Interface to the Routing System Problem Statement
draft-atlas-i2rs-problem-statement-00
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
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|---|---|---|---|
| Authors | Alia Atlas , Thomas Nadeau , David Ward | ||
| Last updated | 2013-02-27 | ||
| Replaces | draft-atlas-irs-problem-statement | ||
| Replaced by | draft-ietf-i2rs-problem-statement, RFC 7920 | ||
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draft-atlas-i2rs-problem-statement-00
Network Working Group A. Atlas, Ed.
Internet-Draft T. Nadeau
Intended status: Informational Juniper Networks
Expires: August 25, 2013 D. Ward
Cisco Systems
February 21, 2013
Interface to the Routing System Problem Statement
draft-atlas-i2rs-problem-statement-01
Abstract
As modern networks grow in scale and complexity, the need for rapid
and dynamic control increases. With scale, the need to automate even
the simplest operations is important, but even more critical is the
ability to quickly interact with more complex operations such as
policy-based controls.
In order to enable applications to have access to and control over
information in the Internet's routing system, we need a publicly
documented interface specification. The interface needs to support
real-time, transaction-based interactions using data models and
encodings that are efficient and potentially different from those
available today. Furthermore, the interface must be tailored to
support a variety of use cases.
This document expands upon these statements of requirements to
provide a detailed problem statement for an Interface to the Internet
Routing System (I2RS).
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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Drafts is at http://datatracker.ietf.org/drafts/current/.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 25, 2013.
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Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. I2RS Model and Problem Area for The IETF . . . . . . . . . . . 3
3. Standard Data-Models of Routing State for Installation . . . . 5
4. Learning Router Information . . . . . . . . . . . . . . . . . . 5
5. Desired Aspects of a Protocol for I2RS . . . . . . . . . . . . 6
6. Existing Management Interfaces . . . . . . . . . . . . . . . . 7
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 9
9. Security Considerations . . . . . . . . . . . . . . . . . . . . 9
10. Informative References . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
As modern networks grow in scale and complexity, the need for rapid
and dynamic control increases. With scale, the need to automate even
the simplest operations is important, but even more critical is the
ability to quickly interact with more complex operations such as
policy-based controls.
With complexity comes the need for more sophisticated automated
applications and orchestration software that can process large
quantities of data, run complex algorithms, and adjust the routing
state as required in order to support the applications, their
calculations and their policies. Changes made to the routing state
of a network by external applications must be verifiable by those
applications to ensure that the correct state has been installed in
the right places.
Mechanisms to support the requirements outlined above have been
developed piecemeal as proprietary solutions to specific situations
and needs. A standard protocol, clearly defined operations that an
application can initiate with that protocol, and data-models to
support such actions would facilitate wide-scale deployment of
interoperable applications and routing systems. That a protocol
designed to facilitate rapid, isolated, secure, and dynamic routing
changes is needed motivates the creation of an Interface to The
Routing System (I2RS).
2. I2RS Model and Problem Area for The IETF
Managing a network of deployed devices running a variety of routing
protocols involves interactions among multiple different components
that exist within the network. Some of these components are virtual
while some are physical; all should be made available to be managed
and manipulated by applications, given that appropriate access,
authentication, and policy hurdles have been crossed. The management
of only some of these components requires standardization, as others
have already been standardized. The I2RS model is intended to
incorporate existing mechanisms where appropriate, and to build
extensions and new protocols where needed. The I2RS model and
problem area proposed for IETF work is illustrated in Figure 1. The
I2RS Agent is associated with a routing element, which may or may not
be co-located with a data-plane. The I2RS Client is used and
controlled by a network application; they may be co-located or the
I2RS Client might be part of a separate application, such as an
orchestrator or controller.
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+***************+ +***************+ +***************+
* Application * * Application * * Application *
+***************+ +***************+ +***************+
| I2RS Client | ^ ^
+---------------+ * *
^ * ****************
| * *
| v v
| +---------------+
| | I2RS Client |
| +---------------+
| ^
|________________ |
| | <== I2RS Protocol
| |
...........................|..|..................................
. v v .
. +*************+ +---------------+ +****************+ .
. * Policy * | | * Routing & * .
. * Database *<***>| I2RS Agent |<****>* Signaling * .
. +*************+ | | * Protocols * .
. +---------------+ +****************+ .
. ^ ^ ^ ^ .
. +*************+ * * * * .
. * Topology * * * * * .
. * Database *<*******+ * * v .
. +*************+ * * +****************+ .
. * +********>* RIB Manager * .
. * +****************+ .
. * ^ .
. v * .
. +*******************+ * .
. * Subscription & * * .
. * Configuration * v .
. * Templates for * +****************+ .
. * Measurements, * * FIB Manager * .
. * Events, QoS, etc. * * & Data Plane * .
. +*******************+ +****************+ .
.................................................................
<--> interfaces inside the scope of I2RS
+--+ objects inside the scope of I2RS
<**> interfaces NOT within the scope of I2RS
+**+ objects NOT within the scope of I2RS
.... boundary of a router participating in the I2RS
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Figure 1: I2RS model and Problem Area
A critical aspect of I2RS is defining a suitable protocol or
protocols to carry messages between the I2RS Clients and the I2RS
Agent, and defining the encapsulation of data within those messages.
This should provide a clear transfer syntax that is straightforward
for applications to use (e.g., a Web Services design paradigm), and
should provide the key features specified in Section 5.
The second critical aspect is semantic-aware data-models for
information in the routing system and in a topology database. The
data-models should be separable across different features of the
managed components, versioned, and combine to provide a network data-
model.
3. Standard Data-Models of Routing State for Installation
There is a need to be able to precisely control routing and signaling
state based upon policy or external measures. This can range from
simple static routes to policy-based routing to static multicast
replication and routing state. This means that, to usefully model
next-hops, the data model employed needs to handle indirection as
well as different types of tunneling and encapsulation. The relevant
MIB modules (for example [RFC4292]) lack the necessary generality and
flexibility. In addition, by having I2RS focus initially on
interfaces to the RIB layer (e.g. RIB, LFIB, multicast RIB, policy-
based routing), the ability to use routing indirection allows
flexibility and functionality that can't be as easily obtained at the
forwarding layer.
Efforts to provide this level of control have focused on
standardizing data models that describe the forwarding plane (e.g.
ForCES [RFC3746]). I2RS posits that the routing system and a
router's OS provide useful mechanisms that applications could
usefully harness to accomplish application-level goals.
In addition to interfaces to the RIB layer, there is a need to
configure the various routing and signaling protocols with differing
dynamic state based upon application-level policy decisions. The
range desired is not available via MIBs at the present time.
4. Learning Router Information
A router has information that applications may require so that they
can understand the network, verify that programmed state is installed
in the forwarding plane, measure the behavior of various flows, and
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understand the existing configuration and state of the router. I2RS
provides a framework for applications to register for asynchronous
notifications and for them to make specific requests for information.
Although there are efforts to extend the topological information
available, even the best of these (e.g., BGP-LS
[I-D.gredler-idr-ls-distribution]) still provides only the current
active state as seen at the IGP layer and above. Detailed
topological state that provides more information than the current
functional status is needed by applications; only the active paths or
links are known versus those potentially available or unknown to the
routing topology.
For applications to have a feedback loop that includes awareness of
the relevant traffic, an application must be able to request the
measurement and timely, scalable reporting of data. While a
mechanism such as IPFIX [RFC5470] may be the facilitator for
delivering the data, the need for an application to be able to
dynamically request that measurements be taken and data delivered is
critical.
There are a wide range of events that applications could use for
either verification of router state before other network state is
changed (e.g. that a route has been installed), to act upon changes
to relevant routes by others, or upon router events (e.g. link up/
down). While a few of these (e.g. link up/down) may be available via
MIB Notifications today, the full range is not - nor is there the
standardized ability to set up the router to trigger different
actions upon an event's occurrence.
5. Desired Aspects of a Protocol for I2RS
This section describes required aspects of a protocol that could
support I2RS. Whether such a protocol is built upon extending
existing mechanisms or requires a new mechanism requires further
investigation.
The key aspects needed in an interface to the routing system are:
Multiple Simultaneous Asynchronous Operations: A single application
should be able to send multiple operations to I2RS without needing
to wait for each to complete before sending the next.
Very Fine Granularity of Data Locking for Writing: When an I2RS
operation is processed, it is required that the data locked for
writing is very granular (e.g. a particular prefix and route)
rather than extremely coarse, as is done for writing
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configuration. This should improve the number of concurrent I2RS
operations that are feasible and reduce blocking delays.
Multi-Headed Control: Multiple applications may communicate to the
same I2RS agent in a minimally coordinated fashion. It is
necessary that the I2RS agent can handle multiple conflicting
requests in a well-known policy-based fashion. Data written can
be owned by different I2RS clients.
Duplex: Communications can be established by either the router or
the application. Similarly, events, acknowledgements, failures,
operations, etc. can be sent at any time by both the router and
the application. The I2RS is not a pure pull-model where only the
application queries to pull responses.
High-Throughput: At a minimum, the I2RS Agent and associated router
should be able to handle hundreds of simple operations per second.
Responsive: It should be possible to complete simple operations
within a sub-second time-scale.
Multi-Channel: It should be possible for information to be
communicated via the interface from different components in the
router without requiring going through a single channel. For
example, for scaling, some exported data or events may be better
sent directly from the forwarding plane, while other interactions
may come from the control-plane. Thus a single TCP session would
not be a good match.
Temporal State for Installation and Expiration: The ability to have
state installed with different lifetimes and different start-times
is very valuable. In particular, the ability of an I2RS client to
request that a pre-sent operation be started based upon a dynamic
event would provide a powerful functionality.
Scalable, Filterable Information Access: To extract information in a
scalable fashion that is more easily used by applications, the
ability to specify filtering constructs in an operation requesting
data or requesting an asynchronous notification is very valuable.
6. Existing Management Interfaces
This section discusses as a single entity the combination of the
abstract data models, their representation in a data language, and
the transfer protocol commonly used with them. While other
combinations are possible, the ways described are those that have
significant deployment.
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There are three basic ways that routers are managed. The most
popular is the command line interface (CLI), which allows both
configuration and learning of device state. This is a proprietary
interface resembling a UNIX shell that allows for very customized
control and observation of a device, and, specifically of interest in
this case, its routing system. Some form of this interface exists on
almost every device (virtual or otherwise). Processing of
information returned to the CLI (called "screen scraping") is a
burdensome activity because the data is normally formatted for use by
a human operator, and because the layout of the data can vary from
device to device, and between different software versions. Despite
its ubiquity, this interface has never been standardized and is
unlikely to ever be standardized. I2RS does not involve CLI
standardization.
The second most popular interface for interrogation of a device's
state, statistics, and configuration is The Simple Network Management
Protocol (SNMP) and a set of relevant standards-based and proprietary
Management Information Base (MIB) modules. SNMP has a strong history
of being used by network managers to gather statistical and state
information about devices, including their routing systems. However,
SNMP is very rarely used to configure a device or any of its systems
for reasons that vary depending upon the network operator. Some
example reasons include complexity, the lack of desired configuration
semantics (e.g., configuration "roll-back", "sandboxing" or
configuration versioning), and the difficulty of using the semantics
(or lack thereof) as defined in the MIB modules to configure device
features. Therefore, SNMP is not considered as a candidate solution
for the problems motivating I2RS.
Finally, the IETF's Network Configuration (or NetConf) protocol has
made many strides at overcoming most of the limitations around
configuration that were just described. However, the lack of
standard data models have hampered the adoption of NetConf.
Naturally, I2RS may help define needed information and data models.
Additional extensions to handle multi-headed control and time-based
state installation and expiration may need to be added to NetConf
and/or appropriate data models.
7. Acknowledgements
The authors would like to thank Ken Gray for his suggestions and
review.
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8. IANA Considerations
This document includes no request to IANA.
9. Security Considerations
Security is a key aspect of any protocol that allows state
installation and extracting of detailed router state. More
investigation remains to fully define the security requirements, such
as authorization and authentication levels.
10. Informative References
[I-D.gredler-idr-ls-distribution]
Gredler, H., Medved, J., Previdi, S., and A. Farrel,
"North-Bound Distribution of Link-State and TE Information
using BGP", draft-gredler-idr-ls-distribution-02 (work in
progress), July 2012.
[RFC3746] Yang, L., Dantu, R., Anderson, T., and R. Gopal,
"Forwarding and Control Element Separation (ForCES)
Framework", RFC 3746, April 2004.
[RFC4292] Haberman, B., "IP Forwarding Table MIB", RFC 4292,
April 2006.
[RFC5470] Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,
"Architecture for IP Flow Information Export", RFC 5470,
March 2009.
Authors' Addresses
Alia Atlas (editor)
Juniper Networks
10 Technology Park Drive
Westford, MA 01886
USA
Email: akatlas@juniper.net
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Thomas D. Nadeau
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
USA
Email: tnadeau@juniper.net
Dave Ward
Cisco Systems
Tasman Drive
San Jose, CA 95134
USA
Email: wardd@cisco.com
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