Network Working Group L. Xia
Internet-Draft D. Zhang
Intended status: Experimental Huawei
Expires: January 5, 2018 Y. Wu
Aliababa Group
R. Kumar
A. Lohiya
Juniper Networks
H. Birkholz
Fraunhofer SIT
July 04, 2017

An Information Model for the Monitoring of Network Security Functions (NSF)


The Network Security Functions (NSF) NSF-facing interface exists between the Service Provider’s management system (or Security Controller) and the NSFs to enforce the security policy provisioning and network security status monitoring. This document focuses on the monitoring part of it and proposes the information model for it.

Status of This Memo

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This Internet-Draft will expire on January 5, 2018.

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Table of Contents

1. Introduction

According to [I-D.ietf-i2nsf-terminology], the interface provided by a NSF (e.g., FW, IPS, Anti-DDOS, or Anti-Virus function) to administrative entities (e.g., NMS, security controller) for configuring security function in the NSF and monitoring the NSF is referred to as a “I2NSF NSF-Facing Interface”. The monitoring part of it is meant to acquire vital information about the NSF via, e.g. notifications, events, records, counters. The monitoring of the NSF plays a very important role in the overall security framework if done in a timely and comprehensive way. The monitoring information generated by a NSF can very well be an early indication of malicious activity, or anomalous behavior, or a potential sign of denial of service attacks.

This draft proposes a comprehensive NSF monitoring information model that provides visibility into NSFs. This document will not go into the design details of NSF-Facing Interfaces. Instead, this draft is focused on specifying the information and illustrates the methods that enable a NSF to provide the information required in order to be monitored in a scalable and efficient way via the NSF-Facing Interface. The information model for monitoring presented in this document is a complement to the information model for the security policy provisioning part of the NSF-Facing Interface specified in [I-D.xibassnez-i2nsf-capability].

2. Terminology

2.1. Key Words

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].

2.2. Definition of Terms

This document uses the terms defined in [I-D.ietf-i2nsf-terminology].

3. Use cases for NSF Monitoring Data

As mentioned earlier, monitoring plays a very critical role in the overall security framework. The monitoring of the NSF provides very valuable information to the security controller in maintaining the provisioned security posture. Besides this, there are various other reasons to monitor the NSFs as listed below:

4. Classification of NSF Monitoring Data

In order to maintain a strong security posture, it is not only necessary to configure NSF security policies but also to continuously monitor NSF by consuming acquirable observable information. This enables security admins to assess what is happening in the network timely. It is not possible to block all the internal and external threats based on static security posture. To achieve this goal, a very dynamic posture with constant visibility is required. This draft defines a set of information elements (and their scope) that can be acquired from NSF and can be used as monitoring information. In essence, these types of monitoring information can be leveraged to support constant visibility on multiple levels of granularity and can be consumed by corresponding functions.

Three basic domains about the monitoring of information originating from a system entity [RFC4949] or a NSF are highlighted in this document.

The Alarm Management Framework in [RFC3877] defines an Event as “something that happens which may be of interest. A fault, a change in status, crossing a threshold, or an external input to the system, for example.” In the I2NSF domain, I2NSF events [I-D.ietf-i2nsf-terminology] are created and the scope of the Alarm Management Framework Events is still applicable due to its broad definition. The model presented in this document elaborates on the work-flow of creating I2NSF events in the context of NSF monitoring and on how initial I2NSF events are created.

As with I2NSF components, every generic system entity can include a set of capabilities [I-D.ietf-i2nsf-terminology] that creates information about the context, composition, configuration, state or behavior of that system entity. This information is intended to be provided to other consumers of informations—and in the scope of this document, to monitor that information in an automated fashion.

4.1. Retention and Emission

Typically, a system entity populates standardized interface, such as SNMP, NETCONF, RESTCONF or CoMI to provide and emit created information directly via NSF-Facing Interfaces [I-D.ietf-i2nsf-terminology]. Alternatively, the created information is retained inside the system entity (or hierarchy of system entities in a composite device) via records or counters that are not exposed directly via NSF-Facing Interfaces.

Information emitted via standardized interfaces can be consumed by an I2NSF Agent [I-D.ietf-i2nsf-terminology] that includes the capability to consume information not only via I2NSF Interfaces but also via interfaces complementary to the standardized interfaces a generic system entity provides.

Information retained on a system entity requires a corresponding I2NSF Agent to access aggregated records of information, typically in the form of logfiles or databases. There are ways to aggregate records originating from different system entities over a network, for examples via Syslog [RFC5424] or Syslog over TCP [RFC6587]. But even if records are conveyed, the result is the same kind of retention in form of a bigger aggregate of records on another system entity.

An I2NSF Agent is required to process fresh [RFC4949] records created by I2NSF Functions in order to provide them to other I2NSF Components via corresponding I2NSF Interfaces timely. This process is effectively based on homogenizing functions that can access and convert specific kinds of records into information that can be provided and emitted via I2NSF interfaces.

Retained or emitted, the information required to support monitoring processes has to be processed by an I2NSF Agent at some point in the work-flow. Typical locations of these I2NSF Agents are:

4.2. Notifications and Events

A specific task of I2NSF Agents is to process I2NSF Policy Rules [I-D.ietf-i2nsf-terminology]. Rules are composed of three clauses: Events, Conditions, and Actions. In consequence, an I2NSF Event is required to trigger an I2NSF Policy Rule. “An I2NSF Event is defined as any important occurrence in time of a change in the system being managed, and/or in the environment of the system being managed.” [I-D.ietf-i2nsf-terminology], which aligns well with the generic definition of Event from [RFC3877].

The model illustrated in this document introduces a complementary type of information that can be conveyed—notification.

An occurrence of a change of context, composition, configuration, state or behavior of a system entity that can be directly or indirectly observed by an I2NSF Agent and can be used as input for an event-clause in I2NSF Policy Rules.
A notification is similar to an I2NSF Event with the exception that it is created by a system entity that is not an I2NSF Component and that its importances is yet to be assessed. Semantically, a notification is not an I2NSF Event in the context of I2NSF, although they can potentially use the exact same information or data model. In respect to [RFC3877], a Notification is a specific subset of events, because they convey information about “something that happens which may be of interest”. In consequence, Notifications can contain information with very low expressiveness or relevance. Hence, additional post-processing functions, such as aggregation, correlation or simple anomaly detection, might have to be employed to satisfy a level of expressiveness that is required for an event-clause of an I2NSF Policy Rule.

It is important to note that the consumer of a notification (the observer) assesses the importance of a notification and not the producer. The producer can include metadata in a notification that supports the observer in assessing the importance (even metadata about severity), but the deciding entity is an I2NSF Agent.

4.3. Unsolicited Poll and Solicited Push

The freshness of the monitored information depends on the acquisition method. Ideally, an I2NSF Agent is accessing every relevant information about the I2NSF Component and is emitting I2NSF Events to a monitoring NSF timely. Publication of events via a pubsub/broker model, peer-2-peer meshes, or static defined channels are only a few examples on how a solicited push of I2NSF Events can be facilitated. The actual mechanic implemented by an I2NSF Component is out of the scope of this document.

Often, corresponding management interfaces have to be queried in intervals or on-demand if required by an I2NSF Policy rule. In some cases, a collection of information has to be conducted via login mechanics provided by a system entity. Accessing records of information via this kind of unsolicited polls can introduce a significant latency in regard to the freshness of the monitored information. The actual definition of intervals implemented by an I2NSF Component is also out of scope of this document.

4.4. I2NSF Monitoring Terminology for Retained Information

Unlike information emitted via notifications and events, records do not require immediate attention from an analyst but may be useful for visibility and retroactive cyber forensic. Depending on the record format, there are different qualities in regard to structure and detail. Records are typically stored in logfiles or databases on a system entity or NSF. Records in the form of logfiles usually include less structures but potentially more detailed information in regard to changes of an system entity’s characteristics. In contrast, databases often use more strict schemas or data models, therefore enforcing a better structure, but inhibit storing information that do not match those models (‘closed world assumption’). Records can be continuously processed by I2NSF Agents that act as I2NSF Producer and emit events via functions specifically tailored to a certain type of record. Typically, records are information generated by NSF or system entity about their operational and informational data, or various changes in system characteristics, such as user activities, network/traffic status, network activity, etc. They are important for debugging, auditing and security forensic.
A specific representation of continuous value changes of information elements that potentially occur in high frequency. A prominent example are network interface counters, e.g. PDU amount or byte amount, drop counters, error counters etc. Counters are useful in debugging and visibility into operational behavior of the NSF. An I2NSF Agent that observes the progression of counters can act as an I2NSF Producer and emit events in respect to I2NSF Policy Rules.

5. Conveyance of NSF Monitoring Information

As per the use cases of NSF monitoring data, information needs to be conveyed to various I2NSF Consumers based on requirements imposed by I2NSF Capabilities and work-flows. There are multiple aspects to be considered in regard to emission of monitoring information to requesting parties as listed below:

6. Basic Information Model for All Monitoring Data

As explained in the above section, there is a wealth of data available from the NSF that can be monitored. Firstly, there must be some general information with each monitoring message sent from an NSF that helps consumer in identifying meta data with that message, which are listed as below:

7. Extended Information Model for Monitoring Data

This section covers the additional information associated with the system messages. The extended information model is only for the structured data such as alarm. Any unstructured data is specified with basic information model only.

[Editors’ note]: This section remains the same as -02 version, although the classification of the monitoring data has been changed from -02 version. The new inconsistency will be addressed in next verion.

7.1. System Alarm

7.1.1. Memory Alarm

The following information should be included in a Memory Alarm:

7.1.2. CPU Alarm

The following information should be included in a CPU Alarm:

7.1.3. Disk Alarm

The following information should be included in a Disk Alarm:

7.1.4. Hardware Alarm

The following information should be included in a Hardware Alarm:

7.1.5. Interface Alarm

The following information should be included in a Interface Alarm:

7.2. System Events

7.2.1. Access Violation

The following information should be included in this event:

7.2.2. Configuration Change

The following information should be included in this event:

7.3. System Log

7.3.1. Access Logs

Access logs record administrators’ login, logout, and operations on the device. By analyzing them, security vulnerabilities can be identified. The following information should be included in operation report:

7.3.2. Resource Utilization Logs

Running reports record the device system’s running status, which is useful for device monitoring. The following information should be included in running report:

7.3.3. User Activity Logs

User activity logs provide visibility into users’ online records (such as login time, online/lockout duration, and login IP addresses) and the actions users perform. User activity reports are helpful to identify exceptions during user login and network access activities.

7.4. System Counters

7.4.1. Interface counters

Interface counters provide visibility into traffic into and out of NSF, bandwidth usage.

7.5. NSF Events

7.5.1. DDoS Event

The following information should be included in a DDoS Event:

7.5.2. Session Table Event

The following information should be included in a Session Table Event:

7.5.3. Virus Event

The following information should be included in a Virus Event:

7.5.4. Intrusion Event

The following information should be included in a Intrustion Event:

7.5.5. Botnet Event

The following information should be included in a Botnet Event:

7.5.6. Web Attack Event

The following information should be included in a Web Attack Alarm:

7.6. NSF Logs

7.6.1. DDoS Logs

Besides the fields in an DDoS Alarm, the following information should be included in a DDoS Logs:

7.6.2. Virus Logs

Besides the fields in an Virus Alarm, the following information should be included in a Virus Logs:

7.6.3. Intrusion Logs

Besides the fields in an Intrusion Alarm, the following information should be included in a Intrusion Logs:

7.6.4. Botnet Logs

Besides the fields in an Botnet Alarm, the following information should be included in a Botnet Logs:

7.6.5. DPI Logs

DPI Logs provide statistics on uploaded and downloaded files and data, sent and received emails, and alert and block records on websites. It’s helpful to learn risky user behaviors and why access to some URLs is blocked or allowed with an alert record.

7.6.6. Vulnerabillity Scanning Logs

Vulnerability scanning logs record the victim host and its related vulnerability information that should to be fixed. the following information should be included in the report:

7.6.7. Web Attack Logs

Besides the fields in an Web Attack Alarm, the following information should be included in a Web Attack Report:

7.7. NSF Counters

7.7.1. Firewall counters

Firewall counters provide visibility into traffic signatures, bandwidth usage, and how the configured security and bandwidth policies have been applied.

7.7.2. Policy Hit Counters

Policy Hit Counters record the security policy that traffic matches and its hit count. It can check if policy configurations are correct.

8. IANA Considerations

This document makes no request of IANA.

Note to RFC Editor: this section may be removed on publication as an RFC.

9. Security Considerations

The monitoring information of NSF should be protected by the secure communication channel, to ensure its confidentiality and integrity. In another side, the NSF and security controller can all be faked, which lead to undesireable results, i.e., leakage of NSF’s important operational information, faked NSF sending false information to mislead security controller. The mutual authentication is essential to protected against this kind of attack. The current mainstream security technologies (i.e., TLS, DTLS, IPSEC, X.509 PKI) can be employed approriately to provide the above security functions.

In addition, to defend against the DDoS attack caused by a lot of NSFs sending massive monitoring information to the security controller, the rate limiting or similar mechanisms should be considered in NSF and security controller, whether in advance or just in the process of DDoS attack.

10. References

10.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC3877] Chisholm, S. and D. Romascanu, "Alarm Management Information Base (MIB)", RFC 3877, DOI 10.17487/RFC3877, September 2004.
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2", FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007.
[RFC5424] Gerhards, R., "The Syslog Protocol", RFC 5424, DOI 10.17487/RFC5424, March 2009.
[RFC6587] Gerhards, R. and C. Lonvick, "Transmission of Syslog Messages over TCP", RFC 6587, DOI 10.17487/RFC6587, April 2012.
[RFC7011] Claise, B., Trammell, B. and P. Aitken, "Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of Flow Information", STD 77, RFC 7011, DOI 10.17487/RFC7011, September 2013.

10.2. Informative References

[I-D.ietf-i2nsf-terminology] Hares, S., Strassner, J., Lopez, D., Xia, L. and H. Birkholz, "Interface to Network Security Functions (I2NSF) Terminology", Internet-Draft draft-ietf-i2nsf-terminology-03, March 2017.
[I-D.xibassnez-i2nsf-capability] Xia, L., Strassner, J., Basile, C. and D. Lopez, "Information Model of NSFs Capabilities", Internet-Draft draft-xibassnez-i2nsf-capability-02, July 2017.
[RFC3954] Claise, B., "Cisco Systems NetFlow Services Export Version 9", RFC 3954, DOI 10.17487/RFC3954, October 2004.


Authors' Addresses

Liang Xia Huawei EMail:
Dacheng Zhang Huawei EMail:
Yi Wu Aliababa Group EMail:
Rakesh Kumar Juniper Networks EMail:
Anil Lohiya Juniper Networks EMail:
Henk Birkholz Fraunhofer SIT EMail: