Flow-state dependent packet selection techniques
draft-krishnan-ipfix-flow-aware-packet-sampling-05
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| Authors | Ramki Krishnan , Ning So | ||
| Last updated | 2013-06-18 | ||
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draft-krishnan-ipfix-flow-aware-packet-sampling-05
IPFIX
Internet Draft R. Krishnan
Intended status: Informational Brocade Communications
Expires: December 2013 Ning So
June 16, 2013 Tata Communications
Flow-state dependent packet selection techniques
draft-krishnan-ipfix-flow-aware-packet-sampling-05.txt
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Abstract
The demands on the networking infrastructure and thus the
switch/router bandwidths are growing exponentially; the drivers are
bandwidth hungry rich media applications, inter data center
communications etc. Using sampling techniques, for a given sampling
rate, the amount of samples that need to be processed is increasing
exponentially especially for applications like security threat
detection. This draft elaborates on flow-state dependent packet
selection techniques and the relevant information models. It
describes how these techniques can be effectively used to reduce the
number of samples for applications like security threat detection.
Table of Contents
1. Introduction...................................................2
1.1. Acronyms..................................................3
1.2. Terminology...............................................3
2. Flow-state dependent packet selection techniques...............3
2.1. Information Model for flow-state dependent packet selection
technique configuration........................................4
2.2. Handling Inactive/Misidentified Large Flows...............5
2.3. Flow-state dependent packet selection - sample and hold...6
2.4. IANA Considerations.......................................6
2.4.1. Registration of Information Elements.................6
2.4.1.1. largeFlowObservationInterval....................6
2.4.1.2. largeFlowBandwidthThreshold.....................6
3. Current sampling techniques for security threat detection......7
4. Application of flow-state dependent packet selection techniques
for security threat detection.....................................7
4.1. Applicability of flow-state dependent packet selection
technique suggested in [ESVA].......Error! Bookmark not defined.
4.2. Applicability of flow-state dependent packet selection
technique suggested in [VRM]........Error! Bookmark not defined.
4.3. Simulation................................................9
5. Security Considerations........................................9
6. Operational Considerations.....................................9
7. Acknowledgements...............................................9
8. References....................................................10
8.1. Normative References.....................................10
8.2. Informative References...................................10
1. Introduction
This draft expands on the flow-state dependent packet selection
techniques described in [FLSEC] for identifying long-lived large
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flows and the relevant information models. This draft also describes
a practical use case for efficient behavioral security detection,
like Denial of Service (DOS) attacks etc., using flow-state dependent
packet selection techniques.
1.1. Acronyms
DOS: Denial of Service
GRE: Generic Routing Encapsulation
MPLS: Multi Protocol Label Switching
NVGRE: Network Virtualization using Generic Routing Encapsulation
TCAM: Ternary Content Addressable Memory
STT: Stateless Transport Tunneling
VXLAN: Virtual Extensible LAN
1.2. Terminology
Large flow(s): long-lived large flow(s)
Small flow(s): long-lived small flow(s) and short-lived small/large
flow(s)
2. Flow-state dependent packet selection techniques
Expanding on the work in [FLSEC] and [RFC 5475], this draft suggests
additional techniques for flow-state dependent packet selection for
identifying large flows. One of these techniques is called Multistage
Filters which is described in [ESVA]. This technique helps in
automatically identifying large flows with a low false positive rate.
This technique can be implemented as an inline solution in
switches/routers and would be expected to operate at line rate.
Besides the Multistage filters technique described in [ESVA],
1) The technique suggested in [VRM] is also applicable. [VRM]
suggests techniques for automatically identifying large flows
using rotating conservative counting Bloom filters with periodic
decay. This technique has a low false positive rate in large flow
misidentification.
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2) The sample and hold technique suggested in [ESVA] is also
applicable. This technique has a low false positive rate in large
flow misidentification.
The large flows which are automatically identified using the above
techniques are populated in the IPFIX flow cache [RFC 6728]. If a
large flow already exists in the IPFIX flow cache, the above
techniques are not applied - this is the reason these are called
flow-state dependent packet selection techniques.
Please note that there is a finite probability of small flows being
misidentified as large flows. These are handled as described in the
section 2.2 "Handling Inactive/Misidentified Large Flows".
2.1. Information Model for flow-state dependent packet selection technique configuration
From a bandwidth and time duration perspective, in order to identify
large flows we define an observation interval and observe the
bandwidth of the flow over that interval. A flow that exceeds a
certain minimum bandwidth threshold over that observation interval
would be considered a large flow.
The two configuration parameters -- the observation interval, and the
minimum bandwidth threshold over that observation interval -- should
be programmable in a switch or a router to facilitate handling of
different use cases and traffic characteristics are defined below.
largeFlowObservationInterval: The minimum time interval to observe a
flow before performing further processing of the flow. Unit is in
milliseconds.
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largeFlowBandwidthThreshold: The minimum bandwidth of the flow during
the observation interval for declaring the flow a large flow. Unit is
in Mbps.
For example, a flow which is at or above 10 Mbps for a time period of
at least 30 seconds could be declared a large flow.
Below is the list of flow-state dependent packet selection technique
Information Elements:
+-----+---------------------------------+-------+------------------------------+
| ID | Name | ID | Name |
+-----+----------------------------------+------+------------------------------+
| TBD | largeFlowObservationInterval | TBD | largeFlowBandwidthThreshold |
| 1 | | 2 | |
+-----+----------------------------------+------+------------------------------+
2.2. Handling Inactive/Misid entified Large Flows
Once a flow has been recognized as a large flow, it should continue
to be recognized as a large flow as long as the traffic received
during an observation interval exceeds some fraction of the bandwidth
threshold, for example 80% of the bandwidth threshold. If the traffic
received during an observation interval falls below a fraction of the
bandwidth threshold, the large flow should be removed from the IPFIX
flow cache.
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2.3. Flow-state dependent packet selection - sample and hold
[FLSEC] suggests some information model parameters for the sample and
hold technique suggested in [ESVA]. The large flow information model
parameters suggested in section 2.1 are complementary to these.
2.4. IANA Considerations
2.4.1. Registration of Information Elements
IANA will register the following IEs in the IPFIX Information
Elements registry at http://www.iana.org/assignments/ipfix/ipfix.xml
IANA Note: please replace TBD1, TBD2, with the assigned values,
throughout the document.
2.4.1.1. largeFlowObservationInterval
Description:
The minimum time interval to observe a flow for performing further
processing of the flow.
Abstract Data Type: unsigned64
ElementId: TBD1
Units: milliseconds
Status: Current
2.4.1.2. largeFlowBandwidthThreshold
Description:
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The minimum bandwidth of the flow during the observation interval
(largeFlowObservationInterval)for declaring the flow a large flow.
Unit is in Mbps.
Abstract Data Type: unsigned64
ElementId: TBD2
Units: Mbps
Status: Current
3. Current sampling techniques for security threat detection
Packet sampling techniques e.g. PSAMP -- [RFC 5474], [RFC 5475], [RFC
5476], [RFC 5477], in switches and routers provide an effective
mechanism for approximate detection of various types of flows --
long-lived large flows and other flows (which include long-lived
small flows, short-lived small/large flows) with minimal packet
replication bandwidth overhead. The packet sampling techniques sample
all flows equally.
A large percentage of the packet samples comprise of long-lived large
(aka large) flows and a small percentage of the packet samples
comprise of other (aka small) flows. The large flows aka top-talkers
consume a large percentage of the bandwidth and small percentage of
the flow space.
The small flows, which are the typical cause of security threats like
Denial of Service (DOS) attacks, scanning attacks etc., consume a
small percentage of the bandwidth and a large percentage of the flow
space.
4. Application of flow-state dependent packet selection techniques for security threat detection
Using the flow-state dependent packet selection techniques described
in Section 2, the large flows or top-talkers can be detected in real-
time with a high degree of accuracy. Only the small flows need to be
sampled -- this makes security threat detection more effective with
minimal sampling overhead.
The steps in security threat detection are described below
1) Large Flow Identification:
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For identifying large flows, use the flow-state dependent packet
selection techniques described in Section 2. This helps in
identifying the large flows aka top-talkers in real-time with a
high degree of accuracy.
2) Large Flow Classification:
The identified large flows can be broadly classified into 2
categories as detailed below.
a. Well behaved (steady rate) large flows, e.g. video streams
b. Bursty (fluctuating rate) large flows e.g. Peer-to-Peer
traffic
The large flows can be sampled at a low rate for further analysis
or need not be sampled. If desired, the large flows could be
exported to a central entity, e.g. Netflow Collector, using IPFIX
protocol [RFC 5101] for further analysis.
3) Small Flow Processing:
The small flows (excluding the large flows) can be sampled at a
normal rate. The small flows can be examined for determining
security threats like DOS attacks (for e.g. SYN floods), Scanning
attacks etc. [FDDOS, PDSN, and ALDS]
Thus, we can see that, security threat detection is possible with
minimal sampling overhead.
4.1. Analysis of various flow-state dependent packet selection techniques
The multistage filter technique suggested in [ESVA] for automatic
identification works well for standard applications generating large
flows, for e.g. video content like movies and catch-up episodes,
backup transactions etc. with a detection time of approximately 30-60
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seconds. These detection times ensure that short-lived large flows,
for e.g. HD video clips, are not unnecessarily recognized.
If faster large flow identification times are desired (much shorter
than 30s), the multistage filter technique suggested in [ESVA] may
pose the following problem that the effective filtered flow size is
phase-dependent: that is, relatively smaller constant-rate flows, for
e.g. HD video clips, beginning early within a counting Bloom filter
reset interval would be unnecessarily detected with the same
probability as relatively larger flows beginning toward the interval.
[VRM] suggests techniques for addressing the above problem using
rotating conservative counting Bloom filters with periodic decay.
4.2. Simulation
Simulation results for these flow-state dependent packet selection
techniques are presented in Appendix A. The goal of the simulation is
to demonstrate the effectiveness of these techniques for security
threat detection in a multi-tenant video streaming data center.
5. Security Considerations
This document does not directly impact the security of the Internet
infrastructure or its applications. In fact, it proposes techniques
which could help in identifying a DOS attack pattern.
6. Operational Considerations
For effectively using the flow-state dependent packet selection
techniques, the operator should adjust the programmable parameters
largeFlowObservationInterval and largeFlowBandwidthThreshold in
switches/routers based on the applications which are being deployed.
7. Acknowledgements
The authors would like to thank Juergen Quittek, Brian Carpenter,
Michael Fargano, Michael Bugenhagen, Jianrong Wong, Brian Trammell
and Paul Aitken for all the support and valuable input.
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8. References
8.1. Normative References
8.2. Informative References
[RFC 5474] N. Duffield et al., "A Framework for Packet Selection and
Reporting", March 2009.
[RFC 5475] T. Zseby et al., "Sampling and Filtering Techniques for IP
Packet Selection", March 2009.
[RFC 5476] B. Claise, Ed. et al., "Packet Sampling (PSAMP) Protocol
Specifications", March 2009.
[RFC 5477] T. Dietz et al., "Information Model for Packet Sampling
Exports", March 2009.
[RFC 5101] B. Claise, "Specification of the IP Flow Information
Export (IPFIX) Protocol for the Exchange of IP Traffic Flow
Information", January 2008
[RFC 6728] G. Muenz et al., "Configuration Data Model for the IP Flow
Information Export (IPFIX) and Packet Sampling (PSAMP) Protocols"
[VRM] G. Bianchi et al., "Measurement Data Reduction through
Variation Rate Metering", INFOCOM 2010
[PDSN] Ignasi Paredes-Oliva et al., "Portscan Detection with Sampled
NetFlow", TMA 2009
[ALDS] Z. Morley Mao et al., "Analyzing Large DDoS Attacks Using
Multiple Data Sources", SIGCOMM 2006
[FDDOS] David Holmes, "The DDoS Threat Spectrum", F5 White paper 2012
[ESVA] C. Estan and G. Varghese, "New Directions in Traffic
Measurement and Accounting", ACM SIGCOMM Internet Measurement
Workshop 2001, San Francisco (CA) Nov. 2001.
Appendix A: Simulation of Flow aware packet sampling
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Goal:
Demonstrate the effectiveness of flow aware packet sampling in a
practical use case, for e.g. multi-tenant video streaming in a data
center.
Test Topology:
Multiple virtual servers (server hosted on a virtual machine)
connected to a virtual switch (vSwitch) which in turn connects to the
data center network using a 10Gbps ethernet interface.
2 virtual servers are active.
First virtual server
. Traffic types
o HD MPEG-4 video streams (bit rate 10Mbps) - 100 - 1Gbps
o SD MPEG-2 video streams (bit rate 4Mbps) - 300 - 1.2Gbps
o Other traffic - 500Mbps (Video clips, DOS attacks (for e.g.
SYN floods), Scanning attacks etc.)
. Aggregate traffic - 2.7Gbps
Second virtual server
. Traffic types
o HD MPEG-4 video streams (bit rate 10Mbps) - 50 - .5Gbps
o SD MPEG-2 video streams (bit rate 4Mbps) - 500 - 2.0Gbps
o Backup transaction - 100Mbps
o Other traffic - 500Mbps (Video clips, DOS attacks (for e.g.
SYN floods), Scanning attacks etc.)
. Aggregate traffic - 3.1Gbps
Total traffic on 2 servers - 5.8Gbps
Existing techniques:
Normal sampling rate - 1:1000
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Total sampled traffic = 5.8Gbps/1000 = 5.8Mbps
Flow aware sampling technique:
Large flow recognition parameters
. Observation interval for large flow - 60 seconds
. Minimum bandwidth threshold over the observation interval -
2Mbps
Aggregate bit rate of large flows = 4.8Gbps
Aggregate bit rate of small flows = 1Gbps
Low sampling rate of large flows - 1:10000
Normal sampling rate of small flows - 1:1000
Total sampled traffic = 4.8Gbps/10000 + 1Gbps/1000 = 1.48Mbps
Percentage improvement in sampling (most of the samples are only
small flows) = (5.8 - 1.48)/5.8 ~= 78%
The small flows can be examined in a central entity like Netflow
Collector for determining security threats like DOS attacks, Scanning
attacks etc. Thus, we can see that, security threat detection is
possible with minimal sampling overhead.
Authors' Addresses
Ram Krishnan
Brocade Communications
San Jose, 95134, USA
Phone: +001-408-406-7890
Email: ramk@brocade.com
Ning So
Tata Communications
Plano, TX 75082, USA
Phone: +001-972-955-0914
Email: ning.so@tatacommunications.com
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