[j-nsp] Junos CoS - how to set PLP bit depending on a Bandwi
dth threshold ?
MPuras at solunet.com
MPuras at solunet.com
Tue Aug 5 12:55:05 EDT 2003
Thanks Robert. I which I would off had that tid bit before diving into CoS
and trying to understand it. That certainly clarifies a lot of my thoughts.
I was not clear on how it was determined. Going back to your comment at the
end of the email, there is an article on the knowledgebase that stated that
Juniper uses bit 2 of the IP ToS field for PLP but that this is proprietary.
Can you elaborate more on that? Thanks.
Mario Puras
SoluNet Technical Support
Mailto: mpuras at solunet.com
Direct: (321) 309-1410
888.449.5766 (USA) / 888.SOLUNET (Canada)
>-----Original Message-----
>From: Robert O'Hara [mailto:rohara at juniper.net]
>Sent: Tuesday, August 05, 2003 11:40 AM
>To: MPuras at solunet.com; Guy.Davies at telindus.co.uk;
>mourad.berkane at lambdanet.fr; juniper-nsp at puck.nether.net
>Subject: RE: [j-nsp] Junos CoS - how to set PLP bit depending on a
>Bandwi dth threshold ?
>
>
>Hi Mario..
>
>When two streams are ingressing the router and are destined
>for the queue, Drop Profiles, along with Policers or Filters,
>can make the packets of one stream more eligible for discard
>than the other.
>
>The PLP (packet loss priority) bit, which can be flexibly
>assigned using a firewall filter match statement may assign
>loss priority HIGH as an action for a packet that meets the
>match criteria (as noted in Guy's earlier email). The PLP
>bit is not part of the IP Precedence or DSCP field. The PLP
>bit is an internal router value that is associated with the
>individual packet and lives within the (notification*). The
>PLP bit never becomes part of the transmitted packet.
>
>* The notification is the internal message that is the result
>of lookup in the packet forwarding engine (PFE). So, do not
>confuse PLP with IP Precedence or DSCP.
>
>So, if we want to use PLP to assign high loss to one type of
>traffic, we would perform the following:
>
>For example:
>
>[edit firewall]
>M20># show
>family inet {
> filter Set_PLP {
> term 1 {
> then {
> loss-priority high;
> accept;
> }
> }
> }
>}
>
>
>Next, the filter is assigned to the ingress logical interface
>whose traffic will have a higher discard eligibility.
>
>[edit interfaces so-0/2/0]
>M20># show
>no-keepalives;
>encapsulation ppp;
>sonet-options {
> fcs 32;
>}
>unit 0 {
> family inet {
> filter {
> input Set_PLP;
> }
> address 1.1.1.1/24;
> }
> family mpls;
>}
>
>Next, the drop profiles are created and queue fullness/drop
>points are assigned:
>
>[edit class-of-service drop-profiles]
>M20># show
>in-contract {
> fill-level 100 drop-probability 100;
>}
>discard-eligible {
> interpolate {
> fill-level [ 0 10 15 17 19 21 22 23 24 25 26 27 28 29 30 ];
> drop-probability [ 0 1 3 5 7 12 15 19 25 31 39 50 63 79 100 ];
> }
>}
>
>Finally, the drop-profiles are assigned to the correct scheduler:
>
>[edit class-of-service schedulers best-effort]
>M20># show
>best-effort {
> transmit-rate remainder exact;
> priority low;
> drop-profile-map loss-priority low protocol any
>drop-profile in-contract;
> drop-profile-map loss-priority high protocol any
>drop-profile discard-eligible;
>}
>
>So - the PLP bit is not part of any published prioritaztion
>scheme and is relevant only within Junos.
>
>Thanks,
>
>Bob O'Hara
>
>Systems Engineer
>Juniper Networks - 'Every Bit IP'
>
>...........................................
>. Email: rohara at juniper.net .
>. Web: http://www.juniper.net .
>...........................................
>
>
>
>-----Original Message-----
>From: juniper-nsp-bounces at puck.nether.net
>[mailto:juniper-nsp-bounces at puck.nether.net]On Behalf Of
>MPuras at solunet.com
>Sent: Tuesday, August 05, 2003 9:51 AM
>To: Guy.Davies at telindus.co.uk; mourad.berkane at lambdanet.fr;
>juniper-nsp at puck.nether.net
>Subject: RE: [j-nsp] Junos CoS - how to set PLP bit depending on a
>Bandwi dth threshold ?
>
>
>Depending on your interfaces, you "could" also set the PLP bit by
>configuring the receive-bucket on the interface and setting
>the overflow
>setting to "tag" although I would prefer using firewall policer.
>
>Just for clarification, does Juniper also uses the LSB in the
>precedence
>field to tag a packet with a drop precedence? I have heard
>that they use a
>different bit (I think it was bit 2) and that it is
>propriatery. Is it the
>same bit when using IP Precendence or DSCP? Could anyone
>clarify please?
>
>
>Also on the example below, why would you want to discard the
>traffic if you
>are setting the PLP and assigning it to a FC?
>
>Thanks for your help.
>
>
>Thanks,
>
>Mario Puras
>SoluNet Technical Support
>Mailto: mpuras at solunet.com
>Direct: (321) 309-1410
>888.449.5766 (USA) / 888.SOLUNET (Canada)
>
>
>
>>-----Original Message-----
>>From: Guy Davies [mailto:Guy.Davies at telindus.co.uk]
>>Sent: Tuesday, August 05, 2003 8:51 AM
>>To: 'Mourad BERKANE'; juniper-nsp at puck.nether.net
>>Subject: RE: [j-nsp] Junos CoS - how to set PLP bit depending on a
>>Bandwi dth threshold ?
>>
>>
>>
>>-----BEGIN PGP SIGNED MESSAGE-----
>>Hash: SHA1
>>
>>Hi Mourad,
>>
>>The simple answer is "yes".
>>
>>firewall {
>> policer <blah> {
>> if-exceeding {
>> bandwidth-percent N;
>> burst-size M;
>> }
>> then {
>> loss-priority (high|low);
>> forwarding-class <foobar>;
>> discard;
>> }
>> }
>>}
>>
>>Regards,
>>
>>Guy
>>
>>- -----Original Message-----
>>From: Mourad BERKANE [ mailto:mourad.berkane at lambdanet.fr
>><mailto:mourad.berkane at lambdanet.fr> ]
>>Sent: Tuesday, August 05, 2003 1:24 PM
>>To: juniper-nsp at puck.nether.net
>>Subject: [j-nsp] Junos CoS - how to set PLP bit depending on a
>>Bandwidth
>>threshold ?
>>
>>
>>
>>
>>Is it possible with current Junos version to associate the
>>class-of-service
>>classification of the *internal* CoS PLP bit(used by RED drop
>>profile) with
>>a bandwidth policer:
>>
>>IF BW > threshold THEN plp-set ELSE plp-clear
>>
>>Hope it's possible :-)
>>
>>Thanks in advance.
>>Mourad
>>
>>
>>-----BEGIN PGP SIGNATURE-----
>>Version: PGP 8.0
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>>iQA/AwUBPy+oSI3dwu/Ss2PCEQIA/QCgzGZdEtpWyhkC1Gr1KRb/fnCja+IAn2GN
>>IvGoUWeB1s4VlBn+xdxPcibg
>>=EO6N
>>-----END PGP SIGNATURE-----
>>
>>
>>
>>
>>
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