Network Working Group I. Bryskin
Internet-Draft Individual
Intended status: Informational X. Liu
Expires: May 7, 2020 Volta Networks
Y. Lee
Sung Kyun Kwan University
J. Guichard
Huawei Technologies
L. Contreras
Telefonica
D. Ceccarelli
Ericsson
J. Tantsura
Apstra Networks
November 4, 2019
SF Aware TE Topology YANG Model
draft-ietf-teas-sf-aware-topo-model-04
Abstract
This document describes a YANG data model for TE network topologies
that are network service and function aware.
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
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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 7, 2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights 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
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Tree Diagrams . . . . . . . . . . . . . . . . . . . . . . 5
1.3. Prefixes in Data Node Names . . . . . . . . . . . . . . . 6
2. Modeling Considerations . . . . . . . . . . . . . . . . . . . 6
3. SF Aware TE Topology Model Structure . . . . . . . . . . . . 7
4. SF Aware TE Topology YANG Module . . . . . . . . . . . . . . 9
5. CSO Data Center Model Structure . . . . . . . . . . . . . . . 16
6. CSO Data Center YANG Module . . . . . . . . . . . . . . . . . 18
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
8. Security Considerations . . . . . . . . . . . . . . . . . . . 24
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
9.1. Normative References . . . . . . . . . . . . . . . . . . 24
9.2. Informative References . . . . . . . . . . . . . . . . . 26
Appendix A. Companion YANG Model for Non-NMDA Compliant
Implementations . . . . . . . . . . . . . . . . . . 27
A.1. SF Aware TE Topology State Module . . . . . . . . . . . . 27
Appendix B. Data Examples . . . . . . . . . . . . . . . . . . . 30
B.1. A Topology with Multiple Connected Network Functions . . 30
B.2. A Topology with an Encapsulated Network Service . . . . . 34
Appendix C. Use Cases for SF Aware Topology Models . . . . . . . 38
C.1. Exporting SF/NF Information to Network Clients and Other
Network SDN Controllers . . . . . . . . . . . . . . . . . 38
C.2. Flat End-to-end SFCs Managed on Multi-domain Networks . 39
C.3. Managing SFCs with TE Constraints . . . . . . . . . . . . 40
C.4. SFC Protection and Load Balancing . . . . . . . . . . . . 41
C.5. Network Clock Synchronization . . . . . . . . . . . . . . 44
C.6. Client - Provider Network Slicing Interface . . . . . . . 44
C.7. Dynamic Assignment of Regenerators for L0 Services . . . 44
C.8. Dynamic Assignment of OAM Functions for L1 Services . . . 46
C.9. SFC Abstraction and Scaling . . . . . . . . . . . . . . . 47
C.10. Dynamic Compute/VM/Storage Resource Assignment . . . . . 47
C.11. Application-aware Resource Operations and Management . . 48
C.12. IANA Considerations . . . . . . . . . . . . . . . . . . . 49
C.13. Security Considerations . . . . . . . . . . . . . . . . . 49
C.14. Acknowledgements . . . . . . . . . . . . . . . . . . . . 49
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Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 49
1. Introduction
RFC Ed.: In this document, please replace all occurrences of 'XXXX'
with the actual RFC number (and remove this note).
Normally network connectivity services are discussed as a means to
inter-connect various abstract or physical network topological
elements, such as ports, link termination points and nodes
[I-D.ietf-teas-yang-te-topo] [I-D.ietf-teas-yang-te]. However, the
connectivity services, strictly speaking, interconnect not the
network topology elements per-se, rather, located on/associated with
the various network and service functions [RFC7498] [RFC7665]. In
many scenarios it is beneficial to decouple the service/network
functions from the network topology elements hosting them, describe
them in some unambiguous and identifiable way (so that it would be
possible, for example, to auto-discover on the network topology
service/network functions with identical or similar functionality and
characteristics) and engineer the connectivity between the service/
network functions, rather than between their current topological
locations.
Today a network offers to its clients far more services than just
connectivity across the network. Large variety of physical, logical
and/or virtual service functions, network functions and transport
functions (collectively named in this document as SFs) could be
allocated for and assigned to a client. As described in the appendix
of this document, there are some important use cases, in which the
network needs to represent to the client SFs at the client's disposal
as topological elements in relation to other elements of a topology
(i.e. nodes, links, link and tunnel termination points) used by the
network to describe itself to the client. Not only would such
information allow for the client to auto-discover the network's SFs
available for the services provisioned for the client, it would also
allow for the client selecting the SFs, duel-optimizing the selection
on the SF location on the network and connectivity means (e.g. TE
tunnels) to inter-connect the SFs. Consequently thus would give to
both the network and the client powerful means for the service
function chain (SFC [RFC7498] [RFC7665]) negotiation to achieve most
efficient and cost effective (from the network point of view) and
most optimal yet satisfying all necessary constraints of SFCs (from
the client's point of view).
This document defines a YANG [RFC7950] data model that allows service
functions to be represented along with TE topology elements.
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The YANG data model in this document conforms to the Network
Management Datastore Architecture (NMDA) [RFC8342].
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14, [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
o Network Function (NF): A functional block within a network
infrastructure that has well-defined external interfaces and well-
defined functional behaviour [ETSI-NFV-TERM]. Such functions
include message router, CDN, session border controller, WAN
cceleration, DPI, firewall, NAT, QoE monitor, PE router, BRAS, and
radio/fixed access network nodes.
o Network Service: Composition of Network Functions and defined by
its functional and behavioural specification. The Network Service
contributes to the behaviour of the higher layer service, which is
characterized by at least performance, dependability, and security
specifications. The end-to-end network service behaviour is the
result of the combination of the individual network function
behaviours as well as the behaviours of the network infrastructure
composition mechanism [ETSI-NFV-TERM].
o Service Function (SF): A function that is responsible for specific
treatment of received packets. A service function can act at
various layers of a protocol stack (e.g., at the network layer or
other OSI layers). As a logical component, a service function can
be realized as a virtual element or be embedded in a physical
network element. One or more service functions can be embedded in
the same network element. Multiple occurrences of the service
function can exist in the same administrative domain. A non-
exhaustive list of service functions includes: firewalls, WAN and
application acceleration, Deep Packet Inspection (DPI), server
load balancers, NAT44 [RFC3022], NAT64 [RFC6146], HTTP header
enrichment functions, and TCP optimizers. The generic term "L4-L7
services" is often used to describe many service functions
[RFC7498].
o Service Function Chain (SFC): A service function chain defines an
ordered or partially ordered set of abstract service functions and
ordering constraints that must be applied to packets, frames, and/
or flows selected as a result of classification. An example of an
abstract service function is a firewall. The implied order may
not be a linear progression as the architecture allows for SFCs
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that copy to more than one branch, and also allows for cases where
there is flexibility in the order in which service functions need
to be applied. The term "service chain" is often used as
shorthand for "service function chain" [RFC7498].
o Connectivity Service: Any service between layer 0 and layer 3
aiming at delivering traffic among two or more end customer edge
nodes connected to provider edge nodes. Examples include L3VPN,
L2VPN etc.
o Link Termination Point (LTP): A conceptual point of connection of
a TE node to one of the TE links, terminated by the TE node.
Cardinality between an LTP and the associated TE link is 1:0..1
[I-D.ietf-teas-yang-te-topo].
o Tunnel Termination Point (TTP): An element of TE topology
representing one or several of potential transport service
termination points (i.e. service client adaptation points such as
WDM/OCh transponder). TTP is associated with (hosted by) exactly
one TE node. TTP is assigned with the TE node scope unique ID.
Depending on the TE node's internal constraints, a given TTP
hosted by the TE node could be accessed via one, several or all TE
links terminated by the TE node [I-D.ietf-teas-yang-te-topo].
o Topology and Orchestration Specification for Cloud Applications
(TOSCA): A language standard specified by OASIS, to describe
service components and their relationships using a service
topology, and management procedures using orchestration processes.
OASIS is a nonprofit consortium that drives the development,
convergence and adoption of open standards for the global
information society.
The following terms are defined in [RFC7950] and are not redefined
here:
o augment
o data model
o data node
1.2. Tree Diagrams
A simplified graphical representation of the data model is presented
in this document, by using the tree format defined in [RFC8340].
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1.3. Prefixes in Data Node Names
In this document, names of data nodes, actions, and other data model
objects are often used without a prefix, as long as it is clear from
the context in which YANG module each name is defined. Otherwise,
names are prefixed using the standard prefix associated with the
corresponding YANG module, as shown in Table 1.
+---------+------------------+------------------------------+
| Prefix | YANG module | Reference |
+---------+------------------+------------------------------+
| inet | ietf-inet-types | [RFC6991] |
| nw | ietf-network | [RFC8345] |
| nt | ietf-network- | [RFC8345] |
| | topology | |
| tet | ietf-te-topology | [I-D.ietf-teas-yang-te-topo] |
| actn-vn | ietf-actn-vn | [I-D.ietf-teas-actn-vn-yang] |
+---------+------------------+------------------------------+
Table 1: Prefixes and Corresponding YANG Modules
2. Modeling Considerations
The model introduced in this document is an augmentation of the TE
Topology model defined in [I-D.ietf-teas-yang-te-topo]. SFs are
modeled as child elements of a TE node similarly to how Link
Termination Points (LTPs) and Tunnel Termination Points (TTPs) are
modeled in the TE Topology model. The SFs are defined as opaque
objects identified via topology unique service-function-id's. Each
SF has one or more Connection Points (CPs) identified via SF-unique
sf-connection-point-id's, over which the SF could be connected to
other SFs resided on the same TE node, as well as to other elements
of the TE node, in particular, to the node's LTPs and/or TTPs. An
interested client may use service-function-id's to look up the SFs in
TOSCA or YANG data store(s) defined by [ETSI-NFV-MAN] to retrieve the
details of the SFs, for example, to understand the SF's mutual
substitutability.
The TE Topology model introduces a concept of Connectivity Matrix
(CM), and uses the CM to describe which and at what costs a TE node's
LTPs could be inter-connected internally across the TE node. The
model defined in this document heavily uses the same concept to
describe the SF connectivity via introducing 3 additional CMs:
1. SF2SF CM (SF to SF Connectivity Matrix). This CM describes which
pairs of SFs could be locally inter-connected, and, if yes, in
which direction, via which CPs and at what costs. In other
words, the SF2SF CM describes how SFs residing on the same TE
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node could be inter-connected into local from the TE node's
perspective SFCs;
2. SF2LTP CM (SF to LTP Connectivity Matrix). This CM describes
how, in which direction and at what costs the TE node's SFs could
be connected to the TE node's LTPs and hence to SFs residing on
neighboring TE nodes that are connected to LTPs at the remote
ends of corresponding TE links;
3. SF2TTP CM (SF to TTP Connectivity Matrix). This CM describes
how, in which direction and at what costs the TE node's SFs could
be connected to the TE node's TTPs and hence to SFs residing on
other TE nodes on the topology that could be inter-connected with
the TE node in question via TE tunnels terminated by the
corresponding TTPs.
In addition to SF2SF CM, the local SF chaining could be described
with the help of ETSI models Virtual Links (VLs) [ETSI-NFV-MAN].
This option is especially useful when the costs of the local chaining
are negligible as compared to ones of the end-to-end SFCs said local
SFCs are part of.
Section 3 and 4 provide the YANG model structure and the YANG module
for SF-aware Topology. Section 5 and 6 provide the YANG model
structure and the YANG module for Data Center Compute Node resource
abstraction. This provides an example of SF2LTP CM where DC compute
nodes are connected to LTPs at the remote ends of the corresponding
TE links. This use-case is described in Section 10 of Appendix C.
3. SF Aware TE Topology Model Structure
module: ietf-te-topology-sf
augment /nw:networks/nw:network/nw:network-types/tet:te-topology:
+--rw sf!
augment /nw:networks/nw:network/nw:node/tet:te
/tet:te-node-attributes:
+--rw service-function
+--rw connectivity-matrices
| +--rw connectivity-matrix* [id]
| +--rw id uint32
| +--rw from
| | +--rw service-function-id? string
| | +--rw sf-connection-point-id? string
| +--rw to
| | +--rw service-function-id? string
| | +--rw sf-connection-point-id? string
| +--rw enabled? boolean
| +--rw direction? connectivity-direction
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| +--rw virtual-link-id? string
+--rw link-terminations
+--rw link-termination* [id]
+--rw id uint32
+--rw from
| +--rw tp-ref? -> ../../../../../../..
/nt:termination-point/tp-id
+--rw to
| +--rw service-function-id? string
| +--rw sf-connection-point-id? string
+--rw enabled? boolean
+--rw direction? connectivity-direction
augment /nw:networks/nw:network/nw:node/tet:te
/tet:information-source-entry:
+--ro service-function
+--ro connectivity-matrices
| +--ro connectivity-matrix* [id]
| +--ro id uint32
| +--ro from
| | +--ro service-function-id? string
| | +--ro sf-connection-point-id? string
| +--ro to
| | +--ro service-function-id? string
| | +--ro sf-connection-point-id? string
| +--ro enabled? boolean
| +--ro direction? connectivity-direction
| +--ro virtual-link-id? string
+--ro link-terminations
+--ro link-termination* [id]
+--ro id uint32
+--ro from
+--ro to
| +--ro service-function-id? string
| +--ro sf-connection-point-id? string
+--ro enabled? boolean
+--ro direction? connectivity-direction
augment /nw:networks/nw:network/nw:node/tet:te
/tet:tunnel-termination-point:
+--rw service-function
+--rw tunnel-terminations
+--rw tunnel-termination* [id]
+--rw id uint32
+--rw service-function-id? string
+--rw sf-connection-point-id? string
+--rw enabled? boolean
+--rw direction? connectivity-direction
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4. SF Aware TE Topology YANG Module
<CODE BEGINS> file "ietf-te-topology-sf@2019-11-03.yang"
module ietf-te-topology-sf {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-te-topology-sf";
prefix "tet-sf";
import ietf-network {
prefix "nw";
reference "RFC 8345: A YANG Data Model for Network Topologies";
}
import ietf-network-topology {
prefix "nt";
reference "RFC 8345: A YANG Data Model for Network Topologies";
}
import ietf-te-topology {
prefix "tet";
reference
"I-D.ietf-teas-yang-te-topo: YANG Data Model for Traffic
Engineering (TE) Topologies";
}
organization
"Traffic Engineering Architecture and Signaling (TEAS)
Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/teas/>
WG List: <mailto:teas@ietf.org>
Editors: Igor Bryskin
<mailto:Igor.Bryskin@huawei.com>
Xufeng Liu
<mailto:Xufeng_Liu@jabil.com>";
description
"Network service and function aware aware TE topology model.
Copyright (c) 2019 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
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without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see the
RFC itself for full legal notices.";
revision 2019-11-03 {
description "Initial revision";
reference "RFC XXXX: SF Aware TE Topology YANG Model";
}
/*
* Typedefs
*/
typedef connectivity-direction {
type enumeration {
enum "to" {
description
"The direction is uni-directional, towards the 'to'
entity direction.";
}
enum "from" {
description
"The direction is uni-directional, from the 'to'
entity direction.";
}
enum "bidir" {
description
"The direction is bi-directional.";
}
}
description
"A type used to indicates whether a connectivity is
uni-directional, or bi-directional. If the relation is
uni-directional, the value of this type indicates the
direction.";
} // connectivity-direction
/*
* Groupings
*/
grouping service-function-node-augmentation {
description
"Augmenting a TE node to be network service and function
aware.";
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container service-function {
description
"Containing attributes related to network services and
network functions";
container connectivity-matrices {
description
"Connectivity relations between network services/functions
on a TE node, which can be either abstract or physical.";
reference
"ETSI GS NFV-MAN 01: Network Functions Virtualisation
(NFV); Management and Orchestration.
RFC7665: Service Function Chaining (SFC) Architecture.";
list connectivity-matrix {
key "id";
description
"Represents the connectivity relations between network
services/functions on a TE node.";
leaf id {
type uint32;
description "Identifies the connectivity-matrix entry.";
}
container from {
description
"Reference to the source network service or
network function.";
leaf service-function-id {
type string;
description
"Reference to a network service or a network
function.";
}
leaf sf-connection-point-id {
type string;
description
"Reference to a connection point on a network
service or a network function.";
}
} // from
container to {
description
"Reference to the destination network service or
network function.";
leaf service-function-id {
type string;
description
"Reference to a network service or a network
function.";
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}
leaf sf-connection-point-id {
type string;
description
"Reference to a connection point on a network
service or a network function.";
}
} // to
leaf enabled {
type boolean;
description
"'true' if this connectivity entry is enabled.";
}
leaf direction {
type connectivity-direction;
description
"Indicates whether this connectivity is
uni-directional, or bi-directional. If the
relation is uni-directional, the value of
this leaf indicates the direction.";
}
leaf virtual-link-id {
type string;
description
"Reference to a virtual link that models this
conectivity relation in the network function
model.";
}
} // connectivity-matrix
} // connectivity-matrices
container link-terminations {
description
"Connectivity relations between network services/functions
and link termination points on a TE node, which can be
either abstract or physical.";
reference
"ETSI GS NFV-MAN 01: Network Functions Virtualisation
(NFV); Management and Orchestration.
RFC7665: Service Function Chaining (SFC) Architecture.";
list link-termination {
key "id";
description
"Each entry of the list represents the connectivity
relation between a network service/function and
a link termination point on a TE node.";
leaf id {
type uint32;
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description "Identifies the termination entry.";
}
container from {
description
"Reference to the link termination point.";
} // from
container to {
description
"Reference to the network service or network
function.";
leaf service-function-id {
type string;
description
"Reference to a network service or a network
function.";
}
leaf sf-connection-point-id {
type string;
description
"Reference to a connection point on a network
service or a network function.";
}
} // to
leaf enabled {
type boolean;
description
"'true' if this connectivity entry is enabled.";
}
leaf direction {
type connectivity-direction;
description
"Indicates whether this connectivity is
uni-directional, or bi-directional. If the
relation is uni-directional, the value of
this leaf indicates the direction.";
}
} // link-termination
}
}
} // service-function-node-augmentation
grouping service-function-ttp-augmentation {
description
"Augmenting a tunnel termination point to be network service
aware.";
container service-function {
description
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"Containing attributes related to network services and
network functions";
container tunnel-terminations {
description
"Connectivity relations between network services/functions
and tunnel termination points on a TE node, which can be
either abstract or physical.";
reference
"ETSI GS NFV-MAN 01: Network Functions Virtualisation
(NFV); Management and Orchestration.
RFC7665: Service Function Chaining (SFC) Architecture.";
list tunnel-termination {
key "id";
description
"Each entry of the list represents the connectivity
relation between a network service/function and
a tunnel termination point on a TE node.";
leaf id {
type uint32;
description "Identifies the termination entry.";
}
leaf service-function-id {
type string;
description
"Reference to a network service or a network
function.";
}
leaf sf-connection-point-id {
type string;
description
"Reference to a connection point on a network
service or a network function.";
}
leaf enabled {
type boolean;
description
"'true' if this connectivity entry is enabled.";
}
leaf direction {
type connectivity-direction;
description
"Indicates whether this connectivity is
uni-directional, or bi-directional. If the
relation is uni-directional, the value of
this leaf indicates the direction.";
}
} // link-termination
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}
}
} // service-function-ttp-augmentation
grouping sf-topology-type {
description
"Identifies the SF aware TE topology type.";
container sf {
presence "Indidates that the TE topology is SF aware.";
description
"Its presence identifies that the TE topology is SF aware.";
}
} // sf-topology-type
/*
* Augmentations
*/
/* Augmentations to network-types/te-topology */
augment "/nw:networks/nw:network/nw:network-types/"
+ "tet:te-topology" {
description
"Defines the SF aware TE topology type.";
uses sf-topology-type;
}
/* Augmentations to te-node-attributes */
augment "/nw:networks/nw:network/nw:node/tet:te/"
+ "tet:te-node-attributes" {
description
"Parameters for SF aware TE topology.";
uses service-function-node-augmentation;
}
augment "/nw:networks/nw:network/nw:node/tet:te/"
+ "tet:information-source-entry" {
description
"Parameters for SF aware TE topology.";
uses service-function-node-augmentation;
}
/* Augmentations to tunnel-termination-point */
augment "/nw:networks/nw:network/nw:node/tet:te/"
+ "tet:tunnel-termination-point" {
description
"Parameters for SF aware TE topology.";
uses service-function-ttp-augmentation;
}
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/* Augmentations to connectivity-matrix */
augment "/nw:networks/nw:network/nw:node/tet:te/"
+ "tet:te-node-attributes/tet-sf:service-function/"
+ "tet-sf:link-terminations/tet-sf:link-termination/"
+ "tet-sf:from" {
description
"Add reference to the link termination point.
This portion cannot be shared with the state module.";
leaf tp-ref {
type leafref {
path "../../../../../../../nt:termination-point/"
+ "nt:tp-id";
}
description
"Reference to the link termination point.";
}
}
}
<CODE ENDS>
5. CSO Data Center Model Structure
module: ietf-cso-dc
+--rw cso
+--rw dc* [id]
| +--rw hypervisor* [id]
| | +--rw ram
| | | +--rw total? uint32
| | | +--rw used? uint32
| | | +--rw free? uint32
| | +--rw disk
| | | +--rw total? uint32
| | | +--rw used? uint32
| | | +--rw free? uint32
| | +--rw vcpu
| | | +--rw total? uint16
| | | +--rw used? uint16
| | | +--rw free? uint16
| | +--rw instance* -> /cso/dc/instance/id
| | +--rw id string
| | +--rw name? string
| +--rw instance* [id]
| | +--rw flavor
| | | +--rw disk? uint32
| | | +--rw ram? uint32
| | | +--rw vcpus? uint16
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| | | +--rw id? string
| | | +--rw name? string
| | +--rw image
| | | +--rw checksum string
| | | +--rw size uint32
| | | +--rw format
| | | | +--rw container? enumeration
| | | | +--rw disk? enumeration
| | | +--rw id? string
| | | +--rw name? string
| | +--rw hypervisor? -> /cso/dc/hypervisor/id
| | +--rw port* -> /cso/dc/network/subnetwork/port
/id
| | +--rw project? string
| | +--rw status? enumeration
| | +--rw id string
| | +--rw name? string
| +--rw image* [id]
| | +--rw checksum string
| | +--rw size uint32
| | +--rw format
| | | +--rw container? enumeration
| | | +--rw disk? enumeration
| | +--rw id string
| | +--rw name? string
| +--rw flavor* [id]
| | +--rw disk? uint32
| | +--rw ram? uint32
| | +--rw vcpus? uint16
| | +--rw id string
| | +--rw name? string
| +--rw dc-monitoring-param* [name]
| | +--rw name string
| | +--rw value-string? string
| +--rw network* [id]
| | +--rw subnetwork* [id]
| | | +--rw port* [id]
| | | | +--rw ip-address? inet:ip-address
| | | | +--rw instance? -> /cso/dc/instance/id
| | | | +--rw project? string
| | | | +--rw status? enumeration
| | | | +--rw id string
| | | | +--rw name? string
| | | +--rw project? string
| | | +--rw status? enumeration
| | | +--rw id string
| | | +--rw name? string
| | +--rw dhcp-agent* [id]
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| | | +--rw enabled? boolean
| | | +--rw pools* [ip-address]
| | | | +--rw ip-address inet:ip-address
| | | +--rw project? string
| | | +--rw status? enumeration
| | | +--rw id string
| | | +--rw name? string
| | +--rw project? string
| | +--rw status? enumeration
| | +--rw id string
| | +--rw name? string
| | +--rw cso-ref? -> /cso/cso-id
| +--rw ap* -> /actn-vn:actn/ap
/access-point-list/access-point-id
| +--rw cso-ref? -> /cso/cso-id
| +--rw id string
| +--rw name? string
+--rw cso-id? string
6. CSO Data Center YANG Module
<CODE BEGINS> file "ietf-cso-dc@2017-01-16.yang"
module ietf-cso-dc
{
namespace "urn:ietf:params:xml:ns:yang:ietf-cso-dc";
prefix "dc";
import ietf-inet-types {
prefix "inet";
}
import ietf-actn-vn {
prefix "actn-vn";
}
revision 2017-01-16 {
description
"Initial revision. This YANG file defines
the reusable base types for CSO DC description.";
reference
"Derived from earlier versions of base YANG files";
}
// Abstract models
grouping resource-element {
leaf id { type string; }
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leaf name { type string; }
}
grouping resource-instance {
leaf project{ type string; }
leaf status {
type enumeration {
enum active;
enum inactive;
enum pending;
}
}
uses resource-element;
}
// Compute models
grouping format {
leaf container {
type enumeration {
enum ami;
enum ari;
enum aki;
enum bare;
enum ovf;
}
default bare;
}
leaf disk {
type enumeration {
enum ami;
enum ari;
enum aki;
enum vhd;
enum vmdk;
enum raw;
enum qcow2;
enum vdi;
enum iso;
}
default qcow2;
}
}
grouping image {
leaf checksum { type string; mandatory true; }
leaf size { type uint32; units 'Bytes'; mandatory true; }
container format {
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uses format;
}
uses resource-element;
}
grouping flavor {
leaf disk { type uint32; units 'GB'; default 0; }
leaf ram { type uint32; units 'MB'; default 0; }
leaf vcpus { type uint16; default 0; }
uses resource-element;
}
grouping ram {
leaf total { type uint32; units 'MB'; }
leaf used { type uint32; units 'MB'; }
leaf free { type uint32; units 'MB'; }
}
grouping disk {
leaf total { type uint32; units 'GB'; }
leaf used { type uint32; units 'GB'; }
leaf free { type uint32; units 'GB'; }
}
grouping vcpu {
leaf total { type uint16; }
leaf used { type uint16; }
leaf free { type uint16; }
}
grouping hypervisor {
container ram {
uses ram;
}
container disk {
uses disk;
}
container vcpu {
uses vcpu;
}
leaf-list instance {
type leafref { path '/cso/dc/instance/id'; } }
uses resource-element;
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}
grouping instance {
container flavor { uses flavor; }
container image { uses image; }
leaf hypervisor {
type leafref { path '/cso/dc/hypervisor/id'; } }
leaf-list port { type leafref {
path '/cso/dc/network/subnetwork/port/id'; } }
uses resource-instance;
}
grouping dc-monitoring-param {
leaf name {
description "dc-monitoring-param identifier"; type string; }
leaf value-string {
description
"Current value for a string parameter";
type string;
}
}
grouping dc {
list hypervisor {
key id;
uses hypervisor;
}
list instance {
key id;
uses instance;
}
list image {
key id;
uses image;
}
list flavor {
key id;
uses flavor;
}
list dc-monitoring-param {
key "name";
uses dc-monitoring-param;
}
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list network {
key id;
uses network;
}
leaf-list ap { type leafref {
path
'/actn-vn:actn/actn-vn:ap/actn-vn:access-point-list/'
+ 'actn-vn:access-point-id';
}
}
leaf cso-ref { type leafref { path "/cso/cso-id"; } }
uses resource-element;
}
container cso {
list dc {
key id;
uses dc;
}
leaf cso-id { type string; }
}
// Network models
grouping ip-address {
leaf ip-address { type inet:ip-address; }
}
grouping dhcp-agent {
leaf enabled { type boolean; }
list pools {
key ip-address;
uses ip-address;
}
uses resource-instance;
}
grouping network {
list subnetwork {
key id;
uses subnetwork;
}
list dhcp-agent {
key id;
uses dhcp-agent;
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}
uses resource-instance;
leaf cso-ref { type leafref { path "/cso/cso-id"; } }
}
grouping subnetwork {
list port {
key id;
uses port;
}
uses resource-instance;
}
grouping port {
leaf ip-address { type inet:ip-address; }
leaf instance { type leafref { path '/cso/dc/instance/id'; } }
uses resource-instance;
}
}
<CODE ENDS>
7. IANA Considerations
This document registers the following namespace URIs in the IETF XML
registry [RFC3688]:
--------------------------------------------------------------------
URI: urn:ietf:params:xml:ns:yang:ietf-te-topology-sf
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
--------------------------------------------------------------------
--------------------------------------------------------------------
URI: urn:ietf:params:xml:ns:yang:ietf-te-topology-sf-state
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
--------------------------------------------------------------------
This document registers the following YANG modules in the YANG Module
Names registry [RFC6020]:
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--------------------------------------------------------------------
name: ietf-te-topology-sf
namespace: urn:ietf:params:xml:ns:yang:ietf-te-topology-packet
prefix: tet-sf
reference: RFC XXXX
--------------------------------------------------------------------
--------------------------------------------------------------------
name: ietf-te-topology-sf-state
namespace: urn:ietf:params:xml:ns:yang:ietf-te-topology-packet-state
prefix: tet-sf-s
reference: RFC XXXX
--------------------------------------------------------------------
8. Security Considerations
The configuration, state, action and notification data defined in
this document are designed to be accessed via the NETCONF protocol
[RFC6241]. The data-model by itself does not create any security
implications. The security considerations for the NETCONF protocol
are applicable. The NETCONF protocol used for sending the data
supports authentication and encryption.
9. References
9.1. Normative References
[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>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
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[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC6991, July 2013,
<https://www.rfc-editor.org/info/rfc6991>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "Network Management Datastore Architecture
(NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
<https://www.rfc-editor.org/info/rfc8342>.
[RFC8345] Clemm, A., Medved, J., Varga, R., Bahadur, N.,
Ananthakrishnan, H., and X. Liu, "A YANG Data Model for
Network Topologies", RFC 8345, DOI 10.17487/RFC8345, March
2018, <https://www.rfc-editor.org/info/rfc8345>.
[I-D.ietf-teas-yang-te-topo]
Liu, X., Bryskin, I., Beeram, V., Saad, T., Shah, H., and
O. Dios, "YANG Data Model for Traffic Engineering (TE)
Topologies", draft-ietf-teas-yang-te-topo-22 (work in
progress), June 2019.
[I-D.ietf-teas-yang-te]
Saad, T., Gandhi, R., Liu, X., Beeram, V., and I. Bryskin,
"A YANG Data Model for Traffic Engineering Tunnels and
Interfaces", draft-ietf-teas-yang-te-22 (work in
progress), November 2019.
[I-D.ietf-teas-actn-vn-yang]
Lee, Y., Dhody, D., Ceccarelli, D., Bryskin, I., and B.
Yoon, "A Yang Data Model for VN Operation", draft-ietf-
teas-actn-vn-yang-07 (work in progress), October 2019.
[ETSI-NFV-MAN]
ETSI, "Network Functions Virtualisation (NFV); Management
and Orchestration", ETSI GS NFV-MAN 001 V1.1.1, December
2014.
[ETSI-NFV-TERM]
ETSI, "Network Functions Virtualisation (NFV); Terminology
for Main Concepts in NFV", ETSI GS NFV 003 V1.2.1,
December 2014.
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[RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022,
DOI 10.17487/RFC3022, January 2001,
<https://www.rfc-editor.org/info/rfc3022>.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
April 2011, <https://www.rfc-editor.org/info/rfc6146>.
[RFC8453] Ceccarelli, D., Ed. and Y. Lee, Ed., "Framework for
Abstraction and Control of TE Networks (ACTN)", RFC 8453,
DOI 10.17487/RFC8453, August 2018,
<https://www.rfc-editor.org/info/rfc8453>.
[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>.
[I-D.defoy-netslices-3gpp-network-slicing]
Foy, X. and A. Rahman, "Network Slicing - 3GPP Use Case",
draft-defoy-netslices-3gpp-network-slicing-02 (work in
progress), October 2017.
[_3GPP.28.801]
3GPP, "Study on management and orchestration of network
slicing for next generation network", 3GPP TR 28.801
V2.0.0, September 2017,
<http://www.3gpp.org/ftp/Specs/html-info/28801.htm>.
9.2. Informative References
[RFC7498] Quinn, P., Ed. and T. Nadeau, Ed., "Problem Statement for
Service Function Chaining", RFC 7498,
DOI 10.17487/RFC7498, April 2015,
<https://www.rfc-editor.org/info/rfc7498>.
[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>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
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Appendix A. Companion YANG Model for Non-NMDA Compliant Implementations
The YANG module ietf-te-topology-sf defined in this document is
designed to be used in conjunction with implementations that support
the Network Management Datastore Architecture (NMDA) defined in
[RFC8342]. In order to allow implementations to use the model even
in cases when NMDA is not supported, the following companion module,
ietf-te-topology-sf-state, is defined as state model, which mirrors
the module ietf-te-topology-sf defined earlier in this document.
However, all data nodes in the companion module are non-configurable,
to represent the applied configuration or the derived operational
states.
The companion module, ietf-te-topology-sf-state, is redundant and
SHOULD NOT be supported by implementations that support NMDA.
As the structure of the companion module mirrors that of the
coorespinding NMDA model, the YANG tree of the companion module is
not depicted separately.
A.1. SF Aware TE Topology State Module
<CODE BEGINS> file "ietf-te-topology-sf-state@2019-11-03.yang"
module ietf-te-topology-sf-state {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-te-topology-sf-state";
prefix "tet-sf-s";
import ietf-te-topology-sf {
prefix "tet-sf";
reference "RFC XXXX: SF Aware TE Topology YANG Model";
}
import ietf-network-state {
prefix "nw-s";
reference "RFC 8345: A YANG Data Model for Network Topologies";
}
import ietf-network-topology-state {
prefix "nt-s";
reference "RFC 8345: A YANG Data Model for Network Topologies";
}
import ietf-te-topology-state {
prefix "tet-s";
reference
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"I-D.ietf-teas-yang-te-topo: YANG Data Model for Traffic
Engineering (TE) Topologies";
}
organization
"Traffic Engineering Architecture and Signaling (TEAS)
Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/teas/>
WG List: <mailto:teas@ietf.org>
Editors: Igor Bryskin
<mailto:Igor.Bryskin@huawei.com>
Xufeng Liu
<mailto:Xufeng_Liu@jabil.com>";
description
"Network service and function aware aware TE topology operational
state model for non-NMDA compliant implementations.
Copyright (c) 2019 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see the
RFC itself for full legal notices.";
revision 2019-11-03 {
description "Initial revision";
reference "RFC XXXX: SF Aware TE Topology YANG Model";
}
/*
* Augmentations
*/
/* Augmentations to network-types/te-topology */
augment "/nw-s:networks/nw-s:network/nw-s:network-types/"
+ "tet-s:te-topology" {
description
"Defines the SF aware TE topology type.";
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uses tet-sf:sf-topology-type;
}
/* Augmentations to connectivity-matrix */
augment "/nw-s:networks/nw-s:network/nw-s:node/tet-s:te/"
+ "tet-s:te-node-attributes" {
description
"Parameters for SF aware TE topology.";
uses tet-sf:service-function-node-augmentation;
}
augment "/nw-s:networks/nw-s:network/nw-s:node/tet-s:te/"
+ "tet-s:information-source-entry" {
description
"Parameters for SF aware TE topology.";
uses tet-sf:service-function-node-augmentation;
}
/* Augmentations to tunnel-termination-point */
augment "/nw-s:networks/nw-s:network/nw-s:node/tet-s:te/"
+ "tet-s:tunnel-termination-point" {
description
"Parameters for SF aware TE topology.";
uses tet-sf:service-function-ttp-augmentation;
}
/* Augmentations to connectivity-matrix */
augment "/nw-s:networks/nw-s:network/nw-s:node/tet-s:te/"
+ "tet-s:te-node-attributes/tet-sf-s:service-function/"
+ "tet-sf-s:link-terminations/tet-sf-s:link-termination/"
+ "tet-sf-s:from" {
description
"Add reference to the link termination point.
This portion cannot be shared with the state module.";
leaf tp-ref {
type leafref {
path "../../../../../../../nt-s:termination-point/"
+ "nt-s:tp-id";
}
description
"Reference to the link termination point.";
}
}
}
<CODE ENDS>
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Appendix B. Data Examples
B.1. A Topology with Multiple Connected Network Functions
Node-1
+----o--o--------------------------o-------+
| | | | |
| \__/ \__ |
| *\/ TTP-1 * * * * * * * * * *\/* |
LTP-4 |* * * * TTP-2 * | LTP-1
o------------*-----------------------------o
| * * |
LTP-3 |* * * * * *| LTP-2
o--- -----o
| \ / |
| \ / |
| \ CP01 CP02/ |
| +----o--------------------------o------+ |
| | VL1| VL4| | |
| | |CP11 |CP33 | |
| | +-o--+ +----+ +-o--+ | |
| | |VNF1| |VNF2| |VNF3| | |
| | +-o-o+ VL2 +--o-+ VL2 +-o-o+ | |
| |CP12| |\----------/ \---------/| |CP32| |
| | | |CP13 CP21 CP31| | | |
| | | | VL2 | | | |
| | | +------------------------+ | | |
| | +----------------------------+ | |
| | VL3 | |
| | Network Service 1 | |
| +--------------------------------------+ |
+------------------------------------------+
The configuration instance data for Node-1 in the above figure could
be as follows:
{
"networks": {
"network": [
{
"network-types": {
"te-topology": {
"sf": {}
}
},
"network-id": "network-sf-aware",
"provider-id": 201,
"client-id": 300,
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"te-topology-id": "te-topology:network-sf-aware",
"node": [
{
"node-id": "Node-1",
"te-node-id": "2.0.1.1",
"te": {
"te-node-attributes": {
"domain-id": 1,
"is-abstract": [null],
"connectivity-matrices": {
},
"service-function": {
"connectivity-matrices": {
"connectivity-matrix": [
{
"id": 10,
"from": {
"service-function-id": "Network Service 1",
"sf-connection-point-id": "CP01"
},
"to": {
"service-function-id": "VNF1",
"sf-connection-point-id": "CP11"
}
"direction": "bidir",
"virtual-link-id": "VL1"
},
{
"id": 13,
"from": {
"service-function-id": "VNF1",
"sf-connection-point-id": "CP12"
},
"to": {
"service-function-id": "VNF3",
"sf-connection-point-id": "CP32"
}
"direction": "bidir",
"virtual-link-id": "VL3"
},
{
"id": 12,
"from": {
"service-function-id": "VNF1",
"sf-connection-point-id": "CP13"
},
"to": {
"service-function-id": "VNF2",
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"sf-connection-point-id": "CP21"
}
"direction": "bidir",
"virtual-link-id": "VL2"
},
{
"id": 23,
"from": {
"service-function-id": "VNF2",
"sf-connection-point-id": "CP21"
},
"to": {
"service-function-id": "VNF3"
"sf-connection-point-id": "CP31"
}
"direction": "bidir",
"virtual-link-id": "VL2"
},
{
"id": 30,
"from": {
"service-function-id": "Network Service 1",
"sf-connection-point-id": "CP02"
},
"to": {
"service-function-id": "VNF3",
"sf-connection-point-id": "CP33"
}
"direction": "bidir",
"virtual-link-id": "VL4"
}
]
},
"link-terminations": {
"link-termination": [
{
"id": 2,
"from": {
"tp-ref": "LTP-2"
},
"to": {
"service-function-id": "Network Service 1",
"sf-connection-point-id": "CP02"
}
"direction": "bidir"
},
{
"id": 3,
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"from": {
"tp-ref": "LTP-3"
},
"to": {
"service-function-id": "Network Service 1",
"sf-connection-point-id": "CP01"
}
"direction": "bidir"
}
]
}
}
}
"tunnel-termination-point": [
{
"tunnel-tp-id": 10001,
"name": "TTP-1",
"service-function-terminations": {
}
},
{
"tunnel-tp-id": 10002,
"name": "TTP-2",
"service-function-terminations": {
}
}
]
},
"termination-point": [
{
"tp-id": "LTP-1",
"te-tp-id": 10001
"te": {
"interface-switching-capability": [
{
"switching-capability": "switching-l2sc",
"encoding": "lsp-encoding-ethernet"
}
]
}
},
{
"tp-id": "LTP-2",
"te-tp-id": 10002
"te": {
"interface-switching-capability": [
{
"switching-capability": "switching-l2sc",
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"encoding": "lsp-encoding-ethernet"
}
]
}
},
{
"tp-id": "LTP-3",
"te-tp-id": 10003
"te": {
"interface-switching-capability": [
{
"switching-capability": "switching-l2sc",
"encoding": "lsp-encoding-ethernet"
}
]
}
},
{
"tp-id": "LTP-4",
"te-tp-id": 10004
"te": {
"interface-switching-capability": [
{
"switching-capability": "switching-l2sc",
"encoding": "lsp-encoding-ethernet"
}
]
}
}
]
}
]
}
]
}
}
B.2. A Topology with an Encapsulated Network Service
In this example, a network service consists of several inter-
connected network functions (NFs), and is represented by this model
as an encapsulated opaque object without the details between its
internals.
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Node-1
+----o--o--------------------------o-------+
| | | | |
| \__/ \__ |
| *\/ TTP-1 * * * * * * * * * *\/* |
LTP-4 |* * * * TTP-2 * | LTP-1
o------------*-----------------------------o
| * * |
LTP-3 |* * * * * *| LTP-2
o--- -----o
| \ / |
| \ / |
| \ CP01 CP02/ |
| +----o--------------------------o------+ |
| | | |
| | Network Service 1 | |
| +--------------------------------------+ |
+------------------------------------------+
The configuration instance data for Node-1 in the above figure could
be as follows:
{
"networks": {
"network": [
{
"network-types": {
"te-topology": {
"sf": {}
}
},
"network-id": "network-sf-aware",
"provider-id": 201,
"client-id": 300,
"te-topology-id": "te-topology:network-sf-aware",
"node": [
{
"node-id": "Node-1",
"te-node-id": "2.0.1.1",
"te": {
"te-node-attributes": {
"domain-id": 1,
"is-abstract": [null],
"connectivity-matrices": {
},
"service-function": {
"connectivity-matrices": {
},
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"link-terminations": {
"link-termination": [
{
"id": 2,
"from": {
"tp-ref": "LTP-2"
},
"to": {
"service-function-id": "Network Service 1",
"sf-connection-point-id": "CP02"
}
"direction": "bidir"
},
{
"id": 3,
"from": {
"tp-ref": "LTP-3"
},
"to": {
"service-function-id": "Network Service 1",
"sf-connection-point-id": "CP01"
}
"direction": "bidir"
}
]
}
}
}
"tunnel-termination-point": [
{
"tunnel-tp-id": 10001,
"name": "TTP-1",
"service-function-terminations": {
}
},
{
"tunnel-tp-id": 10002,
"name": "TTP-2",
"service-function-terminations": {
}
}
]
},
"termination-point": [
{
"tp-id": "LTP-1",
"te-tp-id": 10001
"te": {
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"interface-switching-capability": [
{
"switching-capability": "switching-l2sc",
"encoding": "lsp-encoding-ethernet"
}
]
}
},
{
"tp-id": "LTP-2",
"te-tp-id": 10002
"te": {
"interface-switching-capability": [
{
"switching-capability": "switching-l2sc",
"encoding": "lsp-encoding-ethernet"
}
]
}
},
{
"tp-id": "LTP-3",
"te-tp-id": 10003
"te": {
"interface-switching-capability": [
{
"switching-capability": "switching-l2sc",
"encoding": "lsp-encoding-ethernet"
}
]
}
},
{
"tp-id": "LTP-4",
"te-tp-id": 10004
"te": {
"interface-switching-capability": [
{
"switching-capability": "switching-l2sc",
"encoding": "lsp-encoding-ethernet"
}
]
}
}
]
}
]
}
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]
}
}
Appendix C. Use Cases for SF Aware Topology Models
C.1. Exporting SF/NF Information to Network Clients and Other Network
SDN Controllers
In the context of Service Function Chain (SFC) orchestration one
existing problem is that there is no way to formally describe a
Service or Network Function in a standard way (recognizable/
understood by a third party) as a resource of a network topology
node.
One implication of this is that there is no way for the orchestrator
to give a network client even a ball-park idea as to which network's
SFs/NFs are available for the client's use/control and where they are
located in the network even in terms of abstract topologies/virtual
networks configured and managed specifically for the client.
Consequently, the client has no say on how the SFCs provided for the
client by the network should be set up and managed (which SFs are to
be used and how they should be chained together, optimized,
manipulated, protected, etc.).
Likewise, there is no way for the orchestrator to export SF/NF
information to other network controllers. The SFC orchestrator may
serve, for example, a higher level controller (such as Network
Slicing Orchestrator), with the latter wanting at least some level of
control as to which SFs/NFs it wants on its SFCs and how the Service
Function Paths (SFPs) are to be routed and provisioned, especially,
if it uses services of more than one SFC orchestrator.
The issue of exporting of SF/NF information could be addressed by
defining a model, in which formally described/recognizable SF/NF
instances are presented as topological elements, for example, hosted
by TE, L3 or L2 topology nodes (see Figure 1). The model could
describe whether, how and at what costs the SFs/NFs hosted by a given
node could be chained together, how these intra-node SFCs could be
connected to the node's Service Function Forwarders (SFFs, entities
dealing with SFC NSHs and metadata), and how the SFFs could be
connected to the node's Tunnel and Link Termination Points (TTPs and
LTPs) to chain the intra-node SFCs across the network topology.
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The figure is available in the PDF format.
Figure 1: SF/NF aware TE topology
C.2. Flat End-to-end SFCs Managed on Multi-domain Networks
SFCs may span multiple administrative domains, each of which
controlled by a separate SFC controller. The usual solution for such
a scenario is the Hierarchical SFCs (H-SFCs) [RFC8459], in which the
higher level orchestrator controls only SFs located on domain border
nodes. Said higher level SFs are chained together into higher level
SFCs via lower level (intra-domain) SFCs provisioned and controlled
independently by respective domain controllers. The decision as to
which higher level SFCs are connected to which lower level SFCs is
driven by packet re-classification every time the packet enters a
given domain. Said packet re-classification is a very time-consuming
operation. Furthermore, the independent nature of higher and lower
level SFC control is prone to configuration errors, which may lead to
long lasting loops and congestions. It is highly desirable to be
able to set up and manage SFCs spanning multiple domains in a flat
way as far as the data plane is concerned (i.e. with a single packet
classification at the ingress into the multi-domain network but
without re-classifications on domain ingress nodes).
One way to achieve this is to have the domain controllers expose SF/
NF- aware topologies, and have the higher level orchestrator operate
on the network-wide topology, the product of merging of the
topologies catered by the domain controllers. This is similar in
spirit to setting up, coordinating and managing the transport
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connectivity (TE tunnels) on a multi-domain multi-vendor transport
network.
C.3. Managing SFCs with TE Constraints
Some SFCs require per SFC link/element and end-to-end TE constrains
(bandwidth, delay/jitter, fate sharing/diversity. etc.). Said
constraints could be ensured via carrying SFPs inside overlays that
are traffic engineered with the constrains in mind. A good analogy
would be orchestrating delay constrained L3 VPNs. One way to support
such L3 VPNs is to carry MPLS LSPs interconnecting per-VPN VRFs
inside delay constrained TE tunnels interconnecting the PEs hosting
the VRFs.
_
Figure 2: L3 VPN with delay constraints
Planning, computing and provisioning of TE overlays to constrain
arbitrary SFCs, especially those that span multiple administrative
domains with each domain controlled by a separate controller, is a
very difficult challenge. Currently it is addressed by pre-
provisioning on the network of multiple TE tunnels with various TE
characteristics, and "nailing down" SFs/NFs to "strategic" locations
(e.g. nodes terminating many of such tunnels) in a hope that an
adequate set of tunnels could be found to carry the SFP of a given
TE-constrained SFC. Such an approach is especially awkward in the
case when some or all of the SFs/NFs are VNFs (i.e. could be
instantiated at multiple network locations).
SF/NF-aware TE topology model in combination with TE tunnel model
will allow for the network orchestrator (or a client controller) to
compute, set up and manipulate the TE overlays in the form of TE
tunnel chains (see Figure 3).
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Said chains could be duel-optimized compromising on optimal SF/NF
locations with optimal TE tunnels interconnecting them. The TE
tunnel chains (carrying multiple similarly constrained SFPs) could be
adequately constrained both at individual TE tunnel level and at the
chain end-to-end level.
_
Figure 3: SFC with TE constraints
C.4. SFC Protection and Load Balancing
Currently the combination of TE topology & tunnel models offers to a
network controller various capabilities to recover an individual TE
tunnel from network failures occurred on one or more network links or
transit nodes on the TE paths taken by the TE tunnel's connection(s).
However, there is no simple way to recover a TE tunnel from a failure
affecting its source or destination node. SF/NF-aware TE topology
model can decouple the association of a given SF/NF with its location
on the network topology by presenting multiple, identifiable as
mutually substitutable SFs/NFs hosted by different TE topology nodes.
So, for example, if it is detected that a given TE tunnel destination
node is malfunctioning or has gone out of service, the TE tunnel
could be re-routed to terminate on a different node hosting
functionally the same SFs/NFs as ones hosted by the failed node (see
Figures 6).
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This is in line with the ACTN edge migration and function mobility
concepts [RFC8453]. It is important to note that the described
strategy works much better for the stateless SFs/NFs. This is
because getting the alternative stateful SFs/NFs into the same
respective states as the current (i.e. active, affected by failure)
are is a very difficult challenge.
_
Figure 4: SFC recovery: SF2 on node NE1 fails
At the SFC level the SF/NF-aware TE topology model can offer SFC
dynamic restoration capabilities against failed/malfunctioning SFs/
NFs by identifying and provisioning detours to a TE tunnel chain, so
that it starts carrying the SFC's SFPs towards healthy SFs/NFs that
are functionally the same as the failed ones. Furthermore, multiple
parallel TE tunnel chains could be pre-provisioned for the purpose of
SFC load balancing and end-to-end protection. In the latter case
said parallel TE tunnel chains could be placed to be sufficiently
disjoint from each other.
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_
Figure 5: SFC recovery: SFC SF1-SF2-SF6 is recovered after SF2 on
node N1 has failed
_
Figure 6: SFC recovery: SFC SF1-SF2-SF6 is recovered after node N1
has failed
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C.5. Network Clock Synchronization
Many current and future network applications (including 5g and IoT
applications) require very accurate time services (PTP level, ns
resolution). One way to implement the adequate network clock
synchronization for such services is via describing network clocks as
NFs on an NF-aware TE topology optimized to have best possible delay
variation characteristics. Because such a topology will contain
delay/delay variation metrics of topology links and node cross-
connects, as well as costs in terms of delay/delay variation of
connecting clocks to hosting them node link and tunnel termination
points, it will be possible to dynamically select and provision bi-
directional time-constrained deterministic paths or trees connecting
clocks (e.g. grand master and boundary clocks) for the purpose of
exchange of clock synchronization information. Note that network
clock aware TE topologies separately provided by domain controllers
will enable multi-domain network orchestrator to set up and
manipulate the clock synchronization paths/trees spanning multiple
network domains.
C.6. Client - Provider Network Slicing Interface
3GPP defines network slice as "a set of network functions and the
resources for these network functions which are arranged and
configured, forming a complete logical network to meet certain
network characteristics" [I-D.defoy-netslices-3gpp-network-slicing]
[_3GPP.28.801]. Network slice could be also defined as a logical
partition of a provider's network that is owned and managed by a
tenant. SF/NF-aware TE topology model has a potential to support a
very important interface between network slicing clients and
providers because, on the one hand, the model can describe
holistically and hierarchically the client's requirements and
preferences with respect to a network slice functional, topological
and traffic engineering aspects, as well as of the degree of resource
separation/ sharing between the slices, thus allowing for the client
(up to agreed upon extent) to dynamically (re-)configure the slice or
(re-)schedule said (re-)configurations in time, while, on the other
hand, allowing for the provider to convey to the client the slice's
operational state information and telemetry the client has expressed
interest in.
C.7. Dynamic Assignment of Regenerators for L0 Services
On large optical networks, some of provided to their clients L0
services could not be provisioned as single OCh trails, rather, as
chains of such trails interconnected via regenerators, such as 3R
regenerators. Current practice of the provisioning of such services
requires configuration of explicit paths (EROs) describing identity
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and location of regenerators to be used. A solution is highly
desirable that could:
o Identify such services based, for example, on optical impairment
computations;
o Assign adequate for the services regenerators dynamically out of
the regenerators that are grouped together in pools and
strategically scattered over the network topology nodes;
o Compute and provision supporting the services chains of optical
trails interconnected via so selected regenerators, optimizing the
chains to use minimal number of regenerators, their optimal
locations, as well as optimality of optical paths interconnecting
them;
o Ensure recovery of such chains from any failures that could happen
on links, nodes or regenerators along the chain path.
NF-aware TE topology model (in this case L1 NF-aware L0 topology
model) is just the model that could provide a network controller (or
even a client controller operating on abstract NF-aware topologies
provided by the network) to realize described above computations and
orchestrate the service provisioning and network failure recovery
operations (see Figure 7).
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_
Figure 7: Optical tunnel as TE-constrained SFC of 3R regenerators.
Red trail (not regenerated) is not optically reachable, but blue
trail (twice regenerated) is
C.8. Dynamic Assignment of OAM Functions for L1 Services
OAM functionality is normally managed by configuring and manipulating
TCM/MEP functions on network ports terminating connections or their
segments over which OAM operations, such as performance monitoring,
are required to be performed. In some layer networks (e.g.
Ethernet) said TCMs/MEPs could be configured on any network ports.
In others (e.g. OTN/ODUk) the TCMs/MEPs could be configured on some
(but not all network ports) due to the fact that the OAM
functionality (i.e. recognizing and processing of OAM messages,
supporting OAM protocols and FSMs) requires in these layer networks
certain support in the data plane, which is not available on all
network nodes. This makes TCMs/MEPs good candidates to be modeled as
NFs. This also makes TCM/MEP aware topology model a good basis for
placing dynamically an ODUk connection to pass through optimal OAM
locations without mandating the client to specify said locations
explicitly.
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_
Figure 8: Compute/storage resource aware topology
C.9. SFC Abstraction and Scaling
SF/NF-aware topology may contain information on native SFs/NFs (i.e.
SFs/NFs as known to the provider itself) and/or abstract SFs/NFs
(i.e. logical/macro SFs/NFs representing one or more SFCs each made
of native and/or lower level abstract SFs/NFs). As in the case of
abstracting topology nodes, abstracting SFs/NFs is hierarchical in
nature - the higher level of SF/NF-aware topology, the "larger"
abstract SFs/NFs are, i.e. the larger data plane SFCs they represent.
This allows for managing large scale networks with great number of
SFs/NFs (such as Data Center interconnects) in a hierarchical, highly
scalable manner resulting in control of very large number of flat in
the data plane SFCs that span multiple domains.
C.10. Dynamic Compute/VM/Storage Resource Assignment
In a distributed data center network, virtual machines for compute
resources may need to be dynamically re-allocated due to various
reasons such as DCI network failure, compute resource load balancing,
etc. In many cases, the DCI connectivity for the source and the
destination is not predetermined. There may be a pool of sources and
a pool of destination data centers associated with re-allocation of
compute/VM/storage resources. There is no good mechanism to date to
capture this dynamicity nature of compute/VM/storage resource
reallocation. Generic Compute/VM/Storage resources can be described
and announced as a SF, where a DC hosting these resources can be
modeled as an abstract node. Topology interconnecting these abstract
nodes (DCs) in general is of multi-domain nature. Thus, SF-aware
topology model can facilitate a joint optimization of TE network
resources and Compute/VM/Storage resources and solve Compute/VM/
Storage mobility problem within and between DCs (see Figure 8).
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C.11. Application-aware Resource Operations and Management
Application stratum is the functional grouping which encompasses
application resources and the control and management of these
resources. These application resources are used along with network
services to provide an application service to clients/end-users.
Application resources are non-network resources critical to achieving
the application service functionality. Examples of application
resources include: caches, mirrors, application specific servers,
content, large data sets, and computing power. Application service
is a networked application offered to a variety of clients (e.g.,
server backup, VM migration, video cache, virtual network on-demand,
5G network slicing, etc.). The application servers that host these
application resources can be modeled as an abstract node. There may
be a variety of server types depending on the resources they host.
Figure 9 shows one example application aware topology for video cache
server distribution.
_
Figure 9: Application aware topology
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C.12. IANA Considerations
This document has no actions for IANA.
C.13. Security Considerations
This document does not define networking protocols and data, hence is
not directly responsible for security risks.
C.14. Acknowledgements
The authors would like to thank Maarten Vissers, Joel Halpern, and
Greg Mirsky for their helpful comments and valuable contributions.
Authors' Addresses
Igor Bryskin
Individual
EMail: i_bryskin@yahoo.com
Xufeng Liu
Volta Networks
EMail: xufeng.liu.ietf@gmail.com
Young Lee
Sung Kyun Kwan University
EMail: younglee.tx@gmail.com
Jim Guichard
Huawei Technologies
EMail: james.n.guichard@huawei.com
Luis Miguel Contreras Murillo
Telefonica
EMail: luismiguel.contrerasmurillo@telefonica.com
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Daniele Ceccarelli
Ericsson
EMail: daniele.ceccarelli@ericsson.com
Jeff Tantsura
Apstra Networks
EMail: jefftant.ietf@gmail.com
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