Re: [Idr] some comments about the draft-ietf-idr-5g-edge-service-metadata-02.txt

[Linda Dunbar <[e-mail]>]

Zong Peng,

Thanks for the suggestions. Comments and replies are inserted below

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To: Linda Dunbar <[e-mail]>; kmajumdar <[e-mail]>; rainsword.wang <[e-mail]>; gyan.s.mishra <[e-mail]>
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Subject: [Idr] some comments about the draft-ietf-idr-5g-edge-service-metadata-02.txt

Hi, Linda, and the authors:


    Some comments about draft-ietf-idr-5g-edge-service-metadata-02.txt for your considerations.


    About the metric distribution, I think the BGP method is one of the important ways. And perhaps in CATS, we need to start from the simple cases. However, future extensions should be supported.
 IMHO, the way in this document should be supported in future versions of the CATS metric draft, for the scenario that the service instance does not support the direct notification of the computing information.

    For example, we can extend the format with more information to show it is extensible.
      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Service-Metadata Type       |        Length (2 Octets)      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Flags     |   FormatID    |   AlgoID      |   Reserved    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     |         Value (multiple Metadata sub-TLVs)                    |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              Figure 1: Edge Service Metadata Path Attribute
o  FormatID (1 octets): indicate a specific format, i.e., which set of TLVs would be included.
     o  AlgoID (1 octets): the suggested algorithm to compare the cost to reach the service in different servers.
[Linda] Does "FormatID" and "AlgoID" apply to all the sub-TLVs carried in the "Service-Metadata" Path attribute?  What if the Service metadata carried have different "Formats"?


    Thus, we can define different FormatIDs for different scenarios.


 Another suggestion about the draft is about the migration of the computing information. You can consider whether it is valuable and acceptable.
 In the current CATS framework draft, as shown below, the granularity of the computing information can be per-service instance Or aggregated per-site.
 [Linda] Absolutely should allow metrics Aggregated per-site, per-address-family, or per instance. They are reflected by different sub-TLVs carried within the Metadata Path Attribute.


   Note that, depending on the design considerations and service

   requirements, per-service instance computing-related metrics or

   aggregated per-site computing related metrics (and a combination

   thereof) can be used by a C-PS.  Using aggregated per-site computing

   related metrics appears as a privileged option scalability-wise, but

   relies on Egress CATS-Routers that connect to various service

   instances to select the proper service instance.
 [Linda] Agree
 However, IMHO, we can also merge the computing information in the per Egress Router granularity. The advantage is that we can merge again the computing information if more than one site connect to the Egress. However, more TLVs are needed here.
[Linda] We should allow both of the following scenarios

  *   network & DC are under one administrative control. Application running status & environment can be measured and analyzed by DC & application controller (however still need some algorithms to aggregate them together for meaningful indication)
  *   network operator doesn't have access to the application running status.

Example of Aggregation Descriptions


     It is said that a cluster of servers serving the same Application behind a Layer 7 Load balancer can be considered as one merged Application server.
     In this case, the compute metrics from each server within the site will be merged at the site level.
    Optionally, if the Egress can do another round of load balancing among the local sites that connects directly to it, the Egress can merge again the compute metrics from the local sites. The advantage is that we can reduce the metric information that needs to be transferred in the network. But new TLVs need to be designed.
[Linda] Agree.  How about adding the following section?
5.2 Service Delay Index
For a deployment environment where the network and the Edge Data Centers are under one administrative control, e.g., a Mobile Service Provider, the application/service running status & environment metrics collected by DC & application controller are much more meaningful than the IP layer load measurement collected by the Edge routers as described in Section 4.4.
However, it is not easy to predict which site has "the fastest processing time" or the shortest delay before the service request arrives because:

-       The given service instance shares the same physical infrastructure with many other applications & service instances. Service requests by other applications, UEs, or applications running behavior can impact the processing time for the given service instance.

-       The given service instance can be served by a cluster of servers behind a Load Balancer. To the network, the service is identified by one service ID.

-       The service complexity is different. One service may call many micro services, need to access multiple backend databases, need to go through sophisticated security scrubbing functions, etc. Another service can be responded with a few simple steps. Without application internal logic, it is difficult to estimate processing time.

Here are some metrics, which can be easily collected and measured. They are meaningful in predicting service processing time for a new service request:

o   CPU utilization for the server where the instance is instantiated

o   The network utilization for the links to the server where the instance is instantiated

o   The number of databases that the service instance will access

o   The memory utilization of the databases
While out of scope, we assume there is an algorithm that can derive the Service Delay Index from all the measurements above.

Thank you
Linda



Best Regards
Zongpeng Du

________________________________
[e-mail]<mailto:[e-mail]> & [e-mail]<mailto:[e-mail]>




[Idr] I-D Action: draft-ietf-idr-5g-edge-service-metadata-02.txt

[e-mail]<mailto:[e-mail]> Thu, 04 May 2023 23:17 UTCShow header<https://mailarchive.ietf.org/arch/msg/idr/YPgRgaQsE-YCiXadqcr6D4EsSKk/#>

A New Internet-Draft is available from the on-line Internet-Drafts

directories. This Internet-Draft is a work item of the Inter-Domain Routing

(IDR) WG of the IETF.

   Title           : BGP Extension for 5G Edge Service Metadata

   Authors         : Linda Dunbar

                     Kausik Majumdar

                     Haibo Wang

                     Gyan Mishra

   Filename        : draft-ietf-idr-5g-edge-service-metadata-02.txt

   Pages           : 19

   Date            : 2023-05-04

Abstract:

   This draft describes a new Metadata Path Attribute and some

   sub-TLVs for egress routers to advertise the Edge Service

   Metadata of the directly attached edge services (ES). The Edge

   Service Metadata can be used by the ingress routers in the 5G

   Local Data Network to make path selections not only based on

   the routing cost but also the running environment of the edge

   services. The goal is to improve latency and performance for

   5G edge services.

   The extension enables an edge service at one specific location

   to be more preferred than the others with the same IP address

   (ANYCAST) to receive data flow from a specific source, like

   specific User Equipment (UE).

The IETF datatracker status page for this Internet-Draft is:

https://datatracker.ietf.org/doc/draft-ietf-idr-5g-edge-service-metadata/

There is also an htmlized version available at:

https://datatracker.ietf.org/doc/html/draft-ietf-idr-5g-edge-service-metadata-02

A diff from the previous version is available at:

https://author-tools.ietf.org/iddiff?url2=draft-ietf-idr-5g-edge-service-metadata-02