Need Explanation on router QoS configuration

getawayuser51 · ‎11-28-2016

Hi guys,

I really need thoroughly explanation on the Qos configured on my router by ISP. I dont quite understand the objective here...As I know the bandwidth needs to be set for all traffic & voice needs to be marked EF all along the path.

1) When voice equipment like alcatel & avaya sends out voice packets, it is marked with dscp EF right?

When these marked packets goes into the LAN interface GigabitEthernet1/2, it hits service-policy input qos_input? The packets becomes ip prec 5? due to "set ip precedence 5"

When it exits to the WAN interface GigabitEthernet1/3, it remains as EF or set to ip prec 5?

2)The bandwidth part is policy-map queuing? What is service-policy queuing? policy-map set_bandwidth set bw as10M?

class-map match-all VOICE
match access-group name VOICE-EF
match packet length max 100
class-map match-all VOICE-PREC
match ip precedence 5

class-map match-all EMAIL-PREC
match ip precedence 0
!
policy-map queuing
class VOICE-PREC
priority 3072
class EMAIL-PREC
bandwidth 3072
class class-default
bandwidth 4096

policy-map set_bandwidth
class class-default
shape average 10240000
service-policy queuing

policy-map qos_input
class VOICE
set ip precedence 5
class class-default
set ip precedence 1

policy-map qos_output
class VOICE-PREC
set ip dscp ef
class class-default
set ip dscp af21

policy-map qos
class VOICE-PREC
class EMAIL-PREC
!
interface GigabitEthernet1/2
description LAN
ip address 172.16.1.1 255.255.255.0
service-policy input qos_input
service-policy output qos_output
!
interface GigabitEthernet1/3
description WAN
bandwidth 10240
ip address 202.188.6.3 255.255.255.252
ip nat outside
ip virtual-reassembly in
service-policy input qos
service-policy output set_bandwidth

!

ip access-list extended VOICE-EF
permit ip any any dscp ef

Georg Pauwen · ‎11-29-2016

Hello,

incoming voice traffic marked with dscp ef gets precedence 5 and then gets priority queuing.

I am not sure how the outgoing voice traffic that matches precedence 5 gets dscp ef, since the traffic needs to be marked with precedence 5 first in order to get dscp ef, but there is no criteria in the class-map VOICE-PREC other than it has to match precedence 5. So the question is, where does outgoing traffic get marked as precedence 5 ?

Can you show the output of 'show service-policy interface GigabitEthernet1/2 ? I wonder if anything actually matches the qos_output service policy...

getawayuser51 · ‎11-29-2016

incoming voice traffic marked with dscp ef gets precedence 5 and then gets priority queuing.

I am not sure how the outgoing voice traffic that matches precedence 5 gets dscp ef, since the traffic needs to be marked with precedence 5 first in order to get dscp ef, but there is no criteria in the class-map VOICE-PREC other than it has to match precedence 5. So the question is, where does outgoing traffic get marked as precedence 5 ?

policy-map qos_input
class VOICE
set ip precedence 5

This command marked all class-VOICE (packet marked as EF by Avaya voice switch) as ip prec 5 right?

Also any idea why packet marked as ip prec 5?

Can you show the output of 'show service-policy interface GigabitEthernet1/2 ? I wonder if anything actually matches the qos_output service policy...

yes there are packets matching all policy-map. For voice packets vendor like Avaya & polycom ,the objective is to get EF marking along all the path & when reach WAN, it will be allocated bw according to class.

Joseph W. Doherty · ‎11-29-2016

When voice equipment like alcatel & avaya sends out voice packets, it is marked with dscp EF right?

Usually, especially for VoIP bearer traffic, but believe much VoIP equipment can be configured for how it marks its traffic.

When these marked packets goes into the LAN interface GigabitEthernet1/2, it hits service-policy input qos_input? The packets becomes ip prec 5? due to "set ip precedence 5"

Yes and maybe. VOICE-EF class matches packets marked DSCP EF and less or equal 100 bytes in size.

When it exits to the WAN interface GigabitEthernet1/3, it remains as EF or set to ip prec 5?

Neither, as egress policy doesn't remark.

2)The bandwidth part is policy-map queuing? What is service-policy queuing? policy-map set_bandwidth set bw as10M?

Don't understand your question; don't understand your question; yes, indirectly and it throttles actual available bandwidth with a shaper.

getawayuser51 · ‎11-29-2016

When these marked packets goes into the LAN interface GigabitEthernet1/2, it hits service-policy input qos_input? The packets becomes ip prec 5? due to "set ip precedence 5"

Yes and maybe. VOICE-EF class matches packets marked DSCP EF and less or equal 100 bytes in size.

Does it means tht packet no longer marked as EF but set to ip prec 5? or both marking? but why does it need to set ip prec 5? it is for bandwidth settings?

When it exits to the WAN interface GigabitEthernet1/3, it remains as EF or set to ip prec 5?

Neither, as egress policy doesn't remark.

Then voice EF packets entering LAN GigabitEthernet1/2 & going out WAN GigabitEthernet1/3 carries what marking?

policy-map queuing
class VOICE-PREC
priority 3072
class EMAIL-PREC
bandwidth 3072
class class-default
bandwidth 4096

policy-map set_bandwidth
class class-default
shape average 10240000
service-policy queuing

I meant these policies are working together right?

service-policy queuing map to policy-map queuing?

Thts the way to set bandwidth?

Joseph W. Doherty · ‎11-30-2016

Does it means tht packet no longer marked as EF but set to ip prec 5? or both marking? but why does it need to set ip prec 5? it is for bandwidth settings?

ToS only supports one marking at a time. BTW, IPPrec 5 and DSCP EF overlap bit usage, both have the same first 3 bit settings in ToS. IPPrec doesn't care what the rest of the ToS is, DSCP also uses the next 3 bits. I.e. IPPrec is a 3 bit code and DSCP is a 6 bit code.

Why the policies are doing such marking - I don't know - it's odd.

When it exits to the WAN interface GigabitEthernet1/3, it remains as EF or set to ip prec 5?

It depends on both the original marking and the size of the packet. Without knowing both, cannot answer that question.

Then voice EF packets entering LAN GigabitEthernet1/2 & going out WAN GigabitEthernet1/3 carries what marking?

Ditto as last answer.

I meant these policies are working together right?

Yes, if the traffic flows as you say, i.e. in g1/2 and out g1/3.

Thts the way to set bandwidth?

Unsure exactly what you mean by "set bandwidth".

The egress policy on g1/3, set_bandwidth, shapes all the egress to 10 Mbps. That policy, alone, doesn't care about any traffic markings. However, it has a child policy, queuing, which dequeues based on different class markings, one using IPPrec 5. Also BTW, matching against IPPrec5 also matches against DSCP EF.