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Internet Engineering Task Force D. King
Internet-Draft Old Dog Consulting
Intended status: Informational A. Farrel
Expires: June 2, 2013 Juniper Networks
December 2, 2012
A PCE-based Architecture for Application-based Network Operations
draft-farrkingel-pce-abno-architecture-00.txt
Abstract
Services such as content distribution, distributed databases, or
inter-data center connectivity place a set of new requirements on the
operation of networks. They need on-demand and application-specific
reservation of network connectivity, reliability, and resources (such
as bandwidth). An environment that operates to meet this type of
requirement is said to have Application-Based Network Operations
(ABNO).
ABNO brings together several existing technologies for gathering
information about the resources available in a network, for
consideration of topologies and how those topologies map to
underlying network resources, for requesting path computation, and
for provisioning or reserving network resources. Thus, ABNO may be
seen as the use of a toolbox of existing components enhanced with a
few new elements. The key component within an ABNO is the Path
Computation Element (PCE), which can be used for computing paths and
is further extended to provide policy enforcement capabilities for
ABNO.
This document describes an architecture and framework for ABNO
showing how these components fit together. It provides a cookbook of
existing technologies to satisfy the architecture and meet the needs
of the applications.
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 http://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 April 5, 2013.
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Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://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 ................................................ 2
1.1 Scope ..................................................... 4
2. Application-based Network Operations (ABNO) .................. 4
2.1 Assumptions and Requirements .............................. 4
2.2 Generic Architecture ...................................... 5
2.2.1 ABNO Components ........................................ 6
2.2.2 ABNO Functional Interfaces ............................ 10
3. ABNO Use Cases .............................................. 16
3.1 Inter-AS Connectivity ..................................... 16
3.2 Multi-Layer Networking .................................... 22
3.3 Bandwidth Scheduling ...................................... 25
3.4 Grooming and Regrooming ................................... 26
3.5 Global Concurrent Optimization ............................ 26
3.6 Adaptive Network Planning ................................. 26
4. Security Consideration ...................................... 26
5. IANA Considerations ......................................... 26
6. References .................................................. 26
6.1 Informative References ................................... 26
7. Authors' Addresses .......................................... 29
A. Undefined Interfaces ........................................ 30
1. Introduction
Networks today integrate multiple technologies allowing network
infrastructure to deliver a variety of services to support the
different characteristics and demands of applications. There is an
increasing demand to make the network responsive to service requests
issued directly from the application layer. This differs from the
established model where services in the network are delivered in
response to management commands driven by a human user.
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These application-driven requests and the services they establish
place a set of new requirements on the operation of networks. They
need on-demand and application-specific reservation of network
connectivity, reliability, and resources (such as bandwidth). An
environment that operates to meet this type of application-aware
requirement is said to have Application-Based Network Operation
(ABNO).
The Path Computation Element (PCE) [RFC4655] was developed to provide
path computation services for GMPLS and MPLS networks. The
applicability of PCE can be extended to provide path computation and
policy enforcement capabilities for ABNO platforms and services.
ABNO can provide the following types of service to applications by
coordinating the components that operate and manage the network:
- Optimization of traffic flows between applications to create an
overlay network for communication in use cases such as file
sharing, data caching or mirroring, media streaming, or real-time
communications described as Application Layer Traffic Optimization
(ALTO) [RFC5693].
- Remote control of network components allowing coordinated
programming of network resources through such techniques as
Forwarding and Control Element Separation (ForCES) [RFC3746],
OpenFlow [ONF], and the Interface to the Routing System (I2RS)
[I-D.ward-irs-framework].
- Interconnection of Content Delivery Networks (CDNi) [RFC6707]
through the establishment and resizing of connections between
content distribution networks.
- Network resource coordination to facilitate grooming and
regrooming, bandwidth scheduling, and global concurrent
optimization [RFC5557].
- Virtual Private Network (VPN) planning in support of deployment of
new VPN customers and to facilitate inter-data center connectivity.
This document outlines the architecture and use cases for ABNO, and
shows how the ABNO architecture can be used for co-ordinating control
system and application requests to compute paths, enforce policies,
and manage network resources for the benefit of the applications that
use the network. The examination of the use cases shows the ABNO
architecture as a toolkit comprising many existing components and
protocols and so this document looks like a cookbook.
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1.1 Scope
This document describes a toolkit. It shows how existing functional
components described in a large number of separate documents can be
brought together within a single architecture to provide the function
necessary for ABNO.
In many cases, existing protocols are known to be good enough or
almost good enough to satisfy the requirements of interfaces between
the components. In these cases the protocols are called out as
suitable candidates for use within an implementation of ABNO.
In other cases it is clear that further work will be required, and in
those cases a pointer to on-going work that may be of use will be
provided.
Thus, this document may be seen as providing an applicability
statement for existing protocols, and guidance for developers of new
protocols or protocol extensions.
2. Application Based Network Operations (ABNO)
2.1 Assumptions
The principal assumption underlying this document is that existing
technologies should be used where they are adequate for the task.
Furthermore, when an existing technology is almost sufficient, it is
assumed to be preferable to make minor extensions rather than to
invent a whole new technology.
Note that this document describes an architecture. Functional
components are architectural concepts and have distinct and clear
responsibilities. Pairs of functional components interact at
functional interfaces that are, themselves, architectural concepts.
It is not intended that this architecture constrains implementations.
For example, a stateful and active PCE could be implemented as a
single a server combining the ABNO components of the PCE, the Traffic
Engineering Database, and the Resource Manager (see Section 2.2).
However, the separation of the ABNO functions into separate
functional components with clear interfaces between them enables
implementations to choose which features to include and allows
different functions to be distributed across distinct processes or
even processors.
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2.2 Generic ABNO Architecture
The following diagram illustrates the ABNO architecture. The
components and functional interfaces are discussed in Sections 2.2.1
2.2.2 respectively. The use cases described in Section 3 show how
different components are used selectively to provide different
services.
+--------------------------------------------------------------+
| OSS / NMS |
+-+-----+----+-----------+------------------+----------------+-+
| | | | | |
| | | | +--------------+--------------+ |
| | | | | Application Service | |
| | | | | Coordinator | |
| | | | +-----------+---------------+-+ |
| | | | | | |
+--|-----|----|-----------|---------------|---------------|---|---+
| | | | +----+---------------+------+ | | |
| | | +--+---+ | | +-+---+-+ |
| | | |Policy+--+ ABNO Controller +------+ | |
| | | |Agent | | +--+ | OAM | |
| | | +--+---+ +-+------------+----------+-+ | |Handler| |
| | | | | | | | | | |
| | | | +----+-+ +-------+-------+ | | +---+---+ |
| | | +---+ VNTM |--+ | | | | |
| | | +--+-+-+ | | | +--+---+ | |
| | | | | | PCE | | | I2RS | | |
| | +--+---+ | | | | | |Client| | |
| | | +-------+ | | | | +-+--+-+ | |
| | | TEDs +---------:----+ | | | | | |
| | | | | +-+-----+-------+ | | | | |
| | +-+--+-+ | | | | | | | |
| | | | +-+------------+----------+-+ | | | |
| | | | | Resource Manager | | | | |
| | | | +-----------------+---+-----+ | | | |
+--|----|--|------------------|--------|---|-------|--|-----|-----+
| | | | | | | | |
| +---+------------------+--------+-----------+----+ |
+--/ Client Network Layer \--+
| +----------------------------------------------------+ |
| | | | |
+-+----+----------------------------------+----------+-----+-+
/ Server Network Layers \
+----------------------------------------------------------------+
Figure 1: Generic ABNO Architecture
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2.2.1 ABNO Components
This section describes the functional components shown as boxes in
Figure 1. The interactions between those components, that is the
functional interfaces, are described in Section 2.2.2.
2.2.1.1 NMS and OSS
A Network Management Station (NMS) or an Operations Support System
(OSS) can be used to control, operate, and manage a network. Within
the ABNO architecture, an NMS or OSS may issue high-level service
requests to the ABNO controller. It may also establish policies for
the activities of the components within the architecture.
The NMS and OSS can be consumers of network events reported through
the OAM handler and can act on these reports as well as displaying
them to users and raising alarms. The NMS and OSS can also access
the Traffic Engineering Database (TED) to show the users the current
state of the network.
Lastly, the NMS and OSS may utilize a direct programmatic or
configuration interface to interact with the network elements within
the network.
2.2.1.2 Application Service Coordinator
In addition to the NMS and OSS, services in the ABNO architecture
may be requested by or on behalf of applications. In this context
the term "application" is very broad. An application may be a
program that runs on a host or server and that provides services to a
user, such as video conferencing application. Alternatively, an
application may be a software tool with which a user makes requests
of the network to set up specific services such as end-to-end
connections or scheduled bandwidth reservations. Finally, an
application may be a sophisticated control system that is responsible
for arranging the provision of a more complex network service such as
a virtual private network.
For the sake of this architecture, all of these concepts of an
application are grouped together and are shown as the Application
Service Coordinator since they are all in some way responsible for
coordinating the activity of the network to provide services for use
by applications.
The Application Service Coordinator communicates with the ABNO
Controller to request operations on the network.
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2.2.1.3 ABNO Controller
The ABNO Controller is the main gateway to the network for the NMS,
OSS, and the Application Service Coordinator for the provision of
advanced network coordination and functions. The ABNO Controller
governs the behavior of the network in response to changing network
conditions and in accordance with application network requirements
and policies.
The use cases in Section 3 provide a clearer picture of how the
ABNO Controller interacts with the other components in the ABNO
architecture.
2.2.1.4 Policy Agent
Policy plays a very important role in the control and management of
the network. It is therefore significant in influencing how the key
components of the ANBO architecture operate.
Figure 1 shows the Policy Agent as a component that is configured
by the NMS/OSS with the policies that it applies. The Policy Agent
is possible for propagating those policies into the other components
of the system.
Simplicity in the figure necessitates leaving out many of the policy
interactions that will take place. Although the Policy Agent is only
shown interacting with the ABNO Controller and the Virtual Network
Topology Manager (VNTM), it will also interact with the Path
Computation Element (PCE), the Interface to the Routing System (I2RS)
Client, and the network elements themselves.
2.2.1.5 Interface to the Routing System (I2RS) Client
The Interface to the Routing System (I2RS) is described in
[I-D.ward-irs-framework]. The interface provides a programmatic way
to access (for read and write) the the routing state and policy
information on routers in the network.
The I2RS Client is introduced in [I-D.atlas-irs-problem-statement].
Its purpose is to manage information requests across a number of
routers (each of which runs an I2RS Server) and coordinate setting
or gathering state to/from those routers.
2.2.1.6 OAM Handler
Operations, Administration, and Maintenance (OAM) plays a critical
role in understanding how a network is operating, detecting faults,
and taking the necessary action to react to problems in the network.
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Within the ABNO architecture, the OAM Handler is responsible for
receiving notifications (often called alerts) from the network about
potential problems, for correlating them, and for triggering other
components of the system to take action to preserve or recover the
services that were established by the ABNO Controller. The OAM
Handler also reports network problems and, in particular, service-
affecting problems to the NMS, OSS, and Application Service
Coordinator.
Additionally, the OAM Handler interacts with the devices in the
network to initiate OAM actions within the data plane such as
monitoring and testing.
2.2.1.7 Path Computation Element (PCE)
The Path Computation Element (PCE) is introduced in [RFC4655]. It is
a functional component that services requests to compute paths across
a network graph. In particular, it can generate traffic engineered
routes for MPLS-TE and GMPLS Label Switched Paths (LSPs). The PCE
may receive these requests from the ABNO Controller, from the Virtual
Network Topology Manager, or from network elements themselves.
The PCE operates on a view of the network topology stored in the
Traffic Engineering Database (TED). A more sophisticated computation
may be provided by a Stateful PCE that enhances the TED with
information about the LSPs that are provisioned and operational
within the network as described in [RFC4655] and
[I-D.ietf-pce-stateful-pce].
Additional function in an Active PCE allows a functional component
that includes a Stateful PCE to make provisioning requests to set up
new services or to modify in-place services as described in
[I-D.crabbe-pce-pce-initiated-lsp]. This function may directly
access the network elements, or may be channelled through the
Resource Manager.
Coordination between multiple PCEs operating on different TEDs can
prove useful for performing path computation in multi-domain (for
example, inter-AS) or multi-layer networks.
Since the PCE is a key component of the ABNO architecture, a better
view of its role can be gained by examining the use cases described
in Section 3.
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2.2.1.8 Traffic Engineering Database (TED)
The Traffic Engineering Database (TED) is data store of topology
information about a network that may be enhanced with capability
data (such as metrics or bandwidth capacity) and active status
information (such as up/down status or residual unreserved
bandwidth).
The TED may be built from information supplied by the network or
from data (such as inventory details) sourced through the NMS/OSS.
The principal use of the TED in the ABNO architecture is to provide
the raw data on which the Path Computation Element operates. But
the TED may also be inspected by users at the NMS/OSS to view the
current status of the network, and may provide information to
application services such as Application Layer Traffic Optimization
(ALTO) [RFC5693].
2.2.1.9 Virtual Network Topology Manager (VNTM)
A Virtual Network Topology (VNT) is defined in [RFC5212] as a set of
one or more LSPs in one or more lower-layer networks that provides
information for efficient path handling in an upper-layer network.
For instance, a set of LSPs in a wavelength division multiplexed
(WDM) network can provide connectivity as virtual links in a higher-
layer packet switched network.
The VNT enhances the physical/dedicated links that are available in
the upper-layer network and is configured by setting up or tearing
down the lower-layer LSPs and by advertising the changes into the
higher-layer network. The VNT can be adapted to traffic demands so
that capacity in the higher-layer network can be created or released
as needed. Releasing unwanted VNT resources makes them available in
the lower-layer network for other uses.
The creation of virtual topology for inclusion in a network is not a
simple task. Decisions must be made about which nodes in the upper-
layer it is best to connect, in which lower-layer network to
provision LSPs to provide the connectivity, and how to route the LSPs
in the lower-layer network. Furthermore, some specific actions have
to be taken to cause the lower-layer LSPs to be provisioned and the
connectivity in the upper-layer network to be advertised.
All of these actions and decisions are heavily influenced by policy,
so the Virtual Network Topology Manager (VNTM) [RFC5623] component
that coordinates them takes input from the Policy Agent. The VNTM is
also closely associated with the PCE for the upper-layer network and
each of the PCEs for the lower-layer networks.
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2.2.1.10 Resource Manager
The Resource Manager is responsible for making or channelling
requests for the establishment of LSPs. This may be instructions to
the control plane running in the networks, or may involve the
programming of individual network devices. In the latter case, the
Resource Manager may act as an OpenFlow Controller [ONF].
See Section 2.2.2.6 for more details of the interactions between the
Resource Manager and the network.
2.2.1.11 Client and Server Network Layers
The client and server networks are shown in Figure 1 as illustrative
examples of the fact that the ABNO architecture may be used to
coordinate services across multiple networks where lower-layer
networks provide connectivity in upper-layer networks.
Section 3.2 describes a use case for multi-layer networking.
2.2.2 Functional Interfaces
This section describes the interfaces between functional components
that might be externalized in an implementation allowing the
components to be distributed across platforms. Where existing
protocols might provide all or most of the necessary capabilities
they are noted.
2.2.2.1 Configuration and Programmatic Interfaces
The network devices may be configured or programmed direct from the
NMS/OSS. Many protocols already exist to perform these functions
including:
- SNMP [RFC3412]
- Netconf [RFC6241]
- ForCES [RFC5810]
- OpenFlow [ONF].
From the ABNO perspective, network configuration is a pass-through
function. It can be seen represented on the left hand side of
Figure 1.
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2.2.2.2 TED Construction from the Networks
As described in Section 2.2.1.8, the Traffic Engineering Database
(TED) provides details of the capabilities of the network for use by the ABNO system and the PCE in particular.
The TED can be constructed by participating in the IGP-TE protocols
run by the networks (for example, OSPF-TE [RFC3630] and ISIS-TE
[RFC5305]). Alternatively, the TED may be fed using link-state
distribution extensions to BGP [I-D.ietf-idr-ls-distribution].
The ABNO system may maintain a single TED unified across multiple
networks, or may retain a separate TEDs for each network.
Additionally, an ALTO Server [RFC5693] may provide an abstracted
topology from a network to build an application-level TED that can
be used by a PCE to compute paths between servers and application-
layer entities for the provision of application services.
2.2.2.3 TED Enhancement
The TED may be enhanced by inventory information supplied from the
NMS/OSS. This may supplement the data collected as described in
Section 2.2.2.2 with information that is not normally distributed
within the network such as node types and capabilities, or the
characteristics of optical links.
No protocol is currently identified for this interface, but the
Interface to the Routing System (I2RS) protocol
[I-D.ward-irs-framework] may be a suitable candidate because it is
designed to distribute bulk routing state information in a well-
defined encoding language. Another candidate protocol may be
Netconf [RFC6241] passing data encoded using YANG [RFC6020].
2.2.2.4 TED Presentation
The TED may be presented north-bound from the ABNO system for use by
an NMS/OSS or by the Application Service Coordinator. This allows
users and applications to get a view of the network topology and the
status of the network resources. It also allows planning and
provisioning of application services.
There are several protocols available for exporting the TED north-
bound:
- The ALTO protocol [I-D.ietf-alto-protocol] is deigned to distribute
the abstracted topology used by an ALTO Server and may prove useful
for exporting the TED.
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- The same protocol used to export topology information from the
network can be used to export the topology from the TED.
[I-D.ietf-idr-ls-distribution].
- The Interface to the Routing System (I2RS) [I-D.ward-irs-framework]
will require a protocol that is capable of handling bulk routing
information exchanges that would be suitable for exporting the TED.
2.2.2.5 Network Making Path Computation Requests
As originally specified in the PCE architecture [RFC4655], network
elements can make path computation requests to a PCE using the PCE
protocol (PCEP) [RFC5440]. This facilitates the network setting up
LSPs in response to simple connectivity requests, and it allows the
network to re-optimize or repair LSPs.
2.2.2.6 Resource Manager Control of Networks
As described in Section 2.2.1.10, the Resource Manager makes or
channels requests to provision resources in the network. These
operations can take place at two levels: there can be requests to
program/configure specific resources in the data or forwarding
planes; and there can be requests to trigger a set of actions to be
programmed with the assistance of a control plane.
A number of protocols already exist to provision network resources as
follows:
- Program/configure specific network resources
- ForCES [RFC5810] defines a protocol for separation of the control
element (the Resource Manager) from the forwarding elements in
each node in the network.
- The Generic Switch Management Protocol (GSMP) [RFC3292] is an
asymmetric protocol that allows one or more external switch
controllers (such as the Resource Manager) to establish and
maintain the state of a label switch such as an MPLS switch.
- OpenFlow [ONF] is is a communications protocol that gives an
OpenFlow Controller (such as the Resource Manager) access to the
forwarding plane of a network switch or router in the network.
- Historically, other configuration-based mechanisms have been used
to set up the forwarding/switching state at individual nodes
within networks. Such mechanisms have ranged from non-standard
command line interfaces (CLIs) to various standards-based options
such as TL1 [TL1] and SNMP [RFC3412]. These mechanisms are not
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designed for rapid operation of a network and are not easily
programmatic. They are not proposed for use by the Resource
Controller as part of the ABNO architecture.
- Netconf [RFC6241] provides a more active configuration protocol
that may be suitable for bulk programming of network resources.
Its use in this way is dependent on suitable YANG modules being
defined for the necessary options. Early work in the IETF's
Netmod working group is focused on a higher level of routing
function more comparable with the function discussed in Section
2.2.2.8 [I-D.draft-ietf-netmod-routing-cfg].
- Trigger actions through the control plane
- LSPs can be requested using a management system interface to the
head end of the LSP using tools such as CLIs, TL1 [TL1] or SNMP
[RFC3412]. Configuration at this granularity is not as time-
critical as when individual network resources are programmed
because the main task of programming end-to-end connectivity is
devolved to the control plane. Nevertheless, these mechanisms
remain unsuitable for programmatic control of the network and are
not proposed for use by the Resource Controller as part of the
ABNO architecture.
- As noted above, Netconf [RFC6241] provides a more active
configuration protocol. This may be particularly suitable for
requesting the establishment of LSPs. Work would be needed to
complete a suitable YANG module.
- The PCE protocol (PCEP) [RFC5440] has been proposed as a suitable
protocol for requesting the establishment of LSPs
[I-D.crabbe-pce-pce-initiated-lsp]. This works well because the
protocol elements necessary are exactly the same as used to
respond to a path computation request.
The functional element that issues PCEP requests to establish
LSPs is known as an "Active PCE", however it should be noted that
the ABNO functional components responsible for requesting LSPs
are more likely to be the Resource Manager, the Virtual Network
Topology Manager, and the ABNO Controller itself.
Note that the I2RS does not provide a mechanism for control of
network resources at this level as it is designed to provide control
of routing state in routers, not forwarding state in the data plane.
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2.2.2.7 Auditing the Network
Once resources have been provisioned or connections established in
the network, it is important that the ABNO system can determine the
state of the network. This function falls into four categories:
- Updates to the TED are gathered as described in Section 2.2.2.2.
- OAM can be commissioned and the results inspected by the OAM
Handler as described in Section 2.2.2.13.
- Explicit notification of the successful establishment and the
subsequent state of LSP can be provided through extensions to PCEP
as described in [I-D.ietf-pce-stateful-pce] and
[I-D.crabbe-pce-pce-initiated-lsp].
- ABNO components can may make enquiries and inspect network state
through I2RS or using Netconf.
2.2.2.8 Controlling The Routing System
As discussed in Section 2.2.1.5, the Interface to the Routing System
(I2RS) provides a programmatic way to access (for read and write) the
routing state and policy information on routers in the network. The
I2RS Client issues requests to routers in the network to establish or
retrieve routing state. Those requests utilize the I2RS protocol
which has yet to be selected/designed by the IETF.
2.2.2.9 ABNO Controller Interface to PCE
The ABNO controller needs to be able to consult the PCE to determine
what services can be provisioned in the network. There is no reason
why this interface cannot be based on the standard PCE protocol as
defined in [RFC5440].
2.2.2.10 VNTM Interface to and from PCE
There are two interactions between the Virtual Network Topology
Manager and the PCE.
The first interaction is used when VNTM wants to determine what LSPs
can be set up in a network: in this case it uses the standard PCEP
interface [RFC5440] to make path computation requests.
The second interaction arises when a PCE determines that it cannot
compute a requested path or notices that (according to some
configured policy) a network is short of resources (for example, the
capacity on some key link is close to exhausted). In this case, the
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PCE may notify the VNTM which may (again according to policy) act to
construct more virtual topology. This second interface is not
currently specified although it may be that the I2RS protocol
provides suitable features.
2.2.2.11 ABNO Control Interfaces
The north-bound interface from the ABNO controller is used by the
NMS, OSS, and Application Service Coordinator to request services in
the network in support of applications. The interface will also need
to be able to report the asynchronous completion of service requests
and convey changes in the status of services.
This interface will also need strong capabilities for security,
authentication, and policy.
This interface is not currently specified. It needs to be a
transactional interface that supports the specification of abstract
services with adequate flexibility to facilitate easy extension and
yet be concise and easily parsable.
It is possible that the I2RS protocol (see Section 2.2.2.8) will
support the necessary features.
2.2.2.12 Policy Interfaces
As described in Section 2.2.1.4 and throughout this document, policy
forms a critical component of the ABNO architecture. The role of
policy will include enforcing the following rules and requirements:
- Adding resources on demand should be gated by the authorized
capability.
- Client microflows should not trigger server-layer setup or
allocation.
- Accounting capabilities should be supported.
- Security mechanisms for authorization of requests and capabilities
are required.
Various policy-capable architectures have been defined including a
framework for using policy with a PCE-enabled system [RFC5394].
However, the take-up of the IETF's Common Open Policy Service
protocol (COPS) [RFC2748] has been poor.
New work will be needed to define all of the policy interfaces within
the ABNO architecture. There is some discussion that the I2RS
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protocol may support the configuration and manipulation of policies.
2.2.2.13 OAM and Reporting
The OAM Handler must interact with the networks to perform several
actions:
- Enabling OAM function within the network.
- Performing proactive OAM operations in the network.
- Receiving notifications of network events.
Any of the configuration and programmatic interfaces described in
Section 2.2.2.1 may serve this purpose, although neither Netconf nor
OpenFlow currently supports asynchronous notifications. Additionally
Syslog [RFC5424] is a protocol for reporting events from the network,
and IPFIX [RFC5101] is designed to allow network statistics to be
aggregated and reported.
The OAM Handler also correlates events reported from the network and
reports them onward to the ABNO Controller (which can apply the
information to the recovery of services that it has provisioned) and
to the NMS, OSS, and Application Service Coordinator. The reporting
mechanism used here can be essentially the same as used when events
are reported from the network and no new protocol is needed.
3. ABNO Use Case
This section provides a number of examples of how the ABNO
architecture can be applied to provide application and NMS/OSS driven
network operations.
3.1 Inter-AS Connectivity
The following use case describes how the ABNO framework can be used
set up an end-to-end service across multiple Autonomous Systems
(ASes). Consider the simple network topology shown in Figure 2. The
three ASes (ASa, ASb, and ASc) are connected as ASBRs a1, a2, b1
through b4, c1 and c2. A source node (s) located in ASa is to be
connected to a destination node (d) located in ASc. The optimal path
for the LSP from s to d must be computed, and then the network must
be triggered to set up the LSP.
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+--------------+ +-----------------+ +--------------+
|ASa | |ASb | |ASc |
| | | | | |
| +--+ | | +--+ +--+ | | +--+ |
| |a1|-|-|-|b1| |b3|-|-|-|c1| |
| +-+ +--+ | | +--+ +--+ | | +--+ +-+ |
| |s| | | | | |d| |
| +-+ +--+ | | +--+ +--+ | | +--+ +-+ |
| |a2|-|-|-|b2| |b4|-|-|-|c2| |
| +--+ | | +--+ +--+ | | +--+ |
| | | | | |
+--------------+ +-----------------+ +--------------+
Figure 2: Inter-AS Domain Topology with H-PCE (Parent PCE)
In the ABNO architecture, the following steps are performed to
deliver the service.
1. Request Management
As shown in Figure 3, the NMS/OSS issues a request to the ABNO
Controller for a path between s and d. The ABNO Controller
verifies that the NMS/OSS has sufficient rights to make the
service request.
+---------------------+
| NMS/OSS |
+----------+----------+
|
V
+--------+ +-----------+-------------+
| Policy +-->-+ ABNO Controller |
| Agent | | |
+--------+ +-------------------------+
Figure 3: ABNO Request Management
2. Service Path Computation with Hierarchical PCE
The ABNO Controller needs to determine an end-to-end path for the
LSP. Since the ASes will want to maintain a degree of
confidentiality about their internal resources and topology, they
will not share a TED and each will have its own PCE. In such a
situation, the Hierarchical PCE (H-PCE) architecture described in
[RFC6805] is applicable.
As shown in Figure 4, the ABNO Controller sends a request to the
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parent PCE for an end-to-end path. As described in [RFC6805], the
parent PCE consults is TED that shows the connectivity between
ASes. This helps it understand that the end-to-end path must
cross each of ASa, ASb, and ASc, so it is sends individual path
computation requests to each of PCE a, b, and c to determine the
best options for crossing the ASes.
+-----------------+
| ABNO Controller |
+----+-------+----+
| A
V |
+--+-------+--+ +--------+
+--------+ | | | |
| Policy +-->-+ Parent PCE +---+ AS TED |
| Agent | | | | |
+--------+ +-+----+----+-+ +--------+
/ | \
/ | \
+-----+-+ +---+---+ +-+-----+
| | | | | |
| PCE a | | PCE b | | PCE c |
| | | | | |
+---+---+ +---+---+ +---+---+
| | |
+--+--+ +--+--+ +--+--+
| TEDa| | TEDb| | TEDc|
+-----+ +-----+ +-----+
Figure 4: Path Computation Request with Hierarchical PCE
Each child PCE applies policy to the requests is receives to
determine whether the request is to be allowed and to select the
type of networks resources that can be used in the computation
result. For confidentiality reasons, each child PCE may supply
its computation responses using a path key [RFC5520] to hide the
details of the path segment it has computed.
The parent PCE collates the responses from the children and
applies its own policy to stitch them together into the best end-
to-end path which it returns as a response to the ABNO Controller.
3. Provisioning the End-to-End LSP
There are several options for how the end-to-end LSP gets
provisioned in the ABNO architecture. Some of these are described
below.
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3a. Provisioning from the ABNO Controller With a Control Plane
Figure 5 shows how the ABNO controller makes a request through
the Resource Manager to establish the end-to-end LSP. As
described in Section 2.2.2.6 these interactions can use the
Netconf protocol [RFC6241] or the extensions to PCEP described
in [I-D.crabbe-pce-pce-initiated-lsp]. In either case, the
provisioning request is sent to the head end Label Switching
Router (LSR) and it signals in the control plane (using a
protocol such as RSVP-TE [RFC3209]) so cause the LSP to be
established.
+-----------------+
| ABNO Controller |
+--------+--------+
|
V
+-----+-----+
| Resource |
| Manager |
+-----+-----+
|
V
+--------------------+------------------------+
/ Network \
+-------------------------------------------------+
Figure 5: Provisioning the End-to-End LSP
3b. Provisioning through Programming Network Resources
Another option is that the LSP is provisioned hop by hop from
the Resource Manager using ForCES [RFC5810] or OpenFlow [ONF]
as described in Section 2.2.2.6. In this case, the picture is
the same as shown in Figure 5. The interaction between the
ABNO Controller and the Resource Manager will be PCEP or
Netconf as described in option 3a., and the Resource Manager
will have the responsibility to fan out the requests to the
individual network elements.
3c. Provisioning with an Active PCE
The active PCE is described in Section 2.2.1.7 based on the
concepts expressed in [I-D.crabbe-pce-pce-initiated-lsp]. In
this approach, the process described in 3a is modified such
that the PCE issues a PCEP command to the network direct
without a response being first returned to the ABNO
Controller.
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This situation is shown in Figure 6, and could be modified so
that the Resource Manager still programs the individual
network elements as described in 3b.
+-----------------+
| ABNO Controller |
+----+------------+
|
V
+--+----------+ +-----------+
+--------+ | | | Resource |
| Policy +-->-+ Parent PCE +---->----+ Manager |
| Agent | | | | |
+--------+ +-+----+----+-+ +-----+-----+
/ | \ |
/ | \ |
+-----+-+ +---+---+ +-+-----+ V
| | | | | | |
| PCE a | | PCE b | | PCE c | |
| | | | | | |
+-------+ +-------+ +-------+ |
|
+--------------------------------+------------+
/ Network \
+-------------------------------------------------+
Figure 6: LSP Provisioning with an Active PCE
3d. Provisioning with Active Child PCEs and Segment Stitching
A mixture of the approaches described in 3b and 3c can result
in a combination of mechanisms to program the network to
provide the end-to-end LSP. Figure 7 shows how each child PCE
can be an active PCE responsible for setting up an edge-to-
edge LSP segment across one of the ASes. The ABNO Controller
then uses the Resource Manager to program the inter-AS
connections using ForCES or OpenFlow and the LSP segments are
stitched together following the ideas described in [RFC5150].
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+-----------------+
| ABNO Controller +-------->--------+
+----+-------+----+ |
| A |
V | |
+--+-------+--+ |
+--------+ | | |
| Policy +-->-+ Parent PCE | |
| Agent | | | |
+--------+ ++-----+-----++ |
/ | \ |
/ | \ |
+---+-+ +--+--+ +-+---+ |
| | | | | | |
|PCE a| |PCE b| |PCE c| |
| | | | | | V
+--+--+ +--+--+ +--+--+ |
| | | |
V V V |
+--------+ +--------+ +--------+ |
|Resource| |Resource| |Resource| |
|Manager | |Manager | |Manager | |
+-+------+ +---+----+ +------+-+ |
| | | |
V V V |
+------+-+ +----+---+ +--+-----+ |
/ AS a \=====/ AS b \=====/ AS c \ |
+------------+ A +------------+ A +------------+ |
| | |
+-----+----------------+-----+ |
| Resource Manager +----<-------+
+----------------------------+
Figure 7: LSP Provisioning With Active Child PCEs and Stitching
4. Verification of Service
The ABNO Controller will need to ascertain that the end-to-end LSP
has been set up as requested. In the case of a control plane
being used to establish the LSP, the head end LSR may send a
notification (perhaps using PCEP) to report successful setup, but
to be sure that the LSP is up, the ABNO Controller will request
the OAM Handler to perform Continuity Check OAM in the Data Plane
and report back that the LSP is ready to carry traffic.
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5. Notification of Service Fulfillment
Finally, when the ABNO Controller is satisfied that the requested
service is ready to carry traffic, it will notify the NMS/OSS.
3.2 Multi-Layer Networking
Networks typically comprise of multiple layers. These layers
represent separations of administrative regions, technology, and may
also represent a distinction between client and server networking
roles.
It is preferable to coordinate network resource control and
utilization (i.e., consideration and control of multiple layers),
rather than controlling and optimizing resources at each layer
independently. This facilitates network efficiency and network
automation, and may be defined as inter-layer traffic engineering.
The PCE architecture supports inter-layer traffic engineering
[RFC5623] and, in combination with the ABNO architecture, provides a
suite of capabilities for network resource coordination across
multiple layers.
The following use case demonstrates ABNO used to coordinate
allocation of server-layer network resources to create virtual
topology in a client-layer network in order to satisfy a request for
end-to-end client-layer connectivity. Consider the simple multi-
layer network in Figure 8. There are six packet-layer routers (P1
through P6) and three optical-layer lambda switches (L1 through L3).
There is connectivity in the packet layer between routers P1, P2, and
P3, and also between routers P4, P5, and P6, but there is no packet-
layer connectivity between these two islands of routers perhaps
because of a network failure or perhaps because all existing
bandwidth between the islands has already been used up. However,
there is connectivity in the optical layer between switches L1, L2,
and L3, and the optical network is connected out to routers P3 and
P4 (they have optical line cards). In this example, a packet-layer
connection (an MPLS LSP) is desired between P1 and P6.
+--+ +--+ +--+ +--+ +--+ +--+
|P1|---|P2|---|P3| |P4|---|P5|---|P6|
+--+ +--+ +--+ +--+ +--+ +--+
\ /
\ /
+--+ +--+ +--+
|L1|--|L2|--|L3|
+--+ +--+ +--+
Figure 8: A Multi-Layer Network
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In the ABNO architecture, the following steps are performed to
deliver the service.
1. Request Management
As shown in Figure 9, the Application Service Coordinator issues a
request for connectivity from P1 to P6 in the packet-layer
network. That is, the Application Service Coordinator requests an
MPLS LSP with a specific bandwidth to carry traffic for its
application. The ABNO Controller verifies that the Application
Service Coordinator has sufficient rights to make the service
request.
+---------------------------+
| Application Service |
| Coordinator |
+-------------+-------------+
|
V
+------+ +------------+------------+
|Policy+->-+ ABNO Controller |
|Agent | | |
+------+ +-------------------------+
Figure 9: Application Service Coordinator Request Management
2. Service Path Computation in the Packet Layer
The ABNO Controller sends a path computation request to the
packet layer PCE to compute a suitable path for the requested LSP
as shown in Figure 10. The PCE uses the appropriate policy for
the request and consults the TED for the packet layer. It
determines that no path is immediately available.
+-----------------+
| ABNO Controller |
+----+------------+
|
V
+--------+ +--+-----------+ +--------+
| Policy +-->--+ Packet-Layer +---+ Packet |
| Agent | | PCE | | TED |
+--------+ +--------------+ +--------+
Figure 10: Path Computation Request
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3. Invocation of VNTM and Path Computation in the Optical Layer
After the path computation failure in step 2, instead of notifying
ABNO controller of the failure, the PCE invokes the VNTM to see
whether it can create the necessary link in the virtual network
topology to bridge the gap.
As shown in Figure 11, the packet-layer PCE reports the
connectivity problem to the VNTM, and the VNTM consults policy to
determine what it is allowed to do in this case. Assuming that
the policy allows it, VNTM asks the optical-layer PCE to see
whether it can find a path across the optical network that could
be provisioned to provide a virtual link for the packet layer. In
addressing this request, the optical-layer PCE consults a TED for
the optical-layer network.
+------+
+--------+ | | +--------------+
| Policy +-->--+ VNTM +--<--+ Packet-Layer |
| Agent | | | | PCE |
+--------+ +---+--+ +--------------+
|
V
+---------------+ +---------+
| Optical-Layer +---+ Optical |
| PCE | | TED |
+---------------+ +---------+
Figure 11: Invocation of VNTM and Optical Layer Path Computation
5. Provisioning in the Optical Layer
Once a path has been found across the optical-layer network it
needs to be provisioned. The options follow those in step 3 of
Section 3.1. That is, provisioning can be initiated by the
optical-layer PCE or by its user, the VNTM. The command can be
sent to the head end of the optical LSP (P3) so that the control
plane (for example, GMPLS [RFC3473]) can be used to provision the
LSP. Alternatively, the network resources can be provisioned
direct using any of the mechanisms described in Section 2.2.2.6.
6. Creation of Virtual Topology in the Packet Layer
Once the LSP has been set up in the optical-layer it can be made
available in the packet layer as a virtual link. If the GMPLS
signaling used the mechanisms described in [RFC6107] this process
can be automated within the control plane, otherwise it may
King & Farrel [Page 24]
draft-farrkingel-pce-abno-architecture-00.txt December 2012
require a specific instruction to the head end router of the
optical LSP (for example, through the Interface to the Routing
System).
Once the virtual link is created as shown in Figure 12, it is
advertised in the IGP for the packet-layer network and the link
will appear in the TED for the packet-layer network.
+--------+
+ Packet |
| TED |
+------+-+
A
|
+--+ +--+
|P3|....................|P4|
+--+ +--+
\ /
\ /
+--+ +--+ +--+
|L1|--|L2|--|L3|
+--+ +--+ +--+
Figure 12: Advertisement of a New Virtual Link
7. Path Computation Completion and Provisioning in the Packet Layer
Now there are sufficient resources in the packet-layer network.
The PCE for the packet-layer can complete its work and the MPLS
LSP can be provisioned as described in Section 3.1.
9. Verification and Notification of Service Fulfillment
As discussed in Section 3.1, the ABNO controller will need to
verify that the end-to-end LSP has been correctly established
before reporting service fulfillment to the the Application
Service Coordinator.
Furthermore, it is highly likely that service verification will be
necessary before the optical-layer LSP can be put into service as
a virtual link. Thus, the VNTM will need to coordinate with the
OAM Handler to ensure that the LSP is ready for use.
3.3 Bandwidth Scheduling
This section to be completed in a future revision of this document.
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3.4 Grooming and Regrooming
This section to be completed in a future revision of this document.
This use case will cover the following scenarios:
- Nested LSPs
- Packet Classification (IP flows into LSPs at edge routers)
- Bucket Stuffing
- IP Flows into ECMP Hash Bucket
3.5 Global Concurrent Optimization
This section to be completed in a future revision of this document.
3.6 Adaptive Network Planning
The ABNO architecture provides the capability for reactive network
control of resources based on classification, profiling and
prediction based on current demands and resource utilization. ABNO
would then manipulate server-layer transport network resources,
including OTN and Flexi-grid to meet current and projected demands.
This section to be completed in a future revision of this document.
4. Security Consideration
To be discussed.
5. IANA Considerations
This document makes no requests for IANA action.
6. References
6.1. Informative References
[I-D.atlas-irs-problem-statement]
Atlas, A., Nadeau, T., and Ward, D., "Interface to the
Routing System Problem Statement",
draft-atlas-irs-problem-statement, work in progress.
[I-D.crabbe-pce-pce-initiated-lsp]
Crabbe, E., Minei, I., Sivabalan, S., and Varga, R., "PCEP
Extensions for PCE-initiated LSP Setup in a Stateful PCE
Model", draft-crabbe-pce-pce-initiated-lsp, work in
progress.
King & Farrel [Page 26]
draft-farrkingel-pce-abno-architecture-00.txt December 2012
[I-D.ietf-alto-protocol]
Alimi, R., Penno, R., and Yang, Y., "ALTO Protocol",
draft-ietf-alto-protocol, work in progress.
[I-D.ietf-idr-ls-distribution]
Gredler, H., Medved, J., Previdi, S., Farrel, A., and
Ray, S., "North-Bound Distribution of Link-State and TE
Information using BGP", draft-ietf-idr-ls-distribution,
work in progress.
[I-D.draft-ietf-netmod-routing-cfg]
Lhotka, L., "A YANG Data Model for Routing Management",
draft-ietf-netmod-routing-cfg, work in progress.
[I-D.ietf-pce-stateful-pce]
Crabbe, E., Medved, J., Minei, I., and R. Varga, "PCEP
Extensions for Stateful PCE", draft-ietf-pce-stateful-pce,
work in progress.
[I-D.ward-irs-framework]
Atlas, A., Nadeau, T. and Ward, D., "Interface to the
Routing System Framework", draft-ward-irs-framework, work
in progress.
[ONF] Open Networking Foundation, "OpenFlow Switch Specification
Version 1.1.0 Implemented (Wire Protocol 0x02)", February
2011.
[RFC2748] Durham, D., Ed., Boyle, J., Cohen, R., Herzog, S., Rajan,
R., and A. Sastry, "The COPS (Common Open Policy Service)
Protocol", RFC 2748, January 2000.
[RFC3209] D. Awduche et al., "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC3292] Doria, A., Hellstrand, F., Sundell, K., and Worster, T.,
"General Switch Management Protocol (GSMP) V3", RFC 3292,
June 2002.
[RFC3412] Case, J., Harrington, D., Preshun, R., and Wijnen, B.,
"Message Processing and Dispatching for the Simple Network
Management Protocol (SNMP)", RFC 3412, December 2002.
[RFC3630] Katz, D., Kmpella, K., and Yeung, D., "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630, September
2003.
King & Farrel [Page 27]
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[RFC3746] Yang, L., Dantu, R., Anderson, T., and Gopal, R.,
"Forwarding and Control Element Separation (ForCES)
Framework", RFC 3746, April 2004.
[RFC3473] L. Berger et al., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
January 2003.
[RFC4655] Farrel, A., Vasseur, J.-P., and Ash, J., "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
August 2006.
[RFC5101] B. Claise, "Specification of the IP Flow Information Export
(IPFIX) Protocol for the Exchange of IP Traffic Flow
Information", RFC 5101, January 2008.
[RFC5150] Ayyangar, A., Kompella, K., Vasseur, JP. and Farrel, A.,
"Label Switched Path Stitching with Generalized
Multiprotocol Label Switching Traffic Engineering (GMPLS
TE)", RFC 5150, February 2008.
[RFC5212] Shiomoto, K., Papadimitriou, D., Le Roux, JL., Vigoureux,
M., and Brungard, D., "Requirements for GMPLS-Based Multi-
Region and Multi-Layer Networks (MRN/MLN)", RFC 5212, July
2008.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, October 2008.
[RFC5394] Bryskin, I., Papadimitriou, D., Berger, L. and Ash, J.,
"Policy-Enabled Path Computation Framework", RFC 5394,
December 2008.
[RFC5424] R. Gerhards, "The Syslog Protocol", RFC 5424, March 2009.
[RFC5440] Vasseur, JP. and Le Roux, JL., "Path Computation Element
(PCE) Communication Protocol (PCEP)", RFC 5440, March 2009.
[RFC5520] Bradford, R., Vasseur, JP., and Farrel, A., "Preserving
Topology Confidentiality in Inter-Domain Path Computation
Using a Path-Key-Based Mechanism", RC 5520, April 2009.
[RFC5557] Lee, Y., Le Roux, JL., King, D., and Oki, E., "Path
Computation Element Communication Protocol (PCEP)
Requirements and Protocol Extensions in Support of Global
Concurrent Optimization", RFC 5557, July 2009.
King & Farrel [Page 28]
draft-farrkingel-pce-abno-architecture-00.txt December 2012
[RFC5623] Oki, E., Takeda, T., Le Roux, JL., and Farrel, A.,
"Framework for PCE-Based Inter-Layer MPLS and GMPLS Traffic
Engineering", RFC 5623, September 2009.
[RFC5693] Seedorf, J., and Burger, E., "Application-Layer Traffic
Optimization (ALTO) Problem Statement", RFC 5693, October
2009.
[RFC5810] A. Doria, et al., "Forwarding and Control Element
Separation (ForCES) Protocol Specification", RFC 5810,
March 2010.
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the
Network Configuration Protocol (NETCONF)", RFC 6020,
October 2010.
[RFC6107] Shiomoto, K. and A. Farrel, "Procedures for Dynamically
Signaled Hierarchical Label Switched Paths", RFC 6107,
February 2011.
[RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J., and Bierman,
A., "Network Configuration Protocol (NETCONF)", RFC 6241,
June 2011.
[RFC6707] Niven-Jenkins, B., Le Faucheur, F., and Bitar, N., "Content
Distribution Network Interconnection (CDNI) Problem
Statement", RFC 6707, September 2012.
[RFC6805] King, D. and Farrel, A., "The Application of the Path
Computation Element Architecture to the Determination of a
Sequence of Domains in MPLS and GMPLS", RFC 6805, November
2012.
[TL1] Telcorida, "Operations Application Messages - Language For
Operations Application", GR-831, November 1996.
7. Authors' Addresses
Daniel King
Old Dog Consulting
Email: daniel@olddog.co.uk
Adrian Farrel
Juniper Networks
Email: adrian@olddog.co.uk
King & Farrel [Page 29]
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Appendix A. Undefined Interfaces
This Appendix provides a brief list of interfaces that are not yet
defined at the time of writing. Interfaces where there is a choice
of existing protocols are not listed.
To be completed in future release of this document.
King & Farrel [Page 30]
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