[Search] [txt|pdf|bibtex] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04                                                
Network Working Group                                L. Dunbar
Internet Draft                                         H. Chen
Intended status: Standard                            Futurewei
Expires: September 10, 2021                         Aijun Wang
                                                 China Telecom
                                                March 10, 2021

          OSPF extension for 5G Edge Computing Service
          draft-dunbar-lsr-5g-edge-compute-ospf-ext-04

Abstract
   This draft describes an OSPF extension for routers to
   advertise the running status and environment of the
   directly attached 5G Edge Computing servers. The
   AppMetaData can be used by the routers in the 5G Local Data
   Network to make intelligent decisions to optimize the
   forwarding of flows from UEs. The goal is to improve
   latency and performance for 5G Edge Computing services.

Status of this Memo
   This Internet-Draft is submitted in full conformance with
   the provisions of BCP 78 and BCP 79.

   This Internet-Draft is submitted in full conformance with
   the provisions of BCP 78 and BCP 79. This document may not
   be modified, and derivative works of it may not be created,
   except to publish it as an RFC and to translate it into
   languages other than English.

   Internet-Drafts are working documents of the Internet
   Engineering Task Force (IETF), its areas, and its working
   groups.  Note that other groups may also distribute working
   documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of
   six months and may be updated, replaced, or obsoleted by
   other documents at any time.  It is inappropriate to use
   Internet-Drafts as reference material or to cite them other
   than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt



xxx, et al.           Expires September 10, 2021      [Page 1]


Internet-Draft     OSPF Extension for 5G EC Service

   The list of Internet-Draft Shadow Directories can be
   accessed at http://www.ietf.org/shadow.html

   This Internet-Draft will expire on April 7, 2021.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as
   the document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's
   Legal Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the
   date of publication of this document. Please review these
   documents carefully, as they describe your rights and
   restrictions with respect to this document. Code Components
   extracted from this document must include Simplified BSD
   License text as described in Section 4.e of the Trust Legal
   Provisions and are provided without warranty as described
   in the Simplified BSD License.

Table of Contents


   1. Introduction........................................... 3
      1.1. 5G Edge Computing Background...................... 3
      1.2. Problem#1: ANYCAST in 5G EC Environment........... 4
      1.3. Problem #2: Unbalanced Anycast Distribution due to
      UE Mobility............................................ 5
      1.4. Problem 3: Application Server Relocation.......... 5
   2. Conventions used in this document...................... 5
   3. Solution Overview...................................... 7
      3.1. Flow Affinity to an ANYCAST server................ 8
      3.2. IP Layer Metrics to Gauge App Server Running Status
      ....................................................... 8
      3.3. To Equalize traffic among Multiple ANYCAST
      Locations.............................................. 9
      3.4. Reason for using IGP Based Solution.............. 10
   4. Aggregated Cost Computed by Egress routers............ 11
      4.1. OSPFv3 LSA to carry the Aggregated Cost.......... 11
      4.2. OSPFv2 LSA to carry the Aggregated Cost.......... 11
   5. IP Layer App-Metrics Advertisements................... 11
      5.1. OSPFv3 Extension to carry the App-Metrics........ 12



Dunbar, et al.        Expires September 10, 2021      [Page 2]


Internet-Draft     OSPF Extension for 5G EC Service

      5.2. OSPFv2 Extension to advertise the IP Layer App-
      Metrics............................................... 13
      5.3. IP Layer App-Metrics Sub-TLVs.................... 14
   6. Soft Anchoring of an ANYCAST Flow.... Error! Bookmark not
   defined.
   7. Manageability Considerations.......................... 16
   8. Security Considerations............................... 16
   9. IANA Considerations................................... 16
   10. References........................................... 16
      10.1. Normative References............................ 17
      10.2. Informative References.......................... 17
   11. Acknowledgments...................................... 18

1. Introduction

   This document describes an OSPF extension to distribute the
   5G Edge Computing App running status and environment so
   that other routers in the 5G Local Data Network (LDN) can
   make intelligent decisions to optimize the forwarding of
   flows from UEs. The goal is to improve latency and
   performance for 5G Edge Computing services.

 1.1. 5G Edge Computing Background

   As described in [3GPP-EdgeComputing], it is desirable for a
   mission critical Application to have multiple Application
   Servers hosted in multiple Edge Computing data centers to
   minimize the latency and to optimize the user experience.
   Those Edge Computing data centers are usually very close to
   or co-located with 5G base stations.

   When a UE (User Equipment) initiates application packets
   using the destination address from a DNS reply or its
   cache, the packets from the UE are carried in a PDU session
   through 5G Core [5GC] to the 5G UPF-PSA (User Plan Function
   - PDU Session Anchor). The UPF-PSA decapsulates the 5G GTP
   outer header and forwards the packets from the UEs to the
   Ingress router of the Edge Computing (EC) Local Data
   Network (LDN) which is responsible for forwarding the
   packets to the intended destinations.

   When the UE moves out of coverage of its current gNB (next-
   generation Node B) (gNB1), the handover procedure is
   initiated which includes the 5G SMF (Session Management


Dunbar, et al.        Expires September 10, 2021      [Page 3]


Internet-Draft     OSPF Extension for 5G EC Service

   Function) selecting a new UPF-PSA [3GPP TS 23.501 and TS
   23.502]. When the handover process is complete, the UE has
   a new IP address and the IP point of attachment is to the
   new UPF-PSA. 5GC may maintain a path from the old UPF to
   new the UPF for a short time for SSC [Session and Service
   Continuity] mode 3 to make the handover process more
   seamless.
   +--+
   |UE|---\+---------+                 +------------------+
   +--+    |  5G     |    +---------+  |   S1: aa08::4450 |
   +--+    | Site +--++---+         +----+                |
   |UE|----|  A   |PSA| Ra|         | R1 | S2: aa08::4460 |
   +--+    |      +---+---+         +----+                |
  +---+    |         |  |           |  |   S3: aa08::4470 |
  |UE1|---/+---------+  |           |  +------------------+
  +---+                 |IP Network |       L-DN1
                        |(3GPP N6)  |
     |                  |           |  +------------------+
     | UE1              |           |  |  S1: aa08::4450  |
     | moves to         |          +----+                 |
     | Site B           |          | R3 | S2: aa08::4460  |
     v                  |          +----+                 |
                        |           |  |  S3: aa08::4470  |
                        |           |  +------------------+
                        |           |      L-DN3
   +--+                 |           |
   |UE|---\+---------+  |           |  +------------------+
   +--+    |  5G     |  |           |  |  S1: aa08::4450  |
   +--+    | Site +--++-+--+        +----+                |
   |UE|----|  B   |PSA| Rb |        | R2 | S2: aa08::4460 |
   +--+    |      +--++----+        +----+                |
   +--+    |         |  +-----------+  |  S3: aa08::4470  |
   |UE|---/+---------+                 +------------------+
   +--+                                     L-DN2
           Figure 1: App Servers in different edge DCs


 1.2. Problem#1: ANYCAST in 5G EC Environment

   Increasingly, ANYCAST is used extensively by various
   application providers and CDNs because ANYCAST makes it
   possible to dynamically load balance across server
   locations based on network conditions. With multiple


Dunbar, et al.        Expires September 10, 2021      [Page 4]


Internet-Draft     OSPF Extension for 5G EC Service

   servers having the same ANYCAST address, it eliminates the
   single point of failure and bottleneck at the application
   layer load balancers. Another benefit of using ANYCAST
   address is removing the dependency on how UEs get the IP
   addresses for their Applications. Some UEs (or clients)
   might use stale cached IP addresses for an extended period.

   But, having multiple locations of the same ANYCAST address
   in 5G Edge Computing environment can be problematic because
   all those edge computing Data Centers can be close in
   proximity.  There might be very little difference in the
   routing cost to reach the Application Servers in different
   Edge DCs, which can cause packets from one flow to be
   forwarded to different locations, resulting in service
   glitches.

 1.3. Problem #2: Unbalanced Anycast Distribution due to UE
   Mobility

   UEs' frequent moving from one 5G site to another can make
   it difficult to plan where the App Servers should be
   hosted. When one App server is heavily utilized, other App
   servers of the same address close-by can be very under-
   utilized. Since the condition can be short-lived, it is
   difficult for the application controller to anticipate the
   move and adjust.

 1.4. Problem 3: Application Server Relocation

   When an Application Server is added to, moved, or deleted
   from a 5G Edge Computing Data Center, not only the
   reachability changes but also the utilization and capacity
   for the Data Center might change.

   Note: for the ease of description, the Edge Computing
   server, Application server, App server are used
   interchangeably throughout this document.



2. Conventions used in this document


   A-ER:       Egress Router to an Application Server, [A-ER]
               is used to describe the last router that the
               Application Server is attached. For 5G EC


Dunbar, et al.        Expires September 10, 2021      [Page 5]


Internet-Draft     OSPF Extension for 5G EC Service

               environment, the A-ER can be the gateway router
               to a (mini) Edge Computing Data Center.

   Application Server: An application server is a physical or
               virtual server that hosts the software system
               for the application.

   Application Server Location: Represent a cluster of servers
               at one location serving the same Application.
               One application may have a Layer 7 Load
               balancer, whose address(es) are reachable from
               an external IP network, in front of a set of
               application servers. From IP network
               perspective, this whole group of servers is
               considered as the Application server at the
               location.

   Edge Application Server: used interchangeably with
               Application Server throughout this document.

   EC:         Edge Computing

   Edge Hosting Environment: An environment providing the
               support required for Edge Application Server's
               execution.

               NOTE: The above terminologies are the same as
               those used in 3GPP TR 23.758

   Edge DC:    Edge Data Center, which provides the Edge
               Computing Hosting Environment. It might be co-
               located with 5G Base Station and not only host
               5G core functions, but also host frequently
               used Edge server instances.

   gNB         next generation Node B

   LDN:        Local Data Network

   PSA:        PDU Session Anchor (UPF)

   SSC:        Session and Service Continuity


Dunbar, et al.        Expires September 10, 2021      [Page 6]


Internet-Draft     OSPF Extension for 5G EC Service

   UE:         User Equipment

   UPF:        User Plane Function


   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
   "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
   RECOMMENDED", "MAY", and "OPTIONAL" in this document are to
   be interpreted as described in BCP 14 [RFC2119] [RFC8174]
   when, and only when, they appear in all capitals, as shown
   here.


3. Solution Overview

   From IP Layer, the Application Servers are identified by
   their IP (ANYCAST) addresses. To a router, having multiple
   servers with the same (ANYCAST) address attached to
   different egress routers (A-ER) is same as having multiple
   paths to reach the (ANYCAST) address.

   There are many tools available to influence the path
   section on a router, such as the routing distance, TE
   metrics, policies, etc. This draft describes a solution to
   add "Site-Cost" to influence the path selection. The "Site-
   Cost", which is derived from "site-capacity + load
   measurement + Preference + xxx", can be raw measurements
   collected by the egress routers based on the instructions
   from a controller or can be informed by the App Controller
   periodically.

   The proposed solution is for the egress router (A-ER) that
   have a direct connection to the Application Servers to
   collect desired measurements about the Servers' running
   status and advertise the metrics to other routers in 5G EC
   LDN.

   The solution assumes that the 5G Edge Computing controller
   or management system is aware of the ANYCAST addresses that
   need optimized forwarding. To minimize the processing on
   routers, only the application flows that match with the
   ACLs configured by the 5G Edge Computing controller will
   collect and advertise the desired measurements.






Dunbar, et al.        Expires September 10, 2021      [Page 7]


Internet-Draft     OSPF Extension for 5G EC Service

 3.1. Flow Affinity to an ANYCAST server

   Having multiple Edge Computing Servers or App Layer Load
   Balancers with the same ANYCAST address attached to
   multiple A-ERs, Flow Affinity means routers sending the
   packets of the same flow to the same A-ER even if the cost
   towards the A-ER is no longer optimal.

   Many commercial routers today support some forms of flow
   affinity to ensure packets belonging to one flow be
   forwarded along the same path.

   Editor's note: for IPv6 traffic, Flow Affinity can be
   supported by the routers of the Local Data Network (LDN)
   forwarding the packets with the same Flow Label in the
   packets' IPv6 Header along the same path towards the same
   egress router.

 3.2. IP Layer Metrics to Gauge App Server Running Status

   Most applications do not expose their internal logic to the
   network. Their communications are generally encrypted. Most
   of them do not even respond to PING or ICMP messages
   initiated by routers or network gears.

   [5G-EC-Metrics] describes the IP Layer Metrics that can
   gauge the application servers running status and
   environment:

     - IP-Layer Metric for App Server Load Measurement:
       The Load Measurement to an App Server is a weighted
       combination of the number of packets/bytes to the App
       Server and the number of packets/bytes from the App
       Server which are collected by the A-ER that has the
       direct connection to the App Server.
       The A-ER is configured with an ACL that can filter out
       the packets for the Application Server.
     - Capacity Index:
       Capacity Index is used to differentiate the running
       environment of the attached application server. Some
       data centers can have hundreds, or thousands, of
       servers behind an application server's App Layer Load
       Balancer. Other data centers can have a very small
       number of servers for the application. "Capacity


Dunbar, et al.        Expires September 10, 2021      [Page 8]


Internet-Draft     OSPF Extension for 5G EC Service

       Index", which is a numeric number, is used to
       represent the capacity of the application server
       attached to an A-ER.
     - Site preference index:
       [IPv6-StickyService] describes a scenario that some
       sites are more preferred for handling an application
       than others for flows from a specific UE.

   For ease of description, those metrics, more may be added
   later, are called IP Layer App-Metrics throughout the
   document.


 3.3. To Equalize traffic among Multiple ANYCAST Locations

   The main benefit of using ANYCAST is to leverage the
   network layer information to balance the traffic among
   multiple Application Server locations.

   For 5G Edge Computing environment, the routers in the LDN
   need to be notified of various measurements of the App
   Servers attached to each A-ER to make the intelligent
   decision on where to forward the traffic for the
   application from UEs.

   [5G-EC-Metrics] describes the algorithms that can be used
   by the routers in LDN to compare the cost to reach the App
   Servers between the Site-i or Site-j:

               Load-i * CP-j               Pref-j * Network-Delay-i
Cost-i=min(w *(----------------) + (1-w) *(-------------------------))
              Load-j * CP-i               Pref-i * Network-Delay-j


      Load-i: Load Index at Site-i, it is the weighted
      combination of the total packets or/and bytes sent to
      and received from the Application Server at Site-i
      during a fixed time period.

      CP-i: capacity index at site I, a higher value means
      higher capacity.

      Network Delay-i: Network latency measurement (RTT) to
      the A-ER that has the Application Server attached at the
      site-i.



Dunbar, et al.        Expires September 10, 2021      [Page 9]


Internet-Draft     OSPF Extension for 5G EC Service

      Noted: Ingress nodes can easily measure RTT to all the
      egress nodes by existing IPPM metrics. But it is not so
      easy for ingress nodes to measure RTT to all the App
      Servers. Therefore, "Network-Delay-i", a.k.a. Network
      latency measurement (RTT), is between the Ingress nodes
      and egress nodes. The link cost between the egress nodes
      to their attached servers are embedded in the "capacity
      index".

      Pref-i: Preference index for site-i, a higher value
      means higher preference.

      w: Weight for load and site information, which is a
      value between 0 and 1. If smaller than 0.5, Network
      latency and the site Preference have more influence;
      otherwise, Server load and its capacity have more
      influence.

 3.4. Reason for using IGP Based Solution

    Here are some benefits of using IGP to propagate the IP
    Layer App-Metrics:
    - Intermediate routers can derive the aggregated cost to
      reach the Application Servers attached to different
      egress nodes, especially:
        - The path to the optimal egress node can be more
           accurate or shorter
        - Convergence is shorter when there is any failure
           along the way towards the optimal ANYCAST server.
        - When there is any failure at the intended ANYCAST
           server, all the transient packets can be optimally
           forwarded to another App Server attached to a
           different egress router.
    - Doesn't need the ingress nodes to establish tunnels with
      egress nodes.

    There are limitations of using IGP too, such as:

    - The IGP approach might not suit well to 5G EC LDN
      operated by multiple ISPs networks.
      For LDN operated by multiple IPSs, BGP should be used.
      AppMetaData NLRI Path Attribute [5G-AppMetaData]
      describes the BGP UPDATE message to propagate IP Layer
      App-Metrics crossing multiple ISPs.




Dunbar, et al.        Expires September 10, 2021     [Page 10]


Internet-Draft     OSPF Extension for 5G EC Service

4. Aggregated Cost Computed by Egress Routers

   If all egress routers that have a direct connection to the
   App Servers can get a periodic update of the aggregated
   cost to the App Servers or can be configured with a
   consistent algorithm to compute an aggregated cost that
   takes into consideration the Load Measurement, Capacity
   value, and Preference value, this aggregated cost can be
   considered as the Metric of the link to the App Server.

   In this scenario, there is no protocol extension needed.

 4.1. OSPFv3 LSA to carry the Aggregated Cost

   If the App Servers use IPv6 ANYCAST address, the aggregated
   cost computed by the egress routers can be encoded in the
   Metric field [the interface cost] of Intra-Area-Prefix-LSA
   specified by Section 3.7 of the [ RFC5340].

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     6 (Intra-Area Prefix)     |         TLV Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          0    | Aggregated Cost to the App Server             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | PrefixLength  | PrefixOptions |             0                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Address Prefix                      |
     |                               ...                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                Figure 2: Aggregated Cost to App Server


 4.2. OSPFv2 LSA to carry the Aggregated Cost

   For App Servers in IPv4 address, the Aggregated Cost can be
   encoded in the "Metric" field of the Stub Link LSA [Link
   type =3] specified by Section 12.4 of the [RFC2328].

5. IP Layer App-Metrics Advertisements

   This section describes the OSPF extension that can carry
   the detailed IP Layer Metrics when it is not possible for
   all the egress routers to have a consistent algorithm to
   compute the aggregated cost or some routers need all the
   detailed IP Layer metrics for the App Servers for other
   purposes.



Dunbar, et al.        Expires September 10, 2021     [Page 11]


Internet-Draft     OSPF Extension for 5G EC Service

   Since only a subset of routers within an IGP domain need to
   know those detailed metrics, it makes sense to use the
   OSPFv2 Extended Prefix Opaque LSA for IPv4 and OSPFv3
   Extended LSA with Intra-Area-Prefix TLV to carry the
   detailed sub-TLVs.  For routers that don't care about those
   metrics, they can ignore them very easily.

   It worth noting that not all hosts (prefix) attached to an
   A-ER are ANYCAST servers that need network optimization.
   An A-ER only needs to advertise the App-Metrics for the
   ANYCAST addresses that match with the configured ACLs.

   Draft [draft-wang-lsr-passive-interface-attribute]
   introduces the Stub-Link TLV for OSPFv2/v3 and ISIS
   protocol respectively. Considering the interfaces on an
   edge router that connects to the App servers are normally
   configured as passive interfaces, these IP-layer App-
   metrics can also be advertised as the attributes of the
   passive/stub link. The associated prefixes can then be
   advertised in the "Stub-Link Prefix Sub-TLV" that is
   defined in [draft-wang-lsr-passive-interface-attribute].
   All the associated prefixes share the same characteristic
   of the link. Other link related sub-TLVs defined in
   [RFC8920] can also be attached and applied to the
   calculation of path to the associated prefixes.


 5.1. OSPFv3 Extension to carry the App-Metrics

   For App Servers using IPv6, the OSPFv3 Extended LSA with
   the Intra-Area-Prefix Address TLV specified by the Section
   3.7 of RFC8362 can be used to carry the App-Metrics for the
   attached App Servers.














Dunbar, et al.        Expires September 10, 2021     [Page 12]


Internet-Draft     OSPF Extension for 5G EC Service

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |7 (IPv6 Local-Local Address)   |               Length          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            IPv6 AppServer (ANYCAST) address                   |
      ~                                                               ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Load measurement sub-TLV                           |
      ~                                                               ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Capability sub-TLV                                 |
      ~                                                               ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             Preference sub-TLV                                |
      ~                                                               ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          Figure 3: IPv6 App Server App-Metrics Encoding



 5.2. OSPFv2 Extension to advertise the IP Layer App-Metrics

   For App Servers using IPv4 addresses, the OSPFv2 Extended
   Prefix Opaque LSA with the extended Prefix TLV can be used
   to carry the App Metrics sub-TLVs, as specified by the
   Section 2.1 [RFC7684].


   Here is the proposed encoding:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Type                          | Length                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Route Type    | Prefix Length | AF            | Flags         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Address Prefix (variable)                                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Load Measurement Sub-TLV                                      |
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | capacity Index Sub-TLV                                        |
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Site Preference Sub-TLV                                       |
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



Dunbar, et al.        Expires September 10, 2021     [Page 13]


Internet-Draft     OSPF Extension for 5G EC Service

   Figure 4: App-Metrix Sub-TLVs in OSPFv2 Extended Prefix TLV


 5.3. IP Layer App-Metrics Sub-TLVs

   Two types of Load Measurement Sub-TLVs are specified:

   a) The Aggregated Load Index based on a weighted
     combination of the collected measurements;
   b) The raw measurements of packets/bytes to/from the App
     Server address. The raw measurement is useful when the
     egress routers cannot be configured with a consistent
     algorithm to compute the aggregated load index or the
     raw measurements are needed by a central analytic
     system.


   The Aggregated Load Index Sub-TLV has the following format:

     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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Type (TBD2)           |               Length          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                   Measurement Period                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |           Aggregated Load Index to reach the App Server       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            Figure 5: Aggregated Load Index Sub-TLV

     Type=TBD2 (to be assigned by IANA) indicates that the
     sub-TLV carries the Aggregated Load Measurement Index
     derived from the Weighted combination of bytes/packets
     sent to/received from the App server:

     Index=w1*ToPackets+w2*FromPackes+w3*ToBytes+w4*FromBytes

     Where wi is a value between 0 and 1; w1+ w2+ w3+ w4 = 1.












Dunbar, et al.        Expires September 10, 2021     [Page 14]


Internet-Draft     OSPF Extension for 5G EC Service





   The Raw Load Measurement sub-TLV has the following format:

       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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           Type (TBD3)         |               Length          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                   Measurement Period                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           total number of packets to the AppServer            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           total number of packets from the AppServer          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           total number of bytes to the AppServer              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           total number of bytes from the AppServer            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             Figure 6: Raw Load Measurement Sub-TLV



     Type= TBD3 (to be assigned by IANA) indicates that the
     sub-TLV carries the Raw measurements of packets/bytes
     to/from the App Server ANYCAST address.

     Measurement Period: A user-specified period in seconds,
     default is 3600 seconds.



   The Capacity Index sub-TLV has the following format:

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           Type (TBD3)         |               Length          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                   Capacity Index                              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
               Figure 7: Capacity Index Sub-TLV









Dunbar, et al.        Expires September 10, 2021     [Page 15]


Internet-Draft     OSPF Extension for 5G EC Service

   The Preference Index sub-TLV has the following format:

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           Type (TBD4)         |               Length          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                   Preference Index                            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
               Figure 8: Preference Index Sub-TLV


   Note: "Capacity Index" and "Site preference" can be more
   stable for each site. If those values are configured to
   nodes, they might not need to be included in every OSPF
   LSA.



6. Manageability Considerations

     To be added.

7. Security Considerations


   To be added.

8. IANA Considerations

       The following Sub-TLV types need to be added by IANA
       to OSPFv4 Extended-LSA Sub-TLVs and OSPFv2 Extended
       Link Opaque LSA TLVs Registry.

          - Aggregated Load Index Sub-TLV type
          - Raw Load Measurement Sub-TLV type
          - Capacity Index Sub-TLV type
          - Preference Index Sub-TLV type



9. References






Dunbar, et al.        Expires September 10, 2021     [Page 16]


Internet-Draft     OSPF Extension for 5G EC Service

 9.1. Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to
             Indicate Requirement Levels", BCP 14, RFC 2119,
             March 1997.

   [RFC2328] J. Moy, "OSPF Version 2", RFC 2328, April 1998.

   [RFC7684] P. Psenak, et al, "OSPFv2 Prefix/Link Attribute
             Advertisement", RFC 7684, Nov. 2015.

   [RFC8200] S. Deering R. Hinden, "Internet Protocol, Version
             6 (IPv6) Specification", July 2017.

   [RFC8326] A. Lindem, et al, "OSPFv3 Link State
             advertisement (LSA0 Extensibility", RFC 8362,
             April 2018.


 9.2. Informative References

   [3GPP-EdgeComputing] 3GPP TR 23.748, "3rd Generation
             Partnership Project; Technical Specification
             Group Services and System Aspects; Study on
             enhancement of support for Edge Computing in 5G
             Core network (5GC)", Release 17 work in progress,
             Aug 2020.

   [5G-AppMetaData] L. Dunbar, K. Majumdar, H. Wang, "BGP NLRI
             App Meta Data for 5G Edge Computing Service",
             draft-dunbar-idr-5g-edge-compute-app-meta-data-
             01, work-in-progress, Nov 2020.

   [5G-EC-Metrics] L. Dunbar, H. Song, J. Kaippallimalil, "IP
             Layer Metrics for 5G Edge Computing Service",
             draft-dunbar-ippm-5g-edge-compute-ip-layer-
             metrics-01, work-in-progress, Nov 2020.

   [5G-StickyService] L. Dunbar, J. Kaippallimalil, "IPv6
             Solution for 5G Edge Computing Sticky Service",
             draft-dunbar-6man-5g-ec-sticky-service-00, work-
             in-progress, Oct 2020.


Dunbar, et al.        Expires September 10, 2021     [Page 17]


Internet-Draft     OSPF Extension for 5G EC Service

   [RFC5521] P. Mohapatra, E. Rosen, "The BGP Encapsulation
             Subsequent Address Family Identifier (SAFI) and
             the BGP Tunnel Encapsulation Attribute", April
             2009.

   [BGP-SDWAN-Port] L. Dunbar, H. Wang, W. Hao, "BGP Extension
             for SDWAN Overlay Networks", draft-dunbar-idr-
             bgp-sdwan-overlay-ext-03, work-in-progress, Nov
             2018.

   [SDWAN-EDGE-Discovery] L. Dunbar, S. Hares, R. Raszuk, K.
             Majumdar, "BGP UPDATE for SDWAN Edge Discovery",
             draft-dunbar-idr-sdwan-edge-discovery-00, work-
             in-progress, July 2020.

   [Tunnel-Encap] E. Rosen, et al "The BGP Tunnel
             Encapsulation Attribute", draft-ietf-idr-tunnel-
             encaps-10, Aug 2018.



10. Acknowledgments

   Acknowledgements to Acee Lindem, Gyan Mishra, Jeff
   Tantsura, and Donald Eastlake for their review and
   suggestions.

   This document was prepared using 2-Word-v2.0.template.dot.


















Dunbar, et al.        Expires September 10, 2021     [Page 18]


Internet-Draft     OSPF Extension for 5G EC Service



Authors' Addresses

   Linda Dunbar
   Futurewei
   Email: ldunbar@futurewei.com

   Huaimo Chen
   Futurewei
   Email: huaimo.chen@futurewei.com

   Aijun Wang
   China Telecom
   Email: wangaj3@chinatelecom.cn

































Dunbar, et al.        Expires September 10, 2021     [Page 19]