SFC function mobility with Mobile IPv6
draft-bernardos-dmm-sfc-mobility-03
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Carlos Bernardos
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Alain Mourad
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2021-09-09
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SFC WG CJ. Bernardos
Internet-Draft UC3M
Intended status: Experimental A. Mourad
Expires: March 14, 2022 InterDigital
September 10, 2021
SFC function mobility with Mobile IPv6
draft-bernardos-dmm-sfc-mobility-03
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 specifies Mobile IPv6 extensions to enable
function migration in SFC.
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 March 14, 2022.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(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
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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 . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Function mobility signaling extending Mobile IPv6 . . . . . . 5
4. Mobile IPv6 extensions for SFC function mobility . . . . . . 7
4.1. Service Path Update . . . . . . . . . . . . . . . . . . . 7
4.2. Service Path Acknowledgement . . . . . . . . . . . . . . 9
4.3. New Mobility options . . . . . . . . . . . . . . . . . . 10
4.3.1. Network Service ID . . . . . . . . . . . . . . . . . 10
4.3.2. SFC node . . . . . . . . . . . . . . . . . . . . . . 11
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
6. Security Considerations . . . . . . . . . . . . . . . . . . . 12
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative References . . . . . . . . . . . . . . . . . . 12
8.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
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 specifies Mobile IPv6 extensions to enable function
migration in SFC.
2. Terminology
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].
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 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. Function mobility signaling extending Mobile IPv6
This section describes Mobile IPv6 (MIPv6) extensions to perform
function migration/mobility. This is an example of NS lifecycle
management operation: the update of the location of a given function.
We refer to this as function mobility, though it might involve or not
the actual migration of the function.
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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 | |
| |<-.-.-.-.-.-.-.-.-.>|<-.-.-.-.->| | |
| | | | | | | | |
| | | Node B moves out of | |
| | | the coverage of node D | |
| | | | | | | | |
| 0. Service specific OAM monitoring | | |
|<-.>|<-.-.->|<-.-.-.-.-.>| | | | |
|<-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.->| |
| | | | | | | | |
P-CTRL@A detects D disconnection | | | |
and decides to place F3 at node C | | | |
| | | | | | | | |
| 1a. SPU[NS_ID,(F3,C)] | | | | |
|-.-.-.-.-.-.-.-.-.-.-.-.>| | | | |
| 1b. SPA[NS_ID] | | | | |
|<-.-.-.-.-.-.-.-.-.-.-.-.| | | | |
| 1c. SPU[NS_ID,(F3,C),(F2,B),(F1,A)] | | |
|-.-.-.-.-.->| | | | | | |
| 1d. SPA[NS_ID] | | | | | |
|<-.-.-.-.-.-| | | | | | |
| | | | | | | | |
| 2. Updated F1@A<->F2@B<->F3@C SFC network service |
| |<-.-.-.-.-.-.-.-.-.>| | | | |
| | |<-.-.-.-.-.>| | | | |
| | | | | | | | |
| 3a. SPU[NS_ID,(F3,C),(F2,B),(F1,A)] | |
|-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.->|
| | | | | | | 3b. SPA[NS_ID] |
|<-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-|
| 3c. SPU[NS_ID,(F3,C)] | | | | |
|-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.>| | |
| | | | 3d. SPA[NS_ID] | | |
|<-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-|
| | | | | | | | |
Figure 1: SFC mobility signaling
We next describe the signaling extensions with an example. For the
sake of this example we assume that the function which location is
updated is already available at the new target node (if not, it has
to be previously migrated using any of the solutions available in the
state-of-the-art). The different steps are described next:
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o (The network service F1--F2--F3 is already instantiated and
running. The only SFC P-CTRL active at this point is running at
node A, and there is a candidate one at node B.)
o UE node B is moving out of the coverage of gNB node D.
1. This movement is detected by the active (designated) pseudo
controller running at node A, thanks to local (service specific
OAM) monitoring.
2. The active pseudo controller sends mobility signaling to all
affected nodes, in this case node B (it has to update the network
service path due to the F3 location update) and node C (as it
starts being part of the SFC, hosting F3). The signaling
messages are new mobility messages: Service Path Update (SPU) and
Service Path Acknowledgement (SPA), which contain: (i) the
identifier of the network service (NS_ID), and (ii) the updated
elements of the network service path: (ID, updated location).
The SPA acknowledges that the procedure has been performed
correctly.
3. The network service F1--F2--F3 is updated so it now runs at A, B
and C.
4. Whenever connectivity with nodes D and the centralized SFC
controller is back, the pseudo controller also informs about the
updated SFC path, sending SPU messages, which are acknowledged
with SPA messages.
Note that this is an example of NS lifecycle management (function
mobility) by a SFC pseudo controller, but that other operations are
also possible, such as (non-limiting examples): scaling up/down,
scaling in/out, termination, etc.
4. Mobile IPv6 extensions for SFC function mobility
4.1. Service Path Update
The Service Path Update (SPU) message is used by a CTRL to notify
nodes in an SFC (e.g., SFF) of an update of the service path.
The Service Path Update uses the MH Type value TBD. When this value
is indicated in the MH Type field, the format of the Message Data
field in the Mobility Header is as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence # |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A| Reserved | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Mobility Options .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Sequence #
A 16-bit unsigned integer used by the receiving node to sequence
Binding Updates and by the sending node to match a returned
Service Path Acknowledgement with this Service Path Update.
Acknowledge (A)
The Acknowledge (A) bit is set by the sending mobile node to
request a Service Path Acknowledgement be returned upon receipt of
the Service Path Update.
Reserved
This field is unused for now. The value MUST be initialized to 0
by the sender and MUST be ignored by the receiver.
Lifetime
16-bit unsigned integer. The number of time units remaining
before the service path MUST be considered expired. A value of
zero indicates that the Service Path MUST be deleted. A value of
0xFFFF indicates an infinite lifetime for the Service Path. One
time unit is 4 seconds.
Mobility Options
Variable-length field of such length that the complete Mobility
Header is an integer multiple of 8 octets long. This field
contains zero or more TLV-encoded mobility options. The receiver
MUST ignore and skip any options that it does not understand.
The following options are valid in a Service Path Update:
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Network Service ID.
SFC node.
4.2. Service Path Acknowledgement
The Service Path Acknowledgement (SPA) message is used by a CTRL to
acknowledge a received SPU.
The Service Path Acknowledge uses the MH Type value TBD. When this
value is indicated in the MH Type field, the format of the Message
Data field in the Mobility Header is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence # |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Mobility Options .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Sequence #
A 16-bit unsigned integer used to match the returned Service Path
Acknowledgement with the Service Path Update.
Reserved
This field is unused for now. The value MUST be initialized to 0
by the sender and MUST be ignored by the receiver.
Lifetime
16-bit unsigned integer. The number of time units remaining
before the service path MUST be considered expired. A value of
zero indicates that the Service Path MUST be deleted. A value of
0xFFFF indicates an infinite lifetime for the Service Path. One
time unit is 4 seconds.
Mobility Options
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Variable-length field of such length that the complete Mobility
Header is an integer multiple of 8 octets long. This field
contains zero or more TLV-encoded mobility options. The receiver
MUST ignore and skip any options that it does not understand.
The following options are valid in a Service Path Acknowledgement:
Network Service ID.
4.3. New Mobility options
4.3.1. Network Service ID
The Network Service ID option has the following format:
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 = TBA | Option Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Service Path Identifier (SPI) | Service Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Network Service ID +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.
Service Path Identifier (SPI)
Uniquely identifies a Service Function Path (SFP). Participating
nodes MUST use this identifier for SFP selection. The initial
Classifier MUST set the appropriate SPI for a given classification
result.
Service Index (SI)
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Provides location within the SFP.
Network Service ID
Variable length field that identifies the network service.
4.3.2. SFC node
The SFC node option has the following format:
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 = TBA | Option Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Function ID Length | Node ID Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Function ID +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Node ID +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.
Function ID Length
8-bit unsigned integer. Length of the Function ID field, in
octets.
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Node ID Length
8-bit unsigned integer. Length of the Node ID field, in octets.
Function ID
Variable length field that identifies the function.
Node ID
Variable length field that identifies the node.
There might be multiple SFC node options in a Service Function Update
message, following the options the same order of the SFC/NS.
5. IANA Considerations
TBD.
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", draft-bernardos-sfc-distributed-
control-04 (work in progress), July 2021.
[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>.
8.2. Informative References
[I-D.bernardos-sfc-fog-ran]
Bernardos, C. J., Rahman, A., and A. Mourad, "Service
Function Chaining Use Cases in Fog RAN", draft-bernardos-
sfc-fog-ran-09 (work in progress), March 2021.
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[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
Leganes, Madrid 28911
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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