ASK THE EXPERTS - QoS with Cisco expert Sarala Akella - Page 2

ciscomoderator · ‎03-25-2011

Welcome to the Cisco Support Community Ask the Expert conversation. This is an opportunity to learn about configuration and troubleshooting Quality of Service on routers with Cisco expert Sarala Akella. Sarala is a customer support engineer at the Cisco Technical Assistance Center. She currently works in the WAN team where she focuses on various WAN related issues along with QoS issues on various interfaces. Sarala has been with Cisco for 11 years and has worked as a software engineer in the Network Software and Systems Technology Group. She holds a masters degree in computer engineering from Santa Clara University and a masters degree in mathematics from Osmania University, India.

Remember to use the rating system to let Sarala know if you have received an adequate response.

Sarala might not be able to answer each question due to the volume expected during this event. Remember that you can continue the conversation on the WAN, Routing and Switching discussion forum shortly after the event. This event lasts through April 8, 2011. Visit this forum often to view responses to your questions and the questions of other community members.

prima.ramadhan · ‎03-29-2011

Hi,

anyone has information on how to map traffic in GSM backbone? I mean traffic from SGSN should be classify to which PHB class, whlie traffic from MSC/MGW should go to which PHB class. Please point me to some documents or maybe personal experience in implementing this.

Thanks,

Prima

sakella · ‎04-01-2011

Hello,

This disscussion is specfic to QoS on router. Please post other questions on the support commuity discussion.

Best Regards

-Sarala

jwarner · ‎03-30-2011

Hello again . .

I have a Catalyst 6500 sup720 that has QoS enabled globally with 'mls qos'. Without changing that, is it possible to pick a particular interface and set it back to FIFO behavior? I'm looking for an interface command that will override the globally enabled default. This is 12.2SX.

thanks.

hgo.ros12345 · ‎03-31-2011

hello.

im trying to configure a eagle server, i got the image software from internet i mounted it to get the computer belives that it is a cd, im not really get to install it. could you help how can i get it plis.? hugo_rosario@hotmail.es hdejesus@impletek.com

. Dom Rep.

sakella · ‎03-31-2011

Once we enable the " mls qos" globaly the queues on the interfaces will be created.

But if we don't have any queuing mechanism configured. By default it will be using only queue 0.

So technically it is doing FIFO :-)

So enable mls qos globaly but don't configure any wrr or prioity queue 's .

jwarner · ‎04-03-2011

'mls qos' causes the buffer memory to be broken up into as many queues are supported. Won't most of the memory

get reserved for the inactive unused queues?

Thanks.

sakella · ‎04-04-2011

Hello,

By default system allocates 50 % of memory. The rest is allocated on need basis.

Also you can adjust the queues using

mls qos queue-set output qset-id buffers allocation1 ... allocation4

Here is the link

http://www.cisco.com/en/US/partner/docs/switches/lan/catalyst3750/software/release/12.2_55_se/configuration/guide/swqos.html#wp1179728

Tobias.Pettersson · ‎03-31-2011

Hi Sarala,

I´m about to set up QoS in the enterprise network but there seems to be some limitations on the routers.

We have links going out from Cisco 7600 routers connected to a HiT7025 which provides Ethernet to STM-1 connection. From the HiT7025 we have different numbers of STM-1 going out and I want to limit the egress traffic on the Cisco 7600 depending on the number of STM-1 going out from the HiT7025. I also want to guarantee bandwidth for voice traffic (DSCP 46). The Cisco 7600 is equipped with the following, which from what I can read has very limited QoS features. I have an idea how I could priorities traffic using queuing but that won´t give me a per port policing. I could adjust the max threshold but it would be the same on all ports on the same ASIC. Another option would be to use a policy-map and police traffic on the interfaces but that won´t priorities certain traffic. Do you have any solution for my problem that gives both some kind of policing and priority?

1 24 CEF720 24 port 1000mb SFP WS-X6724-SFP

1 Centralized Forwarding Card WS-F6700-CFC

5 2 Route Switch Processor 720 (Active) RSP720-3C-GE

5 Policy Feature Card 3 7600-PFC3C

5 C7600 MSFC4 Daughterboard 7600-MSFC4

Thanks,

Tobias

sakella · ‎03-31-2011

On 7600 QoS is lttle different compared to other routers.

In most cases for voice configure the strict priority class.
Then police the traffic, This will work exactly like LLQ on other routers for voice.
Here is sample configuration:

Policy Map child-pos
   Class prec1
     priority
    police cir 1000000 bc 31250 be 31250 conform-action transmit exceed-action drop
   Class prec2
     bandwidth remaining 50 (%)
   Class prec3
     bandwidth remaining 30 (%)
   Class class-default
     bandwidth remaining 20 (%)
!
   Class class-default
     bandwidth 2200 (kbps)
     shape average 3000000 12000 12000
     service-policy child-pos
!

Here are the documents for configuring QOs on 7600 with STm1 and flexwan modules

http://www.cisco.com/en/US/docs/routers/7600/install_config/12.2SX_OSM_config/qos.html
http://www.cisco.com/en/US/docs/routers/7600/install_config/flexwan_config/flexqos.html

Alcides Miguel · ‎03-31-2011

Hi Sarala,

1º

I´m new to QoS, and i lov get control and know what real is happening, so my scenario is i've up and running a remote vpn on cisco 2801 using ipsec tunnel, and my teleworkers have access to my internal network to file sharing, email, telefone using Cisco IP Comunicator, i would like to give voice data precedence over file sharing... can it be down over the vpn tunnel?

2º

Another question is i've sapareted router for internet access and, how can i give email high priority through http traffic?

sakella · ‎03-31-2011

For the Ip sec tunnel the encrytion happen at the end points. we can apply the the service policy on the
physical interface. The cryptomap for the ip sec tunnel.

Here is the sample configuration:

access-list 100 permit udp any any range 16384 32000
access-list 101 permit tcp any any eq 1720
access-list 102 permit tcp any any eq 80
access-list 103 permit tcp any any eq 23
!
class-map match-all voip
match access-group 100
class-map match-all voip-control
natch access-group 101
class-map match-all data1
match access-group 102
class-map match-all data2
match access-group 103
!
policy-map llq
class voip
priority 32
class data1
bandwidth 64
class data2
bandwidth 32
class class-default
fair-queue
!
interface Serial1/0
bandwidth 256
service-policy output llq

To answer the 2end question

For the email traffic create a class. check how you can match email traffic in class-map.
May be you can use the ACl and match the ip address of the email server.
In the policy-map you can give bandwidth or priority.

Prioity is not recommended as it will have inbuilt policer and drop excess packets.
snice its email giving appropriate bandwidth will be helpfull.

Here is a good document on configuring QoS for voice

http://www.cisco.com/en/US/partner/tech/tk652/tk698/technologies_tech_note09186a00800f6cf8.shtml

JDMJeffy84 · ‎04-01-2011

Hello Sarala!

Finally my chance to get free consultation wooo!

I'm a bit confuzzled with QoS at the moment, I'm ok with the WAN side -class maps & policy maps... but with LAN QoS I'm struggling!

I have a L3 switching enviornment, and the way we've set up QoS is AutoQos.

I know this method uses Cisco best practises but I want to prioritise some traffic over others. How would I go about this?

From what I've learnt is that QoS only kicks in when the hardware queue is full and congested and that's when the Software queue kicks in (LLQ/CBWFQ)

I can set up the software queue no problemo but I want to enhance the hardware queue, because we have different models throughout the campus, for example 6500 - 3750s

6500 QoS scheduling:       rx-(1q8t), tx-(1p3q8t)
3750 QoS scheduling:       rx-(not configurable on per port basis),
                                       tx-(4q3t) (3t: Two configurable values and one fixed.)

For each different device they have different hardware queues... So how do you map these together with causing too much latency, jitter etc etcly

I know usually switching you don't need QoS but we need to pass SAN traffic through our network (no money for seperate link =[ )

Thanks

sakella · ‎04-01-2011

For the Auto QoS question

- Auto qos would enable priority/standard queues and allocate traffic to the queues based on the QoS markings.

- Enable autoQoS before you configure other QoS commands. If necessary, you can modify the QoS configuration after the autoQoS configuration completes.

To answer the hardware queue I would say

- The markings have significance internal to the device to decide how to process the traffic within each queue. Each hardware/line card has its own queuing structure both Rx/Tx direction, this structure is independent of the adjacent device sending/receiving traffic.

There is no-way/no-need to change the queuing structure of line card.

- ‘Show queuing int Gig detail’ will display the queuing structure of the hardware.

Dennis Olvany · ‎04-01-2011

I have recently done some analysis of dscp values coming in from the internet. Some internet traffic is tagged such that it is utilizes queues on the private wan reserved for voice and video. It is apparent that a trust boundary must be established. The following configlet should be sufficient to retag any inbound internet traffic on a 7200 edge router. I am curious if this is the preferred solution to establish this boundary.

policy-map test
class class-default
set ip dscp default

int wan
service-policy input test

sakella · ‎04-01-2011

I like the idea :-). Just make sure only internet traffic is only matched in the default-class.