Re: [Lsr] I-D Action: draft-ietf-ospf-mpls-elc-15.txt

wangyali <> Thu, 04 June 2020 03:09 UTC

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From: wangyali <>
To: Peter Psenak <>, "" <>
Thread-Topic: [Lsr] I-D Action: draft-ietf-ospf-mpls-elc-15.txt
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Subject: Re: [Lsr] I-D Action: draft-ietf-ospf-mpls-elc-15.txt
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Hi Peter,

Please see inline <Yali2>. Thanks.

-----Original Message-----
From: Peter Psenak [] 
Sent: Wednesday, June 3, 2020 11:04 PM
To: wangyali <>om>;
Subject: Re: [Lsr] I-D Action: draft-ietf-ospf-mpls-elc-15.txt


On 03/06/2020 15:51, wangyali wrote:
> Hi Peter,
> Thanks for your reply. please see inline <Yali>.
> -----Original Message-----
> From: Peter Psenak []
> Sent: Wednesday, June 3, 2020 7:44 PM
> To: wangyali <>om>;
> Subject: Re: [Lsr] I-D Action: draft-ietf-ospf-mpls-elc-15.txt
> Yali,
> On 03/06/2020 13:35, wangyali wrote:
>> Hi authors,
>> After reading this draft, I am not clear with following points.
>> First,  as said " Even though ELC is a property of the node, in some cases it is advantageous to associate and advertise the ELC with a prefix.", what are "some cases" in which it is advantageous to associate and advertise the ELC with a prefix? And ELC is a property of the node, why don't extend the OSPF RI Opaque LSA to carry ELC?
> this has been discussed on the WG alias endlessly, please go over the archives.
> <Yali> Thanks. I think I lost some emails. I will search them. While I suggest give an illustration or some examples about the "some cases" in the draft. Please take it into account.

I will not make any changes to the draft at this point. The draft is in the RFC queue, too late to make changes.
<Yali2> Thanks. I am going over the mail archive to find these cases. I am very willing to learn and understand key points of this draft. 

>> Second, as said " If a router has multiple interfaces, the router MUST NOT announce ELC unless all of its interfaces are capable of processing ELs. ", why do not consider ELC advertisement in link granularity?
> and how do you as a remote router know over which interface, or better line card, the traffic that you are sending going to arrive on a remote node? Does not make much sense.
> <Yali> So can we say that ELC advertisement in node granularity is expressed by host prefix attributes advertisement?

yes, pretty much that is the idea.
<Yali2> I am appreciate if you could summary the reason.

>> Third, as said " If the router supports ELs on all of its interfaces, it SHOULD advertise the ELC with every local host prefix it advertises in OSPF.", what is the "every local host prefix"?
> it's a locally generated host prefix.
>> Last one, as defined that ERLD is advertised in a Node MSD TLV, why the ERLD-MSD type can be received in the OSPFv2 or OSPFv3 Link MSD sub-TLV? " When the ERLD-MSD type is received in the OSPFv2 or OSPFv3 Link MSD Sub-TLV [RFC8476], it MUST be ignored."
> yes, what's wrong with that statement?
> <Yali> I think it will not happen. Why is it necessary to specify this case?

If someone sends this as link MSD, we need to say how to deal with it as in general MSDs can be send as node or link attributes.
<Yali2> OK. I think I got your point and I read sec.4 again. So ERLD advertisement in a Node MSD TLV [RFC8476] is an optional method but not mandatory, is it right?


> regards,
> Peter
>> Best regards,
>> Yali
>> -----Original Message-----
>> From: []
>> Sent: Monday, June 1, 2020 4:42 PM
>> To:
>> Cc:
>> Subject: [Lsr] I-D Action: draft-ietf-ospf-mpls-elc-15.txt
>> A New Internet-Draft is available from the on-line Internet-Drafts directories.
>> This draft is a work item of the Link State Routing WG of the IETF.
>>           Title           : Signaling Entropy Label Capability and Entropy Readable Label Depth Using OSPF
>>           Authors         : Xiaohu Xu
>>                             Sriganesh Kini
>>                             Peter Psenak
>>                             Clarence Filsfils
>>                             Stephane Litkowski
>>                             Matthew Bocci
>> 	Filename        : draft-ietf-ospf-mpls-elc-15.txt
>> 	Pages           : 9
>> 	Date            : 2020-06-01
>> Abstract:
>>      Multiprotocol Label Switching (MPLS) has defined a mechanism to load-
>>      balance traffic flows using Entropy Labels (EL).  An ingress Label
>>      Switching Router (LSR) cannot insert ELs for packets going into a
>>      given Label Switched Path (LSP) unless an egress LSR has indicated
>>      via signaling that it has the capability to process ELs, referred to
>>      as the Entropy Label Capability (ELC), on that LSP.  In addition, it
>>      would be useful for ingress LSRs to know each LSR's capability for
>>      reading the maximum label stack depth and performing EL-based load-
>>      balancing, referred to as Entropy Readable Label Depth (ERLD).  This
>>      document defines a mechanism to signal these two capabilities using
>>      OSPFv2 and OSPFv3 and BGP-LS.
>> The IETF datatracker status page for this draft is:
>> There are also htmlized versions available at:
>> A diff from the previous version is available at:
>> Please note that it may take a couple of minutes from the time of submission until the htmlized version and diff are available at
>> Internet-Drafts are also available by anonymous FTP at:
>> _______________________________________________
>> Lsr mailing list