Peter,
Is the following the correct summary of what you said?
- the egress edge router (A-ER) with the EC Servers directly attached can
advertise the "Site-Cost" via IP prefix reachability TLV associated with the
(anycast) prefix
- using Flexible algorithms to advertise the desired constrained SPF
computation methods, so that constrained IGP path can be computed as desired.
Thank you,
Linda
-----Original Message-----
From: Peter Psenak <[email protected]>
Sent: Friday, November 5, 2021 10:49 AM
To: Linda Dunbar <[email protected]>; [email protected]
Subject: Re: Question about how topology is calculated ( was RE: [Lsr] Looking
for feedback of using Flex Algo to advertise the 5G edge computing associated
metrics
Linda,
On 05/11/2021 16:36, Linda Dunbar wrote:
> Peter,
> You said
> " The flex-algo is a combination of (a)-Calc-Type, (b)-Metric-Type,
> and (c)-constraint"
> Does it mean that "Flex-Algorithm" value of the Flex-Algo Definition
> Sub-TLV is to indicate the combination of (a), (b), (c)?
yes, each flex-algo number represents a specific combination of (a), (b), and
(c), as defined by the user.
> Is the "(c) -constraint" carried in the sub-TLVs of the FAD TLV, such
> as the "FAD Flags Sub-TLV" ?
yes (c) is advertised in FAD.
thanks,
Peter
> Thank you,
> Linda
> -----Original Message-----
> From: Peter Psenak <[email protected]<mailto:[email protected]>>
> Sent: Friday, November 5, 2021 4:43 AM
> To: Linda Dunbar
> <[email protected]<mailto:[email protected]>>;
> [email protected]<mailto:[email protected]>
> Subject: Re: Question about how topology is calculated ( was RE: [Lsr]
> Looking for feedback of using Flex Algo to advertise the 5G edge
> computing associated metrics Linda, On 05/11/2021 00:20, Linda Dunbar
> wrote:
>> Peter,
>> You said:
>> /calculation type refers to how topology is calculated, / I thought
>> that the Flexible Algorithm Exclude/Include Admin Group Sub-TLV is to
>> indicate if a link belongs to a specific topology. Is my
>> understanding correct?
>> By indicating "Exclude/Include" bunch of links for a Calc-Type, does
>> it practically specify the topology?
> that's not how the flex-algorithm is defined.
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdata
> tracker.ietf.org%2Fdoc%2Fhtml%2Fdraft-ietf-lsr-flex-algo-18%23section-
> 4&data=04%7C01%7Clinda.dunbar%40futurewei.com%7Cc14fae9bf42e4fc2a1
> 6408d9a073bf22%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C6377172412
> 70768557%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiL
> CJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=naTIhgLANNDBD5BEgnjWQhG
> o8NcXDV8MISqoq99igFE%3D&reserved=0
> "To provide maximum flexibility, we want to provide a mechanism
> that
> allows a router to (a) identify a particular calculation-type,
> (b)
> metric-type, (c) describe a particular set of constraints, and
> (d)
> assign a numeric identifier, referred to as Flex-Algorithm, to
> the
> combination of that calculation-type, metric-type, and those
> constraints. We want the mapping between the Flex-Algorithm and
> its
> meaning to be flexible and defined by the user.
> The flex-algo is a combination of (a), (b), and (c).
> You are trying to define (a) that would have (b) and (c) hardcoded.
> That does not follow the defined architecture.
> thanks,
> Peter
>> Thank you, Linda
>> -----Original Message-----
>> From: Peter Psenak <[email protected]
>> <mailto:[email protected]<mailto:[email protected]%20<mailto:[email protected]>>>
>> Sent: Thursday, November 4, 2021 1:16 PM
>> To: Linda Dunbar <[email protected]
>> <mailto:[email protected]>>;
> [email protected]<mailto:[email protected]> <mailto:[email protected]>
>> Subject: Re: Question about the FAD Flags Sub-TLV ( was RE: [Lsr]
>> Looking for feedback of using Flex Algo to advertise the 5G edge
>> computing associated metrics Linda, please see inline:
>> On 04/11/2021 18:17, Linda Dunbar wrote:
>>> Peter,
>>> Thank you very much for the valuable feedback. We will move the
>>> content from Section 1, 2, 3 to an appendix per your suggestion.
>>> As for defining a new value in the Flexible Algorithm Definition
>>> Flags Sub-TLV, why can't we use the Metric-Type & Calc-Type to
>>> represent the information carried by the FAD Flags Sub-TLV?
>> because the Metric-Type in flex-algo is referring to link metrics,
>> not to prefix metrics. And Calc-Type you still wan to use SPF, don't you?
>>> draft-dunbar-lsr-5g-edge-compute-01 suggests to add a new value to
>>> the "Metric-Type" to indicate the Aggregated Cost AppMetaData
>>> Metrics included in computing the constrained SPF.
>>> Is it reasonable to use Calc-Type to indicate the options you mentioned?
>> no, calculation type refers to how topology is calculated, not
>> how/which prefix metrics is used.
>> thanks,
>> Peter
>>> For example:
>>>
>>> * Calc-Type-v1: replace the regular prefix metric,
>>> * Calc-Type-v2: the newly added metric is added on top,
>>> * Calc-Type-v3: only used as tiebreaker,
>>> * Calc-Type-v4: use the default prefix metric when the AppMetaData
>>> Metrics is not present. When AppMeteData metrics is not
>>>present,
>>> the prefix is considered normal that doesn't need special
>>>constraint
>>> SPF computation.
>>> * Calc-Type-v5: no transit across areas/domains
>>> * Calc-Type-v6: transit across areas/domains.
>>>
>>> Thank you,
>>> Linda
>>> -----Original Message-----
>>> From: Peter Psenak <[email protected] <mailto:[email protected]
>>> <mailto:[email protected]
> <mailto:[email protected]>>>
>>> Sent: Wednesday, November 3, 2021 7:43 AM
>>> To: Linda Dunbar <[email protected]
>>> <mailto:[email protected]>>;
>> [email protected]<mailto:[email protected]> <mailto:[email protected]> <mailto:[email protected]>
>>> Subject: Re: [Lsr] Looking for feedback of using Flex Algo to
>>> advertise the 5G edge computing associated metrics Hi Linda, I went
>>> through your document and here are my comments:
>>> 1. the section 1, 2, and 3 can probably be summarized in a single
>>> paragraph stating the problem you are trying to solve. The 5G
>>> details are redundant, you may just want to add reference to the parent
>>> document.
>>> 2. FAD is used to advertise how to compute the flex-algo paths, not
>>> to advertise metrics. What I believe you need to define for FAD is a
>>> new bit in the ISIS/OSPF Flexible Algorithm Definition Flags Sub-TLV
>>> to indicate that the calculation should use the new application
>>> prefix metric that you define and how exactly that metric will be
>>> used during
>>> calculation:
>>> a) does it replace the regular prefix metric, is added on top, only
>>> used as tiebreaker, etc,.
>>> b) what happens if the metric is not present with prefix
>>> advertisement, is the prefix considered unreachable for the
>>> flex-algo or do you fallback to regular prefix metric, etc,.
>>> c) how is the propagation of the new metric done between
>>> areas/domains 3. The new application metric should be advertised in
>>> the IP prefix reachability TLV associated with the (anycast) prefix.
>>> 4. How the application metric is calculated, using load, preference,
>>> etc, should be hidden from IGPs. I believe the application metric
>>> should be calculated at the egress router, associated with the
>>> prefix/Server-address and advertised in a form of the resulting value.
>>> If you need to consider Network Delay, you can combine the new app.
>>> metric (for prefixes) with the existing delay metric support (for
>>> links) in the flex-algo, no need to include network delay in the
>>> application metric itself. Advertising all the metadata and asking
>>> IGP at each node to derive the app metric seems sub-optimal, unless
>>> there is an unavoidable reason to do so.
>>> 5. I don't see any reason to define a new application in SABM as you
>>> do in section 7. The existing flex-algo app is sufficient.
>>> thanks,
>>> Peter
>>> On 14/10/2021 00:50, Linda Dunbar wrote:
>>>> LSR experts:
>>>>
>>>> We have updated the draft to reflect the suggestions from LSR WG to
>>>> use Flex Algo to advertise the metrics associated with the
>>>> environment where 5G edge computer servers are running.
>>>>
>>>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fd
>>>> a
>>>> tatracker.ietf.org%2Fdoc%2Fdraft-dunbar-lsr-5g-edge-compute%2F&
>>>> d
>>>> ata=04%7C01%7Clinda.dunbar%40futurewei.com%7Cb88dcb6627dd45adf57a08
>>>> d
>>>> 9a040a148%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637717021742
>>>> 3
>>>> 66778%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiL
>>>> C
>>>> JBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=d8aPiK9HO1hM9pFm9r6C5
>>>> V
>>>> LprerWSVEpJUhVvLvZPPM%3D&reserved=0
>>>>
>>>> In a nutshell, the draft proposes some new values in the Flex Algo
>>>> Definition Sub-TLV
>>>>
>>>> * A new Metric-Type is introduced to indicate the Aggregated Cost
>>>> AppMetaData Metrics included in computing the constrained SPF.
>>>> * Additional subsub-TLVs to be included in the Flex Algo
>>>>Definition
>>>> Sub-TLV to carry the detailed metrics for the constrained SPF.
>>>>
>>>> We are looking for feedback of our revised approach.
>>>>
>>>> Thank you.
>>>>
>>>> Linda Dunbar
>>>>
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