|
<snip>
8.1. New Information Elements / natLimitEvent, natThresholdEvent,
-> typo: " describer in Table below." -> you should remove the "Table 22" and "Table 23" descriptions under those tables, because these won't make any sense when the text is transcribed into IANA's registry. E [Senthil] I am not sure I understand why, because in section 8.1, for natInstanceI, internalAddressRealm, externalAddressRealm we have this format of name/description/data type and references. Why is natLimitEvent and natThresholdEvent different just because they have their values defined?
You misunderstand: I mean the description text immediately underneath the tables, specifically the text which says: "Table 22: Quota Exceeded event table", "Table 23: Threshold event table", and "Table 24: NAT Event ID table". I'm not talking about the table contents. IANA will take the relevant sections from your draft into their IPFIX registry. While "Table NN: whatever" makes perfect sense in the draft, it makes no sense in IANA's IPFIX registry - so IANA would have to selectively edit the definition you're providing. While I'm sure they're capable of doing that, the issue would be avoided if those tables didn't have descriptions. [Senthil2] Ok, understood and fixed.
8.2. Modified Information Elements / natEvent You can't modify the existing values, because there could be an unknown number of existing devices already using those values. I hope that IANA has already sent you feedback from the IPFIX expert reviewers indicating the best way forward. [Senthil2] I have not heard any suggestions yet from IANA, I will wait for the review. Attaching the draft as it stands, with all the comments incorporated, let me know if you have any comments before I publish.
Thanks
Senthil
P. |
Behave S. Sivakumar
Internet-Draft R. Penno
Intended status: Standards Track Cisco Systems
Expires: September 8, 2016 March 7, 2016
IPFIX Information Elements for logging NAT Events
draft-ietf-behave-ipfix-nat-logging-08
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 September 8, 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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(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Deployment . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Event based logging . . . . . . . . . . . . . . . . . . . . . 5
5.1. Logging of destination information . . . . . . . . . . . 6
5.2. Information Elements . . . . . . . . . . . . . . . . . . 6
5.3. Definition of NAT Events . . . . . . . . . . . . . . . . 8
5.4. Quota exceeded Event types . . . . . . . . . . . . . . . 9
5.5. Threshold reached Event types . . . . . . . . . . . . . . 10
5.6. Templates for NAT Events . . . . . . . . . . . . . . . . 10
5.6.1. NAT44 create and delete session events . . . . . . . 11
5.6.2. NAT64 create and delete session events . . . . . . . 11
5.6.3. NAT44 BIB create and delete events . . . . . . . . . 12
5.6.4. NAT64 BIB create and delete events . . . . . . . . . 13
5.6.5. Addresses Exhausted event . . . . . . . . . . . . . . 13
5.6.6. Ports Exhausted event . . . . . . . . . . . . . . . . 14
5.6.7. Quota exceeded events . . . . . . . . . . . . . . . . 14
5.6.7.1. Maximum session entries exceeded . . . . . . . . 14
5.6.7.2. Maximum BIB entries exceeded . . . . . . . . . . 15
5.6.7.3. Maximum entries per user exceeded . . . . . . . . 15
5.6.7.4. Maximum active host or subscribers exceeded . . . 15
5.6.7.5. Maximum fragments pending reassembly exceeded . . 16
5.6.8. Threshold reached events . . . . . . . . . . . . . . 16
5.6.8.1. Address pool high or low threshold reached . . . 16
5.6.8.2. Address and port high threshold reached . . . . . 17
5.6.8.3. Per-user Address and port high threshold reached 17
5.6.8.4. Global Address mapping high threshold reached . . 18
5.6.9. Address binding create and delete events . . . . . . 18
5.6.10. Port block allocation and de-allocation . . . . . . . 19
6. Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.1. IPFIX . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
8.1. New Information Elements . . . . . . . . . . . . . . . . 20
8.2. Modified Information Elements . . . . . . . . . . . . . . 23
9. Management Considerations . . . . . . . . . . . . . . . . . . 24
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9.1. Ability to collect events from multiple NAT devices . . . 24
9.2. Ability to suppress events . . . . . . . . . . . . . . . 24
10. Security Considerations . . . . . . . . . . . . . . . . . . . 24
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
11.1. Normative References . . . . . . . . . . . . . . . . . . 25
11.2. Informative References . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
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]
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.
2. 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.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.
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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 events including Carrier Grade NAT (CGN) events. This
document focuses exclusively on the specification of IPFIX IEs.
[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 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 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.
4. 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.
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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.
A collector may have scale issues if it is overloaded by a large
number of simultaneous events. An appropriate throttling mechanism
shall be used to handle the oversubscription.
The logs that are exported can be used for a variety of reasons. An
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 events.
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.
5. 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. The list of
collectors and its associated information like the transport address,
port and protocol MUST be preserved across reboots.
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. The IPFIX template management is described in
detail in Section 8 of [RFC7011]. The NAT device SHOULD combine as
many events as possible in a single packet to effectively utilize the
network bandwidth.
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5.1. 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
destination information also results in the loss of privacy and hence
should be done with caution. However, this draft provides the
necessary fields to log the destination information in cases where
they should be logged.
5.2. 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
{192.168.16.1, 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 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 assigned yet, and
hence the detailed description of these fields are requested 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 |
| postNAPTdestinationTransportPort | 16 | 228 | Translated |
| | | | Destination |
| | | | port |
| sourceIPv6Address | 128 | 27 | Source IPv6 |
| | | | address |
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| destinationIPv6Address | 128 | 28 | Destination |
| | | | IPv6 address |
| postNATSourceIPv6Address | 128 | 281 | Translated |
| | | | source IPv6 |
| | | | addresss |
| postNATDestinationIPv6Address | 128 | 282 | Translated |
| | | | Destination |
| | | | IPv6 address |
| internalAddressRealm | 8 | TBD | Source |
| | | | Address Realm |
| externalAddressRealm | 8 | 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 |
| natLimitEvent | 32 | TBD | Limit event |
| | | | identifier |
| natThresholdEvent | 32 | TBD | Threshold |
| | | | event |
| | | | identifier |
+----------------------------------+--------+-------+---------------+
Table 1: Template format Table
5.3. 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.
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+--------------------------+--------+
| 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 create | 12 |
| Address binding delete | 13 |
| Port block allocation | 14 |
| Port block de-allocation | 15 |
| Threshold reached | 16 |
+--------------------------+--------+
Table 2: NAT Event ID table
5.4. Quota exceeded Event types
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.
+---------------------------------------+--------+
| 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
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5.5. 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 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.
+---------------------------------------------------------+--------+
| 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
5.6. 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. Depending on the implementation and
configuration various IEs specified can be included or ignored.
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5.6.1. 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.
+----------------------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+----------------------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natInstanceID | 32 | No |
| 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 |
| internalAddressRealm | 8 | No |
| externalAddressRealm | 8 | No |
| natEvent | 8 | Yes |
+----------------------------------+-------------+-----------+
Table 5: NAT44 Session delete/create template
5.6.2. 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.
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+----------------------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+----------------------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natInstanceID | 32 | No |
| 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 |
| internalAddressRealm | 8 | No |
| externalAddressRealm | 8 | No |
| natEvent | 8 | Yes |
+----------------------------------+-------------+-----------+
Table 6: NAT64 session create/delete event template
5.6.3. 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 |
| natInstanceID | 32 | No |
| vlanID/ingressVRFID | 32 | No |
| sourceIPv4Address | 32 | Yes |
| postNATSourceIPv4Address | 32 | Yes |
| protocolIdentifier | 8 | No |
| sourceTransportPort | 16 | No |
| postNAPTsourceTransportPort | 16 | No |
| internalAddressRealm | 8 | No |
| externalAddressRealm | 8 | No |
| natEvent | 8 | Yes |
+-----------------------------+-------------+-----------+
Table 7: NAT44 BIB create/delete event template
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5.6.4. 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 |
| natInstanceID | 32 | No |
| vlanID/ingressVRFID | 32 | No |
| sourceIPv6Address | 128 | Yes |
| postNATSourceIPv4Address | 32 | Yes |
| protocolIdentifier | 8 | No |
| sourceTransportPort | 16 | No |
| postNAPTsourceTransportPort | 16 | No |
| internalAddressRealm | 8 | No |
| externalAddressRealm | 8 | No |
| natEvent | 8 | Yes |
+-----------------------------+-------------+-----------+
Table 8: NAT64 BIB create/delete event template
5.6.5. 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 |
| natInstanceID | 32 | No |
| natEvent | 8 | Yes |
| natPoolID | 32 | Yes |
+---------------+-------------+-----------+
Table 9: Address Exhausted event template
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5.6.6. 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 |
| natInstanceID | 32 | No |
| natEvent | 8 | Yes |
| postNATSourceIPv4Address | 32 | Yes |
| protocolIdentifier | 8 | Yes |
+--------------------------+-------------+-----------+
Table 10: Ports Exhausted event template
5.6.7. 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.
5.6.7.1. 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 |
| natInstanceID | 32 | No |
| natEvent | 8 | Yes |
| natLimitEvent | 32 | Yes |
| configuredLimit | 32 | Yes |
+-----------------+-------------+-----------+
Table 11: Session Entries Exceeded event template
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5.6.7.2. 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 |
| natInstanceID | 32 | No |
| natEvent | 8 | Yes |
| natLimitEvent | 32 | Yes |
| configuredLimit | 32 | Yes |
+-----------------+-------------+-----------+
Table 12: BIB Entries Exceeded event template
5.6.7.3. 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.
+---------------------+-------------+---------------+
| Field Name | Size (bits) | Mandatory |
+---------------------+-------------+---------------+
| timeStamp | 64 | Yes |
| natInstanceID | 32 | No |
| natEvent | 8 | Yes |
| natLimitEvent | 32 | Yes |
| configuredLimit | 32 | Yes |
| vlanID/ingressVRFID | 32 | No |
| sourceIPv4 address | 32 | Yes for NAT44 |
| sourceIPv6 address | 128 | Yes for NAT64 |
+---------------------+-------------+---------------+
Table 13: Per-user Entries Exceeded event template
5.6.7.4. 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.
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+-----------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+-----------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natInstanceID | 32 | No |
| natEvent | 8 | Yes |
| natLimitEvent | 32 | Yes |
| configuredLimit | 32 | Yes |
+-----------------+-------------+-----------+
Table 14: Maximum hosts/subscribers Exceeded event template
5.6.7.5. Maximum fragments pending reassembly exceeded
This event is generated when the number of fragments pending
reassembly reaches the administratively configured limit. The
following is the template of the event.
+----------------------+-------------+---------------+
| Field Name | Size (bits) | Mandatory |
+----------------------+-------------+---------------+
| timeStamp | 64 | Yes |
| natInstanceID | 32 | No |
| natEvent | 8 | Yes |
| natLimitEvent | 32 | Yes |
| configuredLimit | 32 | Yes |
| internalAddressRealm | 8 | Yes |
| vlanID/ingressVRFID | 32 | No |
| sourceIPv4 address | 32 | Yes for NAT44 |
| sourceIPv6 address | 128 | Yes for NAT64 |
+----------------------+-------------+---------------+
Table 15: Maximum fragments pending reassembly Exceeded event
template
5.6.8. 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.
5.6.8.1. 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
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+-------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+-------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natInstanceID | 32 | No |
| natEvent | 8 | Yes |
| natThresholdEvent | 32 | Yes |
| natPoolID | 32 | Yes |
| configuredLimit | 32 | Yes |
+-------------------+-------------+-----------+
Table 16: Address pool high/low threshold reached event template
5.6.8.2. Address and port high threshold reached
This event is generated when the high threshold is reached for the
address pool and ports.
+-------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+-------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natInstanceID | 32 | No |
| natEvent | 8 | Yes |
| natThresholdEvent | 32 | Yes |
| configuredLimit | 32 | Yes |
+-------------------+-------------+-----------+
Table 17: Address port high threshold reached event template
5.6.8.3. 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.
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+---------------------+-------------+---------------+
| Field Name | Size (bits) | Mandatory |
+---------------------+-------------+---------------+
| timeStamp | 64 | Yes |
| natInstanceID | 32 | No |
| natEvent | 8 | Yes |
| natThresholdEvent | 32 | Yes |
| configuredLimit | 32 | Yes |
| vlanID/ingressVRFID | 32 | No |
| sourceIPv4 address | 32 | Yes for NAT44 |
| sourceIPv6 address | 128 | Yes for NAT64 |
+---------------------+-------------+---------------+
Table 18: Per-user Address port high threshold reached event template
5.6.8.4. 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.
+---------------------+-------------+-----------+
| Field Name | Size (bits) | Mandatory |
+---------------------+-------------+-----------+
| timeStamp | 64 | Yes |
| natInstanceID | 32 | No |
| natEvent | 8 | Yes |
| natThresholdEvent | 32 | Yes |
| configuredLimit | 32 | Yes |
| vlanID/ingressVRFID | 32 | No |
+---------------------+-------------+-----------+
Table 19: Global Address mapping high threshold reached event
template
5.6.9. 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.
These binding events happen when the first packet of the first flow
from a host in the private realm.
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+--------------------------------+-------------+---------------+
| Field Name | Size (bits) | Mandatory |
+--------------------------------+-------------+---------------+
| timeStamp | 64 | Yes |
| natInstanceID | 32 | No |
| natEvent | 8 | Yes |
| sourceIPv4 address | 32 | Yes for NAT44 |
| sourceIPv6 address | 128 | Yes for NAT64 |
| Translated Source IPv4 Address | 32 | Yes |
+--------------------------------+-------------+---------------+
Table 20: NAT Address Binding template
5.6.10. 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.
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 |
| natInstanceID | 32 | No |
| 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 |
+--------------------------------+-------------+---------------+
Table 21: NAT Port Block Allocation event template
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6. Encoding
6.1. IPFIX
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.
7. 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.
8. IANA Considerations
8.1. New Information Elements
The following information elements are requested from IANA IPFIX
registry.
Name : natInstanceId
Description: This Information Element identifies an Instance of the
NAT that runs on a NAT middlebox function after the packet passed the
Observation Point.
Abstract Data Type: unsigned32
Data Type Semantics: identifier
Reference:
See RFC 791 [RFC791] 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.
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
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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: unsigned8
Data Type Semantics: identifier
Reference:
See RFC 791 [RFC791] 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.
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: unsigned8
Data Type Semantics: identifier
Reference:
See RFC 791 [RFC791] 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.
Name : natLimitEvent
Description: This Information Element identifies the limit type that
is reported by the event. There are different types of limits as
described in 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 [RFC791] 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.
Name: natThresholdEvent
Description: This Information Element identifies the threshold type
that is reported by the event. There are different types of
thresholds as describer in Table below.
+---------------------------------------------------------+--------+
| 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:
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See RFC 791 [RFC791] 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.
8.2. Modified Information Elements
Name : natEvent
Description: This Information Element identifies a NAT event. The
possible values for NAT events are described below.
Abstract Data Type: unsigned8
Data Type Semantics: identifier
Element ID : 230
New values requested : The values 4-16 are requested as described in
Table below
+--------------------------+--------+
| 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 create | 12 |
| Address binding delete | 13 |
| Port block allocation | 14 |
| Port block de-allocation | 15 |
| Threshold reached | 16 |
+--------------------------+--------+
Table 24
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.
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9. 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.behave-syslog-nat-logging]. This document covers the
additional considerations.
9.1. 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.
9.2. 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.
10. 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.
11. References
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11.1. 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>.
[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>.
[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>.
11.2. 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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[RFC5470] Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,
"Architecture for IP Flow Information Export", RFC 5470,
DOI 10.17487/RFC5470, March 2009,
<http://www.rfc-editor.org/info/rfc5470>.
[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>.
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@xxxxxxxxx
Renaldo Penno
Cisco Systems
170 W Tasman Drive
San Jose, California 95035
USA
Email: repenno@xxxxxxxxx
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