Link Layer Discovery Protocol (LLDP) is an ieee standard
protocol defined in 802.1AB. It's used to discover directly
attached devices (switches, routers, IP Phones, etc.). LLDP advertisements are
encapsulated in LLDP Data Units (LLDPDU) via Type Length Values (TLV).
The standard defines two types of TLVs: Standard and Optional.
LLDP devices must support the
advertisement of Standard TLVs (Chassis ID, Port ID, TTL, etc.), and may also include
optional TLVs'. These optional TLVs' are
where vendor specific advertisements would be defined (model, firmware,
PoE, QoS, etc.).
Typically IP Phones have a single port that supports both a PC
and the phone vlan. Generally the data VLAN is left untagged and the voice VLAN
is tagged. There are three ways that the IP telephone can learn its voice
VLAN:
1) Manually set it on the phone.
2) DHCP options – The phone sends DHCP requests over the data
VLAN, and the DHCP server offer will include vendor specific DHCP options
including the voice VLAN.
3) Use a discovery protocol – LLDP-MED or CDPv2. Here, the
phone will discover the voice VLAN from the switch.
On Provision switches using LLDP-MED, you must first enable lldp
globally and then set the parameter “voice” in the vlan
context for the switch to accept LLDP-MED TLV advertisements.
hpe(config)# lldp run
hpe(config)# vlan
100
hpe(vlan-100) name
"VOICE"
hpe(vlan-100) tagged
<interfaces >
hpe(vlan-100) voice ß Use lldp-med TLVs
sent from the phone
hpe(vlan-100) exit
The two commonly used QoS
marking methods are:
- Class‐of‐Service (CoS) at Layer 2, and
- Differentiated Service Code Point (DSCP) at Layer 3.
CoS (aka 802.1p)
has 8 levels, numbered 0‐7 which map to 8 priority queues on the (egress)
of each Ethernet port. The CoS marking is set in tagged frames only
since the priority (802.1p) field is part of the VLAN tag. Untagged
frames are placed in the CoS level 0 priority queue (or
normal queue).
On most HPE switches CoS values
0‐7 map to priority queues like so:
[1] [2] [0] [3] [4] [5] [6] [7]
Therefore, a CoS 0 priority will be mapped to hardware output
queue Q3 and take precedence over frames marked 1 & 2. Most HP
edge switches have 8 output queues and is configurable to have 4 or 2 if
desired.
hpe(config)#
qos queue-config
2-queues Set the number of egress queues
for each port.
4-queues Set the number of egress queues
for each port.
8-queues Set the number of egress queues
for each port.
hpe(config)#
qos queue-config 4-queues
This command will modify the current running
configuration,
execute 'write memory' to replace the startup
configuration,
and then reboot.
Egress queues will be configured as follows:
4-queues
Do
you want to save current configuration [y/n/^C]?
The default mapping
of CoS values to output queues on an HP edge switch looks like this:
+-------------+-----------------+-----------------+-----------------+
| Cos Value | 8 Output Queues | 4 Output Queues | 2 Output Queues |
+-------------+-----------------+-----------------+-----------------+
| 1 | 1 | 1 | 1 |
| 2 | 2 | 1 | 1 |
| 0 | 3 | 2 | 1 |
| 3 | 4 | 2 | 1 |
| 4 | 5 | 3 | 2 |
| 5 | 6 | 3 | 2 |
| 6 | 7 | 4 | 2 |
| 7 | 8 | 4 | 2 |
+-------------+-----------------+-----------------+-----------------+
In voice deployments, generally the Ethernet switch port is
configured to support 2 VLANs, one for voice and one for data. LLDP is
enabled on these Ethernet ports and can be configured to advertise voice VLAN
ID and QoS information using the Network Policy LLDP TLV.
Generally set prioritization queues for voice, video, and
switch control plane traffic on edge switches as:
Priority Traffic
7 Control plane
6
Routing
5
IP voice
4
IP video
3
Voice signaling
0
Normal Data
1 http, bulk
transfer, etc.
2 http, bulk
transfer, etc.
The priority can either be set on the interface or the vlan. If
you set the priority at the interface level, the switch will not be able to
distinguish normal data traffic from voice.
QoS can also be used to prioritize traffic globally on TCP/UDP
port based traffic. This can be used on soft phones since the switch doesn’t
know the difference between normal data traffic and soft phone voice traffic.
VLAN based prioritization applies to the 802.1p flag in a tagged
(trunked) packet. Therefore it will only prioritize tagged traffic for
the vlan it is set in. As such, the untagged vlan doesn’t have the 802.1p
header and therefore will remain at normal priority (priority 0).
Trust Model
In TRUST model, the edge switch accepts (or trusts) the phones
QoS markings without modifying the priority. Procurve switches default
setting is “trust”.
If the frame is routed, the MAC header is stripped before
routing the packet to its destination. To keep the priority across
routers use DSCP. To prevent users over-riding priority settings, use
strict priority provisioning with CoS and/or DSCP as well.
Non-Trusted Model
In most environments the trust model is fine. Otherwise
you can strictly provision COS priority per interface or vlan. You can
also globally prioritize traffic based on TCP/UDP port numbers. Additionally
you can create a Classifier base QoS Policy to prioritize traffic.
The following example shows the use of LLDP-MED and strict QoS
provisioning to modify the default settings. The VoIP VLAN is set through
LLDP-MED and qos is set via DSCP:
Enable LLDP globally
2920(config)# lldp run
Enable Differential Code Services proritization
2920(config)# qos type-of-service diff-services
Create and configure the telephony VLAN where all of the telephony equipment will run
2920(config)# vlan 10
2920 (vlan-10)# name VOICE_SIGNALING
2920 (vlan-10)# qos dscp 011000 (802.1p pri 3)
Create and configure the voice VLAN
2920(config)# vlan 20
2920 (vlan-20)# name VOICE
2920 (vlan-20)# qos dscp 011110 (802.1p pri 5)
2920 (vlan-20)# voice ßAccept lldp-med TLV's
Create and configure the VIDEO VLAN
2920(config)# vlan 30
2920 (vlan-30)# name VIDEO
2920 (vlan-30)# qos dscp 011100 (802.1p pri 4)
Create and configure the data VLAN.
2920(config)# vlan 40
2920 (vlan-40)# name DATA
2920 (vlan-40)# qos dscp 010010 (802.1p pri 0 - Normal)
In some cases you may want to reduce the number of hardware
queues to 4 or 2. This would allow resources that are by default shared across
8 queues to be shared across 4 or 2 queues. Example:
hp(config)# qos
queue-config 4-queues
This changes the
switch to only use 4 queues (needs a reboot to take affect). You use the show qos queue to verify
hp# show qos queue-config
802.1p
Queue Pri Memory
%
----- --- --------
1 1–2 10
2 0,3 70
3 4–5 10
4 6–7 10
The amount of packet buffer memory allocated to the queues is
pre-defined and not user configurable.
However, the user can change the amount of Guaranteed Minimum
Bandwidth (GMB) allocated to each queue. The default GMB queue settings are:
These defaults can be viewed with the following command:
hp# show bandwidth output
1-5
Outbound Guaranteed Minimum Bandwidth %
Port
Q1 Q2 Q3
Q4 Q5 Q6
Q7 Q8
------ --- --- --- --- --- --- --- ---
1
2 3 30
10 10 10
15 20
2
2 3 30
10 10 10
15 20
3
2 3 30
10 10 10
15 20
4
2 3 30
10 10 10
15 20
5
2 3 30
10 10 10
15 20
These GMB values can be changed on interfaces. This command is
for interface 1 through to 5:
TThis is for 8-queues, if you had the switch set to 4-queues then
then only 4 GMB values is used. The percentages allowed to the queues should
add up to 100%. In the above example GMB for Q5 (video) and Q6 (voice) pulls
bandwidth from the default settings of Q7 (routing traffic) and Q8 (net mgmt).
hp(config)# show bandwidth
output 1-5
Outbound Guaranteed Minimum Bandwidth %
Port
Q1 Q2 Q3
Q4 Q5 Q6
Q7 Q8
------ --- --- --- --- --- --- --- ---
1
2 3 30
10 20 15
10 10
2
2 3 30
10 20 15
10 10
3
2 3 30
10 20 15
10 10
4
2 3 30
10 20 15
10 10
5
2 3 30
10 20 15
10 10
