Internet DRAFT - draft-ietf-i2rs-problem-statement
draft-ietf-i2rs-problem-statement
Network Working Group A. Atlas, Ed.
Internet-Draft Juniper Networks
Intended status: Informational T. Nadeau, Ed.
Expires: November 11, 2016 Brocade
D. Ward
Cisco Systems
May 10, 2016
Interface to the Routing System Problem Statement
draft-ietf-i2rs-problem-statement-11
Abstract
Traditionally, routing systems have implemented routing and signaling
(e.g. MPLS) to control traffic forwarding in a network. Route
computation has been controlled by relatively static policies that
define link cost, route cost, or import and export routing policies.
With the advent of highly dynamic data center networking, on-demand
WAN services, dynamic policy-driven traffic steering and service
chaining, the need for real-time security threat responsiveness via
traffic control, and a paradigm of separating policy-based decision-
making from the router itself, requirements have emerged to more
dynamically manage and program routing systems. These requirements
should allow controlling routing information and traffic paths and
extracting network topology information, traffic statistics, and
other network analytics from routing systems.
This document proposes meeting this need via an Interface to the
Routing System (I2RS).
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on November 11, 2016.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. I2RS Model and Problem Area for the IETF . . . . . . . . . . 3
3. Standard Data-Models of Routing State for Installation . . . 6
4. Learning Router Information . . . . . . . . . . . . . . . . . 6
5. Aspects to be Considered for an I2RS Protocol . . . . . . . . 7
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. Existing Management Interfaces . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Traditionally, routing systems have implemented routing and signaling
(e.g. MPLS) to control traffic forwarding in a network. Route
computation has been controlled by relatively static policies that
define link cost, route cost, or import and export routing policies.
With the advent of highly dynamic data center networking, on-demand
WAN services, dynamic policy-driven traffic steering and service
chaining, the need for real-time security threat responsiveness via
traffic control, and a paradigm of separating policy-based decision-
making from the router itself, the need has emerged to more
dynamically manage and program routing systems in order to control
routing information and traffic paths and to extract network topology
information, traffic statistics, and other network analytics from
routing systems.
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As modern networks continue to grow in scale and complexity and
desired policy has become more complex and dynamic, there is a need
to support rapid control and analytics. The scale of modern networks
and data-centers and the associated operational expense drives the
need to automate even the simplest operations. The ability to
quickly interact via more complex operations to support dynamic
policy is even more critical.
In order to enable network applications to have access to and control
over information in the different vendors' routing systems, a
publicly documented interface is required. The interface needs to
support real-time, asynchronous interactions using efficient data
models and encodings that are based on and extend those previously
defined. Furthermore, the interface must be tailored to provide a
solid base on which a variety of use cases can be supported.
To support the requirements of orchestration software and automated
network applications to dynamically modify the network, there is a
need to learn topology, network analytics, and existing state from
the network as well as to create or modify routing information and
network paths. A feedback loop is needed so that changes made can be
verifiable and so that these applications can learn and react to
network changes.
Proprietary solutions to partially support the requirements outlined
above have been developed to handle specific situations and needs.
Standardizing an interface to the routing system will make it easier
to integrate use of it into a network. Because there are proprietary
partial solutions already, the standardization of a common interface
should be feasible.
It should be noted that during the course of this document, the term
"applications" is used. This is meant to refer to an executable
program of some sort that has access to a network, such as an IP or
MPLS network, via a routing system.
2. I2RS Model and Problem Area for the IETF
Managing a network of systems running a variety of routing protocols
and/or providing one or more additional services (e.g., forwarding,
classification and policing, firewalling) involves interactions
between multiple components within these systems. Some of these
systems or system components may be virtualized, co-located within
the same physical system or distributed. In all cases, it is
desirable to enable network applications to manage and control the
services provided by many, if not all, of these components, subject
to authenticated and authorized access and policies.
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A data-model driven interface to the routing system is needed. This
will allow expansion of what information can be read and controlled
and allow for future flexibility. At least one accompanying protocol
with clearly defined operations is needed; the suitable protocol(s)
can be identified and expanded to support the requirements of an
Interface to the Routing System (I2RS). These solutions must be
designed to facilitate rapid, isolated, secure, and dynamic changes
to a device's routing system. These would facilitate wide-scale
deployment of interoperable applications and routing systems.
The I2RS model and problem area for IETF work is illustrated in
Figure 1. This document uses terminology defined in
[I-D.ietf-i2rs-architecture]. The I2RS Agent is associated with a
routing element, which may or may not be co-located with a data-
plane. The I2RS Client could be integrated in a network application
or controlled and used by one or more separate network applications.
For instance, an I2RS Client could be provided by a network
controller or a network orchestration system that provides a non-I2RS
interface to network applications and an I2RS interface to I2RS
Agents on the systems being managed. The scope of the data-models
used by I2RS extends across the entire routing system and the
selected protocol(s) for I2RS.
As depicted in Figure 1, the I2RS Client and I2RS Agent in a routing
system are objects with in the I2RS scope. The selected protocol(s)
for I2RS extend between the I2RS client and I2RS Agent. All other
objects and interfaces in Figure 1 are outside the I2RS scope for
standardization.
+***************+ +***************+ +***************+
* Application * * Application * * Application *
+***************+ +***************+ +***************+
| I2RS Client | ^ ^
+---------------+ * *
^ * ****************
| * *
| v v
| +---------------+ +-------------+
| | I2RS Client |<------->| Other I2RS |
| +---------------+ | Agents |
| ^ +-------------+
|________________ |
| | <== I2RS Protocol
| |
...........................|..|..................................
. v v .
. +*************+ +---------------+ +****************+ .
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. * 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 Protocol
+--+ objects inside the scope of I2RS-defined behavior
<**> interfaces NOT within the scope of I2RS Protocol
+**+ objects NOT within the scope of I2RS-defined behavior
<== used to point to the interface where the I2RS Protocol
would be used
.... boundary of a router supporting I2RS
Figure 1: I2RS model and Problem Area
The protocol(s) used to carry messages between I2RS Clients and I2RS
Agents should provide the key features specified in Section 5.
I2RS will use a set of meaningful data-models for information in the
routing system and in a topology database. Each data-model should
describe the meaning and relationships of the modeled items. The
data-models should be separable across different features of the
managed components, versioned, and extendable. As shown in Figure 1,
I2RS needs to interact with several logical components of the routing
element: policy database, topology database, subscription and
configuration for dynamic measurements/events, routing signaling
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protocols, and its RIB manager. This interaction is both for writing
(e.g. to policy databases or RIB manager) as well as for reading
(e.g. dynamic measurement or topology database). An application
should be able to combine data from individual routing elements to
provide network-wide data-model(s).
The data models should translate into a concise transfer syntax, sent
via the I2RS protocol, that is straightforward for applications to
use (e.g., a Web Services design paradigm). The information transfer
should use existing transport protocols to provide the reliability,
security, and timeliness appropriate for the particular data.
3. Standard Data-Models of Routing State for Installation
As described in Section 1, there is a need to be able to precisely
control routing and signaling state based upon policy or external
measures. One set of data-models that I2RS should focus on is for
interacting with the RIB layer (e.g. RIB, LIB, multicast RIB,
policy-based routing) to provide flexibility and routing
abstractions. As an example, the desired routing and signaling state
might 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
next-hop indirection and recursion (e.g. a prefix X is routed like
prefix Y) as well as different types of tunneling and encapsulation.
Efforts to provide this level of control have focused on
standardizing data models that describe the forwarding plane (e.g.
ForCES [RFC3746]). I2RS recognizes that the routing system and a
router's OS provide useful mechanisms that applications could
usefully harness to accomplish application-level goals. Using
routing indirection, recursion and common routing abstractions (e.g.
tunnels, LSPs, etc.) provides significant flexibility and
functionality over collapsing the state to individual routes in the
FIB that need to be individually modified when a change occurs.
In addition to interfaces to control the RIB layer, there is a need
to dynamically configure policies and parameter values for the
various routing and signaling protocols based upon application-level
policy decisions.
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, measure the behavior of various flows, and understand the
existing configuration and state of the router. I2RS should provide
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a framework so that applications can register for asynchronous
notifications and can 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.ietf-idr-ls-distribution]) still only provide the current active
state as seen at the IGP and BGP layers. Detailed topological state
that provides more information than the current functional status
(e.g. active paths and links) is needed by applications. Examples of
missing information include paths or link that are potentially
available (e.g. administratively down) or unknown (e.g. to peers or
customers) 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, providing the ability for an application to
dynamically request that measurements be taken and data delivered is
important.
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 (e.g. route-installed,
route-changed, primary LSP changed, etc.)
5. Aspects to be Considered for an I2RS Protocol
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 independent atomic operations via
I2RS without being required 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 requests in a
well-known policy-based fashion. Data written can be owned by
different I2RS Clients at different times; data may even be
overwritten by a different I2RS Client. The details of how this
should be handled are described in [I-D.ietf-i2rs-architecture].
Duplex: Communications can be established by either the I2RS Client
(i.e., that resides within the application or is used by it to
communicate with the I2RS Agent), or the I2RS Agent. 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 a considerable number of operations per
second (for example 10,000 per second to handle many individual
subscriber routes changing simultaneously).
Low-Latency: Within a sub-second time-scale, it should be possible
to complete simple operations (e.g. reading or writing a single
prefix route).
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. One channel, with authorization
and authentication, may be considered primary; only an authorized
client can then request that information be delivered on a
different channel. Writes from a client are only expected on
channels that provide authorization and authentication.
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.
Secure Control and Access: Any ability to manipulate routing state
must be subject to authentication and authorization. Sensitive
routing information also may need to be provided via secure access
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back to the I2RS Client. Such communications must be integrity
protected. Most communications will also require confidentiality.
Extensible and Interoperability: Both the I2RS protocol and models
must be extensible and interoperate between different versions of
protocols and models.
6. Acknowledgements
The authors would like to thank Ken Gray, Ed Crabbe, Nic Leymann,
Carlos Pignataro, Kwang-koog Lee, Linda Dunbar, Sue Hares, Russ
Housley, Eric Grey, Qin Wu, Stephen Kent, Nabil Bitar, Deborah
Brungard, and Sarah Banks for their suggestions and review.
7. IANA Considerations
This document includes no request to IANA.
8. Security Considerations
Security is a key aspect of any protocol that allows state
installation and extracting of detailed router state. The need for
secure control and access is mentioned in Section 5. More
architectural security considerations are discussed in
[I-D.ietf-i2rs-architecture]. Briefly, the I2RS Agent is assumed to
have a separate authentication and authorization channel by which it
can validate both the identity and the permissions associated with an
I2RS Client. Mutual authentication between the I2RS Agent and I2RS
Client is required. Different levels of integrity, confidentiality,
and replay protection are relevant for different aspects of I2RS.
9. References
9.1. Normative References
[I-D.ietf-i2rs-architecture]
Atlas, A., Halpern, J., Hares, S., Ward, D., and T.
Nadeau, "An Architecture for the Interface to the Routing
System", draft-ietf-i2rs-architecture-15 (work in
progress), April 2016.
9.2. Informative References
[I-D.ietf-idr-ls-distribution]
Gredler, H., Medved, J., Previdi, S., Farrel, A., and S.
Ray, "North-Bound Distribution of Link-State and TE
Information using BGP", draft-ietf-idr-ls-distribution-13
(work in progress), October 2015.
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[RFC3746] Yang, L., Dantu, R., Anderson, T., and R. Gopal,
"Forwarding and Control Element Separation (ForCES)
Framework", RFC 3746, DOI 10.17487/RFC3746, April 2004,
<http://www.rfc-editor.org/info/rfc3746>.
[RFC4292] Haberman, B., "IP Forwarding Table MIB", RFC 4292,
DOI 10.17487/RFC4292, April 2006,
<http://www.rfc-editor.org/info/rfc4292>.
[RFC5470] Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,
"Architecture for IP Flow Information Export", RFC 5470,
DOI 10.17487/RFC5470, March 2009,
<http://www.rfc-editor.org/info/rfc5470>.
Appendix A. 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 of these existing standard technologies are possible,
the ways described are those that have significant deployment.
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. CLI standardization is not
considered as a candidate solution for the problems motivating I2RS.
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
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(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, as a new technology
and with the initial lack of standard data models, the adoption of
NETCONF has been slow. I2RS will identify and define as needed
information and data models to support I2RS applications. Additional
extensions to handle multi-headed control may need to be added to
NETCONF and/or appropriate data models.
Authors' Addresses
Alia Atlas (editor)
Juniper Networks
Email: akatlas@juniper.net
Thomas D. Nadeau (editor)
Brocade
Email: tnadeau@lucidvision.com
Dave Ward
Cisco Systems
Email: wardd@cisco.com
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