Setting up QOS in for video conferencing.
rsjimmy
read much about QOS, studied for it, but never really seen it in
action. I just wanted to ask if there are techs here who have
implemented it in their production networks and what sort of pitfalls
to look out for with it. At this point I'm mostly interested in using
it for our video and voice locations, but wanted to know if when doing
so( I assume) it must be implemented all the way through the chain.
ie... remote site - to - core site - to - other remote. Maybe see some
stripped down interface configs to see it in action. Also some areas
cross routers on slower wan circuits and other locations are routed but
are connected gigabit; so I'm a bit interested as to how things are
treated differently over layer 2 connections and layer 3 connections. I
have read all about the ip precedence, the DIffServ, and QOS in
general, but am just really curious to see how it has been done by
someone in the real world out there. I hope I can get som egood input
here.. Thanks
Charlie Root
news:1141661530.0...@u72g2000cwu.googlegroups.com...
The most important thing is to understand your traffic profiles (what kind
of traffic, how much, from where, to where and how does it go), link
utilisation, queueing capabilities of the devices (how many queues
supported, scheduling of transit and self-originated traffic), how to treat
traffic on L2/L3 devices (i.e. do routers need to care about 802.1p settings
or not). Bear in mind that QoS configurations kick-in only when there is
congestion (that is when there is no space left in TX-ring buffer, which is
often much before your link is 90% loaded), all other time it's FIFO. Also,
enabling QoS does increase load on the devices, and more so if configuration
is suboptimal.
While you don't actually have to enable QoS all the way through the chain,
you do need to understand behaviour of the equipment when they don't have
QoS configuration explicitly applied. Obviously the overloaded 2Mbps links
are the first one where you should consider deployment of QoS policies,
while barely loaded gigabit links will hardly show any difference with or
without QoS applied.
If you have more specific questions - feel free to ask.
As for general reading you could start here
http://www.cisco.com/en/US/products/ps6558/products_ios_technology_home.html,
or get a book like "End-to-End QoS Network Design" (ISBN: 1-58705-176-1).
Kind regards,
iLya
J.Cottingim
path that the video/voice traffic would take. That would include Layer
2 in your core network even if it's gigabit attached.
That being said, one thing to remember that QoS only affects traffic on
an interface when there's contention for the available bandwidth. (ie.
Your link is)
Here's some hints...
* Bandwidth monitoring will not necessarily show the need for QoS as
it's normally monitored on an average over 5 minutes.
* If you're using ATM or Frame-Relay, do not oversubscribe the
physical link. Cisco's QoS works on a per-interface (or sub-interface)
basis. If you oversubscribe the link, all bets are off with regards to
QoS.
* If your using a managed MPLS WAN, you'll need to work with your
provider.
======================================================
There are probably a thousand different ways to implement QoS. Here's a
L3 EXAMPLE config for you as requested: (CBWFQ)
Ploycom<--->LAN<--->router-A <--->WAN<---> router-B<--->LAN<--->Polycom
Both routers have similar configs so only one is listed here.
======================================================
class-map match-all AUDIO-CLASS
match access-group name NEW-AUDIO-ACL
class-map match-all VIDEO-CLASS
match access-group name NEW-VIDEO-ACL
!
policy-map VID-CONF-POLICY
class AUDIO-CLASS
priority 96
class VIDEO-CLASS
bandwidth 320
class class-default
fair-queue
!
interface ATM0/0.11 point-to-point
description PVC to Remote Site
ip address 10.1.1.10 255.255.255.248
pvc 1/65
vbr-rt 768 768
oam-pvc manage
service-policy output VID-CONF-POLICY
!
interface FastEthernet0/0
ip address 10.11.1.1 255.255.255.0
!
ip access-list extended NEW-AUDIO-ACL
permit ip host 10.11.1.25 any dscp af41
ip access-list extended NEW-VIDEO-ACL
permit ip any host 10.11.1.25 dscp af42
======================================================
Here's the break down:
The ACL's and class-map's are used to classify the traffic.
The Policy-map assigns priority and bandwidth according to needs.
Then tie it all together on the interface the traffic would exit
from. with the service policy.
Remember that any QoS config is specific to the individual needs. -
taking in account for bandwidth needs, WAN speeds, etc. The example
above does not take in to account anything for routing protocol for
example.
J.Cottingim
rsjimmy
me to take the next step.
Thanks again