The need for QoS, configuration on Extreme Aerohive

January 21, 2021

The need for QoS, configuration on Extreme Aerohive

Introduction

This blogpost will focus on the configuration of QoS policies on Extreme Cloud IQ (Portal). Aiming to provide a real scenario which led to the implementation of QoS for an organisation. Before diving into this I cannot stress on the point that QoS solution will be successful only if it is implemented end to end. The QoS marking and policing if not honoured by the subsequent hops in the access <> distribution <> core.

The Need for QoS

The issues arise when packets do not get prioritisation and are either dropped or queued. The network transmission quality is determined by latency, jitter and packet loss. It becomes even more crucial with Wi-Fi being a shared and half-duplex medium it becomes all the more necessary to mark and prioritise the relevant traffic on the network. One may have 10Gbps internet or more but AP are often the bottlenecks in the network. With the adaptation of VoIP/Skype/Zoom and similar RTP/SIP applications, there is a need to make sure voice/video traffic get priority over other traffic. Moreover, Wireless networks and protocols are mostly designed for data services… so it is normally not possible “ just to drop” Rich Media on top and expect positive results.

Extreme Cloud IQ configuration

Let’s start with looking at the Extreme Cloud IQ configuration.

Classifier Maps

QoS Classifier Maps > Classifier map is used to mark traffic with Extreme Network QoS classes by various QoS classification systems (802.1p/DiffServ/802.11e).

Incoming Traffic – AP prioritises and forwards the incoming traffic as determined by the mapped QoS level.

Outgoing Traffic – AP uses marker maps.

If you login and navigate to below for checking the first option of “Classifier Maps”.

Configure > Network Policies > Edit “Policy Name” > Additional Settings > QoS Options

ExtremeCIoud IQ Pilot
Classifier Maps
WIRELESS NETWORKS
O
O
Network Policies
POLICY DETAILS
MANAGEMENT SERVER
POLICY SETTINGS
NETWORK SERVICES
GOS OPTIONS
Classifier Maps
Marker Maps
QoS Overview
SECURITY
DEVICE TEMPLATES
Classifier Maps
ROUTER SETTINGS
ADDITIONAL SETTINGS
DEPLOY POLICY
Please note that Classifier Maps are only supported by IQ Engine devices and will not take effect on other devices.
Classifier Maps
Maps anonymous incoming traffic into the Extreme Networks
classification system. Traffic classification can be performed based on
following criteria.
Re-use Classifier Maps Settings
(Pick existing settings)
Name •
Description
SERVICES
Services
LYNC
LYNC AUDIO
LYNC CONTROL
SKYPE VOICE
FACETIME
MAC ouls
Classifier-Map
SSIDs
802.1p/Diffserv/802.11e
aos Class
VOICE
VOICE
VOICE
VOICE
VIDEO
Action
PERMIT
PERMIT
PERMIT
PERMIT
PERMIT

The incoming traffic is mapped based on the network/application service defined in the classifier map. In the above screenshot you can see LYNC, LYNC AUDIO and others set as VOICE and action being PERMIT.

MAC OUIs and SSIDs

I haven’t used this in our config but one can choose to map traffic to classes based on either the source/destination MAC OUI in the packet or based on SSID

Add MAC OUI
MAC OUI
Gos Class
Action
Logging
Apple-iPhone
Background
permit
Enable

802.1p/DiffServ/802.11e

802.1p is a layer 2 prioritisation often described as Class of Service can be seen in the TCI field of the Ethernet frame. The 3 bits give 8 different classes as shown below. In my scenario I have used the DiffServ and 802.11e(WMM) for layer 3 QoS.

DiffServ is concerned with classifying packets as they enter the local network. This classification then applies to Flow of traffic where a Flow is defined by 5 elements; Source IP address, Destination IP, Source port, Destination port and the transport protocol. The DSCP QoS is retained end to end and one of the reason it is preferred more than 802.1p.

Before moving to 802.11e, let’s get basics correct.

802.11 use collision avoidance mechanisms unlike collision detection for Ethernet. The DCF (Distributed Coordinated Function) algorithm is used for media access. Regardless of any clients on the medium, a 802.11 WLAN device will wait for a DCF interframe space and then begin the transmission. Once the DIFS is counted down to 0, a random backoff timer is generated if the medium is not free.

Wait Until Medium is Free
Count Down the DIFS &
keep listening to medium
Is the Medium Still Free?
No
Generate a random
backoff value between 0
and CWmin
The DCF
Decision Process
Continually listen to
medium to ensure it
is quiet
Yes
Transmit the
Frame
Done
Was an ACK
received? (i.e.
confirm there was
no collision)
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
Double the previous
cw.
Choose
a new random number between
zero and the new CW, up to a
maximum of CWmax

QoS is not possible with DCF alone and hence 802.11e was ratified. The EDCA (Enhanced Distributed Channel Access) included 4 queues(Background, Best Effort, Video, Voice), AIFS (ACs) and a range of contention windows (CWmin and CWmax). Two additional 802.11e enhancements included TxOP and Call Admission Control (CAC)

EDCA 1 WMM AC
Legacy DCF
Voice
Video
Best Effort
Background
AIFS Number
DIES > 2
2
2
3
7
CWmin
15
3
7
15
15
CWmax
1023
7
15
1023
1023

QoS Classification and Marking: Mapping External Systems to Aerohive Classes
56-63
56 - 63
48-55
48 - 55
40 - 47
40 - 47
32-39
32 - 39
24 • 31
24-31
16 - 23
16 - 23
8-15
8-15
For traffc traversing its wifi interfaces, the HiveAP
maps Aerohive classes to IEEE 802. Ile tramc classes
(defined in the wireless frame header) or to DSCP
values (defined in the layer-3 packet header).
For traffc traversing its Ethernet interface, the HiveAP
maps Aerohive classes to 802.1 p traffic classes
(defined in the layer-2 frame header) or to DSCP
values (defined in the layer-3 packet header).
Wireless
Network
802.11e Traffic Class
7
6
5
4
3
wifiO. 1
DSCP Value
Inbound Outbound
56
48
32
24
16
8
ethO
802.1p Traffic Class
7
6
5
4
3
2
1
Ethernet
Network
DSCP Value
Inbound Outbound
HiveAP
erohive Clas
7
6
5
4
3
2
2
1
802.11e
Wire L2
Header
DSCP
L3
Header
Default mappings of the Aerohive
class system to standard OOS
classification systems
Data
802.1p
Wired L2
Header
DSCP
Header
56
48
40
32
24
16
8
Data

Marker Maps

For outgoing traffic, one can define marker maps to map classes to priority numbers in standard classification systems (802.11e, 802.1p, and DiffServ). After defining classifier and marker maps, you then define classifier and marker profiles that enable one or more of the methods defined in the maps. Finally, you associate those profiles with SSIDs or interfaces to apply the mappings to traffic arriving at or exiting those interfaces.