Tag traffic based on service

[anousakisioannis]

Hello,

I would like to implement QoS based on service (e.g. ftp,smb,voip,etc..)

Our network is being consisted by 3850 L3 switches and all of our sites are being connected through L3 mpls. Our managed 3850 has adjacency with a local managed ISP router on every site.

Below an example of the topology

I was thinking to implement access lists and match the different types of service and then mark them with a dscp value

3850_site1#sh access-lists | sec TEST
Extended IP access list TEST
10 permit tcp 192.168.1.0 0.0.0.255 host 10.1.1.130 eq 445
20 permit tcp 192.168.1.0 0.0.0.255 host 10.1.1.125 eq ftp ftp-data

3850_site1#sh class-map TEST_CLASS
Class Map match-any TEST_CLASS (id 31)
Match access-group name TEST

3850_site1#sh policy-map TEST_POLICY
Policy Map TEST_POLICY
Class TEST_CLASS
set dscp af41

int g1/0/1

  service-policy output TEST_POLICY

Now, in the ISP_router1, there is a preconfigured class-map which matches some dscp values { cs4 af41 af42 af43 ef cs6 } and apply them the 50% of the available bandwidth. The other 50% is Best Effort. 

Below a part of the configuration of ISP

class-map match-any PREMIUM
  match dscp cs4 af41 af42 af43
class-map match-any PREMIUM-PLUS
  match dscp ef cs6
class-map match-any ALL-PREMIUM
  match class-map PREMIUM
  match class-map PREMIUM-PLUS
class-map match-any BASIC-PLUS
  match any

policy-map QOS-SCHEDULER-GI0/0
  class ALL-PREMIUM
    priority 10000
    police 10000000 conform-action transmit exceed-action transmit
  class BASIC-PLUS

policy-map QOS-SHAPER-GI0/0
  class class-default
    shape average 20000000
    service-policy QOS-SCHEDULER-GI0/0

int g0/0

   service-policy output QOS-SHAPER-GI0/0

Of course, the configuration on ISP side can be adjusted based on our needs, e.g. add new dscp values on the classes, etc..

With the current situation, we don't send any tagged traffic, so everything is considered as best effort, which cause problems when you try to access shared documents/folders, etc..

Can you please let me know if the way i am trying to implement QoS is a valid one? 

Any other suggestion/recommendation for this case is more than welcome. 

Thank you

[Joseph W. Doherty]

Yes it's a valid approach, but much depends on what QoS policies your SP will support.

If your SP will/can support FQ in the BE class, that often will meet 90%, or more, of your QoS needs. With FQ in BE, you might only need to tag and provide special treatment for traffic with critical service needs, like VoIP bearer.

[anousakisioannis]

Hello Joseph,

I am very familiar with QoS.

Can you please give me an example of what do you mean below?

thank you

[Joseph W. Doherty]

Most Cisco routers (not L3 switches) would support this:

policy-map sample1
class class-default
fair-queue

The above handles many QoS needs. What you would often add next is a PQ class like:

policy-map sample2
class real-time !e.g. VoIP bearer and/or video conferencing
priority percent 33
class class-default
fair-queue

For the above you would need to define something like:

class-map real-time match any
ip dscp ef

For a policy that can handle 99+%, you might try something like:

policy-map sample3
class real-time
priority percent 33
class HiPriority
bandwidth remaining percent 81
fair-queue
class LoPriority
bandwidth remaining percent 1
fair-queue
class class-default
bandwidth remaining percent 9
fair-queue

In the above, only really critical and light weight flows should go into the HiPriority class. LoPriority is for scavenger and/or low importance bandwidth hogs. You might also not need FQ in HiPriority and/or LoPriority classes.

[anousakisioannis]

Hello,

I have a question regarding the percentages of bandwidth.

For example, if i give 25% on smb, i guarantee this percentage on that traffic in case i have 100% consumption.

If there is available bandwidth and smb traffic requests it, is going to take it or with the percentage we lock a specific amount of bandwidth and nothing more?

[Joseph W. Doherty · Accepted solution]

"For example, if i give 25% on smb, i guarantee this percentage on that traffic in case i have 100% consumption."

Correct, assuming your policy also allocates the remaining 75%.

"f there is available bandwidth and smb traffic requests it, is going to take it or with the percentage we lock a specific amount of bandwidth and nothing more?"

The bandwidth statement doesn't "lock" or cap the bandwidth, it's to guarantee a minimum.

BTW, what actually happens, the bandwidth setting determine the bandwidth allocation ratio between classes. So, for example, if you only allocate two classes and assign each 25%, they be dequeued 1:1, or if both wanted all the bandwidth, each would obtain 50%. If you had 3 classes defined, they would still be dequeued 1:1. So if only two wanted all the bandwidth, each would obtain 50%, but if all 3 wanted all bandwidth, each would obtain 1/3.