Gateway Function for Network Slicing
draft-homma-rtgwg-slice-gateway-01
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Expired".
|
|
|---|---|---|---|
| Authors | Shunsuke Homma , Xavier de Foy , Alex Galis , Luis M. Contreras | ||
| Last updated | 2019-11-03 (Latest revision 2019-07-08) | ||
| Replaces | draft-homma-nfvrg-slice-gateway | ||
| RFC stream | (None) | ||
| Formats | |||
| Additional resources | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-homma-rtgwg-slice-gateway-01
rtgwg S. Homma
Internet-Draft NTT
Intended status: Informational X. de Foy
Expires: May 6, 2020 InterDigital Inc.
A. Galis
University College London
LM. Contreras
Telefonica
November 3, 2019
Gateway Function for Network Slicing
draft-homma-rtgwg-slice-gateway-01
Abstract
This document describes the roles and requirements for a slice
gateway that is a function or function group for handling data plane
traffic, such as connecting/disconnecting and compose/decompose
network slice subnet instances and providing network slices from end
to end. The interworkings between management and control elements at
the management and control planes with the gateway function for
controlling and orchestrating end-to-end network slices are also
presented in this document.
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 May 6, 2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
Homma, et al. Expires May 6, 2020 [Page 1]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
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. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 4
3. Motivations and Roles of SLG . . . . . . . . . . . . . . . . 6
4. Architecture of Network Slicing System . . . . . . . . . . . 8
4.1. Network Slice Management System Architecture . . . . . . 8
5. Requirements for SLG . . . . . . . . . . . . . . . . . . . . 10
5.1. Management of NS as Infrastructure . . . . . . . . . . . 10
5.1.1. Data Plane Aspect . . . . . . . . . . . . . . . . . . 10
5.1.1.1. Identification/Classification . . . . . . . . . . 11
5.1.1.2. Transporting/Forwarding . . . . . . . . . . . . . 11
5.1.1.3. Isolation among NSs . . . . . . . . . . . . . . . 12
5.1.1.4. Service Chaining as Infrastructural
Mechanism(*Optional) . . . . . . . . . . . . . . 13
5.1.2. Control/Management Planes Aspects . . . . . . . . . . 13
5.1.2.1. Interfaces to Controllers or Operation Systems . 13
5.1.2.2. Address Resolution/Routing . . . . . . . . . . . 13
5.1.2.3. Authentication Authorization Accounting (AAA) . . 13
5.1.2.4. Operation Administration and Maintenance(OAM) . . 14
5.1.2.5. Traffic Monitoring . . . . . . . . . . . . . . . 14
5.2. Management of Services on NS (*Optional) . . . . . . . . 14
5.2.1. Data Plane Aspect . . . . . . . . . . . . . . . . . . 14
5.2.1.1. Identification/Classification . . . . . . . . . . 14
5.2.1.2. QoS Control . . . . . . . . . . . . . . . . . . . 14
5.2.1.3. Steering/Service Chaining(Cooperation with VNFs) 15
5.2.2. Control/Management Planes Aspects . . . . . . . . . . 15
5.2.2.1. Interfaces to Service Management Systems . . . . 15
5.2.2.2. Collection of Telemetry information . . . . . . . 15
6. Structure of SLG . . . . . . . . . . . . . . . . . . . . . . 15
7. Deployment of SLG . . . . . . . . . . . . . . . . . . . . . . 16
7.1. Examples of Components Required to Maintain SLG Functions 16
7.2. SLG Types Depending on Locations on NS . . . . . . . . . 17
7.2.1. Edge SLG(E-SLG) . . . . . . . . . . . . . . . . . . . 17
7.2.2. Inter-Subnet SLG(IS-SLG) . . . . . . . . . . . . . . 17
7.2.3. Inter-Domain SLG(ID-SLG) . . . . . . . . . . . . . . 17
7.3. Horizontal Connection . . . . . . . . . . . . . . . . . . 17
7.4. Vertical Connection . . . . . . . . . . . . . . . . . . . 20
Homma, et al. Expires May 6, 2020 [Page 2]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
7.5. Software vs. Hardware . . . . . . . . . . . . . . . . . . 21
8. Interconnection between NSSIs . . . . . . . . . . . . . . . . 21
8.1. Pre-arrangement of transport protocols . . . . . . . . . 21
8.2. Quality Assurance between SLGs . . . . . . . . . . . . . 21
8.3. Secure Interconnection . . . . . . . . . . . . . . . . . 22
9. Interfaces of SLG Controller . . . . . . . . . . . . . . . . 22
9.1. Southbound Interface . . . . . . . . . . . . . . . . . . 22
9.2. Northbound Interface for Higher Operation Systems . . . . 22
9.3. Northbound Interface for Customers/Tenants . . . . . . . 22
10. Security Considerations . . . . . . . . . . . . . . . . . . . 22
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
12. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 22
13. Informative References . . . . . . . . . . . . . . . . . . . 23
Appendix A. Requirements for each SLG Type . . . . . . . . . . . 25
Appendix B. Position of SLG on ETSI NFV MANO . . . . . . . . . . 26
Appendix C. Complemention of Network Slicing in 3GPP . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
1. Introduction
Network slicing is an approach to create separate virtual networks in
support of service depending on several requirements on the same
physical resources, and it enables networks to adapt to requirements,
which is diverse more, inexpensively and flexibly. The overview is
introduced in [Slicing_Tutrial] and [NECOS].
It's also expected to enhance usability of infrastructural networks
for tenants and create new business opportunities. For example, by
using network slices lent from infrastructure operators, other
industrial companies can provide communication services including
ensurance of network transport without having physical
infrastructure.
From a business point of view, a slice includes a combination of all
the relevant network resources, functions, and assets required to
fulfill a specific business case or service, including OSS, BSS and
DevOps processes.
From the network infrastructure point of view, network slice requires
the partitioning and assignment of a set of resources that can be
used in an isolated, disjunctive or non- disjunctive manner for that
slice.
From the tenant point of view, network slice provides different
capabilities, specifically in terms of their management and control
capabilities, and how much of them the network service provider hands
over to the slice tenant. As such there are two kinds of slices: (A)
Inner slices, understood as the partitions used for internal services
Homma, et al. Expires May 6, 2020 [Page 3]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
of the provider, retaining full control and management of them. (B)
Outer slices, being those partitions hosting customer services,
appearing to the customer as dedicated networks.
Network slices are established with combination of various
technologies, such as software defined network (SDN), network
function virtualization (NFV), or traffic engineering, and managed/
operated with automation technologies such as orchestrator.
Assumed use cases of network slices include establishment of virtual
networks whose qualities are guaranteed from end to end under the
supervision of multi-domain orchstrators. In such cases, a network
slice subnet is created on each domain, such as access network and
core network, and an end-to-end network slices is composed of
connected subnets.
Network slice subnets are built based on specifications of the
underlay network, and thus the used technologies might vary.
Therefore, a gateway function, which enables to connect subnets while
adapting the differentiations and forward data packets to/from the
appropriate next subnet, is required.
This document describes the gateway function for network slicing,
called slice gateway or SLG, and its role and requirements. Note
that defining a new data plane technology is not a goal of this
draft. In addition, this draft aims to specify management-related
requirements for an SLG, which may be implemented using existing data
plane technologies.
2. Definition of Terms
This section describes definitions and terminologies related to
network slicing, especially gateway function and interconnection
network slices established in each domain. Other complementary
definitions are described in [I-D.homma-slice-provision-models].
Network Slicing: Network slicing is a technology or an approach to
create separate logical networks in support of services, depending
on several requirements, on the same physical resources. This is
possible by combinations of several network technologies.
Network Slice (NS): An NS is a logical separate network that
provides specific network capabilities and characteristics.
Network Slice Instance (NSI): An NSI is a logical network instance
composed with required infrastructure resources, including
networking (WAN), computing (NFVI) resources, and some include
additional network service functions such as firewall or load-
Homma, et al. Expires May 6, 2020 [Page 4]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
balancer. It is composed of one or more Network Slice Subnet
Instances.
Network Slice Subnet: An NS subnet is is a representation of a set
of resources structuring a part of NSI within a single domain.
Network Slice Subnet Instance (NSSI): An NSSI is a partial logical
network instance represented as a network slicce instance. It is
a minimul unit managed or provided as a network slice. One or
more NSSI structure an NSI or an E2E-NSI.
End-to-End Network Slice Instance (E2E-NSI): An E2E-NS is an NSI
providing connectivity among end points. An E2E-NSI is used for
enphasizing end to end connectivity provided by an NSI.
Network Slice as a Service (NSaaS): An NSaaS is a service delivery
model in which a third-party provider (e.g., vertical customer)
hosts NSs and makes them available to customers. In this model,
there are mainly two roles: NS provider and NS tenant.
Network Slice Provider (NS Provider): An NS provider is a person or
group that designs and instantiates one or more NSIs/NSSIs, and
provides them to NS tenants. In some cases, an NS provider is an
infrastructure operator simultaneously. This includes NSI, NSSI,
and E2E-NSI providers.
Network Slice Tenant (NS Tenant): An NS tenant is a person or group
that rents and occupies NSs from NS providers.
Domain: A domain is a group of a network and devices administrated
as a unit with common rules and procedures.
Administrative Domain: An administrative domain is a group of
networks and devices managed by an administrator.
Resource: A resource is element used to create virtual networks.
There are several types of resources, i.e., connectivity,
computing and storage.
Network Function Virtualization (NFV): NFV is the concept or
technologies to provide dedicated network appliances as software.
Software Defined Network (SDN): SDN is the concept or technologies
to separate network control plane from data plane, and control
network devices dynamically and flexibly.
Virtual Network: A virtual network is a network running a number of
virtual network functions.
Homma, et al. Expires May 6, 2020 [Page 5]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
Virtual Network Function (VNF): A virtual network function (VNF) is
a network function whose functional software is decoupled from
hardware. One or more virtual machines running different software
and processes on top of industry-standard high-volume servers,
switches and storage, or cloud computing infrastructure, and
capable of implementing network functions traditionally
implemented via custom hardware appliances and middleboxes (e.g.,
router, NAT, firewall, load balancer, etc.)
Slice Gateway Function (SLG): An SLG is a function or a group of
functions to connect/disconnect NSSIs. The roles are described in
the following sections.
Business Support System and Operation Support System (BSS/OSS): BSS/
OSS are systems to support service providing and operation of
network devices.
Orchestrator: Orchestrator is an entity to operate network
components automatically. There are several types of
orchestrators including NFV Orchestrator (NFVO) or service
orchestrator defined by ETSI NFV and Open Source MANO (OSM)
([NFV-Architectural-Framework] and [OSM-White-Paper]).
SLG Controller (SLG-Ctrl): An SLG-Ctrl is an entity that controls
SLGs. An SLG-Ctrl is controlled by upper-level operation systems
such as OSS/BSS or orchestrator.
3. Motivations and Roles of SLG
One of the main roles of SLG is the enablement of interworkings
between data plane with management and control elements for
controlling and orchestrating end-to-end slices.
Use cases of network slices are discussed in several Standard
Developing Organizations (SDOs). Some examples are described in use
cases document ([I-D.netslices-usecases]).
In some proposed use cases, an NS is structured across multiple
network domains. The capability of NSSIs might be different because
the components are domain-specific. In particular, the
differentiation in capability between different administrative
domains is large.
Moreover, several variations can be considered on NS provisioning in
NSaaS (ref. [I-D.homma-slice-provision-models]), and some cases need
abstraction of underlay infrastructure to NS tenants. SLG solution
provides controllability of network functionss for manipulation of
Homma, et al. Expires May 6, 2020 [Page 6]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
NSs intensively, and it can be expected to emphasize the
manageability of NSIs in such cases.
For connecting some different NSSIs and providing a NS that
guarantees the prescribed quality from end to end, SLGs are required
to connect such NSSIs. SLGs enable to provide E2E-NSIs independently
of specifications of underlay networks by hiding the differentiations
and connecting between NSSIs. An overview of this concept is shown
in Figure 1. SLGs glue NSSIs established on each domain and provide
an E2E-NSI.
E2E-NSI
________________________A_________________________
/ \
_____________ ____________ _________________
/ // / / /
end +---+ +---+ +---+ +---+ ,---.
host==>|SLG| NSSI#1 |SLG| NSSI#2 |SLG+-+SLG| NSSI#3 ( APL )
+---+ +---+ +---+ +---+ `-----`
/____________//___________/ /________________/
/____________//___________/ /________________/
: : :
: : :
.--. .--. .--.
( )-. ( )-. ( )-.
.' Access ' .' Core ' .' Data '
( Network ) ( Network ) ( Center )
( -' ( -' ( /Cloud -'
'-( ) '-( ) '-( )
'---' '---' '---'
\______ ______/ \_____ _____/ \________ ________/
V V V
Domain#1 Domain#2 Domain#3
\_____________ _____________/ \________ ________/
V V
Domain of Administrator#A Domain of Administrator#B
* Legend
APL: Application
Figure 1: E2E-NSI composed of multiple NSSIs
Moreover, identification of user service traffic and their
allocation/disallocation to the appropriate NSSI are required at the
Homma, et al. Expires May 6, 2020 [Page 7]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
edges of E2E-NSIs, as shown in Figure 2, and SLGs might take on these
roles.
+-----+ _______________
end | |-->/_______________
host ====>| SLG | NSSI#1
|@Edge| _______________
| |-->/______________
| | NSSI#2
| | : :
+-----+
Figure 2: NSSI selection of SLG
Note that, this model has the assumption that transitions of data
packets from one NSSI to another are executed at only SLGs. Also, an
SLG is not necessarily implemented as a single device or virtual
machine (VM).
4. Architecture of Network Slicing System
NSs are composed of several (virtual) network functions and links,
and the charactaristics of each NS are based on the assumed service.
Also, some of NSs are deployed accross multiple administrative
domains. For deploying the appropriate NSs based on each service
requirements, a management system, which enables to control network
resources totally within a domain, and interaction between such
management systems are required.
An SLG is a network function, and SLGs are installed at edge of
NSSIs. NSs are dynamically created, deleted, and moved depending on
requests from network opertor orNS tenants. Therefore, some SLGs
would be required to be VNF for flexible deployment.
This section describes overview of NS management system architecture
(Section 4.1) .
4.1. Network Slice Management System Architecture
The architecture overview of NS management system is shown in
Figure 3.
Homma, et al. Expires May 6, 2020 [Page 8]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
NS Tenant
|
. .|. . . . . . . . . . . . . . . . . . . . .
. +-v---------+ .
. |Portal/GUI +--+ .
. +-+---------+ | . . . . . . . . . .
. | +-v-----------------------+ . . +------------+ .
. | |CSS-Mngr./TNS-Orch. |<------->|CSS-M/TNS-O | .
. | +-+-------+---------------+ . . +-+--------+-+ .
. | | | . . | | .
. +-v-----+ | | . . +-v-----+ | .
. |BSS/OSS|<-----+ | . . |BSS/OSS| | .
. +-+-----+ | . . +-+-----+ | .
. | | . . | | .
. +-v--------------------v-----------+ . . +-v--------v-+ .
. | E2E-Orch./Network Service-Orch. | . . |E2E-O/NS-O | .
. +-+--------------------+-----------+ . . +-+--------+-+ .
. | | . . | | .
. +-v----------------+ +-v----------------+ . . : .
. | Resource Orch.#1 | | Resource Orch.#2 |.. . . . . . . . . . .
. +-+---------+------+ +-+---------+------+ . Administrative
. | | | | . Domain#2
. +-v------++-v------+ +-v------++-v------+ .
. |Network ||NFV | |Network ||NFV | .
. |Ctrl. ||Ctrl. | |Ctrl. ||Ctrl. | .
. +-+------++-+------+ +-+------++-+------+ .
. | | | | .
. +-v------++-v------+ +-v------++-v------+ .
. |Network ||Server | |Network ||Server | .
. |Elements||Resource| |Elements||Resource|.. .
. |in ||in | |in ||in | .
. |Domain#1||Domain#1| |Domain#2||Domain#2| .
. +--------++--------+ +--------++--------+ .
. . . . . . . . . . . . . . . . . . . . . . .
Administrative Domain#1
CSS-Mngr./CSS-M:Cross-Segment Slice Manager
TNS-Orch./TNS-O:Transport Network Slice Orchestrator
Figure 3: Overview of NS Management Architecture
Orchestrators manage whole resources including network elements and
server resources (i.e., routing, bandwidth, compute or storage). In
this figure, the resources including network elements and server
resources are managed by resource orchestrators installed in each
domain, and the E2E-orchestrator and network service orchestrator
handle resource orchestrators.
Homma, et al. Expires May 6, 2020 [Page 9]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
NSs are requested from NS tenants via the portal system and the order
of creations of an NS is given to the E2E orchestrator from the
portal system via BSS/OSS. When an NS across multiple administrative
domains are requested, the portal system that received the request
forwards the order to create NSSIs to the other infrastructure
providers' systems via Cross-Segment Slice Manager. The details of
COMS architecture are described in the architecture document ([I-
D.qiang-coms-architecture]).
SLGs are also controlled via orchestrators. An SLG basically belongs
to a network element, and it might also belong to server resource if
it runs as a VNF. (The position of SLG deployed as a VNF is shown in
Appendix B.)
The information model used in this architecture is described in
information model document
([I-D.qiang-coms-netslicing-information-model]).
5. Requirements for SLG
An SLG is basically a component in the data plane and has the roles
of data packet processing. Moreover, it is required to have
functions for control/management processes such as connecting to
underlay networks or managing NSs.
Furthermore, an SLG might be required to support handling services
provided on NSs in addition to controlling of NS because an SLG is an
edge node on an E2E-NSI.
In this section, we describe the requirements for an SLG in terms of
the following aspects and their interworkings.
1. Data plane for NSs as infrastructure
2. Control/management plane for NSs as infrastructure
3. Data plane for services on NSs
4. Control/management plane for services on NSs
5.1. Management of NS as Infrastructure
5.1.1. Data Plane Aspect
Homma, et al. Expires May 6, 2020 [Page 10]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
5.1.1.1. Identification/Classification
SLGs at the edge of E2E-NSs MUST have the capability to identify and
classify data packets, and assign them to the appropriate E2E-NS.
This requirement varies depending on the location.
Fixed Access: An SLG MUST identify and classify data packet with
access point, including CPE or WiFi-AP, or subscriber ID such as
VLAN-ID. Moreover, in some services, an SLG should identify and
classify data packets based on user device or application used in
the communication.
Mobile Access: An SLG MUST identify and classify data packet with
subscriber-ID such as IMSI, radio-wave bandwidth, or identifier of
tunnels. Moreover, in some services, an SLG should identify and
classify data packets based on application used in the
communication or location of the user equipment (UE).
Connection Point between NSSI: An SLG MUST identify and classify
data packet based on the tunnel-ID or virtual routing and
forwarding (VRF) that received the packets. If specific slice
identifier such as a value mapped in the metadata field of the IP
header is used; an SLG should identify and classify data packets
with the ID.
5.1.1.2. Transporting/Forwarding
SLGs MUST provide functions for transport data packets depending on
the specifications of the underlay networks.
Encapsulation/Decapsulation/Tagging: In network slicing, duplication
of IP addresses of user packets between NSs MUST be accepted,
thus, using techniques that enable separation of a network
logically is preferred. In short, some tunnel protocols or
tagging approaches should be used as transport of NSs. For this
reason, SLG MUST support encapsulation or tagging of data packets
based on the specification of the underlay network. Also, SLG
MUST support the packets' decapsulation or untagging. Examples of
tunnel protocols and tags that can be used for creating NSs on L2/
L3 segments are described below.
L2 Segment: VLAN, MPLS, Segment Routing MPLS (SR-MPLS), PPPoE,
etc.
L3 Segment: GRE, L2TP, GTP-U, VxLAN, IPv6 Segment Routing (SRv6),
etc.
Homma, et al. Expires May 6, 2020 [Page 11]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
VxLAN, SR-MPLS, and SRv6 are described in their specification
documents ([RFC7348], [I-D.ietf-spring-segment-routing-mpls], and
[I-D.ietf-6man-segment-routing-header]).
Translation of Encapsulation/Tagging Form: SLG MUST support to
translate tunnel header or tag of received packets to the
appropriate tunnel header or tag when it forwards data packets to
the next NSSI that has different transport capability.
Distribution of Traffic: Some NSs have multiple route between the
same end points within the same NSSI because of traffic
engineering, switching to a redundant path, or other reasons, and
SLG MAY forward data packets with the appropriate route based on
some trigger information. An example of the overview of this
requirement is shown in Figure 4. In this figure, there are two
routes, main and sub, between SLGs, and an SLG switches forwarding
route depending on the network situation such as congestion
occurrence on the current route.
____________________________
/ . . . . . /
+-----+ . . +-----+
| |. . . .| |
| SLG | | SLG |
| |* * * *| |
+-----+ * * +-----+
/ * * * * * /
/___________________________/
NSSI
*** : Main-route
... : Sub-route
Figure 4: An example of traffic distribution by SLG
5.1.1.3. Isolation among NSs
In NSaaS, isolation control is required for avoiding an NS being
affect by other NSs. Traffic engineering or QoS control is ones of
the most fundamental approaches to prevent disturbances among NSs.
Traffic Shaping/Policing: An SLG MUST execute traffic shaping and
policing at its egress and ingress ports to avoid an NS using
excessive traffic bandwidth.
Homma, et al. Expires May 6, 2020 [Page 12]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
Quality of service (QoS) Control: If there is an order of priority
between NSs on the same underlay infrastructure, an SLG should
remark the appropriate QoS parameter of the outer-most header of
each packet following the preconfigured setting and provide packet
scheduling based on the QoS parameter for providing priority
control. The field that SLG refers may vary depending on the
specification of the underlay network. For example, COS value is
remarked in L2 segments; on the other hand, DSCP value is remarked
in L3 segments.
5.1.1.4. Service Chaining as Infrastructural Mechanism(*Optional)
If an SLG is composed of a combination of several components, a
service chaining mechanism is required to make them work together and
achieve SLG functionality.
Moreover, some NSs may traverse NFVs such as firewalls or cache
servers for providing value-added services to their users. In such
cases, SLG might be required to support service chaining mechanisms,
such as handling of network service header (NSH) defined in
[RFC8300]. If an NS includes the service chaining architecture
defined in [RFC7665], some SLG would be required to support following
functions; classifier(CF), service function forwarder (SFF), and
inter boundary node(IBN). (Details of CF, SFF and IBN are described
in SFC documents; [RFC7665], [RFC8459].)
5.1.2. Control/Management Planes Aspects
5.1.2.1. Interfaces to Controllers or Operation Systems
SLG MUST have interface to its controller or operation systems for
set parameters related to the data plane functions described in
Section 5.1.1. In addition, an SLG at the edges of E2E-NSs MUST have
interfaces to authentication servers.
5.1.2.2. Address Resolution/Routing
An SLG MUST support address resolution or routing mechanisms to
connect to underlay network elements including routers or L2
switches.
5.1.2.3. Authentication Authorization Accounting (AAA)
For preventing entry of irregular traffic to NSs, an SLG at the edge
of E2E-NS MUST support AAA mechanism for incoming traffic. Also,
when an SLG connects to another SLG in other administrative domain,
SLGs should have a mechanism to confirm that the connection is
established with the regular processes. For example, an SLG is
Homma, et al. Expires May 6, 2020 [Page 13]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
required to support authentication of the opponent SLG with key
information indicated from higher-level operation systems.
5.1.2.4. Operation Administration and Maintenance(OAM)
In management of NSs, OAM mechanisms for both underlay and overlay
networks is required for SLGs. For an underlay network, an SLG MUST
have OAM functions to confirm connectivity to interconnect equipment.
For an overlay network as an NS, an SLG MUST have OAM functions to
confirm connectivity to the nodes on the same NS.
5.1.2.5. Traffic Monitoring
An SLG shall support monitoring of traffic amount and latency as a
mechanism for checking whether each of the accomodated NSs is
satisfying its SLA. When an NS can't fulfill its SLA, the SLG MUST
send a notification to any listening system.
5.2. Management of Services on NS (*Optional)
5.2.1. Data Plane Aspect
5.2.1.1. Identification/Classification
In NSaaS, some NS tenants may need delivery of an individual service
to each user, device, or application on the same NS. For such
service deliveries, an SLG might be required to identify and classify
user traffic based on some information such as subscriber ID or
payload of data packets. Also, an SLG should be controllable from
the NS tenant.
5.2.1.2. QoS Control
An NS accommodates several communication devices and SLGs might be
required to have fair queueing mechanisms for maintaining service
quality of each user. Also, different types of service traffic that
have different priorities might coexist on an NS. For example, some
NS providers might provide telephone and internet access services to
their users with an NS. In such cases, SLG might be required to
provide QoS control mechanisms for enforcing priority control based
on service priorities.
These QoS controls are executed depending on the information of inner
packets and are independent of isolation mechanisms as
infrastructure. An SLG might be required to have a hierarchical QoS
control mechanism in case that both QoS controls for services over
NSs and isolation between NSs are required.
Homma, et al. Expires May 6, 2020 [Page 14]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
5.2.1.3. Steering/Service Chaining(Cooperation with VNFs)
SLG might be required to support steering or service chaining
function for conveying data packets to the appropriate network
functions deployed on an NS based on the classification result and
user's contract information.
5.2.2. Control/Management Planes Aspects
5.2.2.1. Interfaces to Service Management Systems
An SLG might have interfaces to controllers for managing user
policies on each NS. Some controllers might be deployed on the same
NS. If some controllers are located at external networks, they might
require SLGs to have APIs.
5.2.2.2. Collection of Telemetry information
In an NSaaS, collection of telemetry information of each NS might be
required for understanding traffic usage. Thus, an SLG might be
required to support to collect and report telemetry information of
connected NSs.
6. Structure of SLG
SLG is composed of data plan entities and controller. SLG Data plane
entity (SLG-D) has functions to manipulate NSSIs and to handle
traffic on slices. In some cases, an SLG-D is composed of several
physical devices and/or virtual instances. Function types supported
by SLG-D are listed Section 5. SLG controller (SLG-C) accomodates
multiple SLG Data plane entities via its southbound interface, and
sets configurations into each SLG-D. SLG-C also has a northbound
interface and it provides accesses to two endpoints: higher operation
systems such as orchestrator, and to external customers and tenants
which own their NSSIs. Then, functionality and controllability
exposed to customers/tenants ashould be limited, and the access must
be secure (i.e., authentication and admission control should be
supported). The overview of SLG structure is shown in Figure 5.
Homma, et al. Expires May 6, 2020 [Page 15]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
Customers/ Operation System
tenants (i.e.,Orchestrator)
| |
| |
+-------+---------+
|
|
+---------+--------+
| SLG Controller |
+---------+--------+
|
+-----+-----+
| |
| +------------------------------+
| |
| |
+-----+----------------------------+ |
| SLG D-plane Entity_1 | |
|.-----. .-----. .----------. | +-------+-------+
|| FIB | | OAM | |Monitoring| .. | | |
|`-----' `-----' `----------' | ... | SLG D-plan |
|.-----. .-----. .-----. .-----. | | Entity_n |
||decap| | QoS | | Fwd | |encap| ..| | |
|`-----' `-----' `-----' `-----' | +---------------+
+----------------------------------+
Figure 5: Overview of SLG Structure
7. Deployment of SLG
This section describes considerations related with deployment of
SLGs.
7.1. Examples of Components Required to Maintain SLG Functions
For providing E2E-NSs on existing network infrastructures, some
components located at boundaries of domains are required to have the
same set of functionality as an SLG. Examples of such components in
each domain type are described below.
Fixed Network: CPE/HGW, Service Edge, Gateway Router, etc.
Mobile Network: User Equipment, Radio-AP, eNodeB, S/P-GW
([TS.36.300-3GPP]), etc.
Data Center: Gateway Router, L2 switch, ToR switch, Server, etc.
Homma, et al. Expires May 6, 2020 [Page 16]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
7.2. SLG Types Depending on Locations on NS
There are mainly three types of SLG for creating E2E-NS across
multiple administrative domains. The requirements of each SLG type
are listed in Appendix A.
7.2.1. Edge SLG(E-SLG)
E-SLG is located at an edge of an E2E-NS, and supports
identification, classification and authentication of user traffic in
addition to fundamental SLG functions, such as transport and
isolation. Also, it might be required to have capabilities for
services delivered on an NS.
7.2.2. Inter-Subnet SLG(IS-SLG)
IS-SLG is located between NSSIs within a single administrative domain
and has only fundamental functions such as QoS control or tranlation
of headers.
This type of SLG enables to separate an NSI into some NSSIs. It will
provide modularities of NSSIs, and simplify the management of NSIs.
However, it is not necessarily required if a common transport
mechanism in all domains is used.
7.2.3. Inter-Domain SLG(ID-SLG)
ID-SLG is located between NSSIs established on different domains. It
supports authentication for connecting to the opponent SLG in
addition to fundamental functions.
7.3. Horizontal Connection
The connection form of an SLG varies depending on which type it is.
Examples of horizontal connection forms of each SLG type are
described below.
E-SLG: An E-SLG accommodates several hosts and NSSIs. This has a
forwarding table of end hosts and insert their packets to the
appropriate NSSI. An overview of this connection is shown in
Figure 6.
Homma, et al. Expires May 6, 2020 [Page 17]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
*Virtual Layer*
+-----+
host#1 ====>| | _______________
| |-->/_______________
host#2 ====>|E-SLG| NSSI#1
| | _______________
host#3 ====>| |-->/_______________
| | NSSI#2
: : | | : :
+-----+
////////////////////////////////////////
*Physical Layer*
,--------------------
[UE#1] -----\ /
[UE#2] -----[Edge] Domain#1
[UE#3] -----/ \
: : `-------------------
Edge: Edge Node
Figure 6: Overview of horizontal connection of E-SLG
IS-SLG: An IS-SLG has the role of mediator between NSSIs and passes
packets received from an NSSI to the next one. If transport
methods used in each domain are different, the IS-SLG translate
packet form to the appropriate one. An overview of this
connection is shown in Figure 7.
Homma, et al. Expires May 6, 2020 [Page 18]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
*Virtual Layer*
+------+
_________ | | ___________
_________/-->|IS-SLG|--> /__________
NSSI#1 | | NSSI#2
+------+
///////////////////////////////////////
*Physical Layer*
--------------. ,--------------
\ /
Domain#1 [ GW ] Domain#2
/ \
--------------' `--------------
GW: Gateway Node
Figure 7: Overview of horizontal connection of IS-SLG
ID-SLG: An ID-SLG passes data packets to another ID-SLG located on a
different administrative domain. Some tunnel established between
them in advance may be used for the passing of packets. An
overview of this connection is shown in Figure 8.
*Virtual Layer*
+------+ +------+
_________ | | ______ | | ___________
_________/-->|ID-SLG|O______)|ID-SLG|-->/__________
NSSI#1 | | Tunnel | | NSSI#2
+------+ +------+
///////////////////////////////////////////////////////
*Physical Layer*
--------------------. ,-------------------
Administrative \ / Administrative
Domain#1 [ GW ]---[ GW ] Domain#2
/ \
--------------------' `-------------------
GW: Gateway Node
Figure 8: Overview of horizontal connection of ID-SLG
Homma, et al. Expires May 6, 2020 [Page 19]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
7.4. Vertical Connection
There are two patterns of vertical connection of SLGs in the middle
of E2E-NSs. The first pattern is that the SLGs accommodate only a
set of NSSIs, which are composition of the same E2E-NS. In this
pattern, such SLGs are not required to support NSSI selection,
however, establishment of a new SLG is required when a new E2E-NS is
created. This might causes extra overheads because of deploying many
SLGs.
The other pattern is that such SLGs are acceptable to accommodate
multiple NSSIs from each domain. In this pattern, SLGs support NSSI
selection. On the other hand, this pattern can restrain the number
of SLGs. Also, it is easy to provide transit of data packets from an
NSSI to another NSSI on the same domain.
The overviews of these patterns are shown in Figure 9 and Figure 10.
+-----+
_________ | | ___________
_________/-->|SLG#1|-->/__________
NSSI#1 | | NSSI#2
+-----+
+-----+
_________ | | ___________
_________/-->|SLG#2|-->/__________
NSSI#3 | | NSSI#4
+-----+
: : :
Figure 9: Overview of vertical connection of SLG: Separated Pattern
+-----+
_________ | | ___________
_________/-->| |-->/__________
NSSI#1 |SLG#1| NSSI#2
_________ | | ___________
_________/-->| |-->/__________
NSSI#3 | | NSSI#4
| |
: | | :
+-----+
Figure 10: Overview of vertical connection of SLG: Shared Pattern
Homma, et al. Expires May 6, 2020 [Page 20]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
7.5. Software vs. Hardware
An SLG can be created as either a software or hardware function. NSs
are virtual networks created depending on requests from external NS
tenants, and thus software would be more compatible with usage for
NSs in terms of flexibility or manageability. Moreover, it enables
to increase or decrease for each function if SLG is composed of
combination of several components. However, it is difficult to
provide high performance or sufficient throughput for carrier-grade
networks with software function. In addition, it would be difficult
to implement sufficient QoS control mechanisms with general servers,
because they requires special hardware structures. An example of
position of SLG in NFV environment is described in Appendix B.
On the other hand, hardware appliances are able to provide high
throughput compared with software. However, they are inflexible in
terms of provisioning.
From the above considerations, operators should prepare SLG in
appropriate ways depending on their usages or locations.
8. Interconnection between NSSIs
SLG provides interconnectivity between NSSIs. The concept and
fundamental framework including the related NS information model are
described in NSSIs interconnection document
([I-D.defoy-coms-subnet-interconnection]).
This section is focused on interconnection between NSSIs established
on different administrative domains, and describes considerations
related to this condition.
8.1. Pre-arrangement of transport protocols
For interconnection between different administrative NSSIs, pre-
arrangement of the transport protocol, which is used to connect
between SLGs is required. Orchestration systems indicate the
protocol and configuration to each SLG.
8.2. Quality Assurance between SLGs
In addition to establishing connection, quality control of
communication is important. SLGs of egress side should execute
traffic shaping to prevent some NSs from excessively occupying the
link between SLGs. Moreover, some SLGs are connected to several
other SLGs that are deployed on the different locations. Therefore
SLGs of the ingress side should execute traffic policing to avoid
Homma, et al. Expires May 6, 2020 [Page 21]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
excessive inflow of traffic into some NSs. The parameters for these
controls are pre-configured by orchestration systems.
The above approaches are ones of the simplest ways to provide quality
assurance of inter-administrative subnets. If there is stricter
isolation request, more considerations would be required.
8.3. Secure Interconnection
For connecting networks of different administrators, secure
interconnection schemes are required. Especially, in an NSaaS,
networks might be connected to several networks, and schemes for
ensuring secure connectivity would be more important.
SLGs confirm whether the opponent SLG is regular when it requests to
connect, and reject the request if the SLG is not regular. In some
cases, SLGs might be confirm whether the inner packets received from
the other SLGs are sent from regular users.
9. Interfaces of SLG Controller
9.1. Southbound Interface
SLG-C supports protocols to communicate with SLG-Ds. Information and
prameters exchanged between SLG-D and SLG-C are TBD.
9.2. Northbound Interface for Higher Operation Systems
TBD
9.3. Northbound Interface for Customers/Tenants
TBD
10. Security Considerations
Requirements and considerations for SLG related to security are
described in Section 5 and Section 8.
11. IANA Considerations
This memo includes no request to IANA.
12. Acknowledgement
The authors would like to thank Li Qiang for her kind review and
valuable feedback.
Homma, et al. Expires May 6, 2020 [Page 22]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
13. Informative References
[I-D.defoy-coms-subnet-interconnection]
Foy, X., Rahman, A., Galis, A.,
kiran.makhijani@huawei.com, k., and L. Qiang,
"Interconnecting (or Stitching) Network Slice Subnets",
draft-defoy-coms-subnet-interconnection-01 (work in
progress), October 2017.
[I-D.homma-slice-provision-models]
Homma, S., Nishihara, H., Miyasaka, T., Galis, A., OV, V.,
Lopez, D., Contreras, L., Ordonez-Lucena, J., Martinez-
Julia, P., Qiang, L., Rokui, R., Ciavaglia, L., and X.
Foy, "Network Slice Provision Models", draft-homma-slice-
provision-models-00 (work in progress), February 2019.
[I-D.ietf-6man-segment-routing-header]
Previdi, S., Filsfils, C., Raza, K., Dukes, D., Leddy, J.,
Field, B., daniel.voyer@bell.ca, d.,
daniel.bernier@bell.ca, d., Matsushima, S., Leung, I.,
Linkova, J., Aries, E., Kosugi, T., Vyncke, E., Lebrun,
D., Steinberg, D., and R. Raszuk, "IPv6 Segment Routing
Header (SRH)", draft-ietf-6man-segment-routing-header-08
(work in progress), January 2018.
[I-D.ietf-spring-segment-routing-mpls]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing with MPLS
data plane", draft-ietf-spring-segment-routing-mpls-11
(work in progress), October 2017.
[I-D.netslices-usecases]
kiran.makhijani@huawei.com, k., Qin, J., Ravindran, R.,
Geng, L., Qiang, L., Peng, S., Foy, X., Rahman, A., Galis,
A., and G. Fioccola, "Network Slicing Use Cases: Network
Customization and Differentiated Services", draft-
netslices-usecases-02 (work in progress), October 2017.
[I-D.qiang-coms-netslicing-information-model]
Qiang, L., Galis, A., 67, 4., kiran.makhijani@huawei.com,
k., Martinez-Julia, P., Flinck, H., and X. Foy,
"Technology Independent Information Model for Network
Slicing", draft-qiang-coms-netslicing-information-model-01
(work in progress), October 2017.
Homma, et al. Expires May 6, 2020 [Page 23]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
[I-D.rokui-5g-transport-slice]
Rokui, R., Homma, S., Lopez, D., Foy, X., Contreras, L.,
Ordonez-Lucena, J., Martinez-Julia, P., Boucadair, M.,
Eardley, P., Makhijani, K., and H. Flinck, "5G Transport
Slice Connectivity Interface", draft-rokui-5g-transport-
slice-00 (work in progress), July 2019.
[NECOS] NECOS, "Novel Enablers for Cloud Slicing",
<hhttp://www.h2020-necos.eu>.
[NFV-Architectural-Framework]
Network Functions Virtualisation (NFV) ETSI Industry
Specification Group (ISG), "Network Functions
Virtualisation (NFV); Architectural Framework", December
2014, <http://www.etsi.org/deliver/etsi_gs/
NFV/001_099/002/01.02.01_60/gs_NFV002v010201p.pdf>.
[OSM-White-Paper]
ETSI, "OSM White Paper", October 2016,
<https://osm.etsi.org/images/OSM-Whitepaper-TechContent-
ReleaseONE-FINAL.pdf>.
[RFC7348] Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
eXtensible Local Area Network (VXLAN): A Framework for
Overlaying Virtualized Layer 2 Networks over Layer 3
Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
<https://www.rfc-editor.org/info/rfc7348>.
[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>.
[RFC8300] Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed.,
"Network Service Header (NSH)", RFC 8300,
DOI 10.17487/RFC8300, January 2018,
<https://www.rfc-editor.org/info/rfc8300>.
[RFC8459] Dolson, D., Homma, S., Lopez, D., and M. Boucadair,
"Hierarchical Service Function Chaining (hSFC)", RFC 8459,
DOI 10.17487/RFC8459, September 2018,
<https://www.rfc-editor.org/info/rfc8459>.
Homma, et al. Expires May 6, 2020 [Page 24]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
[Slicing_Tutrial]
IEEE NetSoft2018, "Network Slicing Landscape Tutorial",
June 2018,
<http://netsoft2018.ieee-netsoft.org/program/tutorials/;
http://discovery.ucl.ac.uk/10051374/>.
[TS.23.501-3GPP]
3rd Generation Partnership Project (3GPP), "3GPP TS 23.501
(V16.0.0): System Architecture for 5G System; Stage 2",
September 2018, <http://www.3gpp.org/ftp//Specs/
archive/23_series/23.501/23501-g00.zip>.
[TS.36.300-3GPP]
3rd Generation Partnership Project (3GPP), "Evolved
Universal Terrestrial Radio Access (E-UTRA) and Evolved
Universal Terrestrial Radio Access Network (E-UTRAN);
Overall description; Stage 2", December 2007,
<http://www.qtc.jp/3GPP/Specs/36300-830.pdf>.
Appendix A. Requirements for each SLG Type
The requirements for each SLG type are listed in Figure 11.
+---------------++-------+-------+-------+----------------+
| || E-SLG |IS-SLG |ID-SLG | Reference |
+=========================================================+
|*Data-Plane of NS as Infrastructure |
+=========================================================+
|Identification/|| M | O | O |Section 5.1.1.1.|
|Classification || | | | |
+---------------++-------+-------+-------+----------------+
|Transport/ || M | O | M |Section 5.1.1.2.|
|Forwarding || | | | |
+---------------++-------+-------+-------+----------------+
|Isolation || M | M | M |Section 5.1.1.3.|
+---------------++-------+-------+-------+----------------+
|Service Chain || O | O | O |Section 5.1.1.4.|
+=========================================================+
|*Control/Management-Plane of NS as Infrastructure |
+=========================================================+
|IF to Ctrl/OpS || M | M | M |Section 5.1.2.1.|
+---------------++-------+-------+-------+----------------+
|Addr Resolution|| M | M | M |Section 5.1.2.2.|
|/Routing || | | | |
+---------------++-------+-------+-------+----------------+
|AAA || M | - | M |Section 5.1.2.3.|
+---------------++-------+-------+-------+----------------+
|OAM || M | M | M |Section 5.1.2.4.|
Homma, et al. Expires May 6, 2020 [Page 25]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
+---------------++-------+-------+-------+----------------+
|Monitoring || M | M | M |Section 5.1.2.5.|
+=========================================================+
|*Data-Plane for Service on NS |
+=========================================================+
|Identification/|| O | - | O |Section 5.2.1.1.|
|Classification || | | | |
+---------------++-------+-------+-------+----------------+
|QoS Control || O | O | O |Section 5.2.1.2.|
+---------------++-------+-------+-------+----------------+
|Steering/ || O | - | O |Section 5.2.1.3.|
|Service Chain || | | | |
+=========================================================+
|*Control/Management-Plane for Service on NS |
+=========================================================+
|IF to Service || O | O | O |Section 5.2.2.1.|
|Manager || | | | |
+---------------++-------+-------+-------+----------------+
|Telemetory || O | O | O |Section 5.2.2.2.|
+---------------++-------+-------+-------+----------------+
M: Mandatry, O: Optional, - : Not Required
Figure 11: List of Requirements for each SLG
Appendix B. Position of SLG on ETSI NFV MANO
Some SLGs and the controllers are deployed and run on NSs as VNFs.
An arechitecture for managing lifecycle of VNFs is under
standardization in ETS NFV MANO.
The mapping of SLG as a VM into ETSI NFV MANO architecture is
described in Figure 12. In some cases, SLGs are deployed with
containor. VNFs are parts of NS compositions and NFV orchestrator
would be controlled by upper control entities such as resource
orchestrator.
Homma, et al. Expires May 6, 2020 [Page 26]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
OSS/BSS, Service-Orch, Resource-Orch
| |
| |
+-v-------+ +-v----------+
|SLG-Ctrl |<-----+ NFV Orch. |
+-+-------+ +-+----------+
| |
,-v-------. |
| SLG | |
:=========: +-v----------+
|VM(GstOS)|<-----+VNF Manager |
`---------' +-+----------+
+---------+ |
| HostOS/ | +-v----------+
| Server |<-----| VIM |
+---------+ +------------+
Figure 12: Position of SLG as a VM on ETSI NFV MANO
Appendix C. Complemention of Network Slicing in 3GPP
The 3GPP 5GS is natively support network slicing (ref.
[TS.23.501-3GPP], and UPF provides some functions for manuplation of
NSs, such as NS selection, QoS control, traffic steering, etc. 3GPP
is responsible for standatdizing user plane manipulation for mobility
management, and interworking with transport on underlay network and
external networks of 5GS such as DNs is out of scope in 3GPP.
SLG will provide complemental definitions of functions and interfaces
for providing E2E-NSI including 5GS. A way of interworking between
transport NS and RAN/UPF is described in
[I-D.rokui-5g-transport-slice].
Further study is TBD.
Authors' Addresses
Shunsuke Homma
NTT
Japan
Email: shunsuke.homma.fp@hco.ntt.co.jp
Homma, et al. Expires May 6, 2020 [Page 27]
Internet-Draft draft-homma-rtgwg-slice-gateway November 2019
Xavier de Foy
InterDigital Inc.
Canada
Email: Xavier.Defoy@InterDigital.com
Alex Galis
University College London
United Kingdom
Email: a.galis@ucl.ac.uk
Luis M. Contreras
Telefonica
Ronda de la Comunicacion, s/n
Sur-3 building, 3rd floor
Madrid 28050
Spain
Email: luismiguel.contrerasmurillo@telefonica.com
URI: http://lmcontreras.com/
Homma, et al. Expires May 6, 2020 [Page 28]