EOS S-series: QoS of VoIP Traffic

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On a special Customer szenario we have a S-Series Switch (Core of HeadQuarter) and S-Series (Core of Branch) and one WAN 100MBit Link which connects both.

Now i want priorize VoIP Packets other this WAN link.

One way to do that is GTAC Article 1737: 
S-Series Quality of Service for VoIP Traffic marked as DSCP Override (AF41)

This way is to write a policy which is bind to every ingress port (which are all except WAN port) and sort this high prio VoIP packets to a higher queue than standard traffic.

My customer ask why i do that so cumersome ?!
He expects that either i configure that priorization globally for the whole switch (means DSCP = EF = highest Queue) oder bind it only to the egress WAN port (priorize VoIP Traffic).

This trigger me to thinking about possibel other solutions. S-Series with EOS 8.42.05.

Is the way with policy on ingress port the only way to achieve the goal or is there a way like my customer believe is should be?

Thanks for all replies.


Regards 
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M.Nees, Embassador

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Posted 1 year ago

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Patrick Koppen

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Hi Matthias,

if packets marked with cos 5 it should work without a policy. Packets get in the right queue
and you only have to configure the egress (wan) port.

If you want DSCP-based qos (like other vendors do) instead of dot1p-based, you can also use
an admin-rule:

set policy rule admin-profile iptos 184 mask 6 admin-pid 11
set policy rule admin-profile iptos 160 mask 6 admin-pid 11
set policy profile 11 name VOIPQOS pvid-status enable pvid 4095 cos 5

Please remember large port buffers of the s-series. On busy 100 Mbit ports you get always a
7ms delay.

Article 1737 sounds weird. Voice data should be EF, voice signaling AF31, CS3 or CS5.
See RFC 4594 Figure 3. DSCP to Service Class Mapping.
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M.Nees, Embassador

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Hi Patrick,

that an exellent suggestion. Using an admin-profile meets much more customers expectation and is easier to handle then binding this specific rule to every physical/logical port.

But how can i verify/troubleshoot the configuration ?
In EXOS i can check the filling of the QP with port QoS-Monitor.

I try adding syslog action to the rules, but i it seems that only flow setup is run through CPU which can trigger the syslog event.

I try a test setup with iperf - but it does not show me the expected behavior (so i fear someting is currently wrong) ...

Regards
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Erik Auerswald, Embassador

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Hello Matthias,

QoS verification on EOS is not as straight-forward as the QoS-monitor of EXOS. Please see How to verify Quality of Service (QoS) configuration is working on EOS products for info.

You need to verify the queue configuration. Marking may be fine, but the packets or frames are not scheduled as needed during congestion.

Thanks,
Erik
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Erik Auerswald, Embassador

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Hi Matthias,

you probably want to change the default queue configuration of the switch as well.

Erik
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Patrick Koppen

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Hi,

I forgot 'cos-status enable'

set policy rule admin-profile iptos 184 mask 6 admin-pid 11
set policy rule admin-profile iptos 160 mask 6 admin-pid 11
set policy profile 11 name VOIPQOS pvid-status enable pvid 4095 cos-status enable cos 5