qos design and deployment ford2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/brkrst-2515.pdf · qos...
TRANSCRIPT
QoS Design and Deployment for Wireless LANs
BRKRST-2515
Robert Barton, P.Eng
Systems Engineer
CCIE #6660
CCDE #2013::6
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Presentation Source Material
• End-to-End QoS Network Design, 2nd Edition
• First Edition is a top selling Cisco Press book, but . . .
– It was time for a 2nd edition!
• Book is organized around PINs (Places in the Network), e.g. Data Center, WAN, Wireless LANs, VPN, Campus
• Content in this session primarily based on the “WLAN QoS Design” section
3
Now Available!
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Agenda
• Wireless QoS Building Blocks
• IEEE 802.11e and Wireless Multimedia (WMM)
• WLAN QoS Tools And Considerations
• Cisco WLC QoS Design Strategies
• Developing A Unified QoS Strategy For The WLAN
• Wrap-up
4
Wireless QoS Building Blocks
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Comparing Wired and Wireless QoS
• Wired environments are Full Duplex, Wireless is Half Duplex
– Half duplex environments are very susceptible to collisions
• Thus, wired QoS is mostly concerned with managing packet loss due to congestion problems (solved with queuing, etc.)
6
Wireless QoS is focused on a much bigger problem:
1. WLAN QoS is mostly concerned with reducing the probability of a collision for high-priority traffic, based on it’s QoS classification
2. Managing congestion is a secondary concern
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Will the Half-Duplex Problem Ever Get Solved?
• IEEE 802.11 High Efficiency WLAN (HEW) Study Group
– As a follow-on to 802.11n/ac, the HEW SG is trying to define the next generation of Wi-Fi
– Full Duplex wireless communication is being discussed
• HEW Task Group is expected to start work this summer
– Don’t expect Full-Duplex Wi-Fi any time soon!
7
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Carrier Sense Multiple Access / Collision Avoidance
• Wired Hubs use CSMA/CD (collision detection)
– A transmitting station will first listen to the medium to see if it is idle before sending it’s frame. When it seems idle, it sends the frame.
– After sending, it listens to see if a collision occurred (the wired link is a closed system)
8
• 802.11 networks use CSMA/CA (collision avoidance)
– Wireless networks have no way to detect that a collision even occurred!
– CSMA/CA accepts collisions will occur, but has a system for dealing with them once they do.
– Hint: what do you do on a conference call when more than one person speaks at the same time?
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Who Gets the Higher Transmission Priority?
9
1. Access Point
2. Wireless Client
3. They all get equal access
Other channel access models have been proposed. These models allow the AP to organizes channel access in a structured way, but these have never been widely adopted
1. Legacy Point Coordination Function (PCF)
2. 802.11e Hybrid Controlled Channel Access (HCCA)
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
The Distributed Coordination Function (DCF) Algorithm for Media Access
1. Listen first to see if any other transmissions are in progress (i.e. the medium is idle)
2. After the channel is idle, pause for a set period of time (known as the DIFS)
3. Send the frame
4. If a collision occurs (because the medium was busy and an ACK wasn’t received), wait until the medium becomes idle before doing anything else
5. Wait another DIFS period
6. Generate a random number, called the Contention Window (CW) and count it down, then try transmitting again
10
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
2 Types of Timers: DIFS and Contention Windows
• When ready to transmit, all stations must first wait the DCF Interframe space (DIFS)
– This is a pre-established wait time observed by all stations (all wait the same DIFS period)
• Once DIFS has expired, a random countdown timer, called the Contention Window (CWmin) begins
– Once CWmin expires, the station sends the frame
– If a collision occurrs (because an ACK wasn’t received), double the first CW up to a value of CWmax until the frame can be sent
11
Random Contention Window (CW)
Time (t)
Medium is Busy
Begin Transmission
DIFS ……….
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
No
12
The DCF Decision Process
Yes
No
Done
Decrement the CW value to zero. If another station begins to
transmit, defer until it is done, then wait another DIFS period before
counting down the CW
Was an ACK received? (i.e.
confirm there was no collision)
Double the previous CW value up to a maximum of
CWmax
Generate a random backoff value between 0
and CWmin
Was the medium idle before the DIFS?
Transmit the Frame
Countdown the DIFS Ye
s
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Consider an Example of Five Stations Trying to Unicast all at Once Putting it Together - DCF In Action:
13
Station A
Station B
Station C
Station D
Station E
Frame
Defer
Defer
Defer
Frame
DIFS DIFS
Defer
Frame
DIFS
Frame
Backoff time
Backoff time remaining
Defer
Defer
Defer
Defer
IEEE 802.11e and Wireless Multimedia (WMM)
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
DCF Needed an Update
• QoS is not possible with DCF:
1. No method of classification (all traffic is treated equally)
2. The DIFS and Contention Window values are the same for all traffic
• IEEE 802.11e was formed and finally ratified in the 802.11e-2007 standard (which is now part of the 802.11e-2012 “rollup”)
– 802.11e set out to make tweaks to DCF that would allows priority handling of high priority traffic
– The Goal: Improve the probability that high priority traffic will be transmitted first
• By the way, what is the difference between IEEE 802.11e and WMM??
15
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Enhanced Distributed Channel Access (EDCA)
1. Establishment of four queues (known as Access Categories, ACs)
2. Instead of a single DIFS timer, give different timers to each AC
3. For each AC, assign a different range of contention window sizes of CWmin and CWmax
4. Transmission Opportunity (TXOP)
5. Call Admission Control (CAC) with TSpec
– Other enhancements were also introduced, including: • Power Save mode
Five Key QoS Enhancements
16
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Access Categories Act like Transmit Queues
17
Background Best Effort Video Voice
Application Data
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
The User Priority (UP) QoS Field
• When wireless frames are transmitted, a 3-bit QoS value known as the User Priority (UP) is written into the 802.11 L2 frame
– This is used to classify wireless traffic and place the frames in the correct AC
18
EDCA / WMM AC Name 802.11e UP Value
Voice 6, 7
Video 4, 5
Best Effort 0, 3
Background 1, 2
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Comparing WLAN QoS Markings Surprising Differences Emerge . . .
19
Traffic Type DSCP 802.11e UP 802.1p CoS WMM Access Category
Network Control 56 (CS7) 7 7 N/A
CAPWAP 48 (CS6) 7 6 N/A
Voice 46 (EF) 6 5 Voice
Interactive Video
34 (AF41) 5 4 Video
Signaling 26 (AF31) 4 3 Video
X-Data 18 (AF21) 3 2 Best Effort
Bulk Data 10 (AF11) 2 1 Background
Best Effort 0 (BE) 0 0 Best Effort
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
EDCA Backoff Timers
• EDCF does the following:
– Variable Arbitration Interframe Spacing (AIFS)
– Variable CWmin and CWmax values depending on traffic type
20
EDCA / WMM AC AIFS Number CWmin CWmax
Legacy DCF DIFS > 2 15 1023
Voice 2 3 7
Video 2 7 15
Best Effort 3 15 1023
Background 7 15 1023
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Understanding the Effect of EDCA Timers
• By combining these timers, the theoretical probability of higher priority frames getting serviced first is greatly improved (but is not guaranteed in every case)
21
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
QoS Enhancements for Voice Applications
• EDCA provides two key key optimizations for voice & video over wireless:
22
2. TXOP is a set period of time when a wireless station may send as many
frames as possible without having to contend with other stations. • With legacy DCF operation, a client can only send one frame at a time
before going through the arbitration process again.
• TXOP gives a specified period of time per client to access the medium so it
can send multiple frames.
1. TSpec (Call Admission Control) provides management of the number of
real-time traffic flows, such as voice and video.
Wireless QoS Tools and Considerations
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
WLAN QoS Toolset Review
24
0 EF
Classification
Marking/Mutation
Shaping/Policing
Queueing
Trust
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
WLAN QoS Toolset Review, Cont’d
25
0 EF
Classification
Marking/Mutation
Shaping/Policing
Queueing
Trust
SET MUTATE
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
WLAN QoS Toolset Review, Cont’d
26
Classification
Marking/Mutation
Shaping/Policing
Queueing
Trust
Line Rate
Shaped Rate
Traffic shaping limits the transmit rate to a value lower than line rate
with Traffic
Shaping
without
Traffic Shaping
Line Rate
Policed Rate
Policing discards traffic which exceeds policed rate
without Policing
with Policing
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
WLAN QoS Toolset Review, Cont’d
27
Classification
Marking/Mutation
Shaping/Policing
Queueing
Trust
Queue 2 (Access Category 2)
Queue 1 (Access Category 1)
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
WLAN QoS Toolset Review, Cont’d
28
Classification
Marking/Mutation
Shaping/Policing
Queueing
Trust
DSCP 46
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
QoS Markings: Upstream vs. Downstream
• Upstream means traffic originating at the client, headed towards the WLC
• Downstream means traffic destined for the WLAN clients
CAPWAP Tunnel
WLC
AP Client
Radio Upstream Network Upstream
Network Downstream Radio Downstream Ethernet
Switch
802.1q/p 802.11e UP
CAPWAP DSCP DSCP
29
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public 30
The Downstream QoS Marking Model
CAPWAP Tunnels Si Si Si Si Si Si
WLAN Controller
AP
Ethernet Switch
CAPWAP Encapsulated DSCP 802.1p DSCP Payload
AP
AP
1 The Ethernet frame is received over an 802.1q trunk by the WLC. The WLC uses the
DSCP value of the IP packet and maps it to the outer DSCP of the CAPWAP tunnel.
802.11 DSCP Payload
1
802.1Q Trunk
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public 31
The Downstream QoS Marking Model
CAPWAP Tunnels Si Si Si Si Si Si
WLAN Controller
AP
Ethernet Switch
802.1p DSCP Payload 11e UP DSCP Payload
2
AP
AP
1 The Ethernet frame is received over an 802.1q trunk by the WLC. The WLC uses the
DSCP value of the IP packet and maps it to the outer DSCP of the CAPWAP tunnel.
2 Once the Ethernet frame is received by the AP, it maps the DSCP value of the IP packet
to the 802.11e UP value on the wireless frame. The frame is then sent to the client.
CAPWAP Encapsulated DSCP
802.11 DSCP Payload
802.1Q Trunk
1
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public 32
The Upstream QoS Marking Model
CAPWAP Encapsulated
CAPWAP Tunnels Si Si Si Si Si Si
WLAN Controller
AP
Ethernet Switch
DSCP
3 1
AP
AP
3 1
802.11 DSCP Payload
802.1Q Trunk
11e UP DSCP Payload
The client 802.11e frame is received by the AP. The AP maps the 802.11e UP value
to the outer CAPWAP IP DSCP header
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public 33
The Upstream QoS Marking Model
CAPWAP Tunnels Si Si Si Si Si Si
WLAN Controller
AP
Ethernet Switch
DSCP 802.1p DSCP Payload
AP
AP
The client 802.11e frame is received by the AP. The AP maps the 802.11e UP value
to the outer CAPWAP IP DSCP header
At the WLC side of the CAPWAP tunnel, the 802.11e frame is bridged to the
Ethernet switch. 2
2
CAPWAP Encapsulated
802.11 DSCP Payload
802.1Q Trunk
3 1
3 1
11e UP DSCP Payload
Cisco WLC QoS Design Strategies
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
AireOS QoS Profiles
• In the past, as a best practice Cisco has recommended using a separate WLAN (SSID) for voice. What if you are using MS Lync or Jabber for Unified Communications?
This is the most misunderstood concept in Cisco WLAN QoS
35
Cisco WLC Profile Name
Maximum DSCP Value for the Profile
Platinum EF (46)
Gold AF41 (34)
Silver DF (0)
Bronze AF11 (10)
• The Four Precious Metal QoS Profiles DO NOT EQUATE to the WMM ACs.
• For WMM-capable stations, this sets the upper limit of the DSCP value allowed on CAPWAP.
• For non-WMM stations, this establishes the DSCP value on the CAPWAP tunnel and maps to the downstream UP value.
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public 36
Example – The QoS Profile Sets a DSCP Ceiling
CAPWAP Tunnels Si Si Si Si Si Si
WLAN Controller
AP
Ethernet Switch
CAPWAP Encapsulated DSCP 802.1p DSCP Payload
UP DSCP Payload
AP
AP
802.11 DSCP Payload
Mixed use WLAN (tablets, phones, etc.) configured for the Gold Profile
DSCP 46 gets Marked down to 34, UP marked to 5
5 34
5
46
802.1Q Trunk
46
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public 37
Step 1: Access the QoS Profile
One of these four default QoS profiles may be used and applied to each WLAN (SSID)
Recommendations:
1. For enterprise class, mixed-use WLANs, use the
Platinum Profile
2. For guest SSIDs use the Bronze Profile • Bronze will classify all traffic to the “background” AC,
with the longest AIFSN and CW wait timers
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Step 2: Configure the QoS Profile
38
Create default bandwidth contracts for each user or each SSID Note bandwidth contracts are
bidirectional (values shown here are examples only)
Set the maximum priority for WMM and non-WMM clients Can optionally set the 802.1p CoS value for the QoS profile
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Step 3: Apply the QoS Profile to the WLAN
39
Choose the QoS profile you want to apply for this WLAN
In this example, the “Platinum” profile is selected
This sets the ceiling on all traffic to DSCP 46 and UP value to 6
You can also set the bi-directional per-user and per-SSID bandwidth contracts from this screen
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public 40
IOS-XE QoS Configuration: Step 1
CAPWAP Tunnels Si Si Si Si Si Si
WLC 5760
AP
Ethernet Switch AP
AP
802.1Q Trunk
WLC5760(config)# table-map DSCP-TO-UP
WLC5760(config-tablemap)# map from 18 to 3
WLC5760(config-tablemap)# map from 24 to 4
WLC5760(config-tablemap)# map from 34 to 5
WLC5760(config-tablemap)# map from 46 to 6
WLC5760(config-tablemap)# default ignore
WLC5760(config)# table-map DSCP-TO-DSCP
WLC5760(config-tablemap)# map from 18 to 18
WLC5760(config-tablemap)# map from 24 to 24
WLC5760(config-tablemap)# map from 34 to 34
WLC5760(config-tablemap)# map from 46 to 46
WLC5760(config-tablemap)# default ignore
Radio Downstream Network Upstream
Define The Table Maps for Upstream and Downstream Radio Traffic
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public 41
IOS-XE QoS Configuration: Steps 2 & 3
WLC 5760
AP
AP
WLC5760(config)# policy-map UPSTREAM
WLC5760(config-pmap)# class-map class-default
WLC5760(config-pmap-c)# set dscp dscp table DSCP-TO-DSCP
!
WLC5760(config)# policy-map DOWNSTREAM
WLC5760(config-pmap)# class class-default
WLC5760(config-pmap-c)# set wlan user-priority dscp table DSCP-TO-UP
WLC5760(config)# wlan ENTERPRISE
!
WLC5760(config-wlan)# service-policy input UPSTREAM
WLC5760(config-wlan)# service-policy output DOWNSTREAM
Create the policy-maps and attach them to the WLAN interface
Apply to the WLAN
upstream and
downstream
Define the
upstream and
downstream
policy maps
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public 42
Dealing With Non-WMM Clients in AireOS
WMM is critical for QoS - it enables 802.11e UP
“Allowed” permits a mix QoS capable and non-QoS capable devices on same WLAN
802.11n and 802.11ac both support WMM
WMM is necessary for channel bonding
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public 43
Dealing With Non-WMM Clients in IOS-XE
Recommendation, with a word of caution:
• Generally, it is recommended to set the WMM Policy to “allowed” on both types of
controllers to allow support of both WMM and legacy (non-WMM clients).
• Non-WMM client packets are defaulted to DSCP/UP zero in IOS-XE, but to the
maximum for the profile in AireOS.
WLC5760(config)# wlan ENTERPRISE
WLC5760(config-wlan)# wmm ?
allowed Allows WMM on the WLAN
require Requires WMM enabled clients on the WLAN
!
WLC5760(config-wlan)# wmm required
!
! This is the default setting for all new WLANs
“WMM required” will reject all
legacy clients that do not
support WMM (a potentially
limiting feature)
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Example: Comparing a WMM Client Using MS Lync
44
CAPWAP Encapsulated
CAPWAP Tunnels Si Si Si Si Si Si
WLAN Controller
AP
Ethernet Switch
11e UP DSCP Payload DSCP 802.1p DSCP Payload
AP
AP
802.11 DSCP Payload
5 34
34
34
34
802.1Q Trunk
The AP Recognizes the
WMM UP value and maps it
automatically to DSCP 34
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Example, Cont’d: With A non-WMM Client (Platinum)
45
CAPWAP Encapsulated
CAPWAP Tunnels Si Si Si Si Si Si
WLAN Controller
AP
Ethernet Switch
802.11 DSCP Payload DSCP 802.1p DSCP Payload
AP
AP
802.11 DSCP Payload
The Client is Not WMM Capable.
AP automatically maps the
CAPWAP DSCP to EF (46)
46
x 34
34
34
802.1Q Trunk
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
AireOS Solution: Alloy QoS
46
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Alloy QoS: QoS Control For Non-WMM Clients
47
Maximum Priority allows you to customize the upper limit QoS marking for a QoS policy
Sets the default QoS markings for all non-WMM clients
Sets maximum DSCP & UP values for WMM clients
Recommendation:
• Use Alloy QoS to treat non-WMM clients as best effort (DSCP and
UP values default to zero).
• If the client doesn’t support QoS, don’t try to give them QoS!
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Configure Call Admission Control (CAC)
• CAC refers to the WLC’s capability
to limit the number of voice or video calls on a per-AP basis.
• CAC limits the number of voice clients which can associate to the Access Point.
• In Load-Based CAC the AP monitors percent of BW that has been used on the radio. The AP only admits new flows if there is enough BW to support a new call.
• SIP-Based CAC requires SIP Snooping (not covered in this presentation)
48
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
CAC Configuration in IOS-XE
49
Recommendation:
• When using voice or video applications, CAC should be
considered a mandatory design element
5760(config)# ap dot11 5ghz cac voice acm
! Enables voice CAC
5760(config)# ap dot11 5ghz cac voice load-based
! This is for the Cisco 792x series phone
5760(config)# ap dot11 5ghz cac voice max-bandwidth <5-85>
! Configure the max RF bandwidth percentage allocated to
WMM clients for voice
5760(config)# ap dot11 5ghz cac voice sip bandwidth 64
! Per-client bandwidth for SIP voice clients
!
5760(config)# ap dot11 5ghz cac video acm
! Enables video CAC
5760(config)# ap dot11 5ghz cac video max-bandwidth <5-85>
Voice CAC configuration
Video CAC configuration
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Introducing Application Visibility & Control (AVC) • Introduced in AireOS 7.4, limited capabilities in IOS-based controllers
• Leverages the IOS NBAR2 Engine – same list of traffic signatures as IOS & XE
– AireOS 7.6 introduces “Protocol Pack” support + Cisco Jabber support
• IOS-XE Controllers are limited to “Visibility” prior to version 3.6
50
• Discover which applications are running on your
corporate and guest WLANs
• Prioritize critical wireless apps and de-prioritize
non-business apps
• Monitor voice and video performance on the
WLAN
AVC In The Wireless LAN Controller
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Key Points To Know About AVC
51
CAPWAP Tunnels
WLC AP
Client
Ethernet
Switch
In AireOS 8.0, AVC can be
applied in a specific direction
(upstream or downstream)
AVC Policy only functions
here in AireOS
AVC Does Not Function
Here in AireOS
AVC Modifies the inner DSCP value,
thus influencing the CAPWAP DSCP
and wireless UP values
AVC Policy functions here
in IOS-XE, but only does
“visibility” today
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
AVC Example: Build A Multimedia AVC Policy
52
More Key Points To Know:
Applications are grouped by class (such as “voice-and-video” shown here)
From AireOS 7.6 Protocol Packs are used for signature updates
Approx. 1100 AVC Signatures available today
Updates made via protocol packs
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
A Simple AVC Remarking Example:
53
AVC has three basic capabilities:
1. Modify the inner packet’s DSCP to a custom value
2. Drop the packet
3. Rate Limit
E.g. Let’s mark MS Lync Media to Gold (DSCP 34)
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
AVC Example Number 2:
54
MS Lync Policy
Cisco Jabber and IP
Phone Policy
Unwanted applications
Policy – drop or police
AVC can be applied in upstream,
downstream, or both directions
AVC can drop unwanted traffic
AVC has ability to police
applications bi-directionally
Note: AireOS 8.0 is shown here
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
AVC Example Cont’d: Apply The AVC Policy
55
1. Navigate to the QoS policy for the WLAN where you want to apply the AVC policy
2. Enable AVC
3. Apply the AVC policy you created to this QoS policy
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
AVC Provides Exceptional Application Visibility
56
Developing a Unified QoS Strategy for the WLAN
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
QoS Features Are Nice, But A QoS Design Is Critical How Does this fit with the Classic Four-Class QoS Model?
58
Transactional
Data
Realtime
Classes
Best Effort
Control
AF
EF
DSCP
DF
CS
Database Apps,
Email, FTP, Backups
CRM Apps
IP Phones,
TelePresense,
WebEx,
Jabber
Application Examples
Everything Else
SIP, Routing Protocols, Etc.
35% BW Guarantee
WRED
33% of BW,
Strict Priority
QoS Handling
25% BW Guarantee
WRED
7% of BW Guarantee
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
A Desired Design Might Look Like This:
59
Transactional Data
Realtime
4-Class Strategic
Enterprise Model
Best Effort
Control
Voice
WMM Model +
802.11e User Priority
Best Effort
Video
Background
UP 7
UP 5
UP 3
UP 2
UP 6
UP 4
UP 0
UP 1
AF21
EF
DSCP
DF
CS3
Wireless traffic is assigned to an EDCA / WMM AC based on the frame’s UP Value.
This model looks reasonable and desirable, but is it realistic?
Note: The Video AC
doesn’t necessarily
need to be used for
video traffic!
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
But It Doesn’t Always Work - Remember This Table?
• Consider the example of SIP signaling (CS3 = DSCP 24)
– 24 is not in the table!
• AP calculates the UP value from the 3 MSB of the DSCP value
– 24 = [011]000
– Therefore, using 011, UP = 3
• SIP Signaling gets assigned UP value of 3
60
Traffic Type DSCP 802.11e UP
Network Control
56 (CS7) 7
CAPWAP 48 (CS6) 7
Voice 46 (EF) 6
Interactive Video
34 (AF41) 5
Signaling 26 (AF31) 4
X-Data 18 (AF21) 3
Bulk Data 10 (AF11) 2
Best Effort 0 (BE) 0
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Downstream: Surprising Mappings Occur!
• Thus, in the downstream direction, SIP signaling ends up in the same AC as Trans-Data and Best Effort
• The default mapping mechanism means only two queues get used
• This can negatively impact wireless performance
61
Transactional Data
Realtime
4-Class Strategic
Enterprise Model
Best Effort
Control
Voice
WMM Model +
802.11e User Priority
Best Effort
Video
Background
UP 7
UP 5
UP 3
UP 2
UP 6
UP 4
UP 0
UP 1
AF21
EF
DSCP
DF
CS3
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Upstream: UP Can Map To The Wrong DSCP
CAPWAP Encapsulated
CAPWAP Tunnels Si Si Si Si Si Si
WLAN Controller
AP
Ethernet Switch
11e UP DSCP Payload DSCP 802.1p DSCP Payload
AP
AP
802.11 DSCP Payload
UP 4 gets mapped to the
WRONG DSPC on the
CAPWAP Tunnel!
24
24
4 24 26
802.1Q Trunk
62
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Problem is Easy to Fix in IOS-XE Use Table Maps To Mark the Correct DSCP and UP Values
63
CAPWAP Tunnels Si Si Si Si Si Si
WLC 5760
AP
Ethernet Switch AP
AP
802.1Q Trunk
WLC5760(config)# table-map RD-DSCP-TO-UP
WLC5760(config-tablemap)# map from 18 to 3
WLC5760(config-tablemap)# map from 24 to 4
WLC5760(config-tablemap)# map from 34 to 5
WLC5760(config-tablemap)# map from 46 to 6
WLC5760(config-tablemap)# default ignore
WLC5760(config)# table-map NU-DSCP-TO-DSCP
WLC5760(config-tablemap)# map from 18 to 18
WLC5760(config-tablemap)# map from 24 to 24
WLC5760(config-tablemap)# map from 34 to 34
WLC5760(config-tablemap)# map from 46 to 46
WLC5760(config-tablemap)# default ignore
Radio Downstream Network Upstream
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
AireOS Solution: Use Mutation On Access Switch
• Example: On upstream, mutate the incorrect DSCP signaling value back to CS3
– Must be applied to every switch port connected to an AP
64
C3750-X(config)# mls qos map dscp-mutation UPSTREAM-MUTATION 26 to 24
! Mutates the DSCP from AF31 back to CS3 to it is correct on the CAPWAP
tunnel header
C3750-X(config)# interface GigabitEthernet1/1/10
! The interface that connects to the AP
C3750-X(config-if)# mls qos trust dscp
! Configures the port to statically trust DSCP on ingress
C3750-X(config-if)# mls qos dscp-mutation UPSTREAM-MUTATION
! Attaches the Upstream DSCP mutation map to the interface on ingress
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Through Manual Mutation Or Table Mapping, You Can Achieve The Desired Result:
65
Transactional Data
Realtime
4-Class Strategic
Enterprise Model
Best Effort
Control
Voice
WMM Model +
802.11e User Priority
Best Effort
Video
Background
UP 7
UP 5
UP 3
UP 2
UP 6
UP 4
UP 0
UP 1
AF21
EF
DSCP
DF
CS3
Wrap-Up
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Key Takeaways
67
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Quality of Service Sessions at Cisco Live 2014
68
Session ID Start Time Title
TECRST-2501 Sunday, 08:00 Enterprise QoS Design Strategy
BRKRST-2509 Tuesday, 08:00 Mastering Data Center QoS
BRKRST-2514 Tuesday, 12:30 Application Optimization and Visibility for
Intelligent WAN (IWAN)
BRKRST-2512 Wednesday, 13:30 Validating QoS using Medianet Media
Awareness
BRKCRS-2501 Thursday, 8:00 AM and
2:30 PM
Campus QoS Design - Simplified
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Participate In The “My Favorite Speaker” Contest
• Promote your favorite speaker through Twitter and you could win $200 of Cisco Press products (@CiscoPress)
• Send a tweet and include
– Your favorite speaker’s Twitter handle @MrRobbarto
– Two hashtags: #CLUS #MyFavoriteSpeaker
• You can submit an entry for more than one of your “favorite” speakers
• Don’t forget to follow @CiscoLive and @CiscoPress
• View the official rules at http://bit.ly/CLUSwin
Promote Your Favorite Speaker and You Could be a Winner
69
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Complete Your Online Session Evaluation
• Give us your feedback and you could win fabulous prizes. Winners announced daily.
• Complete your session evaluation through the Cisco Live mobile app or visit one of the interactive kiosks located throughout the convention center.
Don’t forget: Cisco Live sessions will be available for viewing on-demand after the event at CiscoLive.com/Online
70
© 2014 Cisco and/or its affiliates. All rights reserved. BRKRST-2515 Cisco Public
Continue Your Education
• Demos in the Cisco Campus
• Walk-in Self-Paced Labs
• Table Topics
• Meet the Engineer 1:1 meetings
71