IPFIX Working Group A. Kobayashi, ED.
Internet-Draft NTT PF Lab.
Intended status: Informational February 5, 2009
Expires: August 9, 2009
IPFIX Mediation: Problem Statement
draft-ietf-ipfix-mediators-problem-statement-02
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Abstract
Flow-based measurement is a popular method for various network
monitoring usages. The sharing of flow-based information for
monitoring applications having different requirements raises some
open issues in terms of scalability, reliability, and flexibility
that IPFIX Mediation may help resolve. IPFIX Mediation covers two
classes of mediation: context mediation for traffic data and
transport mediation for transport protocols. This document describes
the problems that network administrators have been facing and the
applicability of IPFIX Mediation.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology and Definition . . . . . . . . . . . . . . . . . . 5
3. IPFIX/PSAMP Documents Overview . . . . . . . . . . . . . . . . 7
3.1. IPFIX Documents Overview . . . . . . . . . . . . . . . . . 7
3.2. PSAMP Documents Overview . . . . . . . . . . . . . . . . . 7
4. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 8
4.1. Approach for IP Traffic Growth . . . . . . . . . . . . . . 8
4.2. Approach to Multifaceted Traffic Measurement . . . . . . . 9
4.3. Approach to Heterogeneous Environment . . . . . . . . . . 9
4.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 9
5. Applicable Examples . . . . . . . . . . . . . . . . . . . . . 10
5.1. Adjusting Flow Granularity . . . . . . . . . . . . . . . . 10
5.2. Hierarchical Collecting Infrastructure . . . . . . . . . . 10
5.3. Correlation of Data Records . . . . . . . . . . . . . . . 10
5.4. Time Composition . . . . . . . . . . . . . . . . . . . . . 11
5.5. Spatial Composition . . . . . . . . . . . . . . . . . . . 11
5.6. Data Retention . . . . . . . . . . . . . . . . . . . . . . 12
5.7. IPFIX Export from Branch Office . . . . . . . . . . . . . 13
5.8. Distributing Data Records . . . . . . . . . . . . . . . . 13
5.9. IPFIX Export Across Domains . . . . . . . . . . . . . . . 14
5.10. Flow-based Sampling and Selection . . . . . . . . . . . . 15
5.11. Interoperability between Legacy Protocols and IPFIX . . . 15
6. Problems with using IPFIX Mediators . . . . . . . . . . . . . 16
6.1. Loss of Original Exporter Information . . . . . . . . . . 16
6.2. Loss of Base Time Information . . . . . . . . . . . . . . 17
6.3. Loss of Option Template Information . . . . . . . . . . . 17
6.4. Observation Domain ID and Template ID Management . . . . . 17
6.5. Transport Sessions Management . . . . . . . . . . . . . . 17
7. Summary and Conclusion . . . . . . . . . . . . . . . . . . . . 19
8. Security Considerations . . . . . . . . . . . . . . . . . . . 21
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
10.1. Normative References . . . . . . . . . . . . . . . . . . . 23
10.2. Informative References . . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25
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1. Introduction
While the IPFIX requirements defined in [RFC3917] mention an
intermediate function, such as an IPFIX Proxy or an Concentrator,
there is no document to define the function called IPFIX Mediation.
IPFIX Mediation is a generic function that covers context mediation
for traffic data and transport mediation for IPFIX transport
protocols that do not affect content. We describes the general
problems that network administrators have been facing and several
applicable IPFIX Mediation categories along with specific terminology
(IPFIX Proxy, Concentrator, etc.). Furthermore, we describe the
problems of IPFIX Mediation with regard to implementation. These
problems can be solved by making additional specifications that do
not affect the present IPFIX protocol specifications defined in
[RFC5101].
This document is structured as follows. Section 2 describes the
terminology used in this document. Section 3 gives an IPFIX/PSAMP
document overview. Section 4 introduces general problems related to
flow-based measurement. Section 5 describes some applicable examples
where IPFIX Mediation would benefit from solutions to such problems.
Finally, section 6 describes the problems an implementation of an
IPFIX Mediation device might face.
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2. Terminology and Definition
The terms in this section are in line with those in the IPFIX
Protocol specifications [RFC5101] and the PSAMP specification
document [I-D.ietf-psamp-protocol]. The terms Observation Point,
Observation Domain, Flow Key, Flow Record, Exporting Process,
Exporter, IPFIX Device, Collecting Process, Collector, IPFIX Message,
Metering Process, and Information Element are defined in the IPFIX
protocol specifications [RFC5101], while the term Packet Report is
defined in the PSAMP specification document
[I-D.ietf-psamp-protocol]. Additional terms required for the IPFIX
Mediation are also defined here. All these terms have an initial
capital letter in this document.
IPFIX Mediation
IPFIX Mediation is a function that can be applied to individual
Data Records and/or Template Records or to entire IPFIX Messages.
IPFIX Mediation offers one or multiple capabilities.
* content mediation that changes Flow information
+ aggregating Data Records based on a new set of Flow Key
fields
+ correlating a set of Data Records for creating new metrics
+ filtering and selecting Data Records
+ modifying Data Records and/or Template Records, which
includes these functions:
- changing the value of specified Information Elements
- adding new Information Elements by deriving further Flow
or packet properties from existing fields or calculating
new metrics
- deleting specified Information Elements
* transport mediation that does not affect content
+ changing the transport protocol that carries IPFIX Messages
+ rerouting entire IPFIX Messages to an appropriate Collecting
Process
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+ replicating Data Records and Template Records or entire
IPFIX Messages
IPFIX Mediation can be included in any IPFIX Devices, such as
routers, switches, and network management systems (NMS).
IPFIX Mediator
An IPFIX Mediator is an IPFIX Device that contains one or more
IPFIX Mediation capabilities.
Original Exporter
An Original Exporter is an IPFIX Device that hosts Observation
Points where the metered IP packets are observed.
IPFIX Proxy
An IPFIX Proxy is an IPFIX Mediation that relays incoming
Transport Sessions to one or multiple Collectors. The protocols
used at the input and the output may be different, which implies
that IPFIX Messages, Data Records, or Template Records need to be
encoded, e.g., converting legacy protocol into IPFIX.
IPFIX Concentrator
An IPFIX Concentrator is an IPFIX Mediation that receives Flow
Records/Packet Reports, aggregates them, then exports the
aggregated Flow Records.
IPFIX Distributor
An IPFIX Distributor is an IPFIX Mediation that distributes
incoming IPFIX Data Records to one or multiple IPFIX Collectors.
The decision as to which IPFIX Collector a Data Record is exported
can be determined by filtering certain field values or other
properties derived from the Data Record.
IPFIX Masquerading Proxy
An IPFIX Masquerading Proxy is an IPFIX Mediation that screens out
parts of input Data Records according to configured policies. It
can thus, for example, hide the network topology information or
customers' IP addresses.
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3. IPFIX/PSAMP Documents Overview
3.1. IPFIX Documents Overview
The IPFIX protocol [RFC5101] provides network administrators with
access to IP flow information. The architecture for the export of
measured IP flow information out of an IPFIX Exporting Process to a
Collecting Process is defined in [I-D.ietf-ipfix-architecture], per
the requirements defined in [RFC3917]. The IPFIX protocol [RFC5101]
specifies how IPFIX Data Records and Templates are carried via a
number of transport protocols from IPFIX Exporting Processes to IPFIX
Collecting Processes. IPFIX has a formal description of IPFIX
Information Elements, their names, types, and additional semantic
information, as specified in [RFC5102]. [I-D.ietf-ipfix-mib]
specifies the IPFIX Management Information Base. Finally,
[I-D.ietf-ipfix-as] describes what types of applications can use the
IPFIX protocol and how they can use the information provided. It
furthermore shows how the IPFIX framework relates to other
architectures and frameworks. The storage of IPFIX Messages in a
file is specified in [I-D.ietf-ipfix-file].
3.2. PSAMP Documents Overview
The framework for packet selection and reporting
[I-D.ietf-psamp-framework] enables network elements to select subsets
of packets by statistical and other methods and to export a stream of
reports on the selected packets to a Collector. The set of packet
selection techniques (sampling, filtering, and hashing) standardized
by PSAMP are described in [I-D.ietf-psamp-sample-tech]. The PSAMP
protocol [I-D.ietf-psamp-protocol] specifies the export of packet
information from a PSAMP Exporting Process to a Collector. Like
IPFIX, PSAMP has a formal description of its Information Elements,
their names, types and additional semantic information. The PSAMP
information model is defined in [I-D.ietf-psamp-info].
[I-D.ietf-psamp-mib] describes the PSAMP Management Information Base.
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4. Problem Statement
Network administrators generally face the problems of flow-based
measurement for scalability, reliability, and flexibility, and some
techniques, such as sampling, aggregating and replicating, have
already been developed. The problems consist of optimizing the
resources of the measurement system while pursuing appropriate
conditions, such as data accuracy, flow granularity, and reliability.
The conditions depend on two factors.
o capacity of measurement system
This consists of the bandwidth of the management network, the
storage capacity, and the performances of the collecting devices
and exporting devices.
o requirement for given applications
This depends on the purpose of the application, such as traffic
engineering, detecting anomaly traffic, and accounting.
The recent continued IP traffic growth has been overwhelming the
capacity of measurement system, and multi-purposing applications and
the heterogeneous environment have further contributed to a complex
situation. The following sub-sections explain problems related to
these two factors.
4.1. Approach for IP Traffic Growth
Enterprise or service provider networks already have multiple 10 Gb/s
links, their total traffic exceeding 100 Gb/s. In the near future,
broadband users' traffic will increase by approximately 40% every
year according to [TRAFGRW]. When operators monitor traffic of 500
Gb/s with a sampling rate of 1/1000, the amount of exported Flow
Records from Exporters could exceed 50 kFlows/s. This value is
beyond the ability of a single Collector.
To deal with this problem, traffic data reduction techniques, such as
sampling or aggregating, have been generally implemented in exporting
devices. These techniques lead to coarse flow granularity or low
data accuracy, resulting in Flows with small traffic volumes that
could easily get lost. Administrators would no longer be able to
investigate traffic change and anomaly traffic, both of which can
currently be detected, unless the collecting infrastructure is
improved.
This implies the necessity of a large-scale collecting infrastructure
and other traffic data reduction techniques other than packet-based
sampling and selection techniques.
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4.2. Approach to Multifaceted Traffic Measurement
A set of conditions (flow granularity and data accuracy) may meet the
requirements of some applications, such as traffic engineering, but
would not meet the requirements of other applications, such as
accounting and QoS performance. Therefore, with a single set of
conditions, multifaceted traffic measurement cannot be accomplished.
To cope with the issue, a exporting device needs to export traffic
data with strictest condition (fine flow granularity and high data
accuracy) required by one of applications. However, it brings about
increasing the load on a exporting device and a collecting device.
4.3. Approach to Heterogeneous Environment
Network administrators use exporting devices from various vendors and
of various software versions or device type (router, switch, or
probe) in a single network domain. This heterogeneous environment
leads to differences in capability, performance, and data format.
For example, a probe and a switch cannot retrieve packet property
information from a route table.
To deal with this problem, a collecting device needs to absorb the
differences. However, equipping all collecting devices with this
extra function is difficult. A sophisticated solution that
introduces individual modules separate from specific devices is
necessary.
4.4. Summary
In optimizing the resources of a measurement system, it is important
to use traffic data reduction techniques at the possible initial
phase, e.g., exporting devices, of the whole system. However, this
implementation is made difficult by heterogeneous environment of
exporting devices.
It implies that the exporter-collector structure model has
limitations, and a mediation function as another functional block is
necessary. The next section shows the limitation of the exporter-
collector structure model and the benefit of IPFIX Mediation
according in applicable examples.
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5. Applicable Examples
5.1. Adjusting Flow Granularity
The simplest types of Flows are those comprised of packets all having
a fixed IP-quintuple of protocol, source and destination IP
addresses, and source and destination port numbers. However, a
shorter Flow Key, such as a triple, a double, or a single Flow Key,
such as a network prefix, peering AS number, or BGP Next-Hop, creates
more aggregated Flow Records. This is especially useful for
measuring traffic exchange in an entire network domain and for easily
adjusting the performance of a Collector.
Implementation analysis:
Implementations for this case depend on where Flow granularity is
adjusted. More suitable implementations uses the configurable
Metering Process in Original Exporters. The cache in the Metering
Process can specify its own set of Flow Keys and extra fields.
The Original Exporter thus creates directly aggregated Flow
Records.
In the case where an unconfigurable Metering Process creating IP-
quintuple Flow Records exists in a line interface module, IPFIX
Mediation in another module can be applied between the Metering
Process and an Exporting Process.
In the case where an Original Exporter creating IP-quintuple Flow
Records exists, an IPFIX Concentrator can be applied between the
Original Exporter and an IPFIX Collector.
5.2. Hierarchical Collecting Infrastructure
As an approach to large-scale measurement systems, a hierarchical
structure is useful for increasing the capacity.
Implementation analysis:
One possible implementation for this case uses an IPFIX
Concentrator. An IPFIX Concentrator with storage capability also
makes a most useful distributed-collection system.
5.3. Correlation of Data Records
The correlation of Data Records provides new metrics, including the
following.
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o One way delay from the correlation of Packet Reports from
different Exporters on the path.
o Rate-limiting ratio from the correlation of Data Records with the
same Flow Key observed at incoming/outgoing interfaces.
o Average/maximum/minimum values from correlating multiple Data
Records.
Implementation analysis:
One possible implementation for this case uses an IPFIX Mediation
located between the Metering Processes and Exporting Processes or
between the Original Exporters and IPFIX Collectors.
5.4. Time Composition
Time composition is defined as the aggregation of consecutive Data
Records with identical Flow Key values. It leads to the same output
as setting a longer active interval timer on Original Exporters. An
advantage is that creating new metrics (average, maximum and minimum
values) from Flow Records with a shorter interval time enables
administrators to keep track of changes that might have happened
during the time interval.
Implementation analysis:
One possible implementation for this case uses an IPFIX Mediation
located between the Metering Processes and Exporting Processes or
between the Original Exporters and IPFIX Collectors.
5.5. Spatial Composition
Spatial composition is defined as the aggregation of Data Records in
a set of Observation Points with an Observation Domain, across
multiple Observation Domains from a single Exporter, or even across
multiple Exporters. It is divided into three types.
o Spatial Composition within one Observation Domain
For example, in the case where a link aggregation exists, Data
Records observed at physical interfaces belonging to a same trunk
can be merged.
o Spatial Composition across Observation Domains, but within a
single Exporter
For example, in the case where a link aggregation exists, Data
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Records observed at physical interfaces belonging to a same trunk
grouping beyond the line interface module can be merged.
o Spatial Composition across Exporters
Data Records observed at different domains, such as the west area
and east area of an ISP network, can be merged.
Implementation analysis:
One possible implementation for this case uses an IPFIX Mediation
located between the Metering Processes and Exporting Processes or
between the IPFIX Exporters and IPFIX Collectors.
5.6. Data Retention
Data retention refers to the storage of traffic data by service
providers and commercial organizations. In accordance with European
Commission directives, operators are required to retain both IP and
voice traffic data, in wired and wireless networks, generated by end
users while using a service provider's services. The goal of data
retention is to ensure that call detail records and Flow Records are
available for the detection, investigation, and prosecution of
serious crimes, if necessary. The European Commission directives
define the following data retention services:
o Fixed telephony (includes fixed voice calls, voicemail, and
conference and data calls)
o Mobile telephony (includes mobile voice calls, voicemail,
conference and data calls, SMS, and MMS)
o Internet telephony (includes every multimedia session associated
with IP multimedia services)
o Internet e-mail
o Internet access
Data retention for Internet access services in particular requires
a　measurement system with reliability and huge storage.
Implementation analysis:
Regarding reliability, the most suitable implementation uses the
SCTP transport protocol between the Original Exporter and
Collector. Otherwise, an IPFIX Proxy next to a legacy exporting
device exports traffic data to the final IPFIX Collector through
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SCTP.
Regarding huge storage, one possible implemantation uses a
decentralized collecting device. If operators need to retrieve
specific traffic data, these collecting devices would need to be
equipped with IPFIX Mediation capabilities.
[ Editor Note]
The authors need to find the data retention reference.
5.7. IPFIX Export from Branch Office
Generally, in large enterprise networks, traffic data from branch
offices are gathered in a central office. However, in the long
distance branch office case, the bandwidth for transport IPFIX is
limited.
Implementation analysis:
One possible implementation for this case uses an IPFIX
Concentrator located in a branch office. The IPFIX Concentrator
then exports aggregated Flow Records to cope with the bandwidth
limitation.
5.8. Distributing Data Records
Recently, several networks have shifted towards integrated networks,
such as the pure IP and MPLS, which includes IPv4, IPv6, and VPN
traffic. Data Record types (IPv4, IPv6, MPLS, and VPN) need to be
analyzed separately and from different perspectives. However,
handling them separately without improving the capability of the
Collector is difficult. Data Records distributed based on the type
can be exported to an appropriate Collector with a specific
application, and this results in the distribution of the load among
multiple Collectors.
Implementation analysis:
One possible implementation for this case uses the replications of
the IPFIX Message in an IPFIX Exporter for multiple IPFIX
Collectors. Each Collector then extracts the Data Record required
by its own applications. However, this increases the load of the
Exporting Process.
A more sophisticated implementation uses an IPFIX Distributor
located between the Metering Processes and Exporting Processes or
between the Original Exporters and IPFIX Collectors. For example,
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in the case of distributing a specific customer's Data Records, an
IPFIX Distributor needs to identify the customer networks. The
Route Distinguisher (RD), ingress interface, peering AS number, or
BGP Next-Hop, or simply the network prefix may be evaluated to
distinguish different customer networks. In the following figure,
the IPFIX Distributor reroutes Data Records on the basis of the RD
value. This system enables each customer's traffic to be
inspected independently.
.---------.
|Traffic |
.---->|Collector|<==>Customer#A
| |#1 |
| '---------'
RD=100:1
.-----------. |
.----------. |IPFIX |----' .---------.
|IPFIX | |Distributor| RD=100:2 |Traffic |
|Exporter#1|------->| |--------->|Collector|<==>Customer#B
| | | | |#2 |
'----------' | |----. '---------'
'-----------' |
RD=100:3
| .---------.
| |Traffic |
'---->|Collector|<==>Customer#C
|#3 |
'---------'
Figure A: Distributing Data Records to Collectors using IPFIX
Distributor
5.9. IPFIX Export Across Domains
IPFIX exports across administrative domains can be used to measure
traffic for wide-area traffic engineering or to analyze Internet
traffic trends. In such cases, administrators need to adhere to
privacy protection policies and prevent access to confidential
traffic measurements by other people. Typically, anonymization
techniques enables the provision of traffic data to other people
without violating these policies.
Generally, anonymization modifies a data set to protect the identity
of the people or entities described by the data set from being
disclosed. It also attempts to preserve sets of network traffic
properties useful for a given analysis while ensuring the data cannot
be traced back to the specific networks, hosts, or users generating
the traffic. For example, IP address anonymization is particularly
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important for avoiding the identification of the users, hosts, and
routers in a network domain. The details of these anonymization
techniques are out of the scope of this document.
Implementation analysis:
One possible implementation for this case uses an anonymization
function at the Original Exporter. However, this increases the
load of the Metering Process at the Original Exporter. A more
flexible implementation uses an IPFIX Masquerading Proxy between
the Original Exporter and Collector.
5.10. Flow-based Sampling and Selection
Generally, the distribution of the number of packets per Flow seems
to be heavy-tailed. Most types of Flow Records are likely to be
small Flows consisting of a small number of packets. The measurement
system is overwhelmed with a huge amount of these small Flows. If
statistics information of small Flows is exported as merged data by
applying a policy or threshold, the load on the measurement system is
reduced. Furthermore, if the flow distribution is known, exporting
only a subset of the Data Records might be sufficient.
Implementation analysis:
One possible implementation for this case uses an IPFIX Mediation
located between the Metering Processes and Exporting Processes or
between the Original Exporters and IPFIX Collectors.
5.11. Interoperability between Legacy Protocols and IPFIX
During the migration process from a legacy protocol such as NetFlow
[RFC3954] to IPFIX, both NetFlow exporting devices and IPFIX
Exporters are likely to coexist in the same network. Operators need
to continue measuring the traffic data from legacy exporting devices,
even after introducing IPFIX Collectors.
Implementation analysis:
One possible implementation for this case uses an IPFIX Proxy that
converts a legacy protocol to IPFIX.
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6. Problems with using IPFIX Mediators
In this section, we focus on the problems related to the use of IPFIX
Mediators in consideration of implementation.
6.1. Loss of Original Exporter Information
Both the Exporter IP address indicated by the source IP address of
the IPFIX session and the Observation Domain ID included in the IPFIX
Message header are likely to be lost by an IPFIX Mediator such as
IPFIX Concentrator. In some cases, the IPFIX Masquerading Proxy
might be made to drop the information. However, in other cases, the
information is necessary for indicating the Observation Point
information from the viewpoint of the entire network domain. Such
information might be necessary for guaranteeing the continuity of the
work of the top level Collector. Even if an IPFIX Mediator could,
with some new mechanism, notify Collectors of this Observation Point
information, older Collectors might not accept it. These Collectors
would then wrongly assume that the IP address of the IPFIX Mediator
is that of the Original Exporter. The Collector, however, sometimes
needs to recognize the Original Exporter (and potentially the
Observation Domain and Observation Point as well) whether Data
Records go through an IPFIX Mediator or not.
In the following figure, a Collector can identify two IP addresses:
10.1.1.3 (IPFIX Mediator) and 10.1.1.2 (Exporter#2). respectively.
The Collector, however, needs to somehow recognize both Exporter#1
and Exporter#2, which are the Original Exporters. Defined
notification methods that can be interpreted by Collectors and
Mediators are thus necessary.
.----------. .--------.
|IPFIX | |IPFIX |
|Exporter#1|--------->|Mediator|---+
| | | | |
'----------' '--------' | .---------.
IP:10.1.1.1 IP:10.1.1.3 '----->|IPFIX |
ODID:10 ODID:0 |Collector|
+----->| |
.----------. | '---------'
|IPFIX | |
|Exporter#2|-----------------------'
| |
'----------'
IP:10.1.1.2
ODID:20
Figure B: Loss of Original Exporter Information.
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6.2. Loss of Base Time Information
The Export Time field included in the IPFIX Message header indicates
the base time for Data Records. IPFIX Information Elements,
described in [RFC5102], have delta time fields that indicate the time
difference from the value of the Export Time field. If the Data
Records include any delta time fields and the IPFIX Mediator
overwrites the Export Time field when sending IPFIX Messages, the
delta time fields become meaningless and, because Collectors cannot
recognize this situation, wrong time values are propagated.
6.3. Loss of Option Template Information
In some cases, depending on the implementation of the IPFIX
Mediators, the information that is reported by the Option Templates
could also be lost. If, for example, the sampling rate is not
communicated to the Collectors, a Collector would miscalculate the
traffic volume. This might lead to crucial problems. Even if an
IPFIX Mediator was to simply relay received Option Template
Information, the values of its scope fields could become meaningless
in the context of a different session. The minimal information to be
communicated by an IPFIX Mediator needs to be defined.
6.4. Observation Domain ID and Template ID Management
The Observation Domain ID is locally unique to an Exporting Process,
just as the Template ID is unique on the basis of the Transport
Session and Observation Domain ID. If IPFIX Mediators were not able
to manage the relations among these identifiers and the incoming
Transport Session information, and if the Template ID was used in the
scope field of Options, the Mediators would, for example, relay wrong
values for the scope field and for "Template Withdraw Message". The
Collector would thus not be able to interpret the Template ID of
"Template Withdraw Message" and of the scope fields of Options. The
Collector would then shut down the IPFIX Transport Session.
6.5. Transport Sessions Management
Maintaining relationships between the incoming Transport Sessions and
the outgoing ones depends on the Mediator's implementation. If
multiple incoming Transport Sessions are relayed to a single outgoing
Transport Session, and if the IPFIX Mediators shuts down its outgoing
Transport Session, Data Records on other incoming Transport Sessions
would not be relayed at all. In the case of resetting of an incoming
session, the behavior of the IPFIX Mediator needs to be defined.
For example, an IPFIX Distributor must maintain the state of the
incoming Transport Sessions in order to manage the Template ID on its
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outgoing Transport Session correctly. In the following figure, even
if the Transport Session from Exporter#1 re-initializes, the IPFIX
Distributor must maintain the validity of the Template IDs to avoid
overlapping the existing ones on the outgoing Transport Session.
.----------. OLD: Template ID 258
|IPFIX | NEW: Template ID 256
|Exporter#1|----+
| | |
'----------' X
.----------. | .-----------. .----------.
|IPFIX | '---------->| | | |
|Exporter#2|--------------->|IPFIX |-------X------>|IPFIX |
| |Template ID 257 |Distributor|Template ID 256| Collector|
'----------' +---------->| | | |
.----------. | '-----------' '----------'
|IPFIX | |
|Exporter#3|----'
| | Template ID 256
'----------'
Figure C: Relaying from Multiple Transport Sessions to Single
Transport Session.
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7. Summary and Conclusion
This document described the problems that network administrators have
been facing, the applicability of IPFIX Mediation to these problems,
and the problems related to the implementation of IPFIX Mediators.
To assist the operations of the Exporters and Collectors, there are
various IPFIX Mediation functions from which the administrators may
select. Examples of the applicability of IPFIX Mediation are as
follows.
o Regarding large-scale measurement system, IPFIX Concentrators or
IPFIX Distributors help to achieve traffic analysis with high data
accuracy and fine flow granularity even as IP traffic grows. As
IPFIX Mediation capabilities, Flow selection sampling,
aggregation, and composition are effective.
o Regarding data retention, IPFIX Mediators enhance the reliability,
and the storage of the measurement system.
o Regarding the distribution of Data Records, this could be
introduced in integrated networks, which mix MPLS VPN and IPv4/
IPv6, more frequently. More sophisticated implementation methods
would enhance the distribution's effectiveness.
o Regarding IPFIX Exporting across domains, IPFIX Masquerading
Proxies help administrators to anonymize or filter Flow Records/
Packet Reports, preventing privacy violations.
o Regarding interoperability, IPFIX Proxies provide interoperability
between legacy protocols and IPFIX, even during the migration
period to IPFIX.
As a result, the benefits of IPFIX Mediation become apparent.
However, there are still some open issues with the use of IPFIX
Mediators.
o Both Observation Point and IPFIX Message header information, such
as the Exporter IP address, Observation Domain ID, and Export Time
field, might be lost. This data should therefore be communicated
between the Original Exporter and Collector via the IPFIX
Mediator.
o Data advertised by Option Templates from the Original Exporter,
such as the sampling rate and sampling algorithm used, might be
lost. If a Collector is not informed of current sampling rates,
traffic information might become worthless.
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o IPFIX Mediators are required to manage Transport Sessions,
Template IDs, and Observation Domain IDs. Otherwise, anomalous
IPFIX messages could be created.
These problems stem from the fact that no standards regarding IPFIX
Mediation have been set. In particular, the minimum set of
information that should be communicated between Original Exporters
and Collectors, the interworking between different IPFIX Transport
Sessions, and the internal components of IPFIX Mediators should be
standardized.
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8. Security Considerations
A flow-based measurement system must prevent potential security
threats: the disclosure of confidential traffic data, injection of
incorrect data, and unauthorized access to traffic data. These
security threats of the IPFIX protocol are covered by the security
considerations section in [RFC5101] and are true of IPFIX Mediation
as well.
And a measurement system must also prevent following security threats
related to IPFIX Mediation.
o attacks against IPFIX Mediator
IPFIX Mediators would be considered a prime target for attacks
instead of IPFIX Exporters and Collectors. IPFIX Proxies or
Masquerading Proxies need to prevent unauthorized access or
denial-of-service (DoS) attacks from untrusted public networks.
o man-in-the-middle attack by untrusted IPFIX Mediator
The Collector-Mediator-Exporter structure model would increase the
risk of the man-in-the-middle attack.
o configuration on IPFIX Mediation
In the case of IPFIX Distributors and IPFIX Masquerading Proxies,
an accidental misconfiguration and unauthorized access to
configuration data could lead to the crucial problem of disclosure
of confidential traffic data.
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9. IANA Considerations
This document has no actions for IANA.
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10. References
10.1. Normative References
[I-D.ietf-ipfix-architecture]
Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,
"Architecture for IP Flow Information Export",
draft-ietf-ipfix-architecture-12 (work in progress) ,
September 2006.
[I-D.ietf-ipfix-as]
Zseby, T., Boschi, E., Brownlee, N., and B. Claise, "IPFIX
Applicability", draft-ietf-ipfix-as-12 (work in
progress) , June 2007.
[I-D.ietf-ipfix-file]
Trammell, B., Boschi, E., Mark, L., Zseby, T., and A.
Wagner, "Specification of the IPFIX File Format",
draft-ietf-ipfix-file-03 (work in progress) ,
October 2008.
[I-D.ietf-ipfix-mib]
Dietz, T., Claise, B., and A. Kobayashi, "Definitions of
Managed Objects for IP Flow Information Export",
draft-ietf-ipfix-mib-05 (work in progress) ,
November 2008.
[I-D.ietf-psamp-framework]
Duffield, N., "A Framework for Packet Selection and
Reporting", draft-ietf-psamp-framework-13 (work in
progress) , June 2008.
[I-D.ietf-psamp-info]
Dietz, T., Claise, B., Aitken, P., Dressler, F., and G.
Carle, "Information Model for Packet Sampling Exports",
draft-ietf-psamp-info-11 (work in progress) ,
October 2008.
[I-D.ietf-psamp-mib]
Dietz, T. and B. Claise, "Definitions of Managed Objects
for Packet Sampling", draft-ietf-psamp-mib-06 (work in
progress) , June 2006.
[I-D.ietf-psamp-protocol]
Claise, B., "Packet Sampling (PSAMP) Protocol
Specifications", draft-ietf-psamp-protocol-09 (work in
progress) , December 2007.
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[I-D.ietf-psamp-sample-tech]
Zseby, T., Molina, M., Duffield, N., Niccolini, S., and F.
Raspall, "Sampling and Filtering Techniques for IP Packet
Selection", draft-ietf-psamp-sample-tech-11 (work in
progress) , July 2008.
[RFC3917] Quittek, J., Zseby, T., Claise, B., and S. Zander,
"Requirements for IP Flow Information Export(IPFIX)",
October 2004.
[RFC3954] Claise, B., "Cisco Systems NetFlow Services Export Version
9", October 2004.
[RFC5101] Claise, B., "Specification of the IP Flow Information
Export (IPFIX) Protocol for the Exchange of IP Traffic
Flow Information", January 2008.
[RFC5102] Quittek, J., Bryant, S., Claise, B., Aitken, P., and J.
Meyer, "Information Model for IP Flow Information Export",
January 2008.
10.2. Informative References
[TRAFGRW] Cho, K., Fukuda, K., Esaki, H., and A. Kato, "The Impact
and Implications of the Growth in Residential User-to-User
Traffic", SIGCOMM2006, pp. 207-218, Pisa, Italy, September
2006. .
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Authors' Addresses
Atsushi Kobayashi
NTT Information Sharing Platform Laboratories
3-9-11 Midori-cho
Musashino-shi, Tokyo 180-8585
Japan
Phone: +81-422-59-3978
Email: akoba@nttv6.net
URI: http://www3.plala.or.jp/akoba/
Haruhiko Nishida
NTT Information Sharing Platform Laboratories
3-9-11 Midori-cho
Musashino-shi, Tokyo 180-8585
Japan
Phone: +81-422-59-3978
Email: nishida.haruhiko@lab.ntt.co.jp
Christoph Sommer
University of Erlangen-Nuremberg
Department of Computer Science 7
Martensstr. 3
Erlangen 91058
Germany
Phone: +49 9131 85-27993
Email: christoph.sommer@informatik.uni-erlangen.de
URI: http://www7.informatik.uni-erlangen.de/~sommer/
Falko Dressler
University of Erlangen-Nuremberg
Department of Computer Science 7
Martensstr. 3
Erlangen 91058
Germany
Phone: +49 9131 85-27914
Email: dressler@informatik.uni-erlangen.de
URI: http://www7.informatik.uni-erlangen.de/~dressler/
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Benoit Claise
Cisco Systems
De Kleetlaan 6a b1
Diegem 1831
Belgium
Phone: +32 2 704 5622
Email: bclaise@cisco.com
Stephan Emile
France Telecom
2 avenue Pierre Marzin
Lannion, F-22307
Fax: +33 2 96 05 18 52
Email: emile.stephan@orange-ftgroup.com
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