Internet DRAFT - draft-ietf-behave-ipfix-nat-logging
draft-ietf-behave-ipfix-nat-logging
Behave S. Sivakumar
Internet-Draft R. Penno
Intended status: Standards Track Cisco Systems
Expires: July 13, 2017 January 9, 2017
IPFIX Information Elements for logging NAT Events
draft-ietf-behave-ipfix-nat-logging-13
Abstract
Network operators require NAT devices to log events like creation and
deletion of translations and information about the resources that the
NAT device is managing. The logs are essential in many cases to
identify an attacker or a host that was used to launch malicious
attacks and for various other purposes of accounting. Since there is
no standard way of logging this information, different NAT devices
log the information using proprietary formats and hence it is
difficult to expect a consistent behavior. The lack of a consistent
way to log the data makes it difficult to write the collector
applications that would receive this data and process it to present
useful information. This document describes the formats for logging
of NAT events.
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 13, 2017.
Copyright Notice
Copyright (c) 2017 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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(http://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Deployment . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Event based logging . . . . . . . . . . . . . . . . . . . . . 5
4.1. Logging of destination information . . . . . . . . . . . 6
4.2. Information Elements . . . . . . . . . . . . . . . . . . 6
4.3. Definition of NAT Events . . . . . . . . . . . . . . . . 8
4.4. Quota exceeded Event types . . . . . . . . . . . . . . . 9
4.5. Threshold reached Event types . . . . . . . . . . . . . . 10
4.6. Templates for NAT Events . . . . . . . . . . . . . . . . 11
4.6.1. NAT44 create and delete session events . . . . . . . 11
4.6.2. NAT64 create and delete session events . . . . . . . 12
4.6.3. NAT44 BIB create and delete events . . . . . . . . . 13
4.6.4. NAT64 BIB create and delete events . . . . . . . . . 13
4.6.5. Addresses Exhausted event . . . . . . . . . . . . . . 14
4.6.6. Ports Exhausted event . . . . . . . . . . . . . . . . 14
4.6.7. Quota exceeded events . . . . . . . . . . . . . . . . 15
4.6.7.1. Maximum session entries exceeded . . . . . . . . 15
4.6.7.2. Maximum BIB entries exceeded . . . . . . . . . . 15
4.6.7.3. Maximum entries per user exceeded . . . . . . . . 15
4.6.7.4. Maximum active host or subscribers exceeded . . . 16
4.6.7.5. Maximum fragments pending reassembly exceeded . . 16
4.6.8. Threshold reached events . . . . . . . . . . . . . . 17
4.6.8.1. Address pool high or low threshold reached . . . 17
4.6.8.2. Address and port high threshold reached . . . . . 17
4.6.8.3. Per-user Address and port high threshold reached 18
4.6.8.4. Global Address mapping high threshold reached . . 18
4.6.9. Address binding create and delete events . . . . . . 19
4.6.10. Port block allocation and de-allocation . . . . . . . 19
5. Management Considerations . . . . . . . . . . . . . . . . . . 20
5.1. Ability to collect events from multiple NAT devices . . . 20
5.2. Ability to suppress events . . . . . . . . . . . . . . . 20
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
7.1. Information Elements . . . . . . . . . . . . . . . . . . 21
7.1.1. natInstanceID . . . . . . . . . . . . . . . . . . . . 21
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7.1.2. internalAddressRealm . . . . . . . . . . . . . . . . 21
7.1.3. externalAddressRealm . . . . . . . . . . . . . . . . 22
7.1.4. natQuotaExceededEvent . . . . . . . . . . . . . . . . 22
7.1.5. natThresholdEvent . . . . . . . . . . . . . . . . . . 23
7.1.6. natEvent . . . . . . . . . . . . . . . . . . . . . . 24
8. Security Considerations . . . . . . . . . . . . . . . . . . . 25
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
9.1. Normative References . . . . . . . . . . . . . . . . . . 25
9.2. Informative References . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
1. Introduction
The IPFIX Protocol [RFC7011] defines a generic push mechanism for
exporting information and events. The IPFIX Information Model
[IPFIX-IANA] defines a set of standard IEs which can be carried by
the IPFIX protocol. This document details the IPFIX Information
Elements(IEs) that MUST be logged by a NAT device that supports NAT
logging using IPFIX, and all the optional fields. The fields
specified in this document are gleaned from [RFC4787] and [RFC5382].
This document and [I-D.ietf-behave-syslog-nat-logging] are written in
order to standardize the events and parameters to be recorded, using
IPFIX [RFC7011] and SYSLOG [RFC5424]respectively. The intent is to
provide a consistent way to log information irrespective of the
mechanism that is used.
This document uses IPFIX as the encoding mechanism to describe the
logging of NAT events. However, the information that is 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 IEs specified for logging must be the same irrespective
of the encoding mechanism used.
1.1. 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 Binding
Information Base (BIB) as it is defined in [RFC6146]. The usage of
the term Information Element (IE) is defined in [RFC7011]. The term
Carrier Grade NAT refers to a large scale NAT device as described in
[RFC6888]
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The IPFIX Information Elements that are NAT specific are created with
NAT terminology. In order to avoid creating duplicate IEs, IEs are
reused if they convey the same meaning. This document uses the term
timestamp for the Information element which defines the time when an
event is logged, this is the same as IPFIX term
observationTimeMilliseconds as described in [IPFIX-IANA]. Since
observationTimeMilliseconds is not self explanatory for NAT
implementors, this document uses the term timeStamp. This document
refers to event templates, that refers to IPFIX template records.
This document refers to log events that refers to IPFIX Flow records.
1.2. 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].
2. Scope
This document provides the information model to be used for logging
the NAT events including Carrier Grade NAT (CGN) events. [RFC7011]
provides guidance on the choices of the transport protocols used for
IPFIX and their effects. 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 logs SHOULD be reliably sent to the collector to
ensure that the log events are not lost. The choice of the actual
transport protocol is beyond the scope of this document.
The existing IANA IPFIX IEs registry [IPFIX-IANA] already has
assignments for most of the NAT logging events. This document uses
the allocated IPFIX IEs and will request IANA for the ones that are
defined in this document but not yet allocated.
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.
The implementation details of the collector application is beyond the
scope of this document.
The optimization of logging the NAT events is left to the
implementation and is beyond the scope of this document.
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3. Deployment
NAT logging based on IPFIX uses binary encoding and hence is very
efficient. IPFIX based logging is recommended for environments where
a high volume of logging is required, for example, where per-flow
logging is needed or in case of Carrier Grade NAT. However, IPFIX
based logging requires a collector that processes the binary data and
requires a network management application that converts this binary
data to a human readable format.
A collector may receive NAT events from multiple CGN devices. The
collector distinguishes between the devices using the source IP
address, source port, and Observation Domain ID in the IPFIX header.
The collector can decide to store the information based on the
administrative policies that are inline with the operator and the
local juridiction. The retention policy is not dictated by the
exporter and is left to the policies that are defined at the
collector.
A collector may have scale issues if it is overloaded by a large
number of simultaneous events. An appropriate throttling mechanism
may be used to handle the oversubscription.
The logs that are exported can be used for a variety of reasons. An
example use case is to do accounting based on when the users logged
on and off. The translation will be installed when the user logs on
and removed when the user logs off. These events create log records.
Another use case is to identify an attacker or a host in a provider
network. The network administrators can use these logs to identify
the usage patterns, need for additional IP addresses etc. The
deployment of NAT logging is not limited to just these cases.
4. Event based logging
An event in a NAT device can be viewed as a state transition as it
relates to the management of NAT resources. The creation and
deletion of NAT sessions and bindings are examples of events as they
result in resources (addresses and ports) being allocated or freed.
The events can happen 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 Table 2. 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. It is
necessary to preserve the list of collectors and its associated
information like the IPv4/IPv6 address, port and protocol across
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reboots so that the configuration information is not lost when the
device is restarted. The NAT device implementing the IPFIX logging
MUST follow the IPFIX specs as specified in RFC 7011.
4.1. Logging of destination information
Logging of destination information in a NAT event has been discussed
in [RFC6302] and [RFC6888]. Logging of destination information
increases the size of each record and increases the need for storage
considerably. It increases the number of log events generated
because when the same user connects to a different destination, it
results in a log record per destination address. Logging of the
source and destination addresses result in loss of privacy. Logging
of destination addresses and ports, pre or post NAT, SHOULD NOT be
done [RFC6888]. However, this draft provides the necessary fields to
log the destination information in cases where they must be logged.
4.2. Information Elements
The templates could contain a subset of the 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, internalAddressRealm, natEvent, timeStamp}
An example of the actual event data record is shown below - in a
human readable form
{192.0.2.1, 203.0.113.100, 192.0.2.104, 192.0.2.104, 14800, 1024, 80,
80, 0, 1, 09:20:10:789}
A single NAT device could be exporting multiple templates and the
collector MUST support receiving multiple templates from the same
source.
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The following is the table of all the IEs that a NAT device would
need to export the events. The formats of the IEs and the IPFIX IDs
are listed below. Some of the IPFIX IEs are not yet assigned. The
detailed description of these fields that are requested are in the
IANA considerations section.
+--------------------------------+------------+-------+-------------+
| Field Name | Size | IANA | Description |
| | (bits) | IPFIX | |
| | | ID | |
+--------------------------------+------------+-------+-------------+
| timeStamp | 64 | 323 | System Time |
| | | | when the |
| | | | event |
| | | | occured. |
| natInstanceId | 32 | TBD | NAT |
| | | | Instance |
| | | | Identifier |
| 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 |
| postNAPTdestinationTransportPo | 16 | 228 | Translated |
| rt | | | Destination |
| | | | port |
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| sourceIPv6Address | 128 | 27 | Source IPv6 |
| | | | address |
| destinationIPv6Address | 128 | 28 | Destination |
| | | | IPv6 |
| | | | address |
| postNATSourceIPv6Address | 128 | 281 | Translated |
| | | | source IPv6 |
| | | | addresss |
| postNATDestinationIPv6Address | 128 | 282 | Translated |
| | | | Destination |
| | | | IPv6 |
| | | | address |
| internalAddressRealm | OctetArray | TBD | Source |
| | | | Address |
| | | | Realm |
| externalAddressRealm | OctetArray | TBD | Destination |
| | | | Address |
| | | | Realm |
| natEvent | 8 | 230 | Type of |
| | | | Event |
| portRangeStart | 16 | 361 | Allocated |
| | | | port block |
| | | | start |
| portRangeEnd | 16 | 362 | Allocated |
| | | | Port block |
| | | | end |
| natPoolID | 32 | 283 | NAT pool |
| | | | Identifier |
| natQuotaExceededEvent | 32 | TBD | Limit event |
| | | | identifier |
| natThresholdEvent | 32 | TBD | Threshold |
| | | | event |
| | | | identifier |
+--------------------------------+------------+-------+-------------+
Table 1: Template format Table
4.3. Definition of NAT Events
The following is the complete list of NAT events and the proposed
event type values. The natEvent IE is defined in the IPFIX IANA
registry in http://www.iana.org/assignments/ipfix/ipfix.xml. The
list can be expanded in the future as necessary. The data record
will have the corresponding natEvent value to indicate the event that
is being logged.
Note that the first two events are marked historic. These values
were defined prior to the existence of this draft and outside the
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IETF working group. These events are not standalone and require more
information need to be conveyed to qualify the event. For example,
the NAT Translation create event does not specify if it is a NAT44 or
NAT64. As a result the Behave WG decided to have explicit definition
for each one of the unique events. The historic events are listed
here for the purpose of completeness and are already defined in the
IPFIX IANA registry. Any compliant implementation SHOULD NOT
implement the events that are marked historic.
+-------------------------------------+--------+
| Event Name | Values |
+-------------------------------------+--------+
| NAT Translation create (Historic) | 1 |
| NAT Translation Delete (Historic) | 2 |
| NAT Addresses exhausted | 3 |
| NAT44 Session create | 4 |
| NAT44 Session delete | 5 |
| NAT64 Session create | 6 |
| NAT64 Session delete | 7 |
| NAT44 BIB create | 8 |
| NAT44 BIB delete | 9 |
| NAT64 BIB create | 10 |
| NAT64 BIB delete | 11 |
| NAT ports exhausted | 12 |
| Quota exceeded | 13 |
| Address binding create | 14 |
| Address binding delete | 15 |
| Port block allocation | 16 |
| Port block de-allocation | 17 |
| Threshold reached | 18 |
+-------------------------------------+--------+
Table 2: NAT Event ID table
4.4. Quota exceeded Event types
The Quota Exceeded event is a natEvent IE described in Table 2. The
Quota exceeded events are generated when the hard limits set by the
administrator has been reached or exceeded. The following table
shows the sub event types for the Quota exceeded or limits reached
event. The events that can be reported are the Maximum session
entries limit reached, Maximum BIB entries limit reached, Maximum
(session/BIB) entries per user limit reached, Maximum active hosts
limit reached or maximum subscribers limit reached and Maximum
Fragments pending reassembly limit reached.
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+---------------------------------------+--------+
| Quota Exceeded Event Name | Values |
+---------------------------------------+--------+
| Maximum Session entries | 1 |
| Maximum BIB entries | 2 |
| Maximum entries per user | 3 |
| Maximum active hosts or subscribers | 4 |
| Maximum fragments pending reassembly | 5 |
+---------------------------------------+--------+
Table 3: Quota Exceeded event table
4.5. Threshold reached Event types
The following table shows the sub event types for the threshold
reached event. The administrator can configure the thresholds and
whenever the threshold is reached or exceeded, the corresponding
events are generated. The main difference between Quota Exceeded and
the Threshold reached events is that, once the Quota exceeded events
are hit, the packets are dropped or mappings wont be created etc,
whereas, the threshold reached events will provide the operator a
chance to take action before the traffic disruptions can happen. A
NAT device can choose to implement one or the other or both.
The address pool high threshold event will be reported when the
address pool reaches a high water mark as defined by the operator.
This will serve as an indication that the operator might have to add
more addresses to the pool or an indication that the subsequent users
may be denied NAT translation mappings.
The address pool low threshold event will be reported when the
address pool reaches a low water mark as defined by the operator.
This will serve as an indication that the operator can reclaim some
of the global IPv4 addresses in the pool.
The address and port mapping high threshold event is generated, when
the number of ports in the configured address pool has reached a
configured threshold.
The per-user address and port mapping high threshold is generated
when a single user uses more address and port mapping than a
configured threshold. We don't track the low threshold for per-user
address and port mappings, because as the ports are freed, the
address will become available. The address pool low threhold event
will then be triggered so that the IPv4 global address can be
reclaimed.
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The Global address mapping high threshold event is generated when the
maximum mappings per-user is reached for a NAT device doing paired
address pooling.
+---------------------------------------------------------+--------+
| Threshold Exceeded Event Name | Values |
+---------------------------------------------------------+--------+
| Address pool high threshold event | 1 |
| Address pool low threshold event | 2 |
| Address and port mapping high threshold event | 3 |
| Address and port mapping per user high threshold event | 4 |
| Global Address mapping high threshold event | 5 |
+---------------------------------------------------------+--------+
Table 4: Threshold event table
4.6. Templates for NAT Events
The following is the template of events that will be logged. The
events below are identified at the time of this writing but the set
of events is extensible. A NAT device that implements a given NAT
event MUST support the mandatory IE's in the templates. Depending on
the implementation and configuration various IEs that are not
mandatory can be included or ignored.
4.6.1. NAT44 create and delete session events
These events 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.
The destination address and port information is optional as required
by [RFC6888]. However, when the destination information is
suppressed, the session log event contains the same information as
the BIB event. In such cases, the NAT device SHOULD NOT send both
BIB and session events.
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+----------------------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+----------------------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| 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 |
| natInstanceID | 32 | No |
| vlanID/ingressVRFID | 32 | No |
| internalAddressRealm | OctetArray | No |
| externalAddressRealm | OctetArray | No |
+----------------------------------+-------------+-----------+
Table 5: NAT44 Session delete/create template
4.6.2. NAT64 create and delete session events
These events will be generated when a NAT64 session is created or
deleted. The following is a template of the event.
+----------------------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+----------------------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| 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 |
| natInstanceID | 32 | No |
| vlanID/ingressVRFID | 32 | No |
| internalAddressRealm | OctetArray | No |
| externalAddressRealm | OctetArray | No |
+----------------------------------+-------------+-----------+
Table 6: NAT64 session create/delete event template
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4.6.3. NAT44 BIB create and delete events
These events will be generated when a NAT44 Bind entry is created or
deleted. The following is a template of the event.
+-----------------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+-----------------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| sourceIPv4Address | 32 | Yes |
| postNATSourceIPv4Address | 32 | Yes |
| protocolIdentifier | 8 | No |
| sourceTransportPort | 16 | No |
| postNAPTsourceTransportPort | 16 | No |
| natInstanceID | 32 | No |
| vlanID/ingressVRFID | 32 | No |
| internalAddressRealm | OctetArray | No |
| externalAddressRealm | OctetArray | No |
+-----------------------------+-------------+-----------+
Table 7: NAT44 BIB create/delete event template
4.6.4. NAT64 BIB create and delete events
These events will be generated when a NAT64 Bind entry is created or
deleted. The following is a template of the event.
+-----------------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+-----------------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| sourceIPv6Address | 128 | Yes |
| postNATSourceIPv4Address | 32 | Yes |
| protocolIdentifier | 8 | No |
| sourceTransportPort | 16 | No |
| postNAPTsourceTransportPort | 16 | No |
| natInstanceID | 32 | No |
| vlanID/ingressVRFID | 32 | No |
| internalAddressRealm | OctetArray | No |
| externalAddressRealm | OctetArray | No |
+-----------------------------+-------------+-----------+
Table 8: NAT64 BIB create/delete event template
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4.6.5. 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 won't be able to create any new
translations until some addresses/ports are freed. This event SHOULD
be rate limited as many packets hitting the device at the same time
will trigger a burst of addresses exhausted events.
The following is a template of the event.
+---------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+---------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| natPoolID | 32 | Yes |
| natInstanceID | 32 | No |
+---------------+-------------+-----------+
Table 9: Address Exhausted event template
4.6.6. 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). This event SHOULD be rate limited as many
packets hitting the device at the same time will trigger a burst of
port exhausted events.
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 |
| natInstanceID | 32 | No |
+--------------------------+-------------+-----------+
Table 10: Ports Exhausted event template
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4.6.7. Quota exceeded events
This event will be generated when a NAT device cannot allocate
resources as a result of an administratively defined policy. The
quota exceeded event templates are described below.
4.6.7.1. Maximum session entries exceeded
The maximum session entries exceeded event is generated when the
administratively configured NAT session limit is reached. The
following is the template of the event.
+-----------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+-----------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| natQuotaExceededEvent | 32 | Yes |
| configuredLimit | 32 | Yes |
| natInstanceID | 32 | No |
+-----------------------+-------------+-----------+
Table 11: Session Entries Exceeded event template
4.6.7.2. Maximum BIB entries exceeded
The maximum BIB entries exceeded event is generated when the
administratively configured BIB entry limit is reached. The
following is the template of the event.
+-----------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+-----------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| natQuotaExceededEvent | 32 | Yes |
| configuredLimit | 32 | Yes |
| natInstanceID | 32 | No |
+-----------------------+-------------+-----------+
Table 12: BIB Entries Exceeded event template
4.6.7.3. Maximum entries per user exceeded
This event is generated when a single user reaches the
administratively configured NAT translation limit. The following is
the template of the event.
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+-----------------------+-------------+---------------+
| Field Name | Size (bits) | Mandatory |
+-----------------------+-------------+---------------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| natQuotaExceededEvent | 32 | Yes |
| configuredLimit | 32 | Yes |
| sourceIPv4 address | 32 | Yes for NAT44 |
| sourceIPv6 address | 128 | Yes for NAT64 |
| natInstanceID | 32 | No |
| vlanID/ingressVRFID | 32 | No |
+-----------------------+-------------+---------------+
Table 13: Per-user Entries Exceeded event template
4.6.7.4. Maximum active host or subscribers exceeded
This event is generated when the number of allowed hosts or
subscribers reaches the administratively configured limit. The
following is the template of the event.
+-----------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+-----------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| natQuotaExceededEvent | 32 | Yes |
| configuredLimit | 32 | Yes |
| natInstanceID | 32 | No |
+-----------------------+-------------+-----------+
Table 14: Maximum hosts/subscribers Exceeded event template
4.6.7.5. Maximum fragments pending reassembly exceeded
This event is generated when the number of fragments pending
reassembly reaches the administratively configured limit. Note that
in case of NAT64, when this condition is detected in the IPv6 to IPv4
direction, the IPv6 source address is mandatory in the template.
Similarly, when this condition is detected in IPv4 to IPv6 direction,
the source IPv4 address is mandatory in the template below. The
following is the template of the event.
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+-----------------------+-------------+----------------+
| Field Name | Size (bits) | Mandatory |
+-----------------------+-------------+----------------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| natQuotaExceededEvent | 32 | Yes |
| configuredLimit | 32 | Yes |
| sourceIPv4 address | 32 | Yes for NAT44 |
| sourceIPv6 address | 128 | Yes for NAT64 |
| natInstanceID | 32 | No |
| vlanID/ingressVRFID | 32 | No |
| internalAddressRealm | OctetArray | No |
+-----------------------+-------------+----------------+
Table 15: Maximum fragments pending reassembly Exceeded event
template
4.6.8. Threshold reached events
This event will be generated when a NAT device reaches a operator
configured threshold when allocating resources. The threshold
reached events are described in the section above. The following is
a template of the individual events.
4.6.8.1. Address pool high or low threshold reached
This event is generated when the high or low threshold is reached for
the address pool. The template is the same for both high and low
threshold events
+-------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+-------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| natThresholdEvent | 32 | Yes |
| natPoolID | 32 | Yes |
| configuredLimit | 32 | Yes |
| natInstanceID | 32 | No |
+-------------------+-------------+-----------+
Table 16: Address pool high/low threshold reached event template
4.6.8.2. Address and port high threshold reached
This event is generated when the high threshold is reached for the
address pool and ports.
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+-------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+-------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| natThresholdEvent | 32 | Yes |
| configuredLimit | 32 | Yes |
| natInstanceID | 32 | No |
+-------------------+-------------+-----------+
Table 17: Address port high threshold reached event template
4.6.8.3. Per-user Address and port high threshold reached
This event is generated when the high threshold is reached for the
per-user address pool and ports.
+---------------------+-------------+---------------+
| Field Name | Size (bits) | Mandatory |
+---------------------+-------------+---------------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| natThresholdEvent | 32 | Yes |
| configuredLimit | 32 | Yes |
| sourceIPv4 address | 32 | Yes for NAT44 |
| sourceIPv6 address | 128 | Yes for NAT64 |
| natInstanceID | 32 | No |
| vlanID/ingressVRFID | 32 | No |
+---------------------+-------------+---------------+
Table 18: Per-user Address port high threshold reached event template
4.6.8.4. Global Address mapping high threshold reached
This event is generated when the high threshold is reached for the
per-user address pool and ports. This is generated only by NAT
devices that use a paired address pooling behavior.
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+---------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+---------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| natThresholdEvent | 32 | Yes |
| configuredLimit | 32 | Yes |
| natInstanceID | 32 | No |
| vlanID/ingressVRFID | 32 | No |
+---------------------+-------------+-----------+
Table 19: Global Address mapping high threshold reached event
template
4.6.9. Address binding create and delete events
These events will be generated when a NAT device binds a local
address with a global address and when the global address is freed.
A NAT device will generate the binding events when it receives 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 | Yes for NAT44 |
| sourceIPv6 address | 128 | Yes for NAT64 |
| Translated Source IPv4 Address | 32 | Yes |
| natInstanceID | 32 | No |
+--------------------------------+-------------+---------------+
Table 20: NAT Address Binding template
4.6.10. 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.
portRangeStart represents the starting value of the range.
portRangeEnd represents the ending value of the range.
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 and
portRangeEnd MUST be specified.
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It is up to the implementation to choose to consolidate log records
in case two consecutive port ranges for the same user are allocated
or freed.
+--------------------------------+-------------+---------------+
| Field Name | Size (bits) | Mandatory |
+--------------------------------+-------------+---------------+
| timeStamp | 64 | Yes |
| natEvent | 8 | Yes |
| sourceIPv4 address | 32 | Yes for NAT44 |
| sourceIPv6 address | 128 | Yes for NAT64 |
| Translated Source IPv4 Address | 32 | Yes |
| portRangeStart | 16 | Yes |
| portRangeEnd | 16 | No |
| natInstanceID | 32 | No |
+--------------------------------+-------------+---------------+
Table 21: NAT Port Block Allocation event template
5. Management Considerations
This section considers requirements for management of the log system
to support logging of the events described above. It first covers
requirements applicable to log management in general. Any additional
standardization required to fullfil these requirements is out of
scope of the present document. Some management considerations are
covered in [I-D.ietf-behave-syslog-nat-logging]. This document
covers the additional considerations.
5.1. Ability to collect events from multiple NAT devices
An IPFIX collector MUST be able to collect events from multiple NAT
devices and be able to decipher events based on the Observation
Domain ID in the IPFIX header.
5.2. Ability to suppress events
The exhaustion events can be overwhelming during traffic bursts and
hence SHOULD be handled by the NAT devices to rate limit them before
sending them to the collectors. For eg. when the port exhaustion
happens during bursty conditions, instead of sending a port
exhaustion event for every packet, the exhaustion events SHOULD be
rate limited by the NAT device.
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6. Acknowledgements
Thanks to Dan Wing, Selvi Shanmugam, Mohamed Boucadir, Jacni Qin
Ramji Vaithianathan, Simon Perreault, Jean-Francois Tremblay, Paul
Aitken, Julia Renouard, Spencer Dawkins and Brian Trammell for their
review and comments.
7. IANA Considerations
7.1. Information Elements
IANA will register the following IEs in the IPFIX Information
Elements registry at http://www.iana.org/assignments/ipfix/ipfix.xml
7.1.1. natInstanceID
Name : natInstanceID
Description: This Information Element uniquely identifies an Instance
of the NAT that runs on a NAT middlebox function after the packet
passed the Observation Point. natInstanceID is defined in RFC 7659
[RFC7659]
Abstract Data Type: unsigned32
Data Type Semantics: identifier
Reference:
See RFC 791 [RFC0791] for the definition of the IPv4 source address
field. See RFC 3022 [RFC3022] for the definition of NAT. See RFC
3234 [RFC3234] for the definition of middleboxes.
7.1.2. internalAddressRealm
Name: internalAddressRealm
Description: This Information Element represents the internal address
realm where the packet is originated from or destined to. By
definition, a NAT mapping can be created from two address realms, one
from internal and one from external. Realms are implementation
dependent and can represent a VRF ID or a VLAN ID or some unique
identifier. Realms are optional and when left unspecified would mean
that the external and internal realms are the same.
Abstract Data Type: octetArray
Data Type Semantics: identifier
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Reference:
See RFC 791 [RFC0791] for the definition of the IPv4 source address
field. See RFC 3022 [RFC3022] for the definition of NAT. See RFC
3234 [RFC3234] for the definition of middleboxes.
7.1.3. externalAddressRealm
Name: externalAddressRealm
Description: This Information Element represents the external address
realm where the packet is originated from or destined to. The
detailed definition is in the internal address realm as specified
above.
Abstract Data Type: octetArray
Data Type Semantics: identifier
Reference:
See RFC 791 [RFC0791] for the definition of the IPv4 source address
field. See RFC 3022 [RFC3022] for the definition of NAT. See RFC
3234 [RFC3234] for the definition of middleboxes.
7.1.4. natQuotaExceededEvent
Values of this Information Element are defined in a registry
maintained by IANA at <http://www.iana.org/assignments/ipfix/
ipfix.xml#TBD-by-IANA>. New assignments of values will be
administered by IANA, subject to Expert Review [RFC5226]. Experts
need to check definitions of new values for completeness, accuracy,
and redundancy.
Name : natQuotaExceededEvent
Description: This Information Element identifies the type of a NAT
quota exceeded event. Values for this Information Element are listed
in the NAT quota exceed event type registry, see
[http://www.iana.org/assignments/ipfix/ipfix.xml#TBD-by-IANA] Initial
values in the registry are defined by the table below.
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+---------------------------------------+--------+
| Quota Exceeded Event Name | Values |
+---------------------------------------+--------+
| Maximum Session entries | 1 |
| Maximum BIB entries | 2 |
| Maximum entries per user | 3 |
| Maximum active hosts or subscribers | 4 |
| Maximum fragments pending reassembly | 5 |
+---------------------------------------+--------+
Table 22
Abstract Data Type: unsigned32
Data Type Semantics: identifier
Reference:
See RFC 791 [RFC0791] for the definition of the IPv4 source address
field. See RFC 3022 [RFC3022] for the definition of NAT. See RFC
3234 [RFC3234] for the definition of middleboxes.
7.1.5. natThresholdEvent
Values of this Information Element are defined in a registry
maintained by IANA at http://www.iana.org/assignments/ipfix/
ipfix.xml#TBD-by-IANA. New assignments of values will be
administered by IANA, subject to Expert Review [RFC5226]. Experts
need to check definitions of new values for completeness, accuracy,
and redundancy.
Name: natThresholdEvent
Description: This Information Element identifies a type of a NAT
threshold event. Values for this Information Element are listed in
the NAT threshhold event type registry, see
<http://www.iana.org/assignments/ipfix/ipfix.xml#TBD-by-IANA>.
Initial values in the registry are defined by the table below.
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+---------------------------------------------------------+--------+
| Threshold Exceeded Event Name | Values |
+---------------------------------------------------------+--------+
| Address pool high threshold event | 1 |
| Address pool low threshold event | 2 |
| Address and port mapping high threshold event | 3 |
| Address and port mapping per user high threshold event | 4 |
| Global Address mapping high threshold event | 5 |
+---------------------------------------------------------+--------+
Table 23
Abstract Data Type: unsigned32
Data Type Semantics: identifier
Reference:
See RFC 791 [RFC0791] for the definition of the IPv4 source address
field. See RFC 3022 [RFC3022] for the definition of NAT. See RFC
3234 [RFC3234] for the definition of middleboxes.
7.1.6. natEvent
The original definition of this Information Element specified only
three values 1, 2, and 3. This definition is replaced by a registry,
to which new values can be added. The semantics of the three
originally defined values remains unchanged. IANA maintains the
registry for values of this Information Element at
<http://www.iana.org/assignments/ipfix/ipfix.xml#TBD-by-IANA>. New
assignments of values will be administered by IANA, subject to Expert
Review [RFC5226]. Experts need to check definitions of new values
for completeness, accuracy, and redundancy.
Name : natEvent
Description: Description: This Information Element identifies a NAT
event. This IE identifies the type of a NAT event. Examples of NAT
events include but not limited to, creation or deletion of a NAT
translation entry, a threshold reached or exceeded etc. Values for
this Information Element are listed in the NAT event type registry,
see [http://www.iana.org/assignments/ipfix/ipfix.xml#TBD-by-IANA] The
NAT Event values in the registry are defined by the Table 2 in
Section 5.3.
Abstract Data Type: unsigned8
Data Type Semantics: identifier
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Element ID : 230
Reference:
See RFC 3022 [RFC3022] for the definition of NAT. See RFC 3234
[RFC3234] for the definition of middleboxes. See [thisRFC] for the
definitions of values 4-16.
8. Security Considerations
The security considerations listed in detail for IPFIX in [RFC7011]
applies to this draft as well. As described in [RFC7011] the
messages exchanged between the NAT device and the collector MUST be
protected to provide confidentiality, integrity and authenticity.
Without those characteristics, the messages are subject to various
kinds of attacks. These attacks are described in great detail in
[RFC7011].
This document re-emphasizes the use of TLS or DTLS for exchanging the
log messages between the NAT device and the collector. The log
events sent in clear text can result in confidential data being
exposed to attackers, who could then spoof log events based on the
information in clear text messages. Hence, the log events SHOULD NOT
be sent in clear text.
The logging of NAT events can result in privacy concerns as result of
exporting information such as source address and port information.
The logging of destinaion information can also cause privacy concerns
but it has been well documented in [RFC6888]. A NAT device can
choose to operate in various logging modes if it wants to avoid
logging of private information. The collector that receives the
information can also choose to mask the private information but
generate reports based on abstract data. It is outside the scope of
this document to address the implementation of logging modes for
privacy considerations.
9. References
9.1. 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,
<http://www.rfc-editor.org/info/rfc2119>.
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[RFC4787] Audet, F., Ed. and C. Jennings, "Network Address
Translation (NAT) Behavioral Requirements for Unicast
UDP", BCP 127, RFC 4787, DOI 10.17487/RFC4787, January
2007, <http://www.rfc-editor.org/info/rfc4787>.
[RFC5382] Guha, S., Ed., Biswas, K., Ford, B., Sivakumar, S., and P.
Srisuresh, "NAT Behavioral Requirements for TCP", BCP 142,
RFC 5382, DOI 10.17487/RFC5382, October 2008,
<http://www.rfc-editor.org/info/rfc5382>.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
April 2011, <http://www.rfc-editor.org/info/rfc6146>.
[RFC6302] Durand, A., Gashinsky, I., Lee, D., and S. Sheppard,
"Logging Recommendations for Internet-Facing Servers",
BCP 162, RFC 6302, DOI 10.17487/RFC6302, June 2011,
<http://www.rfc-editor.org/info/rfc6302>.
[RFC6888] Perreault, S., Ed., Yamagata, I., Miyakawa, S., Nakagawa,
A., and H. Ashida, "Common Requirements for Carrier-Grade
NATs (CGNs)", BCP 127, RFC 6888, DOI 10.17487/RFC6888,
April 2013, <http://www.rfc-editor.org/info/rfc6888>.
[RFC7011] Claise, B., Ed., Trammell, B., Ed., 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,
<http://www.rfc-editor.org/info/rfc7011>.
[RFC7659] Perreault, S., Tsou, T., Sivakumar, S., and T. Taylor,
"Definitions of Managed Objects for Network Address
Translators (NATs)", RFC 7659, DOI 10.17487/RFC7659,
October 2015, <http://www.rfc-editor.org/info/rfc7659>.
9.2. Informative References
[I-D.ietf-behave-syslog-nat-logging]
Chen, Z., Zhou, C., Tsou, T., and T. Taylor, "Syslog
Format for NAT Logging", draft-ietf-behave-syslog-nat-
logging-06 (work in progress), January 2014.
[IPFIX-IANA]
IANA, "IPFIX Information Elements registry",
<http://www.iana.org/assignments/ipfix>.
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[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<http://www.rfc-editor.org/info/rfc791>.
[RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address
Translator (NAT) Terminology and Considerations",
RFC 2663, DOI 10.17487/RFC2663, August 1999,
<http://www.rfc-editor.org/info/rfc2663>.
[RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022,
DOI 10.17487/RFC3022, January 2001,
<http://www.rfc-editor.org/info/rfc3022>.
[RFC3234] Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and
Issues", RFC 3234, DOI 10.17487/RFC3234, February 2002,
<http://www.rfc-editor.org/info/rfc3234>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC5424] Gerhards, R., "The Syslog Protocol", RFC 5424,
DOI 10.17487/RFC5424, March 2009,
<http://www.rfc-editor.org/info/rfc5424>.
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
Email: repenno@cisco.com
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