QoS on 3560G

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Hi,


In looking around these forums, I found a link which has been very helpful in understanding more about QoS implementation.


http://www.cisco.com/en/US/docs/solutions/Enterprise/WAN_and_MAN/QoS_SRND/Enterprise_QoS_SRND.pdf


Here is a quote from that document:


"Always perform QoS in hardware rather than software when a choice exists.

Cisco IOS routers perform QoS in software. This places additional demands on the CPU, depending on the complexity and functionality of the policy. Cisco Catalyst switches, on the other hand, perform QoS in dedicated hardware ASICS and as such do not tax their main CPUs to administer QoS policies. You can therefore apply complex QoS policies at Gigabit/TenGigabitEthernet line speeds in these switches."


We have 3560G switches acting as access switches and are about to buy a router. As the above quote suggests, I would like to use the switches to do the better part of the QoS processing (in hardware), but it is not clear to me that the switches support it. Could someone clarify?


Thes switches have the Standard image (c3560-ipbase-mz.122-35.SE5) which does not appear to support AutoQos Enterprise - only AutoQoS Voip. What does that imply?


-What is the best practice for implementing Q0S on this hardware, in combination with a router?


-What router should we be looking at?


-How do we implement QoS across Vlans, giving higher priority to some vlans?


TIA

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Hi andres,


Thanks for the reply.


I think the document you reference is the same one that I reference earlier in this thread.


What are some of your best practices for QoS?


-Should we have a voice vlan (what about softphones on PCs)?

-What is the general architecture:

-Mark packets at the access switchport?

-Use QoS in the router rather than in the switches?

-Im not able to find a ios image that does QoS enterprise on a 3560S switch. Is this possible?


TIA

If you have already read it - surely you also saw:-


Should we have a voice vlan (what about softphones on PCs)? : Page 105


What is the general architecture: Page 54/58


Mark packets at the access switchport: Page 97


Use QoS in the router rather than in the switches: Page 53/180/230


Im not able to find a ios image that does QoS enterprise on a 3560S switch. Is this possible? : Depends what type of cco login you have, and your service contract - check with your support provider.

Joseph W. Doherty Tue, 07/14/2009 - 04:30
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"We have 3560G switches acting as access switches and are about to buy a router. As the above quote suggests, I would like to use the switches to do the better part of the QoS processing (in hardware), but it is not clear to me that the switches support it. Could someone clarify?"


Many switches do support "some" QoS, and they usually use hardware to provide it (for performance), but such QoS isn't usually as well featured as found on a router. Did you need further clarification?


"Thes switches have the Standard image (c3560-ipbase-mz.122-35.SE5) which does not appear to support AutoQos Enterprise - only AutoQoS Voip. What does that imply? "


Ah, it implies you won't be using Enterprise AutoQos. ;)


Actually, for the 3650, I don't think it's an issue of base image or IOS version, just that the device doesn't support QoS as utilized by Enterprise AutoQos. (See prior answer about limitations of QoS feature support on hardware.)


"What is the best practice for implementing Q0S on this hardware, in combination with a router? "


Can't say since its unclear why you need a router, since a 3560G is a L3 switch (limited L3 with base image, though).


"What router should we be looking at?"


One that serves your needs, which you haven't defined.


"How do we implement QoS across Vlans, giving higher priority to some vlans? "


Mark/tag all traffic from such VLANs such that you can provide it better treatment than traffic from other VLANs. (This implies markings or tags will be unique to some VLAN traffic.)


PS:

BTW, 3560 as access switches wastes their capabilities unless you intend to provide L3 to the edge. If you do intend that, you might want to upgrade their feature set.


Back to your question about router selection, small software routers tend to be good choices for WAN connections, where features rather than perfomance is often more important. However, if you're looking for just LAN routing, a L3 switch might be best choice. Not knowing anything about your LAN, can't suggest a device, although you might not need anything beyond your 3560Gs.

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