I2RS J. Clarke
Internet-Draft G. Salgueiro
Intended status: Informational C. Pignataro
Expires: November 2, 2016 Cisco
May 1, 2016
Interface to the Routing System (I2RS) Traceability: Framework and
Information Model
draft-ietf-i2rs-traceability-09
Abstract
This document describes a framework for traceability in the Interface
to the Routing System (I2RS) and information model for that
framework. It specifies the motivation, requirements, use cases, and
defines an information model for recording interactions between
elements implementing the I2RS protocol. This framework provides a
consistent tracing interface for components implementing the I2RS
architecture to record what was done, by which component, and when.
It aims to improve the management of I2RS implementations, and can be
used for troubleshooting, auditing, forensics, and accounting
purposes.
Status of This Memo
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This Internet-Draft will expire on November 2, 2016.
Copyright Notice
Copyright (c) 2016 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology and Conventions . . . . . . . . . . . . . . . . . 3
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Information Model . . . . . . . . . . . . . . . . . . . . . . 4
5.1. I2RS Traceability Framework . . . . . . . . . . . . . . . 4
5.2. I2RS Trace Log Mandatory Fields . . . . . . . . . . . . . 6
5.3. End of Message Marker . . . . . . . . . . . . . . . . . . 8
6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7. Operational Guidance . . . . . . . . . . . . . . . . . . . . 9
7.1. Trace Log Creation . . . . . . . . . . . . . . . . . . . 9
7.2. Trace Log Temporary Storage . . . . . . . . . . . . . . . 10
7.3. Trace Log Rotation . . . . . . . . . . . . . . . . . . . 10
7.4. Trace Log Retrieval . . . . . . . . . . . . . . . . . . . 10
7.4.1. Retrieval Via Syslog . . . . . . . . . . . . . . . . 11
7.4.2. Retrieval Via I2RS Information Collection . . . . . . 11
7.4.3. Retrieval Via I2RS Pub-Sub . . . . . . . . . . . . . 11
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
9. Security Considerations . . . . . . . . . . . . . . . . . . . 12
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
11.1. Normative References . . . . . . . . . . . . . . . . . . 13
11.2. Informative References . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
The architecture for the Interface to the Routing System
([I-D.ietf-i2rs-architecture]) specifies that I2RS Clients wishing to
retrieve or change routing state on a routing element MUST
authenticate to an I2RS Agent. The I2RS Client will have a unique
identity it provides for authentication, and should provide another,
opaque identity for applications communicating through it. The
programming of routing state will produce a return code containing
the results of the specified operation and associated reason(s) for
the result. All of this is critical information to be used for
understanding the history of I2RS interactions.
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This document describes use cases for I2RS traceability. Based on
these use cases, the document proposes an information model and
reporting requirements to provide for effective recording of I2RS
interactions. In this context, effective troubleshooting means being
able to identify what operation was performed by a specific I2RS
Client, what was the result of the operation, and when that operation
was performed.
Discussions about the retention of the data logged as part of I2RS
traceability, while important, are outside of the scope of this
document.
2. Terminology and Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The architecture specification for I2RS [I-D.ietf-i2rs-architecture]
defines additional terms used in this document that are specific to
the I2RS domain, such as "I2RS Agent", "I2RS Client", etc. The
reader is expected to be familiar with the terminology and concepts
defined in [I-D.ietf-i2rs-architecture].
3. Motivation
As networks scale and policy becomes an increasingly important part
of the control plane that creates and maintains the forwarding state,
operational complexity increases as well. I2RS offers more granular
and coherent control over policy and control plane state, but it also
removes or reduces the locality of the policy that has been applied
to the control plane at any individual forwarding device. The
ability to automate and abstract even complex policy-based controls
highlights the need for an equally scalable traceability function to
provide event-level granularity of the routing system compliant with
the requirements of I2RS (Section 5 of
[I-D.ietf-i2rs-problem-statement]).
4. Use Cases
An obvious motivation for I2RS traceability is the need to
troubleshoot and identify root-causes of problems in these
increasingly complex routing systems. For example, since I2RS is a
high-throughput multi-channel, full duplex and highly responsive
interface, I2RS Clients may be performing a large number of
operations on I2RS Agents concurrently or at nearly the same time and
quite possibly in very rapid succession. As these many changes are
made, the network reacts accordingly. These changes might lead to a
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race condition, performance issues, data loss, or disruption of
services. In order to isolate the root cause of these issues it is
critical that a network operator or administrator has visibility into
what changes were made via I2RS at a specific time.
Some network environments have strong auditing requirements for
configuration and runtime changes. Other environments have policies
that require saving logging information for operational or regulatory
compliance considerations. These requirements therefore demand that
I2RS provides an account of changes made to network element routing
systems.
As I2RS becomes increasingly pervasive in routing environments, a
traceability model offers significant advantages and facilitates the
following use cases:
o Automated event correlation, trend analysis, and anomaly
detection;
o Trace log storage for offline (manual or tools) analysis;
o Improved accounting of routing system operations;
o Standardized structured data format for writing common tools;
o Common reference for automated testing and incident reporting;
o Real-time monitoring and troubleshooting;
o Enhanced network audit, management and forensic analysis
capabilities.
5. Information Model
5.1. I2RS Traceability Framework
This section describes a framework for I2RS traceability based on the
I2RS Architecture. Some notable elements of the architecture are in
this section.
The interaction between the optional northbound application, I2RS
Client, I2RS Agent, the Routing System and the data captured in the
I2RS trace log is shown in Figure 1.
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+----------------+
|Application |
|.............. |
| Application ID |
+----------------+
^
| 0 .. N
|
v
+-------------+
|I2RS Client |
|.............|
| Client ID |
+-------------+
^
| 1 .. N
|
v
+-------------+ +-----------------------------+
|I2RS Agent |---------------->|Trace Log |
| | |.............................|
+-------------+ |Log Entry [1 .. N] |
^ |.............................|
| |Starting Timestamp |
| |Request State |
| |Client ID |
| |Client Priority |
| ^ |Secondary ID |
Operation + | Result Code |Client Address |
Op Data | |Requested Operation |
v | |Applied Operation |
| |Operation Data Present |
| |Requested Operation Data |
| |Applied Operation Data |
| |Transaction ID |
| |Result Code |
| |Ending Timestamp |
| |Timeout Occurred |
v |End Of Message |
+-------------+ +-----------------------------+
|Routing |
|System |
+-------------+
Figure 1: I2RS Interaction Trace Log Capture
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5.2. I2RS Trace Log Mandatory Fields
In order to ensure that each I2RS interaction can be properly traced
back to the Client that made the request at a specific point in time,
the following information MUST be collected and stored by the Agent.
The list below describes the fields captured in the I2RS trace log.
Entry ID: This is a unique identifier for each entry in the I2RS
trace log. Since multiple operations can occur from the same
Client at the same time, it is important to have an identifier
that can be unambiguously associated to a specific entry.
Starting Timestamp: The specific time at which the I2RS operation
entered the specified Request State within the Agent. The time is
passed in the [RFC3339] format. Given that many I2RS operations
can occur in rapid succession, the use of fractional seconds MUST
be used to provide adequate granularity. Fractional seconds
SHOULD be expressed using human-readable 32-bit second and 32-bit
microsecond granularity in second.microsecond format. In the case
when the trace log entry specifies a Request State of COMPLETED
this time will reflect when the operation was first received by
the I2RS Agent.
Request State: The state of the given operation within the I2RS
Agent state machine between the specified Starting and Ending
Timestamps. This can be one of the following values:
PENDING: The request has been receieved and queued for
processing.
IN PROCESS: The request is currently being handled by the I2RS
Agent.
COMPLETED: The request has reached a terminal point.
In the case of the COMPLETED state, the Starting and Ending
Timestamps will cover the entire duration of the operation
including time spent in the PENDING and IN PROCESS states.
Every state transition MAY be logged unless doing so will put an
undue performance burden on the I2RS Agent. However, an entry
with Request State set to COMPLETED MUST be logged for all
operations.
Client Identity: The I2RS Client identity used to authenticate the
Client to the I2RS Agent.
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Client Priority: The I2RS Client priority assigned by the access
control model that authenticates the Client. For example, this
can be set by the NETCONF Access Control Model (NACM) as described
in [RFC6536].
Secondary Identity: This is an opaque identity that may be known to
the Client from a northbound controlling application. This is
used to trace the northbound application driving the actions of
the Client. The Client may not provide this identity to the Agent
if there is no external application driving the Client. However,
this field MUST be logged even if the Client does not provide a
Secondary Identity. In that case, the field will be logged with
an empty value.
Client Address: This is the network address of the Client that
connected to the Agent. For example, this may be an IPv4 or IPv6
address.
Requested Operation: This is the I2RS operation that was requested
to be performed. For example, this may be an add route operation
if a route is being inserted into a routing table. This may not
be the operation that was actually applied to the Agent.
Applied Operation: This is the I2RS operation that was actually
performed. This can differ from the Requested Operation in cases
where the Agent cannot satisfy the Requested Operation. This
field may not be logged unless the Request State is COMPLETED.
Operation Data Present: This is a Boolean field that indicates
whether or not addition per-Operation Data is present.
Requested Operation Data: This field comprises the data passed to
the Agent to complete the desired operation. For example, if the
operation is a route add operation, the Operation Data would
include the route prefix, prefix length, and next hop information
to be inserted as well as the specific routing table to which the
route will be added. If Operation Data is provided, then the
Operation Data Present field MUST be set to TRUE. Some operations
may not provide operation data. In those cases, the Operation
Data Present field MUST be set to FALSE, and this field MUST be
empty. This may not represent the data that was used for the
operation that was actually applied on the Agent.
Applied Operation Data: This field comprises the data that was
actually applied as part of the Applied Operation. If the Agent
cannot satisfy the Requested Operation with the Requested
Operation Data, then this field can differ from the Requested
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Operation Data. This field may not be logged unless the Request
State is COMPLETED.
Transaction ID: The Transaction Identity represents that this
particular operation is part of a long-running I2RS transaction
that can consist of multiple, related I2RS operations. Using this
value, one can relate multiple log entries together as they are
part of a single, overall I2RS operation.
Result Code: This field holds the result of the operation once the
Request State is COMPLETED. In the case of RIB operations, this
MUST be the return code as specified in Section 4 of
[I-D.ietf-i2rs-rib-info-model]. The operation may not complete
with a result code in the case of a timeout. If the operation
fails to complete, it MUST still log the attempted operation with
an appropriate result code.
Timeout Occurred: This is a Boolean field that indicates whether or
not a timeout occurred in the operation. When this is true, the
value of the Ending Timestamp MUST be set to the time the Agent
recorded for the timeout occurrence. This field may not be logged
unless the Request State is COMPLETED.
Ending Timestamp: The specific time at which the I2RS operation
exited the specified Request State within the I2RS Agent. The
time is passed in the [RFC3339] format. Given that many I2RS
operations can occur in rapid succession, the use of fractional
seconds MUST be used to provide adequate granularity. Fractional
seconds SHOULD be expressed using human-readable 32-bit second and
32-bit microsecond granularity in second.microsecond format.
End Of Message: Each log entry SHOULD have an appropriate End Of
Message (EOM) indicator. See section Section 5.3 below for more
details.
5.3. End of Message Marker
Because of variability within I2RS trace log fields, implementors
MUST use a format-appropriate end of message (EOM) indicator in order
to signify the end of a particular record. That is, regardless of
format, the I2RS trace log MUST provide a distinct way of
distinguishing between the end of one record and the beginning of
another. For example, in a linear formated log (similar to syslog)
the EOM marker may be a newline character. In an XML formated log,
the schema would provide for element tags that denote beginning and
end of records. In a JSON formated log, the syntax would provide
record separation (likely by comma-separated array elements).
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6. Examples
This section shows a sample of what the fields and values could look
like.
Entry ID: 1
Starting Timestamp: 2013-09-03T12:00:01.21+00:00
Request State: COMPLETED
Client ID: 5CEF1870-0326-11E2-A21F-0800200C9A66
Client Priority: 100
Secondary ID: com.example.RoutingApp
Client Address: 2001:db8:c0c0::2
Requested Operation: ROUTE_ADD
Applied Operation: ROUTE_ADD
Operation Data Present: TRUE
Requested Operation Data: PREFIX 2001:db8:feed:: PREFIX-LEN 64
NEXT-HOP 2001:db8:cafe::1
Applied Operation Data: PREFIX 2001:db8:feed:: PREFIX-LEN 64
NEXT-HOP 2001:db8:cafe::1
Transaction ID: 2763461
Result Code: SUCCESS(0)
Timeout Occurred: FALSE
Ending Timestamp: 2013-09-03T12:00:01.23+00:00
7. Operational Guidance
Specific operational procedures regarding temporary log storage,
rollover, retrieval, and access of I2RS trace logs is out of scope
for this document. Organizations employing I2RS trace logging are
responsible for establishing proper operational procedures that are
appropriately suited to their specific requirements and operating
environment. In this section we only provide fundamental and
generalized operational guidelines that are implementation-
independent.
7.1. Trace Log Creation
The I2RS Agent interacts with the Routing and Signaling functions of
the Routing Element. Since the I2RS Agent is responsible for
actually making the routing changes on the associated network device,
it creates and maintains a log of operations that can be retrieved to
troubleshoot I2RS-related impact to the network.
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7.2. Trace Log Temporary Storage
The trace information may be temporarily stored either in an in-
memory buffer or as a file local to the Agent. Care should be given
to the number of I2RS operations expected on a given Agent so that
the appropriate storage medium is used and to maximize the
effectiveness of the log while not impacting the performance and
health of the Agent. Client requests may not always be processed
synchronously or within a bounded time period. Consequently, to
ensure that trace log fields, such as "Operation" and "Result Code",
are part of the same trace log record it may require buffering of the
trace log entries. This buffering may result in additional resource
load on the Agent and the network element.
Section 7.3 discusses rotating the trace log in order to preserve the
operation history without exhausting Agent or network device
resources. It is perfectly acceptable, therefore, to use both an in-
memory buffer for recent operations while rotating or archiving older
operations to a local file.
It is outside the scope of this document to specify the
implementation details (i.e., size, throughput, data protection,
privacy, etc.) for the physical storage of the I2RS log file. Data
retention policies of the I2RS traceability log is also outside the
scope of this document.
7.3. Trace Log Rotation
In order to prevent the exhaustion of resources on the I2RS Agent or
its associated network device, it is RECOMMENDED that the I2RS Agent
implements trace log rotation. The details on how this is achieved
are left to the implementation and outside the scope of this
document. However, it should be possible to do file rotation based
on either time or size of the current trace log. If file rollover is
supported, multiple archived log files should be supported in order
to maximize the troubleshooting and accounting benefits of the trace
log.
7.4. Trace Log Retrieval
Implementors are free to provide their own, proprietary interfaces
and develop custom tools to retrieve and display the I2RS trace log.
These may include the display of the I2RS trace log as Command Line
Interface (CLI) output. However, a key intention of defining this
information model is to establish a vendor-agnostic and consistent
interface to collect I2RS trace data. Correspondingly, retrieval of
the data should also be made vendor-agnostic.
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Despite the fact that export of I2RS trace log information could be
an invaluable diagnostic tool for off-box analysis, exporting this
information MUST NOT interfere with the ability of the Agent to
process new incoming operations.
The following three sections describe potential ways the trace log
can be accessed. At least one of these three MUST be used, with the
I2RS mechanisms being preferred as they are vendor-independent
approaches to retrieving the data.
7.4.1. Retrieval Via Syslog
The syslog protocol [RFC5424] is a standard way of sending event
notification messages from a host to a collector. However, the
protocol does not define any standard format for storing the
messages, and thus implementors of I2RS tracing would be left to
define their own format. So, while the data contained within the
syslog message would adhere to this information model, and may be
consumable by a human operator, it would not be easily parseable by a
machine. Syslog MAY be employed as a means of retrieving or
disseminating the I2RS trace log contents.
If syslog is used for trace log retrieval, then existing logging
infrastructure and capabilities of syslog [RFC5424] should be
leveraged without the need to define or extend existing formats. For
example, the various fields described in Section 5.2 SHOULD be
modeled and encoded as Structured Data Elements (referred to as "SD-
ELEMENT"), as described in Section 6.3.1 of [RFC5424].
7.4.2. Retrieval Via I2RS Information Collection
Section 6.7 of the I2RS architecture [I-D.ietf-i2rs-architecture]
defines a mechanism for information collection. The information
collected includes obtaining a snapshot of a large amount of data
from the network element. It is the intent of I2RS to make this data
available in an implementor-agnostic fashion. Therefore, the I2RS
trace log SHOULD be made available via the I2RS information
collection mechanism either as a single snapshot or via a
subscription stream.
7.4.3. Retrieval Via I2RS Pub-Sub
Section 7.6 of the I2RS architecture [I-D.ietf-i2rs-architecture]
goes on to describe notification mechanisms for a feed of changes
happening within the I2RS layer. Specifically, the requirements for
a publish-subscribe system for I2RS are defined in
[I-D.ietf-i2rs-pub-sub-requirements]. I2RS Agents SHOULD support
publishing I2RS trace log information to that feed as described in
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that document. Subscribers would then receive a live stream of I2RS
interactions in trace log format and could flexibly choose to do a
number of things with the log messages. For example, the subscribers
could log the messages to a datastore, aggregate and summarize
interactions from a single Client, etc. The full range of potential
activites is virtually limitless and the details of how they are
performed are outside the scope of this document, however.
8. IANA Considerations
This document makes no request of IANA.
9. Security Considerations
The I2RS trace log, like any log file, reveals the state of the
entity producing it as well as the identifying information elements
and detailed interactions of the system containing it. The
information model described in this document does not itself
introduce any security issues, but it does define the set of
attributes that make up an I2RS log file. These attributes may
contain sensitive information and thus should adhere to the security,
privacy and permission policies of the organization making use of the
I2RS log file.
It is outside the scope of this document to specify how to protect
the stored log file, but it is expected that adequate precautions and
security best practices such as disk encryption, appropriately
restrictive file/directory permissions, suitable hardening and
physical security of logging entities, mutual authentication,
transport encryption, channel confidentiality, and channel integrity
if transferring log files. Additionally, the potentially sensitive
information contained in a log file SHOULD be adequately anonymized
or obfuscated by operators to ensure its privacy.
10. Acknowledgments
The authors would like to thank Alia Atlas for her initial feedback
and overall support for this work. Additionally, the authors
acknowledge Alvaro Retana, Russ White, Matt Birkner, Jeff Haas, Joel
Halpern, Dean Bogdanovich, Ignas Bagdonas, Nobo Akiya, Kwang-koog
Lee, Sue Hares, Mach Chen, and Alex Clemm for their reviews,
contributed text, and suggested improvements to this document.
11. References
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11.1. 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-13 (work in
progress), February 2016.
[I-D.ietf-i2rs-problem-statement]
Atlas, A., Nadeau, T., and D. Ward, "Interface to the
Routing System Problem Statement", draft-ietf-i2rs-
problem-statement-10 (work in progress), February 2016.
[I-D.ietf-i2rs-pub-sub-requirements]
Voit, E., Clemm, A., and A. Prieto, "Requirements for
Subscription to YANG Datastores", draft-ietf-i2rs-pub-sub-
requirements-06 (work in progress), April 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
11.2. Informative References
[I-D.ietf-i2rs-rib-info-model]
Bahadur, N., Kini, S., and J. Medved, "Routing Information
Base Info Model", draft-ietf-i2rs-rib-info-model-08 (work
in progress), October 2015.
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
<http://www.rfc-editor.org/info/rfc3339>.
[RFC5424] Gerhards, R., "The Syslog Protocol", RFC 5424,
DOI 10.17487/RFC5424, March 2009,
<http://www.rfc-editor.org/info/rfc5424>.
[RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration
Protocol (NETCONF) Access Control Model", RFC 6536,
DOI 10.17487/RFC6536, March 2012,
<http://www.rfc-editor.org/info/rfc6536>.
Authors' Addresses
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Joe Clarke
Cisco Systems, Inc.
7200-12 Kit Creek Road
Research Triangle Park, NC 27709
US
Phone: +1-919-392-2867
Email: jclarke@cisco.com
Gonzalo Salgueiro
Cisco Systems, Inc.
7200-12 Kit Creek Road
Research Triangle Park, NC 27709
US
Email: gsalguei@cisco.com
Carlos Pignataro
Cisco Systems, Inc.
7200-12 Kit Creek Road
Research Triangle Park, NC 27709
US
Email: cpignata@cisco.com
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