Internet DRAFT - draft-behringer-autonomic-control-plane
draft-behringer-autonomic-control-plane
Network Working Group M. Behringer
Internet-Draft S. Bjarnason
Intended status: Informational Balaji. BL
Expires: December 22, 2014 T. Eckert
Cisco
June 20, 2014
An Autonomic Control Plane
draft-behringer-autonomic-control-plane-00
Abstract
In certain scenarios, for example when bootstrapping a network, it is
desirable to automatically bring up a secure, routed control plane,
which is independent of device configurations and global routing
table. This document describes an approach for an "Autonomic Control
Plane", which can be used as a "virtual out of band channel" - a
self-managing overlay network, which is independent of configuration,
addressing and routing on the data plane.
Status of This Memo
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This Internet-Draft will expire on December 22, 2014.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
3. Self-Creation of an Autonomic Control Plane . . . . . . . . . 3
3.1. Preconditions . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Adjacency Discovery . . . . . . . . . . . . . . . . . . . 4
3.3. Authenticating Neighbors . . . . . . . . . . . . . . . . 4
3.4. Capability Negotiation . . . . . . . . . . . . . . . . . 5
3.5. Channel Establishment . . . . . . . . . . . . . . . . . . 5
3.6. Context Separation . . . . . . . . . . . . . . . . . . . 5
3.7. Addressing in the ACP . . . . . . . . . . . . . . . . . . 6
3.8. Routing in the ACP . . . . . . . . . . . . . . . . . . . 6
4. Self-Healing Properties . . . . . . . . . . . . . . . . . . . 7
5. Self-Protection Properties . . . . . . . . . . . . . . . . . 7
6. Use Cases for the ACP . . . . . . . . . . . . . . . . . . . . 8
7. The Administrator View . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
11. Change log [RFC Editor: Please remove] . . . . . . . . . . . 9
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
Today, the management and control plane of networks typically runs in
the global routing table, which is dependent on correct configuration
and routing. Misconfigurations or routing problems can therefore
disrupt management and control channels. Traditionally, an out of
band network has been used to recover from such problems, or
personnel is sent on site to access devices through console ports.
However, both options are operationally expensive.
In increasingly automated networks either controllers or autonomic
service agents in the network require a control plane which is
independent of the network they manage, to avoid impacting their own
operations.
This document describes a self-forming, self-managing and self-
protecting "Autonomic Control Plane" (ACP) which is inband on the
network, yet independent of configuration, addressing and routing
problems. It therefore remains operational even in the presence of
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configuration errors, addressing or routing issues, or where policy
could inadvertedly affect control plane connectivity. It serves as a
"virtual out of band channel": An operator can use it to log into
remote devices in such cases. And an SDN controller can use it to
securely bootstrap network devices in remote locations, even if the
network in between is not yet configured; no data-plane dependent
bootstrap configuration is required. An example of such a secure
bootstrap process is described in
[I-D.pritikin-bootstrapping-keyinfrastructures]
2. Problem Statement
An "Autonomic Control Plane" (ACP) provides a solution to some of
today's operational challenges. These fall into three broad
categories:
o Bootstrapping a network while devices are not yet configured.
Bootstrapping a new device today requires all devices between the
controller and the new device to be completely and correctly
addressed, configured and secured. Therefore, bootstrapping a
network happens in layers around the controller. Without console
access it is not possible today to make devices securely reachable
before having configured the entire network between.
o Maintaining reachability of network devices even in the case of
certain forms of misconfiguration and routing issues. For
example: certain AAA misconfigurations can lock an administrator
out of a device; routing or addressing issues can make a device
unreachable; shutting down interfaces over which a current
management session is running can lock an admin irreversibly out
of the device. Traditionally only console access can help recover
from such issues.
o Data plane dependencies for NOC/SDN controller applications:
Certain network changes are today hard to operate, because the
change itself may affect reachability of the devices. Examples
are address or mask changes, routing changes, or security
policies. Today such changes require precise hop-by-hop planning;
an ACP would simplify them.
3. Self-Creation of an Autonomic Control Plane
This section describes the steps to set up an Autonomic Control
Plane, and highlights the key properties which make it
"indestructible" against many inadvert changes to the data plane, for
example caused by misconfigurations.
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3.1. Preconditions
Each autonomic device has a globally unique domain certificate, with
which it can cryptographically assert its membership of the domain.
The document [I-D.pritikin-bootstrapping-keyinfrastructures]
describes how a domain certificate can be automatically and securely
derived from a vendor specific Unique Device Identifier (UDI) or
IDevID certificate.
3.2. Adjacency Discovery
Adjacency discovery exchanges identity information about neighbors,
either the UDI or, if present, the domain certificate (see
Section 3.1. This document assumes the existance of a domain
certificate.
Adjacency discovery provides a table of information of adjacent
neighbours. Each neighbour is identified by an globally unique
device identifier (UDI).
The adjacency table contains the following information about the
adjacent neighbours.
o Globally valid Unique devide identifier (UDI)
o Link Local IPv6 address
o Trust information
o Validity of the trust
Adjacency discovery can populate this table by several means. One
such mechanism is to discover using link local multicast probes,
which has no dependency on configured addressing and is preferable in
an autonomic network.
3.3. Authenticating Neighbors
Each neighbour in the adjacency table is authenticated. The result
of the authentication of the neighbour information is stored in the
adjacency table. We distinguish the following cases:
o Inside the domain: If the domain certificate presented is
validated to be in the same domain as that of the autonomic entity
then the neighbour is deemed to be inside the autonomic domain.
Only entities inside the autonomic domain will by default be able
to establish the autonomic control plane. An ACP channel will be
established.
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o Outside the domain: If there is no domain certificate presented by
the neighbour, or if the domain certificate presented is invalid
or expired, then the neighbour is deemed to be outside the
autonomic domain. No ACP channel will be established.
3.4. Capability Negotiation
Autonomic devices have different capabilities based on the type of
device and where it is deployed. To establish a trusted secure
communication channel, devices must be able to negotiate with each
neighbour a set of parameters for establishing the communication
channel, most notably channel type and security type. The channel
type could be any tunnel mechanism that is feasible between two
adjacent neighbours, for example a GRE tunnel. The security type
could be any of the channel protection mechanism that is available
between two adjacent neighbours on a given channel type, for example
IPSEC. The establishment of the autonomic control plane can happen
after the channel type and security type is negotiated.
3.5. Channel Establishment
After authentication and capability negotiation autonomic nodes
establish a secure channel towards their direct AN neighbours with
the above negotiated parameters. In order to be independent of
configured link addresses, these channels can be implemented in
several ways:
o As a secure IP tunnel (e.g., IPsec), using IPv6 link local
addresses between two adjacent neighbours. This way, the ACP
tunnels are independent of correct network wide routing. They
also do not require larger than link local scope addresses, which
would normally need to be configured or maintained. Each AN node
MUST support this function.
o L2 separation, for example via a separate 802.1q tag for ACP
traffic. This even further reduces dependency against the data
plane (not even IPv6 link-local there required), but may be harder
to implement.
3.6. Context Separation
The ACP is in a separate context from the normal data plane of the
device. This context includes the ACP channels IPv6 forwarding and
routing as well as any required higher layer ACP functions.
In classical network device platforms, a dedicated so called "Virtual
routing and forwarding instance" (VRF) is one logical implementation
option for the ACP. If possible by the platform SW architecture,
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separation options that minimize shared components are preferred.
The context for the ACP needs to be established automatically during
bootstrap of a device and - as necessitated by the implementation
option be protected from being modified unintential from data plane
configuration.
In addition this provides for security, because the ACP is not
reachable from the global routing table. Also, configuration errors
from the data plane setup do not affect the ACP.
3.7. Addressing in the ACP
The channels explained above only establish communication between two
adjacent neighbours. In order for the communication to happen across
multiple hops, the autonomic control plane requires internal network
wide valid addresses and routing. Each autonomic node must create a
loop back interface with a network wide unique address inside the ACP
context mentioned in Section 3.6.
We suggest to create network wide Unique Local Addresses (ULA) in
accordance with [RFC4193] with the following algorithm:
o Prefix FC01::/8
o Global ID: a hash of the domain ID; this way all devices in the
same domain have the same /48 prefix.
o Subnet ID and interface ID: These can be either derived
deterministically from the name of the device, or assigned at
registration time of the device.
3.8. Routing in the ACP
Once ULA address are set up all autonomic entities should run a
routing protocol within the autonomic control plane context. This
routing protocol distributes the ULA created in the previous section
for reachability. The use of the autonomic control plane specific
context eliminates the probable clash with the global routing table
and also secures the ACP from interference from the configuration
mismatch or incorrect routing updates.
The establishment of the routing plane and its parameters are
automatic and strictly within the confines of the autonomic control
plane. Therefore, no manual configuration is required.
All routing updates are automatically secured in transit as the
channels of the autonomic control plane are by default secured.
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The routing protocol inside the ACP should be light weight and highly
scalable to ensure that the ACP does not become a limiting factor in
network scalability. We suggest the use of RPL as one such protocol
which is light weight and scales well for the control plane traffic.
4. Self-Healing Properties
The ACP is self-healing:
o New neighbors will automatically join the ACP after successful
validation and will become reachable using their unique ULA
address across the ACP.
o When any changes happen in the topology, the routing protocol used
in the ACP will automatically adapt to the changes and will
continue to provide reachability to all devices.
o If an existing device gets revoked, it will automatically be
denied access to the ACP as its domain certificate will be
validated against a Certificate Revocation List during
authentication.
5. Self-Protection Properties
As explained in Section 3, the ACP is based on channels being built
between devices which have been previously been authenticated based
on their domain certificates. The channels themselves are protected
using standard encryption technologies like IPsec which provide
additional authentication during channel establishment, data
integrity and data confidentiality protection of data inside the ACP
and in addition, provide replay protection.
An attacker will therefore not be able to join the ACP unless having
a valid domain certificate, also packet injection and sniffing
traffic will not be possible due to the security provided by the
encryption protocol.
The remaining attack vector would be to attack the underlying AN
protocols themselves, either via directed attacks or by denial-of-
service attacks. However, as the ACP is built using link-local IPv6
address, remote attacks are impossible. The ULA addresses are only
reachable inside the ACP context, therefore unreachable from the data
plane. Also, the ACP protocols should be implemented to be attack
resistant and not consume unnecessary resources even while under
attack.
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6. Use Cases for the ACP
The ACP automatically enables a number of use cases which provide
immediate benefits:
o Secure bootstrap of new devices without requiring any
configuration. As explained in Section 3, a new device will
automatically be bootstrapped in a secure fashion and be deployed
with a domain certificate. This will happen without any
configuration, allowing a new device to be shipped directly to the
end-user location without the need for any pre-provisioning.
o Virtual-out-of-band (VooB) control plane which provides
connectivity to all devices regardless of their configuration or
global routing table. This makes it possible to manage devices
without having to configure data plane services or to deploy a
separate management network. It also simplifies management
applications, because changes done by the applications cannot
affect reachability of the devices.
7. The Administrator View
An ACP is self-forming, self-managing and self-protecting, therefore
has minimal dependencies on the administrator of the network.
Specifically, it cannot be configured, there is therefore no scope
for configuration errors on the ACP itself. The administrator may
have the option to enable or disable the entire approach, but
detailed configuration is not possible. This means that the ACP must
not be reflected in the running configuration of devices, except a
possible on/off switch.
While configuration is not possible, an administrator must have full
visibility of the ACP and all its parameters, to be able to do
trouble-shooting. Therefore, an ACP must support all show and debug
options, as for any other network function. Specifically, a network
management system or controller must be able to discover the ACP, and
monitor its health. This visibility of ACP operations must clearly
be separated from visibility of data plane so automated systems will
never have to deal with ACP aspect unless they explicitly desire to
do so.
Since an ACP is self-protecting, a device not supporting the ACP, or
without a valid domain certificate cannot connect to it. This means
that by default a traditional controller or network management system
cannot connect to an ACP. To make this possible for systems not
supporting the ACP natively, the connection to the ACP must be
manually established, through configuration. [EDNOTE: More details
to be provided in a later version of this document.] Long term NMS
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systems might become autonomic devices with domain certificates, and
then automatically join the ACP.
8. Security Considerations
An ACP is self-protecting and there is no need to apply configuration
to make it secure. Its security therefore does not depend on
configuration.
However, the security of the ACP depends on a number of other
factors:
o The usage of domain certificates depends on a valid supporting PKI
infrastructure. If the chain of trust of this PKI infrastructure
is compromised, the security of the ACP is also compromised. This
is typically under the control of the network administrator.
o Security can be compromised by implementation errors (bugs), as in
all products.
Fundamentally, security depends on correct operation, implementation
and architecture. Autonomic approaches such as the ACP largely
eliminate the dependency on correct operation; implementation and
architectural mistakes are still possible, as in all networking
technologies.
9. IANA Considerations
This document requests no action by IANA.
10. Acknowledgements
This work originated from an Autonomic Networking project at Cisco
Systems, which started in early 2010. Many people contributed to
this project and the idea of the Autonomic Control Plane, amongst
which (in alphabetical order): Ignas Bagdonas, Parag Bhide, Alex
Clemm, Toerless Eckert, Yves Hertoghs, Bruno Klauser, Max Pritikin,
Ravi Kumar Vadapalli.
11. Change log [RFC Editor: Please remove]
00: Initial version.
12. References
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[I-D.irtf-nmrg-an-gap-analysis]
Behringer, M., Carpenter, B., and S. Jiang, "Gap Analysis
for Autonomic Networking", draft-irtf-nmrg-an-gap-
analysis-00 (work in progress), April 2014.
[I-D.irtf-nmrg-autonomic-network-definitions]
Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A.,
Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic
Networking - Definitions and Design Goals", draft-irtf-
nmrg-autonomic-network-definitions-00 (work in progress),
December 2013.
[I-D.pritikin-bootstrapping-keyinfrastructures]
Pritikin, M., Behringer, M., and S. Bjarnason,
"Bootstrapping Key Infrastructures", draft-pritikin-
bootstrapping-keyinfrastructures-00 (work in progress),
January 2014.
[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, October 2005.
Authors' Addresses
Michael H. Behringer
Cisco
Email: mbehring@cisco.com
Steinthor Bjarnason
Cisco
Email: sbjarnas@cisco.com
Balaji BL
Cisco
Email: blbalaji@cisco.com
Toerless Eckert
Cisco
Email: eckert@cisco.com
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