• Proposed resolution
• Clarify the reference to QoS field in 6.14
• Suggested Text
• OLD If the QoS field is set, the WTP MUST
  observe and provide policing of the 802.11e
  priority tag to ensure that it does not exceed
  the value provided by the AC.
• NEW if the QoS field in the WLAN frame is set,
  the WTP must observe and provide policing of
  802.11e priority tag to ensure it conforms to the
  value as specified by AC through the IEEE 802.11
  Add WLAN ME (sec 6.1) (or as configured by
  default).

5
Issue 214

• Issue
• Should 802.1X frames be prioritized?
• Should 802.1X frames be sent with different QoS
  than regular 802.11 Data Frames? What is our QoS
  Philosophy for such control traffic?
• Initial Response
• One would think so, and we should possibly
  consider this.
• Status Open as of -03
• Proposed Resolution
• Discuss why we should prioritize 802.1X frames
  w.r.t. other traffic.
• What should the priority be, given that they are
  carried in the data-path?