Behave S. Sivakumar
Internet-Draft R. Penno
Intended status: Standards Track Cisco Systems
Expires: July 18, 2013 January 14, 2013
IPFIX Information Elements for logging NAT Events
draft-sivakumar-behave-nat-logging-06
Abstract
NAT devices are required to log events like creation and deletion of
translations and information about the resources it is managing.
With the wide deployment of Carrier Grade NAT (CGN) devices, the
logging of events have become very important for legal purposes. The
logs are required in many cases to identify an attacker or a host
that was used to launch malicious attacks and/or for various other
purposes of accounting. Since there is no standard way of logging
this information, different NAT devices behave differently and hence
it is difficult to expect a consistent behavior. The lack of a
consistent way makes it difficult to write the collector applications
that would receive this data and process it to present useful
information. This document describes the information that is
required to be logged by the NAT devices.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 18, 2013.
Copyright Notice
Copyright (c) 2013 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
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Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Event based logging . . . . . . . . . . . . . . . . . . . . . 4
4.1. Information Elements . . . . . . . . . . . . . . . . . . . 4
4.2. Definition of NAT Events . . . . . . . . . . . . . . . . . 7
4.3. Quota exceeded - Sub Event types . . . . . . . . . . . . . 8
4.4. Templates for NAT Events . . . . . . . . . . . . . . . . . 8
4.4.1. NAT44 create and delete session event . . . . . . . . 8
4.4.2. NAT64 create and delete session event . . . . . . . . 9
4.4.3. NAT44 BIB create and delete event . . . . . . . . . . 10
4.4.4. NAT64 BIB create and delete event . . . . . . . . . . 10
4.4.5. Addresses Exhausted event . . . . . . . . . . . . . . 10
4.4.6. Ports Exhausted event . . . . . . . . . . . . . . . . 11
4.4.7. Quota exceeded . . . . . . . . . . . . . . . . . . . . 11
4.4.8. Address Binding . . . . . . . . . . . . . . . . . . . 12
4.4.9. Port block allocation and de-allocation . . . . . . . 12
5. Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.1. IPFIX . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
9.1. Normative References . . . . . . . . . . . . . . . . . . . 13
9.2. Informative References . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
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1. Terminology
The usage of the term "NAT device" in this document refer to any
NAT44 and NAT64 devices. The usage of the term "collector" refers to
any device that receives the binary data from a NAT device and
converts that into meaningful information. This document uses the
term "Session" as it is defined in [RFC2663] and the term BIB as it
is defined in [RFC6146]
2. Introduction
This document details the IPFIX Information Elements(IEs) that are
required for logging by a NAT device. The document will specify the
format of the IE's that are required to be logged by the NAT device
and all the optional fields. The fields specified in this document
are gleaned from [RFC4787] and [RFC5382].
2.1. Requirements Language
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].
3. Scope
This document provides the information model to be used for logging
the NAT devices including Carrier Grade NAT (CGN) events. This
document focuses exclusively on the specification of IPFIX IE's.
This document does not provide guidance on the transport protocol
like TCP, UDP or SCTP that is to be used to log NAT events. The log
events SHOULD NOT be lost but the choice of the actual transport
protocol is beyond the scope of this document.
The existing IANA IPFIX Information Elements registry [IPFIX-IANA]
already has assignments for many NAT logging events. For
convenience, this document uses those same Information Elements.
However, as stated earlier, this document is not defining IPFIX or
Netflow 9 as the framework for logging. Rather, the information
contained in these elements is within the scope of this document.
This document assumes that the NAT device will use the existing IPFIX
framework to send the log events to the collector. This would mean
that the NAT device will specify the template that it is going to use
for each of the events. The templates can be of varying length and
there could be multiple templates that a NAT device could use to log
the events.
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The implementation details of the collector application is beyond the
scope of this document.
The optimization of logging the NAT events are left to the
implementation and are beyond the scope of this document.
4. Event based logging
An event in a NAT device can be viewed as a happening as it relates
to the management of NAT resources. The creation and deletion of NAT
sessions and bindings are examples of events as it results in the
resources (addresses and ports) being allocated or freed. The events
can happen either through the processing of data packets flowing
through the NAT device or through an external entity installing
policies on the NAT router or as a result of an asynchronous event
like a timer. The list of events are provided in Section 4.1. Each
of these events SHOULD be logged, unless they are administratively
prohibited. A NAT device MAY log these events to multiple collectors
if redundancy is required. The network administrator will specify
the collectors to which the log records are to be sent.
A collector may receive NAT events from multiple CGN devices and
should be able to distinguish between the devices. Each CGN device
should have a unique source ID to identify themselves. The source ID
is part of the IPFIX template and data exchange.
Prior to logging any events, the NAT device MUST send the template of
the record to the collector to advertise the format of the data
record that it is using to send the events. The templates can be
exchanged as frequently as required given the reliability of the
connection. There SHOULD be a configurable timer for controlling the
template refresh. NAT device SHOULD combine as many events as
possible in a single packet to effectively utilize the network
bandwidth.
4.1. Information Elements
The templates could contain a subset of the Information Elements(IEs)
shown in Table 1 depending upon the event being logged. For example
a NAT44 session creation template record will contain,
{sourceIPv4Adress, postNATSourceIPv4Address, destinationIpv4Address,
postNATDestinationIPv4Address, sourceTransportPort,
postNAPTSourceTransportPort, destinationTransportPort,
postNAPTDestTransportPort, natOriginatingAddressRealm, natEvent,
timeStamp}
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An example of the actual event data record is shown below - in a
readable form
{192.168.16.1, 201.1.1.100, 207.85.231.104, 207.85.231.104, 14800,
1024, 80, 80, 0, 1, 09:20:10:789}
A single NAT device could be exporting multiple templates and the
collector should support receiving multiple templates from the same
source.
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The following is the table of all the IE's that a CGN device would
need to export the events. The formats of the IE's and the IPFIX IDs
are listed below.
+----------------------------------+--------+-------+---------------+
| Field Name | Size | IANA | Description |
| | (bits) | IPFIX | |
| | | ID | |
+----------------------------------+--------+-------+---------------+
| timeStamp | 64 | 323 | System Time |
| | | | when the |
| | | | event |
| | | | occured. |
| vlanID | 16 | 58 | VLAN ID in |
| | | | case of |
| | | | overlapping |
| | | | networks |
| ingressVRFID | 32 | 234 | VRF ID in |
| | | | case of |
| | | | overlapping |
| | | | networks |
| sourceIPv4Address | 32 | 8 | Source IPv4 |
| | | | Address |
| postNATSourceIPv4Address | 32 | 225 | Translated |
| | | | Source IPv4 |
| | | | Address |
| protocolIdentifier | 8 | 4 | Transport |
| | | | protocol |
| sourceTransportPort | 16 | 7 | Source Port |
| postNAPTsourceTransportPort | 16 | 227 | Translated |
| | | | Source port |
| destinationIPv4Address | 32 | 12 | Destination |
| | | | IPv4 Address |
| postNATDestinationIPv4Address | 32 | 226 | Translated |
| | | | IPv4 |
| | | | destination |
| | | | address |
| destinationTransportPort | 16 | 11 | Destination |
| | | | port |
| postNAPTdestinationTransportPort | 16 | 228 | Translated |
| | | | Destination |
| | | | port |
| sourceIPv6Address | 27 | 128 | Source IPv6 |
| | | | address |
| destinationIPv6Address | 128 | 28 | Destination |
| | | | IPv6 address |
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| postNATSourceIPv6Address | 128 | 281 | Translated |
| | | | source IPv6 |
| | | | addresss |
| postNATDestinationIPv6Address | 128 | 282 | Translated |
| | | | Destination |
| | | | IPv6 address |
| natOriginatingAddressRealm | 8 | 229 | Address Realm |
| natEvent | 8 | 230 | Type of Event |
| portRangeStart | 16 | 361 | Allocated |
| | | | port block |
| | | | start |
| portRangeEnd | 16 | 362 | Allocated |
| | | | Port block |
| | | | end |
| portRangeStepSize | 16 | 363 | Step size of |
| | | | next port |
| portRangeNumPorts | 16 | 364 | Number of |
| | | | ports |
+----------------------------------+--------+-------+---------------+
Table 1: Template format Table
4.2. Definition of NAT Events
The following are the list of NAT events and the proposed event
values. The list can be expanded in the future as necessary. The
data record will have the corresponding natEvent value to identify
the event that is being logged.
+--------------------------+--------+
| Event Name | Values |
+--------------------------+--------+
| NAT44 Session create | 1 |
| NAT44 Session delete | 2 |
| NAT Addresses exhausted | 3 |
| NAT64 Session create | 4 |
| NAT64 Session delete | 5 |
| NAT44 BIB create | 6 |
| NAT44 BIB delete | 7 |
| NAT64 BIB create | 8 |
| NAT64 BIB delete | 9 |
| NAT ports exhausted | 10 |
| Quota exceeded | 11 |
| Address Binding | 12 |
| Port block allocation | 13 |
| Port block de-allocation | 14 |
+--------------------------+--------+
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Table 2: NAT Event ID table
4.3. Quota exceeded - Sub Event types
The following table shows the sub event types for the Quota exceeded
event
+---------------------------+--------+
| Quota Exceeded Event Name | Values |
+---------------------------+--------+
| Max Session entries | 1 |
| Max BIB entries | 2 |
| Max entries per user | 3 |
+---------------------------+--------+
Table 3: Sub Event ID table
4.4. Templates for NAT Events
The following is the template of events that will have to logged.
The events below are identified at the time of this writing but the
events are expandable. Depending on the implementation and
configuration various IE's specified can be included or ignored.
4.4.1. NAT44 create and delete session event
This event will be generated when a NAT44 session is created or
deleted. The template will be the same, the natEvent will indicate
whether it is a create or a delete event. The following is a
template of the event.
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+----------------------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+----------------------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| vlanID/ingressVRFID | 32 | No |
| sourceIPv4Address | 32 | Yes |
| postNATSourceIPv4Address | 32 | Yes |
| protocolIdentifier | 8 | Yes |
| sourceTransportPort | 16 | Yes |
| postNAPTsourceTransportPort | 16 | Yes |
| destinationIPv4Address | 32 | No |
| postNATDestinationIPv4Address | 32 | No |
| destinationTransportPort | 16 | No |
| postNAPTdestinationTransportPort | 16 | No |
| natOriginatingAddressRealm | 8 | No |
| natEvent | 8 | Yes |
+----------------------------------+-------------+-----------+
Table 4: NAT44 Session delete/create template
4.4.2. NAT64 create and delete session event
This event will be generated when a NAT64 session is created. The
following is a template of the event.
+----------------------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+----------------------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| vlanID/ingressVRFID | 32 | No |
| sourceIPv6Address | 128 | Yes |
| postNATSourceIPv4Address | 32 | Yes |
| protocolIdentifier | 8 | Yes |
| sourceTransportPort | 16 | Yes |
| postNAPTsourceTransportPort | 16 | Yes |
| destinationIPv6Address | 128 | No |
| postNATDestinationIPv4Address | 32 | No |
| destinationTransportPort | 16 | No |
| postNAPTdestinationTransportPort | 16 | No |
| natOriginatingAddressRealm | 8 | No |
| natEvent | 8 | Yes |
+----------------------------------+-------------+-----------+
Table 5: NAT64 session create/delete event template
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4.4.3. NAT44 BIB create and delete event
This event will be generated when a NAT44 Bind entry is created. The
following is a template of the event.
+-----------------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+-----------------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| vlanID/ingressVRFID | 32 | No |
| sourceIPv4Address | 32 | Yes |
| postNATSourceIPv4Address | 32 | Yes |
| protocolIdentifier | 8 | No |
| sourceTransportPort | 16 | No |
| postNAPTsourceTransportPort | 16 | No |
| natOriginatingAddressRealm | 8 | No |
| natEvent | 8 | Yes |
+-----------------------------+-------------+-----------+
Table 6: NAT44 BIB create/delete event template
4.4.4. NAT64 BIB create and delete event
This event will be generated when a NAT64 Bind entry is created. The
following is a template of the event.
+-----------------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+-----------------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| vlanID/ingressVRFID | 32 | No |
| sourceIPv6Address | 128 | Yes |
| postNATSourceIPv4Address | 32 | Yes |
| protocolIdentifier | 8 | No |
| sourceTransportPort | 16 | No |
| postNAPTsourceTransportPort | 16 | No |
| natOriginatingAddressRealm | 8 | No |
| natEvent | 8 | Yes |
+-----------------------------+-------------+-----------+
Table 7: NAT64 BIB create/delete event template
4.4.5. Addresses Exhausted event
This event will be generated when a NAT device runs out of global
IPv4 addresses in a given pool of addresses. Typically, this event
would mean that the NAT device wont be able to create any new
translations until some addresses/ports are freed. The following is
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a template of the event.
+-------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+-------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| natPoolName | String | Yes |
+-------------+-------------+-----------+
Table 8: NAT Address Exhausted event template
4.4.6. Ports Exhausted event
This event will be generated when a NAT device runs out of ports for
a global IPv4 address. Port exhaustion shall be reported per
protocol (UDP, TCP etc) The following is a template of the event.
+--------------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+--------------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| postNATSourceIPv4Address | 32 | Yes |
| protocolIdentifier | 8 | Yes |
+--------------------------+-------------+-----------+
Table 9: NAT Ports Exhausted event template
4.4.7. Quota exceeded
This event will be generated when a NAT device cannot allocate
resources as a result of an administratively defined policy. The
examples of Quota exceeded are to allow only certain number of NAT
sessions per device, certain number of NAT sessions per user etc.
The following is a template of the event.
+--------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+--------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| natLimitEvent | 32 | Yes |
| sourceIPv4 address | 32 | No |
| sourceIPv6 address | 128 | No |
+--------------------+-------------+-----------+
Table 10: NAT Quota Exceeded event template
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4.4.8. Address Binding
This event will be generated when a NAT device binds a local address
with a global address. This binding event happens when the first
packet of the first flow from a host in the private realm.
+--------------------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+--------------------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| sourceIPv4 address | 32 | No |
| sourceIPv6 address | 128 | No |
| Translated Source IPv4 Address | 32 | 8 |
+--------------------------------+-------------+-----------+
Table 11: NAT Address Binding template
4.4.9. Port block allocation and de-allocation
This event will be generated when a NAT device allocates/de-allocates
ports in a bulk fashion, as opposed to allocating a port on a per
flow basis. NAT devices would do this in order to reduce logs and
potentially to limit the number of connections a subscriber is
allowed to use. In the following Port Block allocation template, the
portRangeStart must be specified. Along with portRangeStart, atleast
one of portRangeEnd, portRangeStepSize or portRangeNumPorts MUST be
specified. If portRangeEnd is specified, it MUST NOT be lesser than
portRangeStart. The value of portRangeStepSize MUST be between 1 and
32K.
+-------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+-------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| portRangeStart | 16 | Yes |
| portRangeEnd | 16 | No |
| portRangeStepSize | 16 | No |
| portRangeNumPorts | 16 | No |
+-------------------+-------------+-----------+
Table 12: NAT Port Block Allocation event template
5. Encoding
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5.1. IPFIX
This document uses IPFIX as the encoding mechanism to describe the
logging of NAT events. However, the information that should be
logged SHOULD be the same irrespective of what kind of encoding
scheme is used. IPFIX is chosen because is it an IETF standard that
meets all the needs for a reliable logging mechanism. IPFIX provides
the flexibility to the logging device to define the data sets that it
is logging. The information elements specified for logging MUST be
the same irrespective of the encoding mechanism used.
6. Acknowledgements
Thanks to Dan Wing, Selvi Shanmugam, Mohamed Boucadir, Jacni Qin
Ramji Vaithianathan, Simon Perreault, Jean-Francois Tremblay and
Julia Renouard for their review and comments.
7. IANA Considerations
8. Security Considerations
None.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address
Translator (NAT) Terminology and Considerations",
RFC 2663, August 1999.
[RFC4787] Audet, F. and C. Jennings, "Network Address Translation
(NAT) Behavioral Requirements for Unicast UDP", BCP 127,
RFC 4787, January 2007.
[RFC5382] Guha, S., Biswas, K., Ford, B., Sivakumar, S., and P.
Srisuresh, "NAT Behavioral Requirements for TCP", BCP 142,
RFC 5382, October 2008.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
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Clients to IPv4 Servers", RFC 6146, April 2011.
9.2. Informative References
[NAT-EVENT-LOG-IANA]
IANA, "NAT event log entities", 2012, <http://
www.iana.org/assignments/nat-event-log/nat-event-log.xml>.
[RFC5101] Claise, B., "Specification of the IP Flow Information
Export (IPFIX) Protocol for the Exchange of IP Traffic
Flow Information", RFC 5101, January 2008.
[RFC5102] Quittek, J., Bryant, S., Claise, B., Aitken, P., and J.
Meyer, "Information Model for IP Flow Information Export",
RFC 5102, January 2008.
[RFC5470] Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,
"Architecture for IP Flow Information Export", RFC 5470,
March 2009.
Authors' Addresses
Senthil Sivakumar
Cisco Systems
7100-8 Kit Creek Road
Research Triangle Park, North Carolina 27709
USA
Phone: +1 919 392 5158
Email: ssenthil@cisco.com
Renaldo Penno
Cisco Systems
170 W Tasman Drive
San Jose, California 95035
USA
Phone:
Email: repenno@cisco.com
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