qos end to end in different wire section

[interfacedy]

Hi, End to end is one of feature of Qos. Please see this connection:  phone ------- (g1/1)switch1(g1/2) -------(g2/1)switch2(Core)

The cable between the phone and port g1/1 at switch1 is 1G 

The cable between g1/2 at switch 1 and g2/1 at switch2 is 10G

The phone send voice traffic(with ef). we have to set dscp trust at g1/1 and g1/2. 

Is it necessary to set dscp trust at g2/1 at switch2?

thanks

[balaji.bandi]

Quality of Service (QoS) is a mechanism or technology that handles network traffic and allocates capacity to ensure the performance of critical services like voice delivered when the links are saturated or fully consumed.

If you looking end to end, then you need to have the same mechanism to be used, where you can and possibly. its not matter is the speed 1GB or 10GB.

[Georg Pauwen]

Hello,

as far as I recall, ports are untrusted by default (which sets the initial internal DSCP value to zero). So in order to extend the assigned DSCP value, the port you mention has to be configured as below:

interface gigabitethernet 2/1
mls qos trust dscp

[interfacedy]

Thank you very much for helping understanding this! The same diagram is below

phone ------- (g1/1)switch1(g1/2) -------(g2/1)switch2(Core)

I believe you are correct. Here is what I think: traffic ef (0.9G for example) from phone entering g1/1 will keep its ef and get better treatment(higher priority) in switch1 and then after traffic ef entering g2/1 at switch2, the traffic lose ef due to no trust config. However the total traffic from the phone side is 1.2G at g2/1 while g2/1 is 10G port. so the voice traffic is not impacted. When the traffic goes back to g1/2, the traffic already lost ef. Although trust dscp at g1/2 at switch1, the traffic cannot have better treatment at this moment because it already lost ef. Is this reason why g2/1 need to trust dscp?  

[balaji.bandi]

Sure if this is inside LAN and in your control, i would deploy end to end QoS, once traffic leaving from end router to Internet we do not have control, but we are sure we marked till last point to assurance of QoS as voice packet get more priority.

[Joseph W. Doherty]

"Older" Cisco switches (e.g. 3500s) QoS was disabled, by default.  With QoS disabled, switch ignores packet's ToS field.

On the same "older" Cisco switches, when QoS was enabled, by default, ingress packet's ToS field was (re)set to zero unless port trusted or an ingress policy tied to the port.

On "later" Cisco switches (e.g. 3850s), QoS is enabled by default and port is implicitly trusted.

(BTW, Cisco ISRs have always implicitly trusted ingress packet's ToS.  Usually, though, by default, there was no difference in handling a packet with ToS set to non-zero.)

[interfacedy]

Thank you all for your reply. How do you answer the below question? I guess cisco document does not talk about it.

phone ------- (g1/1)switch1(g1/2) -------(g2/1)switch2(Core)

Here is what I think: traffic ef (0.9G for example) from phone entering g1/1 will keep its ef and get better treatment(higher priority) in switch1 and then after traffic ef entering g2/1 at switch2, the traffic lose ef due to no trust config. However the total traffic from the phone side is 1.2G at g2/1 while g2/1 is 10G port. so the voice traffic is not impacted. When the traffic goes back to g1/2, the traffic already lost ef. Although trust dscp at g1/2 at switch1, the traffic cannot have better treatment at this moment because it already lost ef. Is this reason why g2/1 need to trust dscp?