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Benchmarking Neighbor Discovery
draft-cerveny-bmwg-ipv6-nd-04

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Authors William J. Cerveny , Ron Bonica
Last updated 2014-02-14
Replaced by draft-ietf-bmwg-ipv6-nd, RFC 8161
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draft-cerveny-bmwg-ipv6-nd-04
Network Working Group                                         W. Cerveny
Internet-Draft                                            Arbor Networks
Intended status: Informational                                 R. Bonica
Expires: August 18, 2014                                Juniper Networks
                                                       February 14, 2014

                    Benchmarking Neighbor Discovery
                     draft-cerveny-bmwg-ipv6-nd-04

Abstract

   This document is a benchmarking instantiation of RFC 6583:
   "Operational Neighbor Discovery Problems" [RFC6583].  It describes a
   general testing procedure and measurements that can be performed to
   evaluate how the problems described in RFC 6583 may impact the
   functionality or performance of intermediate nodes.

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 RFC 2119 [RFC2119].

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 August 18, 2014.

Copyright Notice

   Copyright (c) 2014 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.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Overview of Relevant NDP and Intermediate Node Behavior . . .   3
   4.  Test Setup  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Testing Interfaces  . . . . . . . . . . . . . . . . . . .   6
   5.  Modifiers (Variables) . . . . . . . . . . . . . . . . . . . .   6
     5.1.  Frequency of NDP Triggering Packets . . . . . . . . . . .   6
   6.  Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . .   7
     6.1.  Stale Entry Time Determination  . . . . . . . . . . . . .   7
       6.1.1.  General Testing Procedure . . . . . . . . . . . . . .   7
     6.2.  Neighbor Cache Exhaustion Determination . . . . . . . . .   7
       6.2.1.  General Testing Procedure . . . . . . . . . . . . . .   8
     6.3.  Determine Neighbor Discovery Behavior during address scan   8
       6.3.1.  General Testing Procedure . . . . . . . . . . . . . .   8
     6.4.  Pre-established Flow Treatment  . . . . . . . . . . . . .   8
       6.4.1.  General Testing Procedure . . . . . . . . . . . . . .   8
     6.5.  Stopped Flow Recovery Behavior  . . . . . . . . . . . . .   9
       6.5.1.  General Testing Procedure . . . . . . . . . . . . . .   9
   7.  Measurements Explicitly Excluded  . . . . . . . . . . . . . .   9
     7.1.  DUT CPU Utilization . . . . . . . . . . . . . . . . . . .   9
     7.2.  Malformed Packets . . . . . . . . . . . . . . . . . . . .   9
   8.  DUT Initialization  . . . . . . . . . . . . . . . . . . . . .   9
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  10
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     12.2.  Informative References . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   This document is a benchmarking instantiation of RFC 6583:
   "Operational Neighbor Discovery Problems" [RFC6583].  It describes a
   general testing procedure and measurements that can be performed to
   evaluate how the problems described in RFC 6583 may impact the
   functionality or performance of intermediate nodes.

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2.  Terminology

   Intermediate Node  A router, switch, firewall or any other device
      which separates end-nodes.  The tests in this document can be
      completed with any intermediate node which maintains a neighbor
      cache, although not all measurements and performance
      characteristics may apply.

   Neighbor Cache  The neighbor cache is a database which correlates the
      link-layer address and the adjacent interface with an IPv6
      address.

   Neighbor Discovery  See Section 1 of RFC 4861 [RFC4861]

   Scanner Network  The network from which the scanning tested is
      connected.

   Scanning Interface  The interface from which the scanning activity is
      conducted.

   Stale Entry Time  This is the duration for which a neighbor cache
      entry marked "Reachable" will continue to be marked "Reachable" if
      an update for the address is not received.

   Target Network  The network for which the scanning tests is targeted.

   Target Network Destination Interface  The interface that resides on
      the target network, which is primarily used to measure DUT
      performance while the scanning activity is occurring.

3.  Overview of Relevant NDP and Intermediate Node Behavior

   In a traditional network, an intermediate node must support a mapping
   between a connected node's IP address and the connected node's link-
   layer address and interface the node is connected to.  With IPv4,
   this process is handled by ARP [RFC0826].  With IPv6, this process is
   handled by NDP and is documented in [RFC4861].  With IPv6, when a
   packet arrives on one of an intermediate node's interfaces and the
   destination address is determined to be reachable via an adjacent
   network:

   1.  The intermediate node first determines if the destination IPv6
       address is present in its neighbor cache.

   2.  If the address is present in the neighbor cache, the intermediate
       node forwards the packet to the destination node using the
       appropriate link-layer address and interface.

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   3.  If the destination IPv6 address is not in the intermediate node's
       neighbor cache:

       1.  An entry for the IPv6 address is added to the neighbor cache
           and the entry is marked "INCOMPLETE".

       2.  The intermediate node sends a neighbor solicitation packet to
           the solicited-node multicast address on the interface
           considered on-link.

       3.  If a solicited neighbor advertisement for the IPv6 address is
           received by the intermediate node, the neighbor cache entry
           is marked "REACHABLE" and remains in this state for 30
           seconds.

       4.  If a neighbor advertisement is not received, the intermediate
           node will continue sending neighbor solicitation packets
           every second until either a neighbor solicitation is received
           or the maximum number of solicitations has been sent.  If a
           neighbor advertisement is not received in this period, the
           entry can be discarded.

   There are two scenarios where a neighbor cache can grow to a very
   large size:

   1.  There are a large number of real nodes connected via an
       intermediate node's interface and a large number of these nodes
       are sending and receiving traffic simultaneously.

   2.  There are a large number of addresses for which a scanning
       activity is occuring and no real node will respond to the
       neighbor solicitation.  This scanning activity can be
       unintentional or malicious.  In addition to maintaining the
       "INCOMPLETE" neighbor cache entry, the intermediate node must
       send a neighbor solicitation packet every second for the maximum
       number of socicitations.  With today's network link bandwidths, a
       scanning event could cause a lot of entries to be added to the
       neighbor cache and solicited for in the time that it takes for a
       neighbor cache entry to be discarded.

   An intermediate node's neighbor cache is of a finite size and can
   only accommodate a specific number of entries, which can be limited
   by available memory or a preset operating system limit.  If the
   maximum number of entries in a neighbor cache is reached, the
   intermediate node must either drop an existing entry to make space
   for the new entry or deny the new IP address to MAC address/
   interface mapping with an entry in the neighbor cache.  In an extreme

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   case, the intermediate node's memory may become exhausted, causing
   the intermediate node to crash or begin paging memory.

   At the core of the neighbor discovery problems presented in RFC 6583
   [RFC6583], unintentional or malicious IPv6 traffic can transit the
   intermediate node that resembles an IP address scan similar to an
   IPv4-based network scan.  Unlike IPv4 networks, an IPv6 end network
   is typically configured with a /64 address block, allowing for
   upwards of 2**64 addresses.  When a network node attempts to scan all
   the addresses in a /64 address block directly attached to the
   intermediate node, it is possible to create a huge amount of state in
   the intermediate node's neighbor cache, which may stress processing
   or memory resources.

   Section 7.1 of RFC 6583 recommends how intermediate nodes should
   behave when the neighbor cache is exceeded.  Section 6 of RFC 6583
   [RFC6583] recommends how damage from an IPv6 address scan may be
   mitigated.  Section 6.2 of RFC 6583 [RFC6583] discusses queue tuning.

4.  Test Setup

   The network needs to minimally have two subnets: one from which the
   scanner(s) source their scanning activity and the other which is the
   target network of the address scans.

   It is assumed that the latency for all network segments is neglible.
   By default, the target network's subnet shall be 64-bits in length,
   although some tests may involve increasing the prefix length.

   Although packet size shouldn't have a direct impact, packet per
   second (pps) rates will have an impact.  Smaller packet sizes should
   be utilized to facilitate higher packet per second rates.

   For purposes of this test, the packet type being sent by the scanning
   device isn't important, although most scanning applications might
   want to send packets that would elicit responses from nodes within a
   subnet (such as an ICMPv6 echo request).  Since it is not intended
   that responses be evoked from the target network node, such packets
   aren't necessary.

   At the beginning of each test the intermediate node should be
   initialized.  Minimally, the neighbor cache should be cleared.

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   Basic format of test network.  Note that optional "non-participating
   network" is a third network not related to the scanner or target
   network.

+---------------+             +-----------+              +--------------+
|               |   Scanner   |           |   Target     |              |
|   Scanning    |-------------|    DUT    |--------------|Target Network|
| src interface |   Network   |           |   Network    |dst interface |
|               |             |           |              |              |
+---------------+             +-----------+              +--------------+

4.1.  Testing Interfaces

   Two tester interfaces are configured for most tests:

   o  Scanning source (src) interface: This is the interface from which
      test packets are sourced.  This interface sources traffic to
      destination IPv6 addresses on the target network from a single
      link-local address, similar to how an adjacent intermediate node
      would transit traffic through the intermediate node.

   o  Target network destination (dst) interface: This interface
      responds to neighbor solicitations as appropriate and confirms
      when an intermediate node has forwarded a packet to the interface
      for consumption.  Where appropriate, the target network
      destination interface will respond to neighbor solicitations with
      a unique link-layer address per IPv6 address solicited.

5.  Modifiers (Variables)

5.1.  Frequency of NDP Triggering Packets

   The frequency of NDP triggering packets could be as high as the
   maximum packet per second rate that the scanner network will support
   (or is rated for).  However, it may not be necessary to send packets
   at a particularly high rate.  In fact a goal of testing could be to
   identify if the DUT is able to withstand scans at rates which
   otherwise would not impact the performance of the DUT.

   Optimistically, the scanning rate should be incremented until the
   DUT's performance begins deteriorating.  Depending on the software
   and system being used to implement the scanning, it may be
   challenging to achieve a sufficient rate.  Where this maximum
   threshold cannot be determined, the test results should note the
   highest rate tested and that DUT performance deterioration was not
   noticed at this rate.

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   The lowest rate tested should be the rate for which packets can be
   expected to have an impact on the DUT -- this value is of course,
   subjective.

6.  Tests

6.1.  Stale Entry Time Determination

   This test determines the time interval when the intermediate node
   (DUT) identifies an address as stale.

   RFC 4861, section 6.3.2 [RFC4861] states that an address can be
   marked "stale" at a random value between 15 and 45 seconds (as
   defined via constants in the RFC).  This test confirms what value is
   being used by the intermediate node.  Note that RFC 4861 states that
   this random time can be changed "at least every few hours."

6.1.1.  General Testing Procedure

   1.  Send a packet to an address in target network.  Observe that the
       intermediate node sends neighbor solicitation to the solicited-
       node multicast address on the target network, for which tester
       destination interface responds with a neighbor advertisement.
       The intermediate node should create an entry in neighbor cache
       for the address, marking the address as "reachable".  The packet
       should be forwarded to the tester destination interface.

   2.  Wait one second.

   3.  Send packet from tester source address to tester destination
       address.  Determine if intermediate node sends neighbor
       solicitation.  If intermediate node does send neighbor
       solicitation, the stale entry time has not been exceeded.

   4.  If a neighbor solicitation was not sent after one second, wait 2
       seconds send packet.  If neighbor solicitation was not received,
       incrementing the wait time by one second and repeat this process
       until the intermediate node sends a neighbor solicitation for the
       address.  The stale entry time is the number of seconds that
       elapsed between the first packet and when the neighbor
       solicitation was sent.

6.2.  Neighbor Cache Exhaustion Determination

   Discover the point at which the neighbor cache is exhausted and
   evaluate intermediate node behavior when this threshold is reached.

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6.2.1.  General Testing Procedure

   1.  Send packets incrementally to addresses, simultaneously resending
       packets of previously discovered addresses within the stale entry
       time.

   2.  Observe what happens when one address greater than the maximum
       neighbor cache size ("n") is reached.  When "n+1" is reached, if
       either the first or most recent cache entry are dropped, this may
       be acceptable.

   3.  Confirm intermediate node doesn't crash when "n+1" is reached.

6.3.  Determine Neighbor Discovery Behavior during address scan

   This test is a prerequisite for later tests, for which it is
   confirmed how an intermediate node behaves in the presence of an
   address scan.  If adding the flow after the address scan results in
   abnormal behavior, it will be difficult to evaluate correct behavior
   for later tests.

6.3.1.  General Testing Procedure

   1.  Start sending n/2 (n determined in "Neighbor Cache Exhaustion"
       test) flows at a rate of one packet per second to valid addresses
       (valid addresses are defined as addresses for which the tester
       responds to neighbor solicitation).

   2.  Send n/2 + 1 flow and determine if intermediate node takes a long
       time to process NS/NA for valid addresses.

6.4.  Pre-established Flow Treatment

   This test expands on "Determine neighbor discovery behavior during
   address scan".  This test confirms behavior described in RFC 6483,
   where it is expected that in the presence of an address scan, flows
   for successfully cached addresses will continue to flow across the
   intermediate node.

6.4.1.  General Testing Procedure

   1.  Start n/2 flows (one packet per second per flow) to valid
       addresses.

   2.  Start address scan to invalid addresses (addresses without
       responding host).

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   3.  Determine if flows continue for existing, valid flows continue
       without unexpected loss or delay.

6.5.  Stopped Flow Recovery Behavior

   This test determines how a stopped flow recovers from the stale state
   in the presence of an address scan.  It confirms that the
   intermediate node continues to prefer addresses that had previously
   been added to the neighbor cache, even when the address is marked
   "stale" in the neighbor cache.

6.5.1.  General Testing Procedure

   1.  Start n/2 flows (one packet per second per flow) to valid
       addresses.

   2.  Start address scan to invalid addresses (addresses without
       responding host).

   3.  Stop one flow to valid address.

   4.  Wait stale time period for address to be marked "stale" in
       intermediate node neighbor cache.

   5.  Restart stopped flow and confirm that address is marked "active"
       immediately (not stuck behind address scan).

7.  Measurements Explicitly Excluded

   These are measurements which aren't recommended because of the
   itemized reasons below:

7.1.  DUT CPU Utilization

   This measurement relies on the DUT to provide utilization
   information, which is subjective.

7.2.  Malformed Packets

   This benchmarking test is not intended to test DUT behavior in the
   presence of malformed packets.

8.  DUT Initialization

   At the beginning of each test, the neighbor cache of the DUT should
   be initialized.

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9.  IANA Considerations

   This document makes no request of IANA.

   Note to RFC Editor: this section may be removed on publication as an
   RFC.

10.  Security Considerations

   Benchmarking activities as described in this memo are limited to
   technology characterization using controlled stimuli in a laboratory
   environment, with dedicated address space and the constraints
   specified in the sections above.

   The benchmarking network topology will be an independent test setup
   and MUST NOT be connected to devices that may forward the test
   traffic into a production network, or misroute traffic to the test
   management network.

   Further, benchmarking is performed on a "black-box" basis, relying
   solely on measurements observable external to the DUT/SUT.  Special
   capabilities SHOULD NOT exist in the DUT/SUT specifically for
   benchmarking purposes.

   Any implications for network security arising from the DUT/SUT SHOULD
   be identical in the lab and in production networks.

11.  Acknowledgements

   Helpful comments and suggestions were offered by Al Morton, Joel
   Jaeggli, Nalini Elkins, Scott Bradner, and Ram Krishnan, on the BMWG
   e-mail list and at BMWG meetings.  Precise grammatical corrections
   and suggestions were offered by Ann Cerveny.

12.  References

12.1.  Normative References

   [RFC0826]  Plummer, D., "Ethernet Address Resolution Protocol: Or
              converting network protocol addresses to 48.bit Ethernet
              address for transmission on Ethernet hardware", STD 37,
              RFC 826, November 1982.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2544]  Bradner, S. and J. McQuaid, "Benchmarking Methodology for
              Network Interconnect Devices", RFC 2544, March 1999.

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   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              September 2007.

   [RFC5180]  Popoviciu, C., Hamza, A., Van de Velde, G., and D.
              Dugatkin, "IPv6 Benchmarking Methodology for Network
              Interconnect Devices", RFC 5180, May 2008.

   [RFC6583]  Gashinsky, I., Jaeggli, J., and W. Kumari, "Operational
              Neighbor Discovery Problems", RFC 6583, March 2012.

12.2.  Informative References

   [RFC7048]  Nordmark, E. and I. Gashinsky, "Neighbor Unreachability
              Detection Is Too Impatient", RFC 7048, January 2014.

Authors' Addresses

   Bill Cerveny
   Arbor Networks
   2727 South State Street
   Ann Arbor, MI  48104
   USA

   Email: wcerveny@arbor.net

   Ron Bonica
   Juniper Networks
   2251 Corporate Park Drive
   Herndon, VA  20170
   USA

   Email: rbonica@juniper.net

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