Benchmarking Neighbor Discovery Problems
draft-cerveny-bmwg-ipv6-nd-02

Network Working Group                                         W. Cerveny
Internet-Draft                                            Arbor Networks
Intended status: Informational                          October 17, 2013
Expires: April 20, 2014

                Benchmarking Neighbor Discovery Problems
                     draft-cerveny-bmwg-ipv6-nd-02

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 April 20, 2014.

Copyright Notice

   Copyright (c) 2013 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
   (http://trustee.ietf.org/license-info) in effect on the date of

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   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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   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.  Maximum number of valid hosts . . . . . . . . . . . . . .   7
       6.1.1.  Test Streams  . . . . . . . . . . . . . . . . . . . .   7
       6.1.2.  General Testing Procedure . . . . . . . . . . . . . .   7
       6.1.3.  Discussion  . . . . . . . . . . . . . . . . . . . . .   8
     6.2.  Stable-state time . . . . . . . . . . . . . . . . . . . .   8
       6.2.1.  Test streams  . . . . . . . . . . . . . . . . . . . .   8
       6.2.2.  General Testing Procedure . . . . . . . . . . . . . .   8
       6.2.3.  Discussion  . . . . . . . . . . . . . . . . . . . . .   9
     6.3.  NDP Prioritization: Behavior with stale neighbor entries    9
       6.3.1.  Test Streams  . . . . . . . . . . . . . . . . . . . .   9
       6.3.2.  General Testing Procedure . . . . . . . . . . . . . .   9
       6.3.3.  Discussion  . . . . . . . . . . . . . . . . . . . . .  10
     6.4.  NDP Prioritizaton: Entries never present in neighbor
           cache . . . . . . . . . . . . . . . . . . . . . . . . . .  10
       6.4.1.  Test Streams  . . . . . . . . . . . . . . . . . . . .  10
       6.4.2.  General Testing Procedure . . . . . . . . . . . . . .  10
       6.4.3.  Discussion  . . . . . . . . . . . . . . . . . . . . .  10
     6.5.  NDP Prioritization: Unreachable addresses only  . . . . .  10
       6.5.1.  Test Streams  . . . . . . . . . . . . . . . . . . . .  10
       6.5.2.  General Testing Procedure . . . . . . . . . . . . . .  10
       6.5.3.  Discussion  . . . . . . . . . . . . . . . . . . . . .  10
   7.  Measurements Explicitly Excluded  . . . . . . . . . . . . . .  11
     7.1.  DUT CPU Utilization . . . . . . . . . . . . . . . . . . .  11
     7.2.  Malformed Packets . . . . . . . . . . . . . . . . . . . .  11
   8.  DUT initialization  . . . . . . . . . . . . . . . . . . . . .  11
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  11
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12
   12. Normative References  . . . . . . . . . . . . . . . . . . . .  12
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  12

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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.

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]

   Non-participating Network  Network connected to DUT, for which nodes
      are neither active participants nor directly impacted by the test
      traffic.

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

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

   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:

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   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.

   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.

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   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
   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.

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

   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 |
   |               |             |           |              |              |
   +---------------+             +-----------+              +--------------+
                                       |
                                       |
                              +-----------------+
                              |                 |
                              |Non-participating|
                              |    network      |
                              |                 |
                              +-----------------+

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 and in fact a goal of testing could be to

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   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 deteration was not
   noticed at this rate.

   The lowest rate tested should be the rate for which packets can be
   expected to have an impact on the DUT -\u002D this value is of
   course, subjective.

6.  Tests

6.1.  Maximum number of valid hosts

   This test evaluates how many hosts can be actively sending and
   receiving traffic on a network and still have connectivity across the
   intermediate node, calculated as the maximum number of valid hosts
   per second averaged over a 30 second period.

6.1.1.  Test Streams

   Two streams are defined:

   1.  Stream tester-new, sourced from the scanning source interface,
       sets up new addresses in the neighbor cache by sending packets,
       where each packet is sent to a unique IPv6 address by ascending
       order in the target network.  If the packet is received at the
       target network interface, the address has been set up with an
       entry in the neighbor cache.

   2.  Stream tester-renew, sourced from the scanning source interface,
       sends traffic to existing addresses, where frequency of packets
       is between a millisecond and a second.

6.1.2.  General Testing Procedure

   1.  Transit packets matching stream tester-new.  Inittially, the rate
       for packets sent by tester-new should be a rate for which it is
       expected the intermediate node can transit.  The rate should be
       increased until addresses are no longer being added to the
       neighbor cache as confirmed by neighbor solicitations no longer
       being sent by the intermediate node or the maximum bandwidth of
       the scanner or target network has been met, as measured by

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       comparing the traffic being transited with the maximum bandwidth
       of the links connecting to the intermediate node.

   2.  Once the maximum rate for stream tester-new has been determined,
       transit packets for stream tester-new until 30 seconds have
       evolved.  Then send packets matching the tester-renew stream
       every second.  This specific step should be continued until
       packets in either stream don't reach the target network
       destination interface.

   3.  If all packets from the tester-renew stream don't reach the
       target network destination interface before the completion of the
       2 minute test, reduce the rate of the tester-new stream and
       repeat the test until all packets in both streams are received by
       the target network interface.

6.1.3.  Discussion

   The maximum number of valid hosts per second as calculated over a 30
   second period is the rate for which all packets are transited to the
   target network interface in step 3 above.

   This test is useful for confirming that there are no significant
   limitations in the intermediate node's capabilities, as defined by
   the intermediate node's intended deployment model and network.  For
   example, if the intermediate node is intended for deployment where
   maximum traffic throughput is expected to be in the 1-Mbps range, it
   may not appropriate to require the intermediate node to perform
   acceptably where the traffic rate exceeds 10-Mbps.

6.2.  Stable-state time

   Given that it is possible to determine the maximum number of valid
   hosts per 30 second period without exceeding the capabilities of the
   tester or test network, this test determines how long it takes for
   the neighbor cache get into a reasonable state after the intermediate
   node has gotten into a state where packets are dropped.  The period
   between when the disabling traffic is stopped and when the
   intermediate node no longer drops packets should be recorded.

6.2.1.  Test streams

   The test streams should be the same as those defined for "Maximum
   number of valid hosts."

6.2.2.  General Testing Procedure

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   1.  Replicate behavior in "maximum number of valid hosts" until
       packets are not being received by the target network destination
       interface.

   2.  Back off the rate to a point just below where packets previously
       were not received by the target network interface.

   3.  Measure the duration in seconds required until all packets are
       consistently received by the target network interface.

6.2.3.  Discussion

   This test confirms the rate at which an intermediate node recovers
   from a scanning incident where it's neighbor cache and potentially
   other processes are overwhelmed.

6.3.  NDP Prioritization: Behavior with stale neighbor entries

   This test attempts to quantify how NDP prioritization, as discussed
   in RFC 6583 [RFC6583], is handled by the intermediate node.  Priority
   should be given to hosts that have been seen before.

6.3.1.  Test Streams

   The test streams are the same as those defined for "Maximum number of
   valid hosts," with the addition of a "tester-unreachable" stream.
   This additional stream consists of sending packets for which the
   target network destination interface will not respond with neighbor
   advertisements.

6.3.2.  General Testing Procedure

   1.  Send stream tester-new packets at a maximum rate as determined by
       "Maximum number of valid hosts."

   2.  Slow down stream tester-renew until one gets into refreshing
       every 6 seconds.  If an address is in the "stale" state, it
       should get priority over new request.

   3.  Increase timer on stream tester-renew.

   4.  Stream tester-renew should always get responses.  Stream tester-
       renew packets should always be recieved by the target network
       destination interface.

   5.  Stream tester-new should not always get responses.  Stream
       tester-unreachable packets should not always be received by the
       target network destination interface.

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6.3.3.  Discussion

6.4.  NDP Prioritizaton: Entries never present in neighbor cache

   This test is identical to the first NDP prioritization test, except
   that reachability to nodes that never existed in the neighbor cache
   are confirmed.

6.4.1.  Test Streams

6.4.2.  General Testing Procedure

6.4.3.  Discussion

   NDP should prefer nodes that had previously been in the neighbor
   cache.

6.5.  NDP Prioritization: Unreachable addresses only

   This test evaluates the impact that scanning for non-existent
   addresses across an intermediate node has on the intermediate node's
   ability to respond to NDP requests for valid nodes which had never
   been reached before.

6.5.1.  Test Streams

   There are two streams in this test: one consists of a significant
   flow of scanning traffic for non-existent nodes and the other
   comprises of attempting to reach existing nodes that had previously
   not had entries in the neighbor cache.

6.5.2.  General Testing Procedure

   1.  Send stream tester-unreachable at a high rate for approximately
       30 seconds, continuing traffic until the end of the test.

   2.  Send stream tester-new at a very low rate (perhaps once per
       second).  Measure the rate at which the target network
       destination interface receives the packet.

6.5.3.  Discussion

   This test is intended to measure the real scenario where scanning is
   occuring on an otherwise idle network and there are a "handful" of
   real nodes on an end network which are being denied service because
   the NDP process cannot be completed in a timely manner.

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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.

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.

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11.  Acknowledgements

12.  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.

   [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.

Author's Address

   Bill Cerveny
   Arbor Networks

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