Distributed SFC control operation
draft-bernardos-sfc-distributed-control-operation-06
| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Carlos J. Bernardos , Alain Mourad | ||
| Last updated | 2023-03-13 | ||
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| Intended RFC status | (None) | ||
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draft-bernardos-sfc-distributed-control-operation-06
SFC WG CJ. Bernardos
Internet-Draft UC3M
Intended status: Experimental A. Mourad
Expires: 14 September 2023 InterDigital
13 March 2023
Distributed SFC control operation
draft-bernardos-sfc-distributed-control-operation-06
Abstract
Service function chaining (SFC) allows the instantiation of an
ordered set of service functions and subsequent "steering" of traffic
through them. In order to set up and maintain SFC instances, a
control plane is required, which typically is centralized. In
certain environments, such as fog computing ones, such centralized
control might not be feasible, calling for distributed SFC control
solutions. This document describes a general framework for
distributed SFC operation.
Status of This Memo
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This Internet-Draft will expire on 14 September 2023.
Copyright Notice
Copyright (c) 2023 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
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Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Problem statement . . . . . . . . . . . . . . . . . . . . . . 5
4. Distributed SFC control operation . . . . . . . . . . . . . . 7
4.1. P-CTRL taking over C-CTRL . . . . . . . . . . . . . . . . 8
4.1.1. P-CTRL taking over C-CTRL due to a local monitoring
event . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1.2. P-CTRL taking over C-CTRL due to a C-CTRL failure . . 10
4.1.3. C-CTRL gaining back control . . . . . . . . . . . . . 12
4.2. Inter P-CTRL seamless handover . . . . . . . . . . . . . 13
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
6. Security Considerations . . . . . . . . . . . . . . . . . . . 14
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.1. Normative References . . . . . . . . . . . . . . . . . . 14
8.2. Informative References . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction
Virtualization of functions provides operators with tools to deploy
new services much faster, as compared to the traditional use of
monolithic and tightly integrated dedicated machinery. As a natural
next step, mobile network operators need to re-think how to evolve
their existing network infrastructures and how to deploy new ones to
address the challenges posed by the increasing customers' demands, as
well as by the huge competition among operators. All these changes
are triggering the need for a modification in the way operators and
infrastructure providers operate their networks, as they need to
significantly reduce the costs incurred in deploying a new service
and operating it. Some of the mechanisms that are being considered
and already adopted by operators include: sharing of network
infrastructure to reduce costs, virtualization of core servers
running in data centers as a way of supporting their load-aware
elastic dimensioning, and dynamic energy policies to reduce the
monthly electricity bill. However, this has proved to be tough to
put in practice, and not enough. Indeed, it is not easy to deploy
new mechanisms in a running operational network due to the high
dependency on proprietary (and sometime obscure) protocols and
interfaces, which are complex to manage and often require configuring
multiple devices in a decentralized way.
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Service Functions are widely deployed and essential in many networks.
These Service Functions provide a range of features such as security,
WAN acceleration, and server load balancing. Service Functions may
be instantiated at different points in the network infrastructure
such as data center, the WAN, the RAN, and even on mobile nodes.
Service functions (SFs), also referred to as VNFs, or just functions,
are hosted on compute, storage and networking resources. The hosting
environment of a function is called Service Function Provider or
NFVI-PoP (using ETSI NFV terminology).
Services are typically formed as a composition of SFs (VNFs), with
each SF providing a specific function of the whole service. Services
also referred to as Network Services (NS), according to ETSI
terminology.
With the arrival of virtualization, the deployment model for service
function is evolving to one where the traffic is steered through the
functions wherever they are deployed (functions do not need to be
deployed in the traffic path anymore). For a given service, the
abstracted view of the required service functions and the order in
which they are to be applied is called a Service Function Chain
(SFC). An SFC is instantiated through selection of specific service
function instances on specific network nodes to form a service graph:
this is called a Service Function Path (SFP). The service functions
may be applied at any layer within the network protocol stack
(network layer, transport layer, application layer, etc.).
The concept of fog computing has emerged driven by the Internet of
Things (IoT) due to the need of handling the data generated from the
end-user devices. The term fog is referred to any networked
computational resource in the continuum between things and cloud. A
fog node may therefore be an infrastructure network node such as an
eNodeB or gNodeB, an edge server, a customer premises equipment
(CPE), or even a user equipment (UE) terminal node such as a laptop,
a smartphone, or a computing unit on-board a vehicle, robot or drone.
In fog computing, the functions composing an SFC are hosted on
resources that are inherently heterogeneous, volatile and mobile
[I-D.bernardos-sfc-fog-ran]. This means that resources might appear
and disappear, and the connectivity characteristics between these
resources may also change dynamically. These scenarios call for
distributed SFC control solutions, where there are SFC pseudo
controllers, enabling autonomous SFC self-orchestration capabilities.
The concept of SFC pseudo controller (P-CTRL) is described in
[I-D.bernardos-sfc-distributed-control], as well different procedures
for their discovery and initialization.
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This document introduces a framework for local distributed SFC
operation, by allowing P-CTRLs to temporarily substitute the central
controller (C-CTRL) in its task to carry out the global lifecycle
management of the given SFC.
2. Terminology
The following terms used in this document are defined by the IETF in
[RFC7665]:
Service Function (SF): a function that is responsible for specific
treatment of received packets (e.g., firewall, load balancer).
Service Function Chain (SFC): for a given service, the abstracted
view of the required service functions and the order in which they
are to be applied. This is somehow equivalent to the Network
Function Forwarding Graph (NF-FG) at ETSI.
Service Function Forwarder (SFF): A service function forwarder is
responsible for forwarding traffic to one or more connected
service functions according to information carried in the SFC
encapsulation, as well as handling traffic coming back from the
SF.
SFI: SF instance.
Service Function Path (SFP): the selection of specific service
function instances on specific network nodes to form a service
graph through which an SFC is instantiated.
The following terms are defined and used in this document:
SFC Pseudo Controller (P-CTRL): logical entity
[I-D.bernardos-sfc-distributed-control], complementing the SFC
controller/orchestrator found in current architectures and
deployments. It is service specific, meaning that it is defined
and meaningful in the context of a given network service.
Compared to existing SFC controllers/orchestrators, which manage
multiple SFCs instantiated over a common infrastructure, pseudo
controllers are constrained to service specific lifecycle
management.
SFC Central Controller (C-CTRL): central control plane logical
entity in charge of configuring and managing the SFC components
[RFC7665].
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3. Problem statement
Mobile network architectures are evolving to support network
virtualization and service function orchestration. Current Service
Function Chain (SFC) architectures [RFC7665] rely on a centralized
controller/orchestrator (C-CTRL) which shall be connected to all the
hosts participating in a given SFC. This poses issues and
inefficiencies in fog computing environments especially because of
the mobility and volatility of some hosts, as well as the associated
signaling overhead.
These problems can be alleviated by enabling autonomous SFC self-
orchestration (SOC), based on the concept of SFC pseudo controller
(P-CTRL) introduced in [I-D.bernardos-sfc-distributed-control]. A
pseudo controller is capable of substituting (at least temporarily
and partially) the centralized SFC controller in situations where the
centralized controller may not be able to perform its functions
(e.g., when the connectivity with some hosts is broken).
[I-D.bernardos-sfc-distributed-control] introduces the role of the
SFC pseudo controller and describes mechanisms to select and
initialize a service-specific SFC pseudo controller among host nodes
which are participating in the SFC. This document specifies
mechanisms to enable an SFC pseudo controller trigger and control NS
lifecycle management operations, such as migration of NS functions,
chains or parts of a chain.
Figure 1 shows an exemplary scenario where a host UE makes use of an
NS composed of the chain of SFs F1-F2-F3. These functions may be
application functions -- using 3GPP jargon -- network functions or
over-the-top functions. Non-limiting examples of these functions
are: load balancers, traffic steering, performance enhancement
proxies (PEPs), video transcoders, firewalls, etc. In this example,
F1 instance runs on a first UE (node A), F2 instance runs on a second
UE (node B), and F3 instance runs on a gNB (node D). SFC pseudo
controller instances are assumed running on UE node A and D (which is
a gNB). Node A and B are connected via D2D communications. If all
the UEs move out of the coverage of the gNB node D, the service chain
will then need to be reconfigured to maintain service continuity as
gNB node D is hosting one function (F3) of the chain and would become
disconnected. Since gNB node D is also providing the UEs with
connectivity to the network infrastructure where the SFC central
controller is hosted, this type of event cannot be resolved by the
SFC controller, as the nodes hosting the functions would be
disconnected from the central controller. Similar problems arise in
highly mobile/volatile and/or latency-demanding scenarios, where
centralized lifecycle management becomes unsuitable.
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o
node B |
+--------|-+ F1+-·-·-+F2+-·-·-+F3 SFC
| ········ |
<==== | |P-CTRL| |
| ········ |
+-·-·-+F2 |
o / +---+------+ ________
| · · _( )_
+--------|-+ / / _( +--------+ )_
| | · · (_ | C-CTRL | _)
| | / / (_+--------+_)
| |· | (________)
| +-·-·/ ·
| F1 | | ( (oo) )
+----------+ · o /\ ········
node A | | /\/\ |P-CTRL|
+-----·--|-+ /\/\/\········
| | | /\/ \/\ (F3)
| · | node D
<==== | | |
| + |
| F3 |
+----------+
node C
Figure 1: Example scenario: disrupted SFC due to mobility
In these scenarios, an SFC pseudo controller can substitute (at least
temporarily and partially) the centralized SFC controller when the
latter is not available or able to perform a given task. This
document proposes solutions addressing the following problem: How to
enable SFC pseudo controllers to perform NS lifecycle management
operations, such as migration of functions, service chains or parts
of a chain? This requires solving the sub-problems listed below.
* When a SFC centralized controller (C-CTRL) is in charge, what
mechanisms and exchanges are needed between the C-CTRL and a SFC
pseudo-controller (P-CTRL), and the nodes, so as to facilitate a
seamless transition from C-CTRL to P-CTRL (due to an event, e.g.
failure, of the C-CTRL)?
* When P-CTRL takes over from the C-CTRL, what actions shall it take
towards other P-CTRLs, so as to sustain seamless transition if a
first P-CTRL fails (e.g., moving from P-CTRL A to P-CTRL B)?
* When C-CTRL is back into the picture, how shall the control
transfer seamlessly back from P-CTRL to C-CTRL?
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4. Distributed SFC control operation
A key concept is to allow a P-CTRL to take over temporarily and
partially from the C-CTRL to perform NS lifecycle management
decisions. The definition, selection and initialization of a P-CTRL
is covered in [I-D.bernardos-sfc-distributed-control].
Using Figure 1, we can think of an example where a function (F3) is
migrated from node D to node C, triggered by the move of nodes A and
B hosting F1 and F2 away from the coverage of node D hosting F3
(nodes A nd B are UEs within coverage of node D which is a gNB). The
P-CTRL in node B performs OAM operations locally and monitors the NS-
specific SLAs. Upon detecting or predicting that the NS-specific
SLAs may not be met in the near future, P-CTRL A takes actions to
temporary and partially substitute C-CTRL, and starts performing
local NS lifecycle management operations (e.g., instantiating F3 on
node C, since current hosting node -- node D --is predicted to become
unreachable soon).
Note that, in the previous example, the prediction and local NS
lifecycle management operations could have been performed by P-CTRL
running at node D as well. We have assumed that the active
(designated) P-CTRL is running at node B, but could have been at node
D as well, which would imply the need to also migrate the active
P-CTRL role to node B.
Thanks to enabling P-CTRL B to perform local NS lifecycle management
decisions, service continuity will be guaranteed when C-CTRL fails or
is out of reach.
The "activation" of P-CTRL operation only occurs when C-CTRL cannot
properly operate (e.g., it is disconnected from the SFC or it is not
reacting fast enough to the local changing conditions). For example,
P-CTRL can send a scaling command to a given node, in order to adapt
the resources to the current NS demands. P-CTRL would also notify
this to C-CTRL, as soon as the connection to C-CTRL is recovered so
that both are synchronized.
In order to support the operation of P-CTRLs complementing or
replacing the operation of the C-CTRL, the following operations are
needed:
* When an NS is onboarded, the C-CTRL receives an NS descriptor
(NSD), together with the VNF descriptors (VNFDs) of the functions
composing the service, and the Operations, Administration and
Maintenance Descriptor (OAMD), which includes the information of
what needs to be monitored to ensure a given SLA.
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* When the NS is instantiated, in addition to the regular
orchestration decisions (e.g., placement of functions on available
resources, etc.), the C-CTRL, based on its knowledge of existing
P-CTRLs, decides how monitoring is going to be performed. This
includes: (i) What is monitored by each P-CTRL node (e.g., vCPU
load, bandwidth of a certain link, etc.) and how (e.g., active,
passive or hybrid monitoring); (ii) Which orchestrators are in
charge of collecting and processing the measurements.
Currently defined mechanisms assume a semi-static environment and the
standardized message flows do not support dynamic migration of the
SFC controller role to other entities. Therefore, new signaling
flows need to be defined between C-CTRL and P-CTRLs and in-between
P-CTRLs: (i) allowing prediction of events via local monitoring and
faster reaction, (ii) enabling orchestration when C-CTRL is
temporarily unreachable, and (iii) supporting migrating CTRL role to
P-CTRLs.
4.1. P-CTRL taking over C-CTRL
There are two main triggers for a P-CTRL to take over from the
C-CTRL: a local monitoring event or a C-CTRL failure. We specify
next the procedures for each of these two triggers.
4.1.1. P-CTRL taking over C-CTRL due to a local monitoring event
In this case, the C-CTRL has delegated some monitoring actions to the
P-CTRL, as indicated in the OAMD sent by the C-CTRL to the P-CTRL.
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+---------+ +----+ +---------+ +---------+ +----------+ +------+
| node A | | C | | node B | | node D | | 3GPP | | SFC |
|P-CTRL F1| | F3 | |P-CTRL F2| |P-CTRL F3| |ctrl plane| |C-CTRL|
+--+----+-+ +----+ +--+----+-+ +--+----+-+ +----------+ +------+
| | | | | | | | |
| F1@A<->F2@B<->F3@D SFC network service | |
| |<-·-·-·-·-·-·-·-·-·>|<-·-·-·-·->| |A.Serv. OAM |
| | | | | | | |<-·-·-·-·-·>|
| | | | |B.Serv. OAM monitor. | |
| | | | |-·-·-·-·-·-·-·-·-·-·>| |
| | | | |<-·-·-·-·-·-·-·-·-·-·| |
| | | | | | | | |
| | | | |C.Serv. OAM monitor. | |
| | | | |<-·-·-| | | |
| | | | |-·-·-·-·-·-·-·-·-·-·>| |
| | | | |<-·-·-·-·-·-·-·-·-·-·| |
| | | | |-·-·->| | | |
| | D.Serv. OAM monitor. | | | |
| | |<-·-·->| | | | | |
| | | |<-·-·-·-·->| | | |
|<-·>|<-·-·-·-·-·-·->| | | | | |
|<-·-·-·-·-·-·-·-·-·>| | | | | |
| | | | | | | | |
| | P-CTRL@B detects that it's | | |
| | loosing connectivity with D | | |
| | | | | | | | |
| | Orch. signal. | | | | | |
| | |<-·-·->| | | | | |
| |<-·-·-·-·-·-·->| | | | | |
| | | | | Sync. with C-CTRL | |
| | | | |<·-·-·-·-·-·-·-·-·-·>| |
| | | | | | | | |
Figure 2: P-CTRL taking over C-CTRL due to a local monitoring event
A detailed message sequence chart is shown in Figure 2. The
different steps are described next:
* (We assume that the network service has been instantiated and
there is traffic: F1@A--F2@B--F3@D).
* C-CTRL runs overall OAM monitoring of the network services. This
can be done for example by contacting the 3GPP network to obtain
different network analytics via NEF. This is shown in the figure
as A.
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* P-CTRLs are running service specific OAM monitoring actions, as
indicated in the OAMD sent by the C-CTRL in the network service
instantiation procedure. This requires signaling procedures.
Various non-limiting example options are possible:
- The P-CTRL may directly obtain information metrics from
different network functions through the network exposure
function (NEF). This is shown in the figure as B.
- The P-CTRL may indirectly obtain the information metrics
through the local AF or NF hosted on the UE, which interacts
with any other entity inside or outside 3GPP (e.g., AF to AF,
NF to AF, or NF to NF) and then parse these on the interface to
the P-CTRL. If the function hosted on the UE is an NF, and the
info is about 3GPP network data analytics, then the NF will go
get some data from NWDAF and locally at the UE, expose these to
the P-CTRL. This is shown in the figure as C.
- In addition to the former (mutually exclusive approaches), it
is also possible to perform local OAM monitoring via standalone
procedures, such as local OAM monitoring and the use of SFC
OAM. This is shown in the figure as D.
The interface between the P-CTRL and the SFC functions running on
the UE to obtain OAM metrics may be a local API, or standard
interface like IETF SFC OAM, or like the interface between 3GPP
NWDAF and an NWDAF service consumer.
* At a certain point in time, a local monitoring event, which cannot
be detected by the C-CTRL, triggers the whole process. In the
example of the figure P-CTRL@node B detects that B is losing
connectivity with node D.
* The P-CTRL takes an orchestration decision based on its local
knowledge and signals it to the involved nodes. The decision
consists in migrating/moving F3 from node D to C. New extensions
to MIPv6 are used, as described in TBD. Alternatively, extensions
to IETF SFC NSH can also be used, as described in TBD.
* The P-CTRL also informs the C-CTRL to keep it synchronized.
Similarly, the C-CTRL can then update other P-CTRLs if needed.
New extensions to NSH are used (NS lifecycle management), as
described in TBD.
4.1.2. P-CTRL taking over C-CTRL due to a C-CTRL failure
In this case, the P-CTRL detects/predicts a C-CTRL failure (e.g., it
becomes unreachable).
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+---------+ +----+ +---------+ +---------+ +----------+ +------+
| node A | | C | | node B | | node D | | 3GPP | | SFC |
|P-CTRL F1| | F3 | |P-CTRL F2| |P-CTRL F3| |ctrl plane| |C-CTRL|
+--+----+-+ +----+ +--+----+-+ +--+----+-+ +----------+ +------+
| | | | | | | | |
| F1@A<->F2@B<->F3@D SFC network service | |
| |<-·-·-·-·-·-·-·-·-·>|<-·-·-·-·->| | |
| | | | | | | | |
| | | | | C-CTRL connectivity failure |
| | | | |<·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·->|
| P-CTRL@B detects that connectivity | |
| with C-CTRL is lost (or about to be) | |
| | | | | | | | |
| | | | | Sync with C-CTRL (if |
| | | | | failure is predicted) |
| | | | |<·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·->|
| | P-CTRL@B becomes the | | | |
| | CTRL for the service | | | |
| | | | | | | | |
| P-CTRL activation | | | | | |
|<-·-·-·-·-·-·-·-·-·>| | | | | |
| | | | | | | | |
| | Orch. signal. | | | | | |
| | |<-·-·->| | | | | |
| |<-·-·-·-·-·-·->| | | | | |
| | | | | | | | |
Figure 3: P-CTRL taking over C-CTRL due to a C-CTRL failure
A detailed message sequence chart is shown in Figure 3. The
different steps are described next:
* (We assume that the network service has been instantiated and
there is traffic: F1@A--F2@B--F3@D).
* A failure can be detected by a P-CTRL via multiple mechanisms,
such as: (i) Sending periodic keep-alive messages to the C-CTRL;
(ii) Transport-layer mechanisms that allow detecting connectivity
failures; (iii) Observing a lack of action from the C-CTRL upon an
event that requires an orchestration action.
* A failure can also be predicted by a P-CTRL, by using local
monitoring information.
* When a C-CTRL failure is detected, the designated backup P-CTRL
takes over the orchestration of the network service, by:
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- Notifying other P-CTRLs, as well as selecting a new designated
backup P-CTRL. This involves the synchronization of relevant
information (orchestration DBs, descriptors, etc.) with C-CTRL
(if the failure is predicted). This is done through new IETF
SFC NSH extensions (NS lifecycle management), as described in
TBD.
- The P-CTRL becoming the SFC controller/orchestrator. From this
point of time on, the P-CTRL can send orchestration signaling.
Extensions to IETF NSH or MIPv6 can be used, as described in
TBD and TBD.
4.1.3. C-CTRL gaining back control
We describe next, using an example, how a C-CTRL may get back the
orchestration control, temporarily delegated to a P-CTRL.
+---------+ +----+ +---------+ +---------+ +----------+ +------+
| node A | | C | | node B | | node D | | 3GPP | | SFC |
|P-CTRL F1| | F3 | |P-CTRL F2| |P-CTRL F3| |ctrl plane| |C-CTRL|
+--+----+-+ +----+ +--+----+-+ +--+----+-+ +----------+ +------+
| | | | | | | | |
| | | | | Connectivity OK notification |
| | | | | | | |-·-·-·-·-·->|
| | | |-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·>|
| | | | | | | | |
| | | | Request to take over SFC control |
| | | |<·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-|
| | | | Orchestration state sync. |
| | | |-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·>|
| | | | | | | | |
| | | | | | | | C-CTRL
| | | | | | | | regains
| | | | | | | | control
| | | | Notification C-CTRL back in control |
|<-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-|
| | | | | | | | |
Figure 4: C-CTRL gaining back control
A detailed message sequence chart is shown in Figure 4. The
different steps are described next:
* When a C-CTRL loses connectivity with the nodes involved in a
service, it enters into recovery mode, waiting for the
connectivity to be recovered. C-CTRL can learn that connectivity
has been regained using NSH OAM signaling or 3GPP signaling from
the NEF or the P-CTRL itself.
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* When connectivity is gained back to a P-CTRL, the C-CTRL signals
its availability so the P-CTRL can give back the control of the
service. To do so, IETF SFC NSH extensions (NS lifecycle
management) can be used, as described in TBD.
* The C-CTRL becomes now the active SFC controller/orchestrator for
the service.
* The C-CTRL notifies to other P-CTRLs that it is back in control of
the service, using IETF SFC NSH extensions (NS lifecycle
management), as described in TBD.
4.2. Inter P-CTRL seamless handover
In scenarios with no C-CTRL reachability, it might be needed to
transition from one P-CTRL to another one (e.g., because of mobility
of the nodes while the C-CTRL is not reachable).
Reactive transition is supported as for the case of C-CTRL failure.
Proactive/seamless transition is addressed as follows.
+---------+ +----+ +----+ +---------+ +----------+ +------+
| node A | | C | | B | | node D | | 3GPP | | SFC |
|P-CTRL F1| | F3 | | F2 | |P-CTRL F3| |ctrl plane| |C-CTRL|
+--+----+-+ +----+ +----+ +--+----+-+ +----------+ +------+
| | | | | | | |
| F1@A<->F2@B<->F3@D SFC network service | |
| |<-·-·-·-·-·-·->|<-·-·-·-·->| | |
| | | | | | | |
| | | | P-CTRL@D can no | |
| | | | longer act as CTRL | |
| | | | | | | |
Notification to other P-CTRLs| | | |
|<-·-·-·-·-·-·-·-·-·-·-·-·-·| | | |
Request to take over control | | | |
|-·-·-·-·-·-·-·-·-·-·-·-·-·>| | | |
Orchestration state sync | | | |
|<-·-·-·-·-·-·-·-·-·-·-·-·-·| | | |
| | | | | | | |
P-CTRL@A becomes| | | | | |
the CTRL for | | | | | |
the service | | | | | |
| | | | | | | |
Figure 5: Inter P-CTRL seamless handover
A detailed message sequence chart is shown in Figure 5. The
different steps are described next:
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* (We assume that the network service has been instantiated and
there is traffic: F1@A--F2@B--F3@D).
* When the active (designated) P-CTRL detects that it might not be
able to operate in the near future (lack of resources, battery,
moving away, etc.), a notification is sent to other P-CTRLs using
new IETF SFC NSH extensions (NS lifecycle management), as
described in TBD.
* Each P-CTRL receiving the notification message that is ready to
take over the role of active P-CTRL sends a message to the current
P-CTRL, which selects one. New IETF SFC NSH extensions are used
to convey this signaling.
* At this point, the new P-CTRL becomes the SFC controller/
orchestrator of the service.
5. IANA Considerations
N/A.
6. Security Considerations
TBD.
7. Acknowledgments
The work in this draft has been partially supported by the H2020
5Growth (Grant 856709) and 5G-DIVE projects (Grant 859881).
8. References
8.1. Normative References
[I-D.bernardos-sfc-distributed-control]
Bernardos, C. J. and A. Mourad, "Distributed SFC control
for fog environments", Work in Progress, Internet-Draft,
draft-bernardos-sfc-distributed-control-06, 5 September
2022, <https://datatracker.ietf.org/doc/html/draft-
bernardos-sfc-distributed-control-06>.
8.2. Informative References
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[I-D.bernardos-sfc-fog-ran]
Bernardos, C. J. and A. Mourad, "Service Function Chaining
Use Cases in Fog RAN", Work in Progress, Internet-Draft,
draft-bernardos-sfc-fog-ran-10, 22 October 2021,
<https://datatracker.ietf.org/doc/html/draft-bernardos-
sfc-fog-ran-10>.
[RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
Chaining (SFC) Architecture", RFC 7665,
DOI 10.17487/RFC7665, October 2015,
<https://www.rfc-editor.org/info/rfc7665>.
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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