NMRG LM. Contreras
Internet-Draft Telefonica
Intended status: Informational P. Lucente
Expires: 9 January 2025 NTT
T. Velivassaki
Synelixis
July 2024
Interconnection Intents
draft-contreras-nmrg-interconnection-intents-05
Abstract
This memo introduces the use case of the usage of intents for
expressing advance interconnection features, further than traditional
IP peering.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Evolution of Network interconnection . . . . . . . . . . . . 3
2.1. Potential interconnection intent types . . . . . . . . . 3
2.2. Interconnection intent lifecycle . . . . . . . . . . . . 4
2.3. Protocol aspects . . . . . . . . . . . . . . . . . . . . 6
3. Interconnection intent structure . . . . . . . . . . . . . . 6
3.1. Structure of the Intents . . . . . . . . . . . . . . . . 7
3.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2.1. Example 1. Conventional IP peering . . . . . . . . . 8
3.2.2. Example 2. interconnection of service functions in
different domains . . . . . . . . . . . . . . . . . . 9
3.2.3. Example 3. Delivery of composite service functions at
the edge and cloud continuum . . . . . . . . . . . . 10
4. Lessons Learned . . . . . . . . . . . . . . . . . . . . . . . 11
5. Security Considerations . . . . . . . . . . . . . . . . . . . 12
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
The success of Internet-based services has been built on top of the
global reachability of content accessed by the end-users, which is
facilitated by the interconnection of individual networks owned by
distinct service providers constituting independent administrative
domains.
Such interconnection services have been initially based simply on
delivery of IP traffic between the interconnected parties leveraging
on BGP. This peer model enables full connectivity. However, the
traditional interconnection model shows some limitations when
additional information to that related to routing is needed.
New network capabilities based on programmability and virtualization
are producing service situations where a connectivity-only approach
is not sufficient. The increasing availability of computing
capabilities internal to the networks, or attached to them, enable
new scenarios where those capabilities can be consumed through the
advertisement or exposure of these execution environments (i.e., in
terms of compute, storage and associated networking resources). Such
information from an interconnected provider can be obtained from e.g.
[I-D.llc-teas-dc-aware-topo-model].
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In addition or complementary to that, even services or network
functions could be advertised in order to make them available for
interconnection. For example, as service we could consider the
advertisement of CDN capabilities as in CDNi approach [RFC7336],
while as network function we could consider functions like firewall,
CGNAT, etc, present in the network
[I-D.ietf-teas-sf-aware-topo-model].
All these scenarios present clear evolutions of the interconnection
model which can not be simply expressed through existing mechanisms,
or at least, cannot be expressed in a simple (and comprehensive) way
with such existing mechanisms. Here is where an advanced
interconnection intent can assist on declaring the goal of the
interconnection transcending pure IP traffic exchange and including
more advance capabilities as the ones mentioned before.
2. Evolution of Network interconnection
It becomes clear the trend to increasingly rely on multi-domain
scenarios for the provision of services. For instance, the access
today to an on-demand OTT video on Internet implies the interaction
of more than one single administrative domain. Thus, end-to-end
service delivery over multiple providers or domains is becoming the
norm.
Complex network services leveraging on virtualization solutions and
different infrastructure environments pertaining to distinct
administrative domains (i.e., operated and managed by distinct
providers) can be easily foreseen.
It is then necessary to explore mechanisms for interconnecting that
multiple domain environments in a common, portable way independently
of the owner of such infrastructure.
In addition to that, the evolution of edge and cloud computing has
enabled scenarios of seamless service delivery across such diverse
resources. Moreover, high availability requirements urge for
considering multi-cluster service deployment and delivery for the
network functions.
2.1. Potential interconnection intent types
The interconnection intent should provide enough abstractions to
express a variety of interconnection options.
The purpose of the interconnection intent can be multiple:
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* To enable multi-domain network service programming, by soliciting
interconnection of service / network functions in different
domains
* To enable multi-domain deployment of virtualized network
functions, by advertising the availability of compute and storage
resources in different domains
* To facilitate multi-domain network function or service charging,
by advertising (cumulative) costs in the different domains
* To enable delivery of service functions in the edge and cloud
continuum
* To enable traffic interchange, ie. IP as in traditional peering
or optical
* To put in place the right collection of policies to implement and
operate the interconnection
* To facilitate whatever combination of all of them
2.2. Interconnection intent lifecycle
[RFC9315] defines an intent lifecycle composed of two phases, namely
fulfillment and assurance. Figure 1 captures the intent procedure
for the fulfillment phase.
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User Space : Translation / IBS : Network Ops
: Space : Space
: :
+----------+ : +----------+ +-----------+ : +-----------+
Fulfill |recognize/|---> |translate/|-->| learn/ |-->| configure/|
|generate | | | | plan/ | | provision |
|intent |<--- | refine | | render | : | |
+----------+ : +----------+ +-----------+ : +-----------+
: :
.........................................................................
Provider A : Provider B
---------- : ----------
:
- Select interconn. : - Mapping of intent types to : - Establishment of
intent type : protocols / APIs for : protocol sessions
- Specify targeted : conveying targeted resources : or API requests
resources (i.e., : - Parametrization of that : for configure or
routes, compute : protocols / APIs, e.g. : provisioning
quotes, service : leveraging on data models : targeted resources
functions, etc.) : :
: :
Figure 1: Fulfillment phase of the Interconnection Intent
Similarly, Figure 2 sketches the intent procedure for the assurance
phase.
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: +--------+ :
: |validate| : +----------+
: +----^---+ <----| monitor/ |
Assure +-------+ : +---------+ +-----+---+ : | observe/ |
|report | <---- |abstract |<---| analyze | <----| |
+-------+ : +---------+ |aggregate| : +----------+
: +---------+ :
.....................................................................
Provider A : Provider B
---------- : ----------
:
- Analysis of the : - Checking of monitored data : - Collection of
reported metrics : for internal closed loops : telemetry info
against the intent : to ensure committed SLOs : related to allocated
request : (inner closed loop) : resources (i.e.,
- Trigger of actions : - Aggregation of data : routes, compute
if needed, e.g., : producing an abstracted view: quotes, service
new intent (outer : fitted to the intent request: functions, etc.)
closed loop) : :
Figure 2: Assurance phase of the Interconnection Intent
Both Fulfillment and Assurance phases are integral part of the
interconnection intent.
2.3. Protocol aspects
Ultimately the ideas and notions elaborated in this document will
need to find room in a framework made of one or multiple protocols
(ie. BGP, LISP, ALTO, etc.) and/or API definitions. While the exact
definition of such framework is left as future work, in this document
we intend to perform some seminal work in this sense (ie. identify
existing protocols that could fit, determine gaps of such protocols,
etc.).
3. Interconnection intent structure
In order to address the different interconnection intent types
described in section 2.1, the structure of the intent should be
sufficiently flexible to allow the expression of different targets.
Thus, the intent structure could include:
* Information of the type of data traffic being subject of the
interconnection intent (e.g., IP prefixes involved) among
providers.
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* Service functions expected to be supported by the peer provider.
These could be expressed in terms of type of service function and
number of instances required. Furthermore, it can be necessary to
consider how the service functions are expected to be connected in
terms of topology (i.e., service function graph).
* Resources expected to be offered by the peer provider. These
could be expressed in terms of raw values of number of CPUs,
memory and storage size, or bandwidth capacity, or alternatively,
in terms of quotas grouping resources in a predefined manner.
* Constraints that could apply to whatever of the elements included
in the interconnection intent, including traffic steering ones.
Aspects such as committed rates, burst size, cumulative traffic,
service function affinity, redundancy, traffic engineering (e.g.,
latency), etc., could be part of such constraints.
* Further information that could be necessary for delivering an end-
to-end service by means of the intent.
3.1. Structure of the Intents
Different Standardization Development Organizations (SDOs) are
working on the area of intents. This is the case of ETSI ZSM
[ZSM011], ETSI NFV [IFA050], or 3GPP [TS 28312].
The structure of the declarative intent model along those SDOs
follows a common design, considering a number of classes (i.e.,
objects that can be instantiated) and data types (i.e., assigned
values) as described next:
* Expectation: it refers to the expectation(s) of an intent
including the requirements, goals, constraints and context that
apply to it.
* Target: it refers to the behavioral outcomes resulting from the
configurations derived from the intent expectation. A given
intent expectation may include various targets.
* Condition: it applies to the value of the target.
* Context: It describes constraints or conditions applicable to the
intent expectation.
The same model will be followed in this document for exemplifying
possible interconnection intents.
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Note: Further alignment is yet needed with the referenced models in
other SDOs.
3.2. Examples
Section 2.1 presented potential interconnection intent types. This
section proposes examples of declarative intents for those
interconnection cases.
Note: further versions will refine and complete the examples.
3.2.1. Example 1. Conventional IP peering
Conventional IP peering leverages on BGP for performing interdomain
interconnection between two Autonomous Systems (AS). The
conventional IP peering intent could consider the following details:
* Peer AS number (ASN) and IP address
* Peering authentication (e.g., MD5)
* Traffic levels (e.g., PIR, CIR, etc)
The following intent can serve for the purposes of requesting peering
in a declarative manner from peer A (with ASN N and IP address ipA)
to peer B (with ASN M and IP address ipB)
* IntentExpectation: IP_peering
* - IntentTarget: AutonomousSystem
- o IntentTargetValue: M
o IntentContext: ASorigin = N
* - IntentTarget: IP_address
- o IntentTargetValue: ipB
o IntentContext: IPorigin = ipA
* - IntentTarget: CIR
- o IntentTargetValue: 1 Gbps
* - IntentTarget: Authentication
- o IntentTargetValue: MD5
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As result of the intent, peering session between providers could be
trigger by automated means, such as for instance
[I-D.ramseyer-grow-peering-api]. Proper translation of the intent to
[I-D.ramseyer-grow-peering-api] is left for further work.
3.2.2. Example 2. interconnection of service functions in different
domains
Service functions could be deployed in different administrative
domains, being of interest to interconnect them for creating a
service chain. An interconnection of this kind could consider as
relevant information:
* Service function in peer domain
* Preferred location (i.e., geographical area)
* Connection Service Level Objectives (e.g., bandwidth, latency,
etc)
* Preferred peering point (in terms of existing peering session
identified by peer Ip address)
The following intent can serve for the purposes of requesting
interconnection with a service function SF2 of peer B from service
function SF1 from peer A, with the expectation of connecting both
service functions observing a bandwidth capacity of up to 1 Gbps
during 90% of the time, and a latency lower than 10 ms.
* IntentExpectation: SF_interconnect
* - IntentTarget: ServiceFunction
- o IntentTargetValue: SF2
o IntentContext: SForigin = SF1
* - IntentTarget: Location
- o IntentTargetValue: Zone_X
* - IntentTarget: SLO_Bandwidth
- o IntentTargetValue: 1 Gbps
o IntentTargetContext: 90%
* IntentTarget: SLO_Latency
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* - IntentTargetValue: 10 ms
- IntentTargetCondition: lower than
3.2.3. Example 3. Delivery of composite service functions at the edge
and cloud continuum
Service functions may collectively deliver composite functionality in
the context of a service chain. In addition, service functions can
be delivered at different parts of the network, including the edge of
the network. For the delivery of such composite service functions,
performance characteristics should be assured coherently for seamless
service delivery in the continuum. Therefore, service function
delivery at diverse network parts should consider:
* The service chain in which the service function belongs to
* The node types (e.g. edge, cloud, etc.)) in which the service
functions may be executed
* Computational Service Level Objectives (e.g., virtual cpu, memory,
or storage)
* Connection Service Level Objectives (e.g., bandwidth, latency,
etc.)
The intent for expressing an expectation of interconnection of
service function SF1 of peer A to service function SF2 of peer B,
potentially delivered in resources across the edge-cloud continuum
and which together deliver composite functionality, can be formulated
as follows.
* IntentExpectation: SF_continuum
* - IntentTarget: ServiceFunction
- o IntentTargetValue: SF2
o IntentContext: SFcomposite = SF0
* - IntentTarget: NodeType
- o IntentContext: EdgeCloud
* - IntentTarget: SLO_Vcpu
- o IntentTargetValue: 2
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o IntentTargetCondition: greater than
* - IntentTarget: SLO_Vram
- o IntentTargetValue: 4
o IntentTargetCondition: greater than
* - IntentTarget: SLO_Bandwidth
- o IntentTargetValue: 1 Gbps
o IntentTargetContext: 90%
* IntentTarget: SLO_Latency
* - IntentTargetValue: 10 ms
- IntentTargetCondition: lower than
A working example is available on NEMO source code [NEMO_API].
4. Lessons Learned
The experimental part of this document is yet a work in progress.
However some initial lessons can be derived from it, as follows:
* New services imbricate an interplay of cloud and network
technologies. Furthermore, such services typically involved more
than one provider, and could span multiple administrative domains.
Finding proper ways of automating service deployment and operation
is a must, and requires the possibility of triggering actions in
cloud and network. Intents can play a relevant role there,
because their level of abstraction.
* Multiple adaptors could be required due to the different
technologies underneath, both at cloud and network levels.
Different cloud managers (e.g., Kubernetes, Openstack, etc) and
network automation capabilities (e.g., SDN controller, Network
Slice controller, overlay solutions, etc) could participate of a
single service.
* Common, abstract intents should be defined and agreed among
parties so to enable automation in multi-domain scenarios. This
implies common understanding and expectations of the intents, as
well as negotiation capabilities and monitoring, for intent
assessment in this scenarios where contractual relationships will
happen.
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This section will be further elaborated as long as the experimental
work advances.
5. Security Considerations
To be done.
6. IANA Considerations
This draft does not include any IANA considerations
7. References
[I-D.ietf-teas-sf-aware-topo-model]
Bryskin, I., Liu, X., Lee, Y., Guichard, J., Contreras, L.
M., Ceccarelli, D., Tantsura, J., and D. Shytyi, "SF Aware
TE Topology YANG Model", Work in Progress, Internet-Draft,
draft-ietf-teas-sf-aware-topo-model-13, 4 July 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-sf-
aware-topo-model-13>.
[I-D.llc-teas-dc-aware-topo-model]
Lee, Y., Liu, X., and L. M. Contreras, "DC aware TE
topology model", Work in Progress, Internet-Draft, draft-
llc-teas-dc-aware-topo-model-03, 10 July 2023,
<https://datatracker.ietf.org/doc/html/draft-llc-teas-dc-
aware-topo-model-03>.
[I-D.ramseyer-grow-peering-api]
Aguado, C., Griswold, M., Ramseyer, J., Servin, A. L., and
T. Strickx, "Peering API", Work in Progress, Internet-
Draft, draft-ramseyer-grow-peering-api-05, 30 May 2024,
<https://datatracker.ietf.org/doc/html/draft-ramseyer-
grow-peering-api-05>.
[IFA050] "ETSI NFV IFA 050. Management and Orchestration; Intent
Management Service Interface and Information Model
Specification", <https://portal.etsi.org/eWPM/
index.html#/schedule?wki_id=69576>.
[NEMO_API] "NEMO source code; Intent API",
<https://gitlab.eclipse.org/eclipse-research-labs/nemo-
project/nemo-service-management/intent-based-sdk_api/
intent-api>.
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[RFC7336] Peterson, L., Davie, B., and R. van Brandenburg, Ed.,
"Framework for Content Distribution Network
Interconnection (CDNI)", RFC 7336, DOI 10.17487/RFC7336,
August 2014, <https://www.rfc-editor.org/info/rfc7336>.
[RFC9315] Clemm, A., Ciavaglia, L., Granville, L. Z., and J.
Tantsura, "Intent-Based Networking - Concepts and
Definitions", RFC 9315, DOI 10.17487/RFC9315, October
2022, <https://www.rfc-editor.org/info/rfc9315>.
[TS28312] "3GPP TS 28.312. Management and orchestration; Intent
driven management services for mobile networks (Release
17)", <https://www.3gpp.org/ftp/Specs/
archive/28_series/28.312/28312-h60.zip>.
[ZSM011] "ETSI ZSM 011. Zero-touch network and Service Management
(ZSM); Intent-driven autonomous networks; Generic
aspects", <https://www.etsi.org/deliver/etsi_gr/
ZSM/001_099/011/01.01.01_60/gr_ZSM011v010101p.pdf>.
Contributors
The following people have contributed to this document.
Guillermo Sanchez Illan (guillermo.sanchezillan@telefonica.com),
Telefonica.
Artemios Tomaras (tomaras@synelixis.com), Synelixis.
Theodore Zahariadis (zahariad@synelixis.com), Synelixis.
Acknowledgments
This work has been partially funded by the European Union under
Horizon Europe project NEMO (NExt generation Meta Operating system)
grant number 101070118.
Authors' Addresses
Luis M. Contreras
Telefonica
Ronda de la Comunicacion, s/n
Sur-3 building, 1st floor
28050 Madrid
Spain
Email: luismiguel.contrerasmurillo@telefonica.com
URI: http://lmcontreras.com/
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Paolo Lucente
NTT
Siriusdreef 70-72
2132 Hoofddorp, WT
Netherlands
Email: paolo@ntt.net
Terpsichori Helen Velivassaki
Synelixis
Farmakidou 10
34100 Chalkida
Greece
Email: terpsi@synelixis.com
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