04-30-2008 07:35 PM - edited 03-03-2019 09:46 PM
Hi,
My OSPF neighbors reset them selves, I want to apply qos for HELLO and SLA traffic. I want to mark them but not sure how much bandwidth I need to allocate for it.
Can someone please advise or an approperaite estimate/config?
Regards
05-01-2008 12:45 AM
Hi,
you can create a policy marking local traffic - originated by the router - with a specific IP preference value. Note, by default OSPF packets will be marked with IP preference 6. On the interfaces you can then include a class for this traffic in your policy-map. It is hard to tell which amount of bandwidth you should allocate, as this depends on parameters like interface bandwidth and also on how much local traffic the router generates. An example:
ip local policy route-map IPP6
route-map IPP6 permit 10
match ip address LocalPrioTraffic
set ip precedence 6
ip access-list extended LocalPrioTraffic
permit ospf any any
permit tcp any any eq telnet
permit tcp any eq telnet any
permit udp any any eq snmp
!
! Match your local traffic here, like telnet, SNMP, IPSLA, etc.
!
class-map match-any NMS
match ip precedence 6
policy-map MyQoS
class NMS
bandwidth percent 10
class class-default
fair-queue
random-detect
interface Serial0
ip address 10.1.1.1 255.255.255.252
bandwidth 128
service-policy output MyQoS
For a detailed syntax description please have a look at
http://www.cisco.com/en/US/docs/ios/12_2/iproute/command/reference/1rfindp1.html#wpxref37880
Be aware the service-policy will also "catch" all transit telnet traffic, respectively all traffic marked with IP precedence 6 and you need to allocate enough resources for the combined traffic (local+transit).
Hope this helps! Please use the rating system.
Regards, Martin
05-01-2008 04:28 PM
thanks for the suggestion, do I need to set IP LOCAL-POLICY given that the ospf traffic are marked with IP precedence 6. what about the policy below? isn't it enough to treat the ospf traffic as desired.
clss-map OSPF-TRAFFIC
match ip precedence 6
policy-map MY-POLICY
class OSPF-TRAFFIC
bandwidth percent 10
Given that OSPF traffics are marked with IP precedence 6 by default, I can just match them and give it 10% of the bandwidth.
Regards
05-01-2008 01:10 AM
Hello,
a reference document could be RFC 1245 "OSPF Protocol Analysis" where OSPF bandwidth usage is studied.
You have to take in account that even in a stable network LSAs are refreshed evry 30 minutes.
The bandwidth usage depends from the number of IP routes in the OSPF database.
OSPF packets have usually IP Prec = 6 so you can create a class-map for them and defines some bandwidth for it in a CBWFQ scheduler.
You don't need to mark OSPF packets.
Received OSPF packets are placed in a queue for process switching.
Because the bandwidth command in CBWFQ does not imply a fixed reservation don't be afraid of giving too much bandwidth to OSPF traffic.
Some platforms like a C3640 and other small ones have a system queue for routing traffic but other platforms like c7500 and 12000 haven't got one and you need to define one.
hope to help
Giuseppe
05-01-2008 04:32 PM
Thanks for the suggestion, this is what I am leaning towards as well and I have asked "mheusing" to confirm.
05-01-2008 01:21 PM
By default only 75% of the bandwidth configured on an ineterface is used by traffic. Rest 25% is reserved for use by protocol related traffic which include the Hello's & LSA's u were talking about. So if u are using default interface configurations, there seems no need to use any qos features.
05-01-2008 04:35 PM
Can you please post us the link for reference as I am not quite sure what the default interface configuration is. Because by default an interface doesn't have a bandwidth statement but it it's configured I assume it changes the default behaviour and there are other similar configs...
05-01-2008 11:13 PM
Hello,
this is not true for all the router platforms.
Best Regards
Giuseppe
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