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ALTO WG                                                         J. Zhang
Internet-Draft                                         Tongji University
Intended status: Informational                                    K. Gao
Expires: 14 January 2021                              Sichuan University
                                                           LM. Contreras
                                                              Telefonica
                                                            A. Escribano
                                                                   Alten
                                                                 P. Cano
                                                              UST Global
                                                                 F. Cano
                                                              Telefonica
                                                            13 July 2020


    Considerations of Deploying ALTO using BGP - Link State (BGP-LS)
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                       draft-zhang-alto-bgp-ls-01

Abstract

   This document discusses the requirements and deployment
   considerations of providing Application-Layer Traffic Optimization
   (ALTO) information in the inter-domain scenario using Border Gateway
   Protocol - Link State (BGP-LS) extension.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on 14 January 2021.



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Copyright Notice

   Copyright (c) 2020 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 (https://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
   2.  New Problem Statement and Working Items . . . . . . . . . . .   3
   3.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  ALTO Inter-domain Deployment Problem  . . . . . . . . . .   4
     3.2.  BGP-LS Background and Benefits for ALTO . . . . . . . . .   4
     3.3.  ALTO Deployment Problem using BGP-LS  . . . . . . . . . .   5
   4.  Requirements for Deploying ALTO in the Inter-domain Scenario
           using BGP-LS  . . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  Basic Requirements  . . . . . . . . . . . . . . . . . . .   6
     4.2.  BGP-LS specific Requirements  . . . . . . . . . . . . . .   6
   5.  ALTO Deployment Considerations using BGP-LS . . . . . . . . .   7
     5.1.  Provisioning of Topology Information  . . . . . . . . . .   7
     5.2.  Provisioning of Routing Information . . . . . . . . . . .   7
     5.3.  Provisioning of Performance Metric Information  . . . . .   7
   6.  Configuration Interfaces of Map Calculation . . . . . . . . .   7
     6.1.  Configuration Interface of Network Map Calculation  . . .   7
     6.2.  Configuration Interface of Cost Map Calculation . . . . .   8
     6.3.  Configuration Examples  . . . . . . . . . . . . . . . . .   9
   7.  Test Scenarios  . . . . . . . . . . . . . . . . . . . . . . .  14
     7.1.  Test Environment Setup  . . . . . . . . . . . . . . . . .  14
     7.2.  Test Approach . . . . . . . . . . . . . . . . . . . . . .  14
     7.3.  Test Results  . . . . . . . . . . . . . . . . . . . . . .  14
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15









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1.  Introduction

   The major component of the Application-Layer Traffic Optimization
   (ALTO) [RFC7285] deployment is the network information collection.
   [RFC7971] discussed multiple options to collect the network
   information from the inter-domain networks.

   To collection the related network information for ALTO, the following
   high-level questions should be considered:

   *  Can the ALTO service realistically discover that information?

   *  Is the distribution of that information allowed by the operators
      of that service?

   *  Is it information that a client cannot find easily some other way?

   The Border Gateway Protocol - Link State (BGP-LS) extension [RFC7752]
   is one of the popular options and has been deployed in many
   Autonomous Systems (ASes) in recent years [TODO: Need some
   reference].

   BGP-LS enables ALTO server to provide underlay inter-domain topology
   information using the link-state information in IGP domains.

   To leverage BGP-LS to generate ALTO information effectively, some
   requirements for deployment should be considered.

   This document discusses these requirements and the corresponding
   deployment considerations.

   Additionally, this document describes some inter-domain scenarios to
   test the deployment.

2.  New Problem Statement and Working Items

   This document was initially written to summarize ALTO deployment
   consideration using BGP-LS.  However, authors are finding new
   interesting practical problems when pushing the deployment to large-
   scale ISP networks.

   Authors identify two problems:

   Problem 1: how to efficiently obtain fine-grained global ALTO
   information from multiple networks?

   Problem 2: how to efficiently reconstruct and disseminate the ALTO
   information upon dynamics?



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   Considering the scale of the ISP carrier networks and the frequency
   of network dynamicity, the previous design cannot survive.  We have
   to target a systemtic design to support (1) distributed information
   collection, and (2) calculation and incremental information
   recomputation.

   Thus, authors propose a hierarchical architecture to deploy ALTO
   servers.  To make the deployment in different small networks
   compatible with each other, the interfaces to allow interoperations
   between different ALTO servers are required.  Although we can design
   and implement those interfaces outside the scope of ALTO, we believe
   making ALTO provide this capability by itself can be a more coherent
   approach and also have more potential benefits.

   We are still heavily working on the initial specification.  No more
   details are added in the current document.  But we have already done
   a paper submission to talk about the initial design.  For people
   interested in this work, please feel free to contact us.

3.  Background

3.1.  ALTO Inter-domain Deployment Problem

   [RFC7971] discusses considerations of ALTO deployment in different
   network scenarios.  The inter-domain network is the most common
   scenario to deploy ALTO.

   In practice, the following approaches are used to collect information
   from the network:

   *  Interior Gateway Protocols (IGPs, e.g., OSPF, IS-IS): intra-domain
      topology, link weights

   *  Border Gateway Protocol (BGP): inter-domain topology, prefixes, AS
      numbers, AS distances, or other BGP metrics

   *  Network Management Protocols (NMPs, e.g., SNMP, Netconf): latency,
      utilization, bandwidth

3.2.  BGP-LS Background and Benefits for ALTO

   BGP-LS [RFC7752] is designed to allow a BGP speaker to advertise the
   link state database (LSDB) or traffic engineering database (TED) of
   its connected IGP area.

   BGP-LS defines a new address family, link state, in the BGPv4
   framework [RFC4271].




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   Using BGP-LS, the ALTO server can communicate to only BGP speakers to
   collect all those information.

3.3.  ALTO Deployment Problem using BGP-LS

   A simple deployment solution is to connect the ALTO server as a BGP
   reflector client of every BGP speakers in the network.  However, this
   solution is expensive and redundant.  And because of the BGP updates,
   the ALTO server could receive a lot of inconsistent redundant
   informaiton.  To avoid the redundancy and inconsistency of the
   collected information, a deployment solution should be minimal.

   To understand what is a minimal solution to deploy ALTO using BGP-LS,
   the following questions are raised:

   *  Is it necessary to connect the ALTO server to every AS within a
      BGP session?

   *  Does the session between the ALTO server and each AS have to
      enable BGP-LS?

   *  If using BGP-LS, can the number of necessary BGP sessions be
      reduced?

   The following example shows a minimal deployment in a simple example
   topology.

   Consider the following AS-level topology as an example.  Assuming all
   the BGP sessions between ASes have enabled BGP-LS, the BGP speaker on
   AS B can received the IGP topologies from all the three ASes.  Thus,
   to make sure the ALTO server collect all the inter-domain and intra-
   domain topology information, the minimal deployment could be to set
   up the the ALTO server as a BGP reflector of the BGP speaker on AS B.

   +--------+   +--------+   +---------+
   | AS A   |---| AS B   |---| AS C    |
   +--------+   +--------+   +---------+
        | BGP     / BGP-LS
        |        /
        |       /
   +-------------+
   | ALTO Server |
   +-------------+

                    Figure 1: Example AS-level Topology






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   However, it is not enough for collecting the routing information.  As
   the BGP is a destination-based routing protocol, AS B could not
   receive the routing information between endpoints from AS A and AS C.
   To get the missing routing information, the ALTO server should also
   connect read the BGP RIB of AS A or AS C at least.

   As the result, the minimal solution is to establish a BGP session to
   AS B with BGP-LS and another BGP session to AS A (or AS C) without
   BGP-LS.

   The following part of this document will discuss how to achieve the
   minimal ALTO deployment using BPG-LS in detail.  Specifically, two
   questions are required to be answered:

   *  Which BGP speakers are required to be connected to the ALTO
      server?

   *  Which BGP sessions are required to enable BGP-LS?

4.  Requirements for Deploying ALTO in the Inter-domain Scenario using
    BGP-LS

4.1.  Basic Requirements

   The following basic requirements are required by ALTO inter-domain
   deployment in any case.

   Req 1: The ALTO server MUST be able to collect topology information
   from multiple IGP areas.

   Req 2: The ALTO server MUST be able to collect routing information
   for any pairs of endpoints.

   Req 3: The ALTO server MUST be able to collect performance metrics
   across routes.

4.2.  BGP-LS specific Requirements

   The following additional requirements are required by ALTO deployment
   when using BGP-LS.

   Req 4: The ALTO server SHOULD only communicate with necessary BGP
   speakers.

   Req 5: The ALTO server SHOULD only enable BGP-LS advertisement in
   necessary BGP sessions between BGP speakers.





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5.  ALTO Deployment Considerations using BGP-LS

   This section discusses some deployment considerations about how to
   address the basic requirements (Req 1-3) when satisfying the BGP-LS
   specific requirements (Req 4-5).

5.1.  Provisioning of Topology Information

   As BGP-LS advertisement cannot be propagated to remote the remote
   ASes, each BGP speaker can only discover directly peered IGP
   topologies using BGP-LS.

   To satisfy Req 4, the ALTO server should only communicate to transit
   networks or IXPs using BGP-LS.  As the IGP topology of a stub network
   can always be discovered by its peered transit networks or IXPs, so
   it is not necessary to communicate with the stub network.

   Specifically, the ALTO server should find a minimal BGP speaker set
   whose peered networks can cover all IGP domains.

5.2.  Provisioning of Routing Information

   As BGP is a destination-based routing protocol, a stub network can
   receive all the inter-domain routing information from all the
   reachable destinations via BGP.

   Thus, to satisfy Req 4, the ALTO server should only communicate to
   stub networks using BGP, as the inter-domain routing information from
   the transit networks is not necessary.

   Assuming the ALTO server has already collected the complete topology
   information using BGP-LS, the ALTO server will have the LSDB of every
   IGP domain.

   To satisfy Req 5, all the BGP sessions connected to the stub networks
   do not have to enable BGP-LS.

5.3.  Provisioning of Performance Metric Information

   TBD.

6.  Configuration Interfaces of Map Calculation

6.1.  Configuration Interface of Network Map Calculation







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   rw network-map-config* [resource-id]
   +--rw resource-id      alto-types:resource-id
   +--rw description?     string
   +--rw (params)
   |  +--:(bgp)
   |     +--rw bgp-params
   |        +--rw bgp-rib* [rib-id]
   |           +--rw rib-id       rib:rib-id
   |           +--rw topology-id? topology:topology-id
   |           +--rw bgp-ls?      boolean
   +--rw (algorithm)
      +--:(first-hop-cluster)
         +--rw first-hop-cluster-algorithm
            +--rw inspect-igp     boolean

   To generate a network map, one or more BGP RIBs that could provide
   the topology information MUST specified.  Each BGP RIB MAY include a
   pre-computed topology from the RIB, and an option indicating if the
   BPG-LS is enabled.

   The "inspect-igp" option in the "first-hop-cluster-algorithm" field
   indicates if the ALTO server exposes information about the IGP
   topologies.  If it is true, the ALTO server will inspect all the IGP
   topolgies from the BGP RIBs that enalbe BGP-LS (whose "bgp-ls" option
   is true).

6.2.  Configuration Interface of Cost Map Calculation

   rw cost-map-config* [resource-id]
   +--rw resource-id              alto-types:resource-id
   +--rw description?             string
   +--rw dependent-network-map    alto-types:resource-id
   +--rw (general-params)
   |  +--:(bgp)
   |     +--rw bgp-params
   |        +--rw alternative-bgp-rib* [rib-id]
   |           +--rw rib-id            rib:rib-id
   |           +--rw topology-id?      topology:topology-id
   |           +--rw bgp-ls?           boolean
   +--rw cost-type* [cost-mode,cost-metric]
      +rw cost-mode                    alto-types:cost-mode
      +rw cost-metric                  alto-types:cost-metric
      +rw (params)?

   To generate a cost map, besides the dependent network map, one or
   more alternative BGP RIBs could be specified to provide necessary
   routing information to the ALTO server.




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6.3.  Configuration Examples

   Example Network

   .----------------------------.                    .------------.
   | 1.1.1.0/24    6.6.6.0/24   |                    | 8.8.8.0/24 |
   |     |             |        |                    |     |      |
   |   +-+--+        +-+--+     |                    |   +-+--+   |
   |   | R1 +--------+ R6 |     |    .------------.  |   | R8 |   |
   |   +-+--+        +-+--+     |    | 3.3.3.0/24 |  |   +-+--+   |
   |     |             |        |    |    |       |  |     |      |
   |     |           +-+--+     |    |  +-+--+    |  |   +-+--+   |
   |     +-----------+ R2 +- - -|- - | -+ R3 +- - | -|- -+ R7 |   |
   |                 +----+     |    |  +++--+    |  |   +----+   |
   |                   |        |    |   ..       |  |            |
   |                 +-+--+     |    |   ..AS 200 |  |     AS 300 |
   | 5.5.5.0/24------+ R5 |     |    `------------'  `------------'
   |                 +-+--+     |        ..
   |                   |        |        ..
   |   AS 100        +-+--+     |        ..
   |                 | R4 +- - -|- - - - +.
   |                 +-+--+     |         .
   `----------------------------'         .
                       .                  .
                       .                  .
                       .         +--------+----+
                       +- - - - -+ ALTO Server |
                                 +-------------+

   R2 - R3: BGP-LS
   R4 - R3: BGP-LS
   R7 - R3: BGP-LS
   R3 - ALTO: BGP-LS
   R4 - ALTO: BGP

                                  Figure 2

   Config a network map:













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   POST /restconf/config/alto-maps/network-map-config/bgp-networkmap
   HOST: alto-config.example.com
   Content-Type: application/json
   Content-Length: TBD

   {
     "network-map-config": {
       "resource-id": "bgp-networkmap",
       "bgp-params": {
         "bgp-rib": [
           {
             "rib-id": "as200-r3",
             "bgp-ls": true
           }
         ]
       },
       "first-hop-cluster-algorithm": {
         "inspect-igp": true
       }
     }
   }

   Test to fetch the network map:




























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   GET /alto/networkmap/example
   HOST: alto.example.com

   HTTP/1.1 200 OK
   Content-Length: TBD
   Content-Type: application/alto-networkmap+json

   {
     "meta": {
       "vtag": {
         "resource-id": "bgp-networkmap",
         "tag": "da65eca2eb7a10ce8b059740b0b2e3f8eb1d4785"
       }
     },
     {
       "network-map": {
         "PID100.R1": {
           "ipv4": [ "1.1.1.0/24" ]
         },
         "PID100.R5": {
           "ipv4": [ "5.5.5.0/24" ]
         },
         "PID100.R6": {
           "ipv4": [ "6.6.6.0/24" ]
         },
         "PID200.R3": {
           "ipv4": [ "3.3.3.0/24" ]
         },
         "PID300.R8": {
           "ipv4": [ "8.8.8.0/24" ]
         }
       }
     }
   }

   Config a cost map:















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   POST /restconf/config/alto-maps/cost-map-config/bgp-costmap
   HOST: alto-config.example.com
   Content-Type: application/json
   Content-Length: TBD

   {
     "cost-map-config": {
       "resource-id": "bgp-costmap",
       "dependent-network-map": "bgp-networkmap",
       "bgp-params": {
         "alternative-bgp-rib": [
           {
             "rib-id": "as100-r4",
             "bgp-ls": false
           }
         ]
       },
       "cost-type": [
         {
           "cost-mode": "numerical",
           "cost-metric": "hopcount"
         }
       ]
     }
   }

   Test to fetch the cost map:
























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   GET /alto/costmap/bgp-costmap
   HOST: alto.example.com

   HTTP/1.1 200 OK
   Content-Length: TBD
   Content-Type: application/alto-costmap+json

   {
     "meta": {
       "vtag": {
         "resource-id": "bgp-costmap",
         "tag": "c0ce023b8678a7b9ec00324673b98e54656d1f6d"
       },
       "dependent-vtags": [
         {
           "resource-id": "bgp-networkmap",
           "tag": "da65eca2eb7a10ce8b059740b0b2e3f8eb1d4785"
         }
       ],
       "cost-type": {
         "cost-mode": "numerical",
         "cost-metric": "hopcount"
       }
     },
     "cost-map": {
       "PID100.R1": {
         "PID100.R1": 1, "PID100.R5": 3, "PID100.R6": 2,
         "PID200.R3": 3, "PID300.R8": 5
       },
       "PID100.R5": {
         "PID100.R1": 3, "PID100.R5": 1, "PID100.R6": 3,
         "PID200.R3": 3, "PID300.R8": 5
       },
       "PID100.R6": {
         "PID100.R1": 2, "PID100.R5": 3, "PID100.R6": 1,
         "PID200.R3": 3, "PID300.R8": 5
       },
       "PID200.R3": {
         "PID100.R1": 3, "PID100.R5": 3, "PID100.R6": 3,
         "PID200.R3": 1, "PID300.R8": 3
       },
       "PID300.R8": {
         "PID100.R1": 5, "PID100.R5": 5, "PID100.R6": 5,
         "PID200.R3": 3, "PID300.R8": 1
       }
     }
   }




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7.  Test Scenarios

7.1.  Test Environment Setup

7.2.  Test Approach

7.3.  Test Results

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.

   [RFC7285]  Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S.,
              Previdi, S., Roome, W., Shalunov, S., and R. Woundy,
              "Application-Layer Traffic Optimization (ALTO) Protocol",
              RFC 7285, DOI 10.17487/RFC7285, September 2014,
              <https://www.rfc-editor.org/info/rfc7285>.

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/info/rfc7752>.

   [RFC7971]  Stiemerling, M., Kiesel, S., Scharf, M., Seidel, H., and
              S. Previdi, "Application-Layer Traffic Optimization (ALTO)
              Deployment Considerations", RFC 7971,
              DOI 10.17487/RFC7971, October 2016,
              <https://www.rfc-editor.org/info/rfc7971>.

   [RFC8571]  Ginsberg, L., Ed., Previdi, S., Wu, Q., Tantsura, J., and
              C. Filsfils, "BGP - Link State (BGP-LS) Advertisement of
              IGP Traffic Engineering Performance Metric Extensions",
              RFC 8571, DOI 10.17487/RFC8571, March 2019,
              <https://www.rfc-editor.org/info/rfc8571>.

8.2.  Informative References




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   [I-D.ietf-alto-cost-calendar]
              Randriamasy, S., Yang, Y., WU, Q., Lingli, D., and N.
              Schwan, "Application-Layer Traffic Optimization (ALTO)
              Cost Calendar", Work in Progress, Internet-Draft, draft-
              ietf-alto-cost-calendar-21, 17 March 2020,
              <http://www.ietf.org/internet-drafts/draft-ietf-alto-cost-
              calendar-21.txt>.

   [I-D.ietf-alto-incr-update-sse]
              Roome, W. and Y. Yang, "ALTO Incremental Updates Using
              Server-Sent Events (SSE)", Work in Progress, Internet-
              Draft, draft-ietf-alto-incr-update-sse-22, 20 March 2020,
              <http://www.ietf.org/internet-drafts/draft-ietf-alto-incr-
              update-sse-22.txt>.

   [I-D.ietf-alto-path-vector]
              Gao, K., Randriamasy, S., Yang, Y., and J. Zhang, "ALTO
              Extension: Path Vector", Work in Progress, Internet-Draft,
              draft-ietf-alto-path-vector-10, 9 March 2020,
              <http://www.ietf.org/internet-drafts/draft-ietf-alto-path-
              vector-10.txt>.

   [I-D.ietf-alto-unified-props-new]
              Roome, W., Randriamasy, S., Yang, Y., Zhang, J., and K.
              Gao, "Unified Properties for the ALTO Protocol", Work in
              Progress, Internet-Draft, draft-ietf-alto-unified-props-
              new-11, 9 March 2020, <http://www.ietf.org/internet-
              drafts/draft-ietf-alto-unified-props-new-11.txt>.

   [I-D.wang-idr-bgpls-inter-as-topology-ext]
              Wang, A. and H. Chen, "BGP-LS Extension for Inter-AS
              Topology Retrieval", Work in Progress, Internet-Draft,
              draft-wang-idr-bgpls-inter-as-topology-ext-02, 13 August
              2018, <http://www.ietf.org/internet-drafts/draft-wang-idr-
              bgpls-inter-as-topology-ext-02.txt>.

   [RFC8189]  Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost
              Application-Layer Traffic Optimization (ALTO)", RFC 8189,
              DOI 10.17487/RFC8189, October 2017,
              <https://www.rfc-editor.org/info/rfc8189>.

Authors' Addresses









Zhang, et al.            Expires 14 January 2021               [Page 15]


Internet-Draft              ALTO using BGP-LS                  July 2020


   Jingxuan Jensen Zhang
   Tongji University
   4800 Cao'An Hwy
   Shanghai
   201804
   China

   Email: jingxuan.zhang@tongji.edu.cn


   Kai Gao
   Sichuan University
   No.24 South Section 1, Yihuan Road
   Chengdu
   610000
   China

   Email: kaigao@scu.edu.cn


   Luis M. Contreras
   Telefonica
   Ronda de la Comunicacion, s/n
   28050 Madrid
   Spain

   Email: luismiguel.contrerasmurillo@telefonica.com


   Anais Escribano
   Alten
   Carrer de Josep Pla, 2
   08019 Barcelona
   Spain

   Email: anais.escribano@alten.es


   Patricia Cano
   UST Global
   Ramirez de Arellano 29
   28043 Madrid
   Spain

   Email: Patricia.Diez@ust-global.com






Zhang, et al.            Expires 14 January 2021               [Page 16]


Internet-Draft              ALTO using BGP-LS                  July 2020


   Francisco Cano
   Telefonica
   Avenida del Conocimiento, 12
   18016 Granada
   Spain

   Email: franciscojose.canohila@telefonica.com












































Zhang, et al.            Expires 14 January 2021               [Page 17]


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