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Keywords: IPv6, Scaling, NDP
Internet Engineering Task Force (IETF) W. Cerveny
Request for Comments: 8161 Arbor Networks
Category: Informational R. Bonica
ISSN: 2070-1721 R. Thomas
Juniper Networks
May 2017
Benchmarking the Neighbor Discovery Protocol
Abstract
This document provides benchmarking procedures for the Neighbor
Discovery Protocol (NDP). It also proposes metrics by which an NDP
implementation's scaling capabilities can be measured.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc8161.
Copyright Notice
Copyright (c) 2017 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
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.
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Table of Contents
1. Introduction ....................................................2
1.1. Requirements Language ......................................4
2. Test Setup ......................................................4
2.1. Device Under Test (DUT) ....................................4
2.1.1. Interfaces ..........................................4
2.1.2. Neighbor Discovery Protocol (NDP) ...................5
2.1.3. Routing .............................................5
2.2. Tester .....................................................6
2.2.1. Interfaces ..........................................6
2.2.2. Neighbor Discovery Protocol (NDP) ...................6
2.2.3. Routing .............................................6
2.2.4. Test Traffic ........................................7
2.2.5. Counters ............................................8
3. Tests ...........................................................8
3.1. Baseline Test ..............................................8
3.1.1. Procedure ...........................................9
3.1.2. Baseline Test Procedure Flow Chart ..................9
3.1.3. Results ............................................11
3.2. Scaling Test ..............................................11
3.2.1. Procedure ..........................................11
3.2.2. Scaling Test Procedure Flow Chart ..................13
3.2.3. Results ............................................15
4. Measurements Explicitly Excluded ...............................15
4.1. DUT CPU Utilization .......................................15
4.2. Malformed Packets .........................................15
5. IANA Considerations ............................................16
6. Security Considerations ........................................16
7. Normative References ...........................................16
Acknowledgments ...................................................16
Authors' Addresses ................................................17
1. Introduction
When an IPv6 node forwards a packet, it executes the following
procedure:
o Identifies the outbound interface and IPv6 next hop.
o Queries a local Neighbor Cache (NC) to determine the IPv6 next
hop's link-layer address.
o Encapsulates the packet in a link-layer header. The link-layer
header includes the IPv6 next hop's link-layer address.
o Forwards the packet to the IPv6 next hop.
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IPv6 nodes use the Neighbor Discovery Protocol (NDP) [RFC4861] to
maintain the NC. Operational experience [RFC6583] shows that when an
implementation cannot maintain a sufficiently complete NC, its
ability to forward packets is impaired.
NDP, like any other protocol, consumes processing, memory, and
bandwidth resources. Its ability to maintain a sufficiently complete
NC depends upon the availability of the above-mentioned resources.
This document provides benchmarking procedures for NDP. Benchmarking
procedures include a Baseline Test and an NDP Scaling Test. In both
tests, the Device Under Test (DUT) is an IPv6 router. Two physical
links (A and B) connect the DUT to a Tester. The Tester sends
traffic through Link A to the DUT. The DUT forwards that traffic,
through Link B, back to the Tester.
The above-mentioned traffic stream contains one or more interleaved
flows. An IPv6 Destination Address uniquely identifies each flow.
Or, said another way, every packet within a flow has the same IPv6
Destination Address.
In the Baseline Test, the traffic stream contains exactly one flow.
Because every packet in the stream has the same IPv6 Destination
Address, the DUT can forward the entire stream using exactly one NC
entry. NDP is exercised minimally, and no packet loss should be
observed.
The NDP Scaling Test is identical to the Baseline Test, except that
the traffic stream contains many flows. In order to forward the
stream without loss, the DUT must maintain one NC entry for each
flow. If the DUT cannot maintain one NC entry for each flow, packet
loss will be observed and attributed to NDP scaling limitations.
This document proposes an NDP scaling metric, called NDP-MAX-
NEIGHBORS. NDP-MAX-NEIGHBORS is the maximum number of neighbors to
which an IPv6 node can send traffic during periods of high NDP
activity.
The procedures described herein reveal how many IPv6 neighbors an NDP
implementation can discover. They also provide a rough estimate of
the time required to discover those neighbors. However, that
estimate does not reflect the maximum rate at which the
implementation can discover neighbors. Maximum rate discovery is a
topic for further exploration.
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The test procedures described herein assume that NDP does not compete
with other applications for resources on the DUT. When NDP competes
for resources, its scaling characteristics may differ from those
reported by the benchmarks described and may vary over time.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2. Test Setup
+---------------+ +-----------+
| | | |
| | Link A | Device |
| |------------>| Under |
| Tester | | Test |
| |<------------| (DUT) |
| | Link B | |
+---------------+ +-----------+
Figure 1: Test Setup
The DUT is an IPv6 router. Two links (A and B) connect the DUT to
the Tester. Link A capabilities must be identical to Link B
capabilities. For example, if the interface to Link A is a 10
Gigabit Ethernet port, the interface to Link B must also be a 10
Gigabit Ethernet port.
2.1. Device Under Test (DUT)
2.1.1. Interfaces
DUT interfaces are numbered as follows:
o Link A - 2001:2:0:0::2/64
o Link B - 2001:2:0:1::1/64
Both DUT interfaces should be configured with a 1500-byte MTU.
However, if they cannot support a 1500-byte MTU, they may be
configured with a 1280-byte MTU.
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2.1.2. Neighbor Discovery Protocol (NDP)
NDP is enabled on both DUT interfaces. Therefore, the DUT emits both
solicited and unsolicited Router Advertisement (RA) messages. The
DUT emits an RA message at least once every 600 seconds and no more
frequently than once every 200 seconds.
When the DUT sends an RA message, it includes the following
information:
o Router Lifetime - 1800 seconds
o Reachable Time - 0 seconds
o Retrans Time - 0 seconds
o Source Link-Layer Address - link-layer address of DUT interface
o M-bit is clear (0)
o O-bit is clear (0)
The above-mentioned values are chosen because they are the default
values specified in RFC 4861.
NDP manages the NC. Each NC entry represents an on-link neighbor and
is identified by the neighbor's on-link unicast IP address. As per
RFC 4861, each NC entry needs to be refreshed periodically. NDP
refreshes NC entries by exchanging Neighbor Solicitation (NS) and
Neighbor Advertisement (NA) messages.
No static NC entries are configured on the DUT.
2.1.3. Routing
The DUT maintains a direct route to 2001:2:0:0/64 through Link A. It
also maintains a direct route to 2001:2:0:1/64 through Link B. No
static routes or dynamic routing protocols are configured on the DUT.
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2.2. Tester
2.2.1. Interfaces
Interfaces are numbered as follows:
o Link A - 2001:2:0:0::1/64
o Link B - Multiple addresses are configured on Link B. These
addresses are drawn sequentially from the 2001:2:0:1::/64 address
block. The first address is 2001:2:0:1::2/64. Subsequent
addresses are 2001:2:0:1::3/64, 2001:2:0:1::4/64,
2001:2:0:1::5/64, etc. The number of configured addresses should
be the expected value of NDP-MAX-NEIGHBORS times 1.1.
Both Tester interfaces should be configured with a 1500-byte MTU.
However, if they cannot support a 1500-byte MTU, they may be
configured with a 1280-byte MTU.
2.2.2. Neighbor Discovery Protocol (NDP)
NDP is enabled on both Tester interfaces. Therefore, upon
initiation, the Tester sends Router Solicitation (RS) messages and
waits for Router Advertisement (RA) messages. The Tester also
exchanges Neighbor Solicitation (NS) and Neighbor Advertisement (NA)
messages with the DUT.
No static NC entries are configured on the Tester.
2.2.3. Routing
The Tester maintains a direct route to 2001:2:0:0/64 through Link A.
It also maintains a direct route to 2001:2:0:1/64 through Link B. No
static routes or dynamic routing protocols are configured on the
Tester.
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2.2.4. Test Traffic
The Tester sends a stream of test traffic through Link A to the DUT.
The test traffic stream contains one or more interleaved flows.
Flows are numbered 1 through N, sequentially.
Within each flow, each packet contains an IPv6 header, and each IPv6
header contains the following information:
o Version - 6
o Traffic Class - 0
o Flow Label - 0
o Payload Length - 0
o Next Header - IPv6-NoNxt (59)
o Hop Limit - 255
o Source Address - 2001:2:0:0::1
o Destination Address - The first 64 bits of the Destination Address
are 2001:2:0:1::. The next 64 are uniquely associated with the
flow. Every packet in the first flow carries the Destination
Address 2001:2:0:1::2. Every subsequent flow has an IP address
one greater than the last (i.e., 2001:2:0:1::3, 2001:2:0:1::4,
etc.).
In order to avoid link congestion, test traffic is offered at a rate
not to exceed 50% of available link bandwidth. In order to avoid
burstiness and buffer occupancy, every packet in the stream is
exactly 40 bytes long (i.e., the length of an IPv6 header with no
IPv6 payload). Furthermore, the gap between packets is identical.
During the course of a test, the number of flows that the test stream
contains may increase. When this occurs, the rate at which test
traffic is offered remains constant. For example, assume that a test
stream is offered at a rate of 1,000 packets per second. This stream
contains two flows, each contributing 500 packets per second to the
1,000 packet per second aggregate. When a third stream is added to
the flow, all three streams must contribute 333 packets per second in
order to maintain the 1,000 packet per second limit. (As in this
example, rounding error is acceptable.)
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The DUT attempts to forward every packet in the test stream through
Link B to the Tester. It does this because:
o Every packet in the test stream has a Destination Address drawn
from the 2001:2:0:1::/64 address block.
o The DUT has a direct route to 2001:2:0:1/64 through Link B.
2.2.5. Counters
On the Tester, two counters are configured for each flow. One
counter, configured on Link A, increments when the Tester sends a
packet belonging to the flow. The other counter, configured on Link
B, increments when the Tester receives a packet from the flow. In
order for a packet to be associated with a flow, the following
conditions must all be true:
o The IPv6 Destination Address must be that of the flow.
o The IPv6 Next Header must be IPv6-NoNxt (59).
The following counters also are configured on both Tester Interfaces:
o RS packets sent
o RA packets received
o NS packets sent
o NS packets received
o NA packets sent
o NA packets received
o Total packets sent
o Total packets received
3. Tests
3.1. Baseline Test
The purpose of the Baseline Test is to ensure that the DUT can
forward every packet in the test stream, without loss, when NDP is
minimally exercised and not operating near its scaling limit.
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3.1.1. Procedure
o On the DUT, clear the NC.
o On the Tester, clear all counters.
o On the Tester, set a timer to expire in 60 seconds.
o On the Tester, start the test stream with exactly one flow (i.e.,
IPv6 Destination Address equals 2001:2:0:1::2).
o Wait for either the timer to expire or the packets-received
counter associated with the flow to increment.
o If the timer expires, stop the test stream and end the test.
o If the packets-received counter increments, pause the traffic
stream, log the initial counter values, clear the counters, reset
the timer to expire in 1800 seconds, and restart the traffic
stream.
o When the timer expires, stop the test stream, wait sufficient time
for any queued packets to exit, log the final counter values, and
end the test.
3.1.2. Baseline Test Procedure Flow Chart
+--------------------------+
| On the DUT, clear the NC |
+-------------|------------+
|
+------------------v------------------+
| On the Tester, clear all counters |
+------------------|------------------+
|
+------------------v-----------------+
| On the Tester, set a |
| timer to expire in |
| 60 seconds |
+------------------|-----------------+
|
+------------------v-----------------+
|On the Tester, start the test stream|
|with exactly one flow (i.e., IPv6 |
|Destination Address equals |
|2001:2:0:0:1::2) |
+------------------|-----------------+
|
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|
+------------------v-----------------+
|Wait for either the timer to expire |
|or packets-received counter |
|associated with the flow to |
|increment |
+------------------|-----------------+
|
/-------v-------\
/ \ Yes +--------------+
|Did timer expire?|-------| End the test |
\ / +--------------+
\-------|-------/
| No
|
/---------v--------\
/ \ No +--------------+
|Did packets-received|------| End the test |
|counter increment? | +--------------+
\ /
\---------|--------/
| Yes
|
+------------------v-----------------+
|Pause traffic stream, log initial |
|counter values, clear the counters, |
|reset the timer to expire in 1800 |
|seconds, and restart traffic stream |
+------------------|-----------------+
|
+------------------v-----------------+
|When timer expires, stop the test |
|stream, wait sufficient time for |
|any queued packets to exit, log the |
|final counter values |
+------------------|-----------------+
|
+----v---+
|End test|
+--------+
Figure 2: Baseline Test Procedure Flow Chart
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3.1.3. Results
The log contains initial and final values for the following counters:
o packets-sent
o packets-received
The initial values of packets-sent and packets-received may be equal
to one another. If these values are identical, none of the initial
packets belonging to the flow were lost. However, if the initial
value of packets-sent is greater than the initial value of packets-
received, initial packets were lost. This loss of initial packets is
acceptable.
The final values of packets-sent and packets-received should be equal
to one another. If they are not, an error has occurred. Because
this error is likely to affect Scaling Test results, the error must
be corrected before the Scaling Test is executed.
3.2. Scaling Test
The purpose of the Scaling Test is to discover the number of
neighbors to which an IPv6 node can send traffic during periods of
high NDP activity. We call this number NDP-MAX-NEIGHBORS.
3.2.1. Procedure
Execute the following procedure:
o On the DUT, clear the NC.
o On the Tester, clear all counters.
o On the Tester, set a timer to expire in 60 seconds.
o On the Tester, start the test stream with exactly one flow (i.e.,
IPv6 Destination Address equals 2001:2:0:1::2).
o Wait for either the timer to expire or the packets-received
counter associated with the flow to increment.
o If the timer expires, stop the test stream and end the test.
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o If the packets-received counter increments, execute the following
procedure N times, starting at 2 and ending at the expected value
of NDP-MAX-NEIGHBORS times 1.1.
* Pause the test stream.
* Log the time and the value of N minus one.
* Clear the packets-sent and packets-received counters associated
with the previous flow (i.e., N minus one).
* Reset the timer to expire in 60 seconds.
* Add the next flow to the test stream (i.e., IPv6 Destination
Address is a function of N).
* Restart the test stream.
* Wait for either the timer to expire or the packets-received
counter associated with the new flow to increment.
After the procedure described above has been executed N times, clear
the timer and reset it to expire in 1800 seconds. When the timer
expires, stop the stream, log all counters, and end the test (after
waiting sufficient time for any queued packets to exit).
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3.2.2. Scaling Test Procedure Flow Chart
+--------------------------+
| On the DUT, clear the NC |
+-------------|------------+
|
+------------------v------------------+
| On the Tester, clear all counters |
+------------------|------------------+
|
+------------------v-----------------+
| On the Tester, set a |
| timer to expire in |
| 60 seconds |
+------------------|-----------------+
|
+------------------v-----------------+
|On the Tester, start the test stream|
|with exactly one flow (i.e., IPv6 |
|Destination Address equals |
|2001:2:0:0:1::2) |
+------------------|-----------------+
|
+------------------v-----------------+
|Wait for either the timer to expire |
|or packets-received counter |
|associated with the flow to |
|increment |
+------------------|-----------------+
|
/-------v-------\
/ \ Yes +--------------+
|Did timer expire?|-------| End test |
\ / | and return |
\-------|-------/ +--------------+
| No
|
/---------v--------\
/ \ No +--------------+
|Did packets-received|------| End test |
|counter increment? | | and return |
\ / +--------------+
\---------|--------/
| Yes
|
+------v------+
| N=2 |
+------|------+
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|
/--------------v-------------\
/ Is \ No +----------+
| N < NDP-MAX-NEIGHBORS |----| End test |
-------| times 1.1 | +----------+
| \ /
| \--------------|-------------/
| | Yes
| +-----------v----------+
| |Pause the test stream |
| +-----------|----------+
| |
| +----------v----------+
| |Log the time and the |
| |value of N minus one |
| +----------|----------+
| |
| +-----------v-----------+
| |Clear the packets-sent |
| |and packets-received |
| |counters associated |
| |with the previous flow |
| |(i.e., N minus one) |
| +-----------|-----------+
| |
| +----------v----------+
| |Reset the timer to |
| |expire in 60 seconds |
| +----------|----------+
| |
| +--------------v---------------+
| |Add the next flow to the test |
| |stream (i.e., IPv6 Destination|
| |Address is a function of N) |
| +--------------|---------------+
| |
| +------v------+
| | N=N+1 |
| +------|------+
| |
| +----------v------------+
------------|Restart the test stream|
+-----------------------+
Figure 3: Scaling Test Procedure Flow Chart
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3.2.3. Results
The test report includes the following:
o A description of the DUT (make, model, processor, memory, and
interfaces)
o Rate at which the Tester offers test traffic to the DUT (measured
in packets per second)
o A log that records the time at which each flow was introduced to
the test stream and the final value of all counters
o The expected value of NDP-MAX-NEIGHBORS
o The actual value of NDP-MAX-NEIGHBORS
NDP-MAX-NEIGHBORS is equal to the number of counter pairs where
packets-sent is equal to packets-received. Two counters are members
of a pair if they are both associated with the same flow. If
packets-sent is equal to packets-received for every counter pair, the
test should be repeated with a larger expected value of NDP-MAX-
NEIGHBORS.
If an implementation abides by the recommendation of Section 7.1 of
RFC 6583, for any given counter pair, packets-received will either be
equal to zero or packets-sent.
The log documents the time at which each flow was introduced to the
test stream. This log reveals the effect of NC size to the time
required to discover a new IPv6 neighbor.
4. Measurements Explicitly Excluded
These measurements aren't recommended because of the itemized reasons
below:
4.1. DUT CPU Utilization
This measurement relies on the DUT to provide utilization
information, which is not externally observable (not black-box).
However, some testing organizations may find the CPU utilization is
useful auxiliary information specific to the DUT model, etc.
4.2. Malformed Packets
This benchmarking test is not intended to test DUT behavior in the
presence of malformed packets.
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5. IANA Considerations
This document does not require any IANA actions.
6. 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 or System Under
Test (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.
7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007,
<http://www.rfc-editor.org/info/rfc4861>.
[RFC6583] Gashinsky, I., Jaeggli, J., and W. Kumari, "Operational
Neighbor Discovery Problems", RFC 6583,
DOI 10.17487/RFC6583, March 2012,
<http://www.rfc-editor.org/info/rfc6583>.
Acknowledgments
Helpful comments and suggestions were offered by Al Morton, Joel
Jaeggli, Nalini Elkins, Scott Bradner, and Ram Krishnan on the BMWG
email list and at BMWG meetings. Precise grammatical corrections and
suggestions were offered by Ann Cerveny.
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Authors' Addresses
Bill Cerveny
Arbor Networks
2727 South State Street
Ann Arbor, MI 48104
United States of America
Email: wcerveny@arbor.net
Ron Bonica
Juniper Networks
2251 Corporate Park Drive
Herndon, VA 20170
United States of America
Email: rbonica@juniper.net
Reji Thomas
Juniper Networks
Elnath-Exora Business Park Survey
Bangalore, KA 560103
India
Email: rejithomas@juniper.net
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