Mailing List Archive: Juniper CoS - Classifiers specifically

Just looking to bounce this off anyone in the know.

As I learn more about Juniper CoS in Junos, it appears to me that a Juniper
device comes by default acting as a Behavior Aggregate classifier on each
interface that has an ip address enabled. I'm saying this since I have IP's
on 3 interfaces, and I'm seeing Junos assign a default classifier to each of
those logical units.

I'm saying BA since I understand a BA classifier is one assigned using
class-of-service classifier like I see here. and not the other type MFC
(multi-field classifier) which uses a firewall filter

I'm wondering if the BA classifier stops working once an MFC is applied. It
sure seems to in testing. I feel like I've seen a diagram at some point or
document stating that MFC comes before BA in the CoS process chain. but I'm
not sure. If anyone has that link/doc please send it. I'd like to know for
sure.

Oh, btw, were in the world is all this default CoS stuff derived from? I'd
like to think it's in a file somewhere that I can see in shell perhaps. But
maybe not. Maybe it's actually compiled into the Junos operating systems
itself. Or is there a way to see "show configuration" with a special option
that shows automatic/default stuff like all this CoS info?

The available default classifiers.

root@srx-1> show class-of-service classifier | grep classifier

Classifier: dscp-default, Code point type: dscp, Index: 7

Classifier: dscp-ipv6-default, Code point type: dscp-ipv6, Index: 8

Classifier: dscp-ipv6-compatibility, Code point type: dscp-ipv6, Index: 9

Classifier: exp-default, Code point type: exp, Index: 10

Classifier: ieee8021p-default, Code point type: ieee-802.1, Index: 11

Classifier: ipprec-default, Code point type: inet-precedence, Index: 12

Classifier: ipprec-compatibility, Code point type: inet-precedence, Index:
13

Classifier: ieee8021ad-default, Code point type: ieee-802.1ad, Index: 41

The ipprec-compatibility classifier I find assigned to enabled interfaces.

root@srx-1> show class-of-service interface | grep
"object|classifier|logical"

Logical interface: ge-0/0/0.0, Index: 74

Object Name Type Index

Classifier ipprec-compatibility ip 13

Logical interface: ge-0/0/1.0, Index: 75

Object Name Type Index

Classifier ipprec-compatibility ip 13

Logical interface: irb.0, Index: 73

Object Name Type Index

Classifier ipprec-compatibility ip 13

Details of the classifier I see assigned to my enabled interfaces.

root@srx-1> show class-of-service classifier name ipprec-compatibility

Classifier: ipprec-compatibility, Code point type: inet-precedence, Index:
13

Code point Forwarding class Loss priority

000 best-effort low

001 best-effort high

010 best-effort low

011 best-effort high

100 best-effort low

101 best-effort high

110 network-control low

111 network-control high

(no user defined cos config is present)

root@srx-1> show configuration class-of-service | display set

root@srx-1>

Aaron

aaron1@gvtc.com

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Hey Aaron,

> I'm wondering if the BA classifier stops working once an MFC is applied. It
> sure seems to in testing. I feel like I've seen a diagram at some point or
> document stating that MFC comes before BA in the CoS process chain. but I'm
> not sure. If anyone has that link/doc please send it. I'd like to know for
> sure.

The implied default classifier is there until something else is
configured. As you say, you can review what is currently applied by
'show class-of-service interface'. And yes, firewall based
classification is done after the cos classifier, so firewall based
classification overrides what our cos configuration classified packet
to. You can use this to accomplish QPPB, such as instead of BGP based
blackholing, you'd have BGP based class downgrade for some
specifically selected SADDR or DADDR, signalled by BGP.

> Oh, btw, were in the world is all this default CoS stuff derived from? I'd
> like to think it's in a file somewhere that I can see in shell perhaps. But
> maybe not. Maybe it's actually compiled into the Junos operating systems
> itself. Or is there a way to see "show configuration" with a special option
> that shows automatic/default stuff like all this CoS info?

I believe they are compiled in. Juniper does also have a more
appropriate way to inject defaults via 'show configuration groups
junos-defaults', but that is not being used here. Of course this is
the common case, for any NOS vendor defaults are typically compiled
in, not injected via some common configuration scheme, in many cases
this is mandatory, because having no default is impossible, like you
cannot not have MTU.

The standard QoS config in Junos allows any internet user to have
their own protected 5% via class selector 6 and 7, potentially
disrupting your signalling protocols. I consider all Junos devices
misconfigured if QoS policy for edge interfaces is not explicitly
defined by the operator.

--
++ytti
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