Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-ioam-sr-04

Stewart,

If we want to make sure that packets are processed at evey node, is the 
new FEC complementary to the ACH-header or an alternative?

/Loa

On 05/01/2021 00:30, Stewart Bryant wrote:
> 
> 
>> On 4 Jan 2021, at 14:38, Rakesh Gandhi (rgandhi) 
>> <rgandhi=40cisco.com@dmarc.ietf.org 
>> <mailto:rgandhi=40cisco.com@dmarc.ietf.org>> wrote:
>>
>> <RG> Yes, this is similar to the entropy label where a mid-point node 
>> needs to scan the label stack to find the indicator label. We can add 
>> some text to clarify this. There is already an optimization to use a 
>> different indicator label for HbH compared to E2E case to 
>> unnecessarily avoid parsing the IOAM data fields.
> 
> The EL is entirely optional to process. It is no more than a hint to use 
> in ECMP and there is no architectural requirement to find it to operate 
> correctly.
> 
> If iOAM is purely a option then you could scan the stack and hope that 
> you can reach down far enough to find it. Though there is a fight to see 
> who gets to be the lowest label in range of the forwarding parser.
> 
> If you want to be sure that iOAM is processed HxH then you really need 
> to run it on a new FEC with that behaviour built into the FEC. That 
> would be the architected way of doing this in MPLS.
> 
> - Stewart
> 
> 
> 
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-- 

Loa Andersson                        email: loa@pi.nu
Senior MPLS Expert                          loa.pi.nu@gmail.com
Bronze Dragon Consulting             phone: +46 739 81 21 64