Internet DRAFT - draft-bernardos-cats-anchoring-service-mobility
draft-bernardos-cats-anchoring-service-mobility
CATS WG CJ. Bernardos
Internet-Draft UC3M
Intended status: Standards Track A. Mourad
Expires: 2 September 2024 InterDigital
1 March 2024
Service Mobility-Enabled Computing Aware Traffic Steering using IP
address anchoring
draft-bernardos-cats-anchoring-service-mobility-00
Abstract
The IETF CATS WG addresses the problem of how the network
infrastructure can steer traffic between clients of a service and
sites offering the service, considering both network metrics (such as
bandwidth and latency), and compute metrics (such as processing,
storage capabilities, and capacity).
This document defines new extensions and procedures for a terminal
connected to a network infrastructure, to benefit from transparent
service migration adapting to specific connectivity and computing
requirements, so traffic is always steered to an instance meeting
both requirements. Both CATS-aware and -unaware terminals are
considered. Exemplary signaling control messages and operation
extending the well-known Proxy Mobile IPv6 protocol are also defined.
Status of This Memo
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provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on 2 September 2024.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction and Problem Statement . . . . . . . . . . . . . 2
1.1. Use case scenario . . . . . . . . . . . . . . . . . . . . 2
1.2. Problem statement . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Enabling service continuity with IP anchor mobility for
CATS . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. OPTION A: terminal-initiated . . . . . . . . . . . . . . 5
3.2. OPTION B: ECR-initiated . . . . . . . . . . . . . . . . . 9
3.3. OPTION C: CATS controller-initiated . . . . . . . . . . . 9
4. Proxy Mobile IPv6 signaling extensions to enable service
mobility with IP address service-specific anchoring for
CATS . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1. New ECR mobility option . . . . . . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
8. Informative References . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction and Problem Statement
1.1. Use case scenario
Let's consider a possible use case scenario, just for the sake of
illustrating the scenario. A terminal is running an AR/VR/XR
application (note that this is just an example, other services would
also benefit from compute and connectivity traffic steering). Part
of this service is executed in the network infrastructure, posing
some requirements on the connectivity (e.g., delay between the
terminal and the node where the service is executed on the network
infrastructure) and computing resources (e.g., capabilities to render
the XR video within a certain latency budget). Within the network
domain where the terminal is connected to there are multiple sites
capable of hosting the service, each with potentially different
connectivity and computing characteristics. Figure 1 shows an
exemplary scenario. Considering the connectivity and computing
latencies (just as an example of metrics), the best service site is
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#n-1 in the example used in the Figure.
________________
( ---------- )
( | | )
( ---------- | )
________________ ( | | | ) ________________
( ---------- ) ( ---------- | | ) ( ---------- )
( | | ) ( |service | |- ) ( | | )
( ---------- | ) ( |contact | | ) ( ---------- | )
( | | | ) ( |instance|-- ) ( | | | )
( ---------- | | ) ( ---------- ) ( ---------- | | )
( |service | |- ) ( Serv. site #N-1 ) ( |service | |- )
( |contact | | ) -------+---------- ( |contact | | )
( |instance|-- ) Computing \ ( |instance|-- )
( ---------- ) delay:4ms \ ( ---------- )
( Serv. site #1 ) --------+-- ( Serv. site #N )
-------+-------- ----| ECR#N-1 |---- ---------+-----
\ Computing -- ----------- -- Computing /
\ delay:10ms Networking delay:5ms /
---+----- delay:7ms ------+--
( | ECR#1 | // | ECR#N | )
( --------- // --------- )
( Networking // Networking )
( delay:5ms // delay:15ms )
( // )
( // )
( // )
( // )
( // )
( --------- --------- )
-------| ICR#1 |---------------------| ICR#2 |--------
--------- ---------
(·)
(·)
------
| UE |
------
Figure 1: Exemplary scenario
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1.2. Problem statement
The main problem that this document tries to address is the
following. Networking systems do not have mechanisms yet to service
mobility mechanisms optimized for connectivity and computing-aware
traffic steering, which consider both connectivity and computing
status to dynamically select where a service runs for a given
terminal.
Based on the former, this document proposes solutions to enable the
network to react and adapt to connectivity and computing conditions,
triggering optimal service migration based on service-specific IP
anchor mobility. In particular, this document addresses the
following questions: (i) what mechanisms does the network need to
implement to facilitate the migration of a service so its
requirements in terms of computing and networking are maintained?;
and, (ii) how to steer traffic to a new service instance location
after moving the service, in a transparent manner to the terminal, by
using IP anchor mobility?
2. Terminology
The following terms used in this document are defined by the IETF:
ECR. Egress CATS router.
ICR. Ingress CATS router.
3. Enabling service continuity with IP anchor mobility for CATS
We describe next an example of operation and signaling for the
network to perform service mobility. Three different embodiments are
described next, for variations (OPTIONS) of the procedures: terminal
initiated, ECR-initiated and CATS-controller initiated. In addition
to the functionality defined in
[I-D.bernardos-cats-ip-address-anchoring], this documents defines a
new functionality:
* Service mobility: it deals with the procedures required to (i)
detect or predict a change of the current conditions, jointly
considering computing and networking, requiring of a service
mobility operation; (ii) selecting the best target service
instance location, and (iii) triggering the service mobility by
orchestrating the service anchor mobility and requesting service
migration to a new site. For example, a terminal or ECR might use
this functionality to perform active monitoring of a service with
CATS agents running at the current ICR, ECR and or service site.
It is also used to perform the actual service anchor mobility.
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3.1. OPTION A: terminal-initiated
Next, we assume service mobility is triggered by a CATS-aware
terminal. By having a CATS agent running on the terminal, it can
perform different monitoring actions to predict or detect the need to
migrate a service from one site to another. This CATS agent might,
for example, interact with other CATS agents deployed on ICRs, ECRs
and service sites.
In the following we describe a service anchor mobility procedure for
CATS, initiated by a CATS-aware terminal. Following the terminal
initiation, the network infrastructure is capable to select a target
service instance meeting the connectivity and computing requirements
of the service, with signaling procedures defined to perform a
transparent anchor migration to a new site, facilitating the service
migration in a transparent way for the terminal. Extensions and new
behavior are highlighted. Note that variations are possible over
this exemplary signaling diagram.
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+----+ +-----+ +-------------+ +---------------+ +-------------+ +----+
| | | | | site #1 | | site #N-1 | | site #N | |CATS|
|term| |ICR#1| |ECR#1 ag. SCI| |ECR#N-1 ag. SCI| |ECR#N ag. SCI| |ctrl|
+----+ +-----+ +--+----+---+-+ +----+----+---+-+ +--+----+---+-+ +----+
| | | | | | | | | | | |
| | O. Service instance running at site #n-1. | | |
| | Tunnel established between ICR#1 and ECR#N-1 | |
| | | | | | | | | | | |
| 1. An external or internal trigger is received regarding |
| a change in the compute or networking conditions |
| | | | | | | | | | | |
|1a. CATS agent at terminal reports a perceived change on service|
|·····>| | | | | | | | | | |
| | | | | | | | | | | |
| |2a.CATS query(service ID, terminal ID, ICR ID, CATS reqs.)
| |······>|<··>| | | | | | | | |
| |········································>|<··>| | |
| 3a.CATS response(service ID, terminal ID, ECR ID, CATS cond.)
| |<······| | | | | | | | | |
| |<········································| | | |
| | | | | | | | | | | |
| 4a. Service anchor/ECR@site#n is selected as best | |
| | | | | | | | | | | |
5a.CATS request(service ID, terminal ID, ICR ID, CATS reqs., IP pref.)
|···············································>| | | |
| | | | | | | | | | | |
|6.CATS ACK(service ID, terminal ID, ECR ID, CATS cond., IP prefix)
|<···············································| | | |
| | | | | | | | | | | |
| 7.New tunnel for IP pref. established beetween ICR#1 and ECR#N |
| | | | | | | | | | | |
| | 8.Service migration from site#N-1 to site#N | | |
| | | | | | | | | | | |
| 9. Service specific traffic| | | | | | |
|<---->|<--------------------------------------->|<------>| |
| | | | | | | | | | | |
Figure 2: Exemplary signaling
Figure 2 shows the message sequence chart of the IP anchor mobility
for CATS, initiated by a CATS-aware terminal (OPTION A), which is
explained next:
0. A service/app has been already instantiated on a service site
(for example, by using the mechanisms specified in
[I-D.bernardos-cats-ip-address-anchoring]). In this example, the
site where the service/app consumed by the terminal is currently
instantiated is site #n-1. The terminal is connected to ICR #1
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and there is a service tunnel between ICR#1 and ECR#N-1. This
service/app requires some functionality to be run on the network
infrastructure (e.g., an AR/VR/XR service). This service has
specific requirements in terms of both connectivity and computing
(CATS requirements).
1. An internal or external trigger is generated regarding a change
in the computing of networking conditions, making the current
selected service site not feasible for the running service (i.e.,
CATS requirements cannot be met). In this OPTION A, the terminal
is CATS-aware, and it the node that detects the change in the
conditions (how this is made is outside the scope of this
document, but possible mechanisms include: monitoring at service/
app level, in-situ monitoring by the terminal, etc.) and sends a
trigger to the ICR.
2. The ICR sends a query to all (but currently used) ECRs of the
domain, or a subset selected based on the location of the ICR.
This query may include the following parameters:
i. Service ID: an identifier of the service requested by the
terminal. This allows to check if the service can be
instantiated or it is already instantiated.
ii. Terminal ID: an identifier of the terminal requesting the
service. This is useful for example for affinity purposes.
It might not include information that can be used to
identify the user.
iii. ICR ID: identifier of the requesting ICR.
iv. CATS requirements: list of requirements, e.g., connectivity
and computing requirements.
3. Each ECR, possibly after checking with the CATS agent of the
site(s) it provides connectivity, responds, including the
following information:
i. The ICR sends a query to all ECRs of the domain, or a
subset selected based on the location of the ICR. This
query may include the following parameters:
i. Service ID.
ii. Terminal ID.
iii. ECR ID: identifier of the ECR sending the response.
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iv. CATS conditions: how the site meets each of the
requirements included in the request.
v. (Optional): URI to get to the service instance.
A CATS agent at a site might be collocated with the ECR.
Examples of a CATS agent at a site are network controllers
or orchestrators at the site. Note that the way a CATS
agent at an ECR may interact with the CATS agent of the
site is out of the scope of this document. Examples
include using monitoring and telemetry interfaces with an
orchestrator managing the site.
ii. Based on the received responses, and considering both
networking and computing metrics and policies, the ICR
selects an ECR (#n).
iii. The ICR requests the proposed/selected ECR to establish a
traffic steering session with it, sending a CATS request.
This request includes the same information that was
included in the CATS query (to facilitate stateless
operation of the ECRs while being queried), plus the
following additional parameters:
* ECR prefix: currently in use IP prefix IP to the
terminal to reach the service instance.
* Lifetime: requested duration for the association between
the ICR and the ECR.
iv. The selected ECR responds back with an acknowledgement,
including the following information:
i. Service ID.
ii. Terminal ID.
iii. ECR ID: identifier of the ECR sending the response.
iv. CATS conditions: how the site meets each of the
requirements included in the request.
v. IP prefix assigned for the terminal to use to reach
the service instance. It should match the one
included in the request.
vi. Lifetime: granted duration of the association between
the ICR and the ECR.
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v. An IP tunnel is established between the ICR and the new
ECR. Optionally (not shown in the figure), the ICR might
send a CATS request with cero lifetime to the old ECR to
remove the old tunnel.
vi. The previous message triggers the service migration (from
site #n to site #n-1). The specific mechanism is out of
the scope of this document. Note that some preparation/
migration steps might be conducted in parallel (e.g., after
messages #1 and #3) to accelerate the process, making this
step just the final trigger for the service migration. At
site #n, the prefix used by the terminal for accessing the
service is configured to be used by migrated instance.
This might requires routing updates to be perfomed in the
site, potentially controlled by a CATS agent running in the
site.
vii. Traffic of the service for this terminal is steered using
the IP tunnel.
3.2. OPTION B: ECR-initiated
TBD.
3.3. OPTION C: CATS controller-initiated
TBD.
4. Proxy Mobile IPv6 signaling extensions to enable service mobility
with IP address service-specific anchoring for CATS
The control plane extensions introduced in the previous section can
be implemented over different protocols. This section specifies
extensions to Proxy Mobile IPv6. Only new options additional to what
is defined in [I-D.bernardos-cats-ip-address-anchoring] are included.
4.1. New ECR mobility option
The new ECR option has the following format:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved | Addr. Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ New ECR IP address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Message fields:
* Option Type: TBA by IANA.
* Option Length: 8-bit unsigned integer. Length of the option, in
octets, excluding the Option Type and Option Length fields.
* Addr. Length: 8-bit unsigned integer. Length of the New ECR IP
address field, in octets.
* New ECR IP address: variable length field that includes IP address
of the new ECR.
5. IANA Considerations
TBD.
6. Security Considerations
TBD.
7. Acknowledgments
The work of Carlos J. Bernardos in this document has been partially
supported by the Horizon Europe PREDICT-6G (Grant 101095890), DESIRE-
6G (Grant 101096466) and UNICO I+D 6G-DATADRIVEN-04 project.
8. Informative References
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[I-D.bernardos-cats-ip-address-anchoring]
Bernardos, C. J. and A. Mourad, "Computing Aware Traffic
Steering using IP address anchoring", Work in Progress,
Internet-Draft, draft-bernardos-cats-ip-address-anchoring-
01, 29 February 2024,
<https://datatracker.ietf.org/doc/html/draft-bernardos-
cats-ip-address-anchoring-01>.
Authors' Addresses
Carlos J. Bernardos
Universidad Carlos III de Madrid
Av. Universidad, 30
28911 Leganes, Madrid
Spain
Phone: +34 91624 6236
Email: cjbc@it.uc3m.es
URI: http://www.it.uc3m.es/cjbc/
Alain Mourad
InterDigital Europe
Email: Alain.Mourad@InterDigital.com
URI: http://www.InterDigital.com/
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