Network Working Group
INTERNET-DRAFT
Expires in: July 2004
Scott Poretsky
Quarry Technologies
Brent Imhoff
Wiltel Communications
January 2004
Terminology for Benchmarking
IGP Data Plane Route Convergence
<draft-ietf-bmwg-igp-dataplane-conv-term-02.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Table of Contents
1. Introduction .................................................2
2. Existing definitions .........................................2
3. Term definitions..............................................3
3.1 Convergence Event.........................................3
3.2 Network Convergence.......................................3
3.3 Route Convergence.........................................4
3.4 Full Convergence..........................................4
3.5 Convergence Packet Loss...................................5
3.6 Convergence Event Instant.................................5
3.7 Convergence Recovery Instant..............................6
3.8 Rate-Derived Convergence Time.............................6
3.9 Convergence Event Transition..............................7
3.10 Convergence Recovery Transition..........................7
3.11 Loss-Derived Convergence Time............................8
3.12 Sustained Forwarding Convergence Time...................................9
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3.13 Restoration Convergence Time.............................9
3.14 Packet Sampling Interval.................................10
3.15 Local Interface..........................................10
3.16 Neighbor Interface.......................................11
3.17 Remote Interface.........................................11
3.18 Preferred Egress Interface...............................11
3.19 Next-Best Egress Interface...............................12
3.20 Stale Forwarding.........................................12
4. Security Considerations.......................................12
5. References....................................................13
6. Author's Address..............................................13
7. Full Copyright Statement......................................14
1. Introduction
This draft describes the terminology for benchmarking IGP Route
Convergence. The motivation and applicability for this
benchmarking is provided in [1]. The methodology to be used for
this benchmarking is described in [2]. The methodology and
terminology to be used for benchmarking route convergence can be
applied to any link-state IGP such as ISIS [3] and OSPF [4]. The
data plane is measured to obtain black-box (externally observable)
convergence benchmarking metrics. The purpose of this document is
to introduce new terms required to complete execution of the IGP
Route Convergence Methodology [2].
An example of Route Convergence as observed and measured from the
data plane is shown in Figure 1. The graph in Figure 1 shows
Forwarding Rate versus Time. Time 0 on the X-axis is on the far
right of the graph. The components of the graph and metrics are
defined in the Term Definitions section of this document.
Recovery Convergence Event Time = 0sec
Maximum ^ ^ ^
Forwarding Rate--> ----\ Packet /---------------
\ Loss /<----Convergence
Convergence------->\ / Event Transition
Recovery Transition \ /
\_____/<------100% Packet Loss
X-axis = Time
Y-axis = Forwarding Rate
Figure 1. Convergence Graph
2. Existing definitions
For the sake of clarity and continuity this RFC adopts the template
for definitions set out in Section 2 of RFC 1242. Definitions are
indexed and grouped together in sections for ease of reference.
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.
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3. Term Definitions
3.1 Convergence Event
Definition:
The occurrence of a planned or unplanned action in the network
that results in a change to an entry in the route table.
Discussion:
Convergence Events include link loss, routing protocol session
loss, router failure, and better next-hop.
Measurement Units:
N/A
Issues:
None
See Also:
Convergence Packet Loss
Convergence Event Instant
3.2 Network Convergence
Definition:
The completion of updating of all routing tables, including the
FIB, in all routers throughout the network.
Discussion:
Network Convergence can be approximated to the sum of Route
Convergence for all routers in the network. Network Convergence
can be determined by recovery of the forwarding rate to equal
the offer load, no stale forwarding, and no blenders[5][6].
Measurement Units:
N/A
Issues:
None
See Also:
Route Convergence
Stale Forwarding
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3.3 Route Convergence
Definition:
Recovery from a Convergence Event indicated by the DUT
forwarding rate equal to the offered load.
Discussion:
Route Convergence is the action of all components of the router
being updated with the most recent route change(s) including the
RIB and FIB, along with software and hardware tables. Route
Convergence can be observed externally by the rerouting of data
Traffic to a new egress interface.
Measurement Units:
N/A
Issues:
None
See Also:
Network Convergence
Full Convergence
Convergence Event
3.4 Full Convergence
Definition:
Route Convergence for an entire FIB.
Discussion:
When benchmarking convergence it is useful to measure
the time to converge an entire route table. For example,
a Convergence Event can be produced for an OSPF table of 5000
routes so that the time to converge routes 1 through 5000
is measured.
Measurement Units:
N/A
Issues:
None
See Also:
Network Convergence
Route Convergence
Convergence Event
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3.5 Convergence Packet Loss
Definition:
The amount of packet loss produced by a Convergence Event
until Route Convergence occurs.
Discussion:
Packet loss can be observed as a reduction of forwarded
traffic from the maximum forwarding rate.
Measurement Units:
number of packets
Issues:
None
See Also:
Route Convergence
Convergence Event
Rate-Derived Convergence Time
Loss-Derived Convergence Time
3.6 Convergence Event Instant
Definition:
The time instant that a Convergence Event occurs.
Discussion:
Convergence Event Instant is observable from the data
plane as the precise time that the device under test begins
to exhibit packet loss.
Measurement Units:
hh:mm:ss:uuu
Issues:
None
See Also:
Convergence Event
Convergence Packet Loss
Convergence Recovery Instant
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3.7 Convergence Recovery Instant
Definition:
The time instant that Full Convergence is measured
and maintained for at least an additional five seconds.
Discussion:
Convergence Recovery Instant is measurable from the data
plane as the precise time that the device under test
achieves Full Convergence.
Measurement Units:
hh:mm:ss:uuu
Issues:
None
See Also:
Convergence Packet Loss
Convergence Event Instant
3.8 Rate-Derived Convergence Time
Definition:
The amount of time for Convergence Packet Loss to
persist upon occurrence of a Convergence Event until
occurrence of Route Convergence.
Discussion:
Rate-Derived Convergence Time can be measured as the time
difference from the Convergence Event Instant to the
Convergence Recovery Instant, as shown with Equation 1.
(eq 1) Rate-Derived Convergence Time =
Convergence Recovery Instant - Convergence Event Instant.
Rate-Derived Convergence Time should be measured at the maximum
forwarding rate. Failure to achieve Full Convergence results in
a Rate-Derived Convergence Time benchmark of infinity.
Measurement Units:
seconds/milliseconds
Issues:
None
See Also:
Convergence Packet Loss
Convergence Recovery Instant
Convergence Event Instant
Full Convergence
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3.9 Convergence Event Transition
Definition:
The characteristic of a router in which forwarding rate
gradually reduces to zero after a Convergence Event.
Discussion:
The Convergence Event Transition is best observed for
Full Convergence.
Measurement Units:
seconds/milliseconds
Issues:
None
See Also:
Convergence Event
Rate-Derived Convergence Time
Convergence Packet Loss
Convergence Recovery Transition
3.10 Convergence Recovery Transition
Definition:
The characteristic of a router in which forwarding rate
gradually increases to equal the offered load.
Discussion:
The Convergence Recovery Transition is best observed for
Full Convergence.
Measurement Units:
seconds/milliseconds
Issues:
None
See Also:
Full Convergence
Rate-Derived Convergence Time
Convergence Packet Loss
Convergence Event Transition
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3.11 Loss-Derived Convergence Time
Definition:
The amount of time it takes for Route Convergence to
to be achieved as calculated from the Convergence Packet
Loss.
Discussion:
Loss-Derived Convergence Time can be calculated from
Convergence Packet Loss that occurs due to a Convergence Event
and Route Convergence, as shown with Equation 2.
(eq 2) Loss-Derived Convergence Time =
Convergence Packets Loss / Forwarding Rate
NOTE: Units for this measurement are
packets / packets/second = seconds
Measurement Units:
seconds/milliseconds
Issues:
Loss-Derived Convergence time gives a better than
actual result when converging many routes simultaneously.
Rate-Derived Convergence Time takes the Convergence Recovery
Transition into account, but Loss-Derived Convergence Time
ignores the Route Convergence Recovery Transition because
it is obtained from the measured Convergence Packet Loss.
Ideally, the Convergence Event Transition and Convergence
Recovery Transition are instantaneous so that the
Rate-Derived Convergence Time = Loss-Derived Convergence Time.
However, router implementations are less than ideal.
For these reasons the preferred reporting benchmark for IGP
Route Convergence is the Rate-Derived Convergence Time.
Guidelines for reporting Loss-Derived Convergence Time are
provided in [2].
See Also:
Route Convergence
Convergence Packet Loss
Rate-Derived Convergence Time
Convergence Event Transition
Convergence Recovery Transition
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3.12 Sustained Forwarding Convergence Time
Definition:
The amount of time for Route Convergence to be achieved for
cases in which there is no packet loss.
Discussion:
Sustained Forwarding Convergence Time is the IGP Route Convergence
benchmark to be used for Convergence Events that produce
a change in next-hop without packet loss.
Measurement Units:
seconds/milliseconds
Issues:
None
See Also:
Route Convergence
Rate-Derived Convergence Time
Loss-Derived Convergence Time
3.13 Restoration Convergence Time
Definition:
The amount of time for the router under test to restore
traffic to the original outbound port after recovery from
a Convergence Event.
Discussion:
Restoration Convergence Time is the amount of time to
Converge back to the original outbound port. This is achieved
by recovering from the Convergence Event, such as restoring
the failed link. Restoration Convergence Time is measured
using the Rate-Derived Convergence Time calculation technique,
as provided in Equation 1. It is possible, but not desired
to have the Restoration Convergence Time differ from the
Rate-Derived Convergence Time.
Measurement Units:
seconds or milliseconds
Issues:
None
See Also:
Convergence Event
Rate-Derived Convergence Time
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3.14 Packet Sampling Interval
Definition:
The rate at which the tester (test equipment) polls to make
measurements for arriving packet flows.
Discussion:
Metrics measured at the Packet Sampling Interval include
packets received and Convergence Packet Loss.
Measurement Units:
seconds or milliseconds
Issues:
Packet Sampling Interval can influence the Convergence Graph.
This is particularly true as implementations achieve Full
Convergence in less than 1 second. The Convergence Event
Transition and Convergence Recovery Transition can become
exaggerated when the Packet Sampling Interval is too long.
This will produce a larger than actual Rate-Derived
Convergence Time. The recommended value for configuration
of the Packet Sampling Interval is provided in [2].
See Also:
Convergence Packet Loss
Convergence Event Transition
Convergence Recovery Transition
3.15 Local Interface
Definition:
An interface on the DUT.
Discussion:
None
Measurement Units:
N/A
Issues:
None
See Also:
Neighbor Interface
Remote interface
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3.16 Neighbor Interface
Definition:
The interface on the neighbor router or tester that is
directly linked to the DUT's Local Interface.
Discussion:
None
Measurement Units:
N/A
Issues:
None
See Also:
Local Interface
Remote interface
3.17 Remote Interface
Definition:
An interface on a neighboring router that is not directly
connected to any interface on the DUT.
Discussion:
None
Measurement Units:
N/A
Issues:
None
See Also:
Local interface
Neighbor Interface
3.18 Preferred Egress Interface
Definition:
The outbound interface on DUT to the preferred next-hop.
Discussion:
Preferred Egress Interface is the egress interface prior to
a Convergence Event
Measurement Units:
N/A
Issues:
None
See Also:
Next-Best Egress Interface
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3.19 Next-Best Egress Interface
Definition:
The outbound interface on DUT to the second-best next-hop.
Discussion:
Next-Best Egress Interface is the egress interface after
a Convergence Event.
Measurement Units:
N/A
Issues:
None
See Also:
Preferred Egress Interface
3.20 Stale Forwarding
Definition:
Forwarding of traffic to route entries that no longer exist
or to route entries with next-hops that are no longer preferred.
Discussion:
Stale Forwarding can be caused by a Convergence Event and is
also known as a "black-hole" since it may produce packet loss.
Stale Forwarding exists until Network Convergence is achieved.
Measurement Units:
N/A
Issues:
None
See Also:
Network Convergence
4. Security Considerations
Documents of this type do not directly affect the security of
Internet or corporate networks as long as benchmarking
is not performed on devices or systems connected to operating
networks.
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5. References
[1] Poretsky, S., "Benchmarking Applicability for IGP Data Plane
Route Convergence", draft-ietf-bmwg-igp-dataplane-conv-app-02,
work in progress, January 2004.
[2] Poretsky, S., "Benchmarking Methodology for IGP Data Plane
Route Convergence", draft-ietf-bmwg-igp-dataplane-conv-meth-02,
work in progress, January 2004.
[3] Callon, R., "Use of OSI IS-IS for Routing in TCP/IP and Dual
Environments", RFC 1195, December 1990.
[4] Moy, J., "OSPF Version 2", RFC 2328, IETF, April 1998.
[5] S. Casner, C. Alaettinoglu, and C. Kuan, "A Fine-Grained View
of High Performance Networking", NANOG 22, May 2001.
[6] L. Ciavattone, A. Morton, and G. Ramachandran, "Standardized
Active Measurements on a Tier 1 IP Backbone", IEEE Communications
Magazine, pp90-97, June, 2003.
6. Author's Address
Scott Poretsky
Quarry Technologies
8 New England Executive Park
Burlington, MA 01803
USA
Phone: + 1 781 395 5090
EMail: sporetsky@quarrytech.com
Brent Imhoff
WilTel Communications
3180 Rider Trail South
Bridgeton, MO 63045 USA
Phone: +1 314 595 6853
EMail: brent.imhoff@wcg.com
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7. Full Copyright Statement
Copyright (C) The Internet Society (1998). All Rights
Reserved.
This document and translations of it may be copied and
furnished to others, and derivative works that comment on or
otherwise explain it or assist in its implementation may be
prepared, copied, published and distributed, in whole or in
part, without restriction of any kind, provided that the above
copyright notice and this paragraph are included on all such
copies and derivative works. However, this document itself may
not be modified in any way, such as by removing the copyright
notice or references to the Internet Society or other Internet
organizations, except as needed for the purpose of developing
Internet standards in which case the procedures for copyrights
defined in the Internet Standards process must be followed, or
as required to translate it into languages other than English.
The limited permissions granted above are perpetual and will
not be revoked by the Internet Society or its successors or
assigns. This document and the information contained herein is
provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE
INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY
THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY
RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR PURPOSE.
Poretsky, Imhoff [Page 14]
Network Working Group
INTERNET-DRAFT
Expires in: July 2004
Scott Poretsky
Quarry Technologies
Brent Imhoff
Wiltel Communications
January 2004
Benchmarking Methodology for
IGP Data Plane Route Convergence
<draft-ietf-bmwg-igp-dataplane-conv-meth-02.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Table of Contents
1. Introduction ...............................................2
2. Existing definitions .......................................2
3. Test Setup..................................................2
3.1 Test Topologies............................................2
3.2 Test Considerations........................................4
3.2.1 IGP Selection............................................4
3.2.2 BGP Configuration........................................4
3.2.3 IGP Route Scaling........................................5
3.2.4 Timers...................................................5
3.2.5 Convergence Time Metrics.................................5
3.2.6 Offered Load.............................................5
3.2.7 Interface Types..........................................5
3.3 Reporting Format...........................................6
4. Test Cases..................................................6
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4.1 Convergence Due to Link Failure............................6
4.1.1 Convergence Due to Local Interface Failure...............6
4.1.2 Convergence Due to Neighbor Interface Failure............7
4.1.3 Convergence Due to Remote Interface Failure..............7
4.2 Convergence Due to PPP Session Failure.....................8
4.3 Convergence Due to IGP Adjacency Failure...................9
4.4 Convergence Due to Route Withdrawal........................9
4.5 Convergence Due to Cost Change.............................10
4.6 Convergence Due to ECMP Member Interface Failure...........10
4.7 Convergence Due to Parallel Link Interface Failure.........11
5. Security Considerations.....................................12
6. References..................................................12
7. Author's Address............................................12
8. Full Copyright Statement....................................13
1. Introduction
This draft describes the methodology for benchmarking IGP Route
Convergence. The applicability of this testing is described in
[1] and the new terminology that it introduces is defined in [2].
Service Providers use IGP Convergence time as a key metric of
router design and architecture. Customers of Service Providers
observe convergence time by packet loss, so IGP Route Convergence
is considered a Direct Measure of Quality (DMOQ). The test cases
in this document are black-box tests that emulate the network
events that cause route convergence, as described in [1]. The
black-box test designs benchmark the data plane accounting for
all of the factors contributing to convergence time, as discussed
in [1]. The methodology (and terminology) for benchmarking route
convergence can be applied to any link-state IGP such as ISIS [3]
and OSPF [4].
2. Existing definitions
For the sake of clarity and continuity this RFC adopts the template
for definitions set out in Section 2 of RFC 1242. Definitions are
indexed and grouped together in sections for ease of reference.
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.
3. Test Setup
3.1 Test Topologies
Figure 1 shows the test topology to measure IGP Route Convergence due
to local Convergence Events such as SONET Link Failure, PPP Session
Failure, IGP Adjacency Failure, Route Withdrawal, and route cost
change. These test cases discussed in section 4 provide route
convergence times that account for the Event Detection time, SPF
Processing time, and FIB Update time. These times are measured
by observing packet loss in the data plane.
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--------- Ingress Interface ---------
| |<------------------------------| |
| | | |
| | Preferred Egress Interface | |
| DUT |------------------------------>|Tester |
| | | |
| |~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~>| |
| | Next-Best Egress Interface | |
--------- ---------
Figure 1. IGP Route Convergence Test Topology for Local Changes
Figure 2 shows the test topology to measure IGP Route Convergence
time due to remote changes in the network topology. These times are
measured by observing packet loss in the data plane. In this
topology the three routers are considered a System Under Test (SUT).
NOTE: All routers in the SUT must be the same model and identically configured.
----- -----------
| | Preferred | |
----- |R2 |---------------------->| |
| |-->| | Egress Interface | |
| | ----- | |
|R1 | | Tester |
| | ----- | |
| |-->| | Next-Best | |
----- |R3 |~~~~~~~~~~~~~~~~~~~~~~>| |
^ | | Egress Interface | |
| ----- -----------
| |
|--------------------------------------
Ingress Interface
Figure 2. IGP Route Convergence Test Topology
for Remote Changes
Figure 3 shows the test topology to measure IGP Route Convergence
time with members of an ECMP Set. These times are measured by
observing packet loss in the data plane. In this topology, the DUT
is configured with each Egress interface as a member of an ECMP set
and the Tester emulates multiple next-hop routers (emulates one
router for each member).
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--------- Ingress Interface ---------
| |<--------------------------------| |
| | | |
| | ECMP Set Interface 1 | |
| DUT |-------------------------------->| Tester|
| | . | |
| | . | |
| | . | |
| |~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~>| |
| | ECMP Set Interface N | |
--------- ---------
Figure 3. IGP Route Convergence Test Topology
for ECMP Convergence
Figure 4 shows the test topology to measure IGP Route Convergence
time with members of a Parallel Link. These times are measured by
observing packet loss in the data plane. In this topology, the DUT
is configured with each Egress interface as a member of a Parallel
Link and the Tester emulates the single next-hop router.
--------- Ingress Interface ---------
| |<--------------------------------| |
| | | |
| | Parallel Link Interface 1 | |
| DUT |-------------------------------->| Tester|
| | . | |
| | . | |
| | . | |
| |~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~>| |
| | Parallel Link Interface N | |
--------- ---------
Figure 4. IGP Route Convergence Test Topology
for Parallel Link Convergence
3.2 Test Considerations
3.2.1 IGP Selection
The test cases described in section 4 can be used for ISIS or
OSPF. The Route Convergence test methodology for both is
identical. The IGP adjacencies are established on the Preferred
Egress Interface and Next-Best Egress Interface.
3.2.2 BGP Configuration
The obtained results for IGP Route Convergence may vary if
BGP routes are installed. It is recommended that the IGP
Convergence times be benchmarked without BGP routes installed.
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3.2.3 IGP Route Scaling
The number of IGP routes will impact the measured IGP Route
Convergence because convergence for the entire IGP route table is
measured. For results similar to those that would be observed in
an operational network it is recommended that the number of
installed routes closely approximate that for routers in the
network.
3.2.4 Timers
There are some timers that will impact the measured IGP Convergence
time. The following timers should be configured to the minimum value
prior to beginning execution of the test cases:
Timer Recommended Value
----- -----------------
SONET Failure Indication Delay <10milliseconds
IGP Hello Timer 1 second
IGP Dead-Interval 3 seconds
LSA Generation Delay 0
LSA Flood Packet Pacing 0
LSA Retransmission Packet Pacing 0
SPF Delay 0
3.2.5 Convergence Time Metrics
The recommended value for the Packet Sampling Interval [2] is
100 milliseconds. Rate-Derived Convergence Time [2] is the
preferred benchmark for IGP Route Convergence. This benchmark
must always be reported when the
Packet Sampling Interval [2] <= 100 milliseconds.
If the test equipment does not permit the Packet Sampling
Interval to be set as low as 100 msec, then both the
Rate-Derived Convergence Time and Loss-Derived Convergence
Time [2] must be reported.
3.2.6 Offered Load
An offered Load of maximum forwarding rate at a fixed packet size
is recommended for accurate measurement. The duration of offered
load must be greater than the convergence time.
3.2.7 Interface Types
All test cases in this methodology document may be executed with
any interface type. SONET is recommended and specifically
mentioned in the procedures because it can be configured to have
no or negligible affect on the measured convergence time.
Ethernet (10Mb, 100Mb, 1Gb, and 10Gb) is not preferred since
broadcast media are unable to detect loss of host and rely upon
IGP Hellos to detect session loss.
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3.3 Reporting Format
For each test case, it is recommended that the following reporting
format be completed:
Parameter Units
--------- -----
IGP (ISIS or OSPF)
Interface Type (GigE, POS, ATM, etc.)
Packet Size bytes
IGP Routes number of IGP routes
Packet Sampling Interval seconds or milliseconds
IGP Timer Values
SONET Failure Indication Delay seconds or milliseconds
IGP Hello Timer seconds or milliseconds
IGP Dead-Interval seconds or milliseconds
LSA Generation Delay seconds or milliseconds
LSA Flood Packet Pacing seconds or milliseconds
LSA Retransmission Packet Pacing seconds or milliseconds
SPF Delay seconds or milliseconds
Benchmarks
Rate-Derived Convergence Time seconds or milliseconds
Loss-Derived Convergence Time seconds or milliseconds
Restoration Convergence Time seconds or milliseconds
4. Test Cases
4.1 Convergence Due to Link Failure
4.1.1 Convergence Due to Local Interface Failure
Objective
To obtain the IGP Route Convergence due to a local link
failure event at the DUT's Local Interface.
Procedure
1. Advertise matching IGP routes from Tester to DUT on
Preferred Egress Interface [2] and Next-Best Egress Interface
[2] using the topology shown in Figure 1. Set the cost of the
routes so that the Preferred Egress Interface is the preferred
next-hop.
2. Send traffic at maximum forwarding rate to destinations
matching all IGP routes from Tester to DUT on Ingress Interface
[2].
3. Verify traffic routed over Preferred Egress Interface.
4. Remove SONET on DUT's Local Interface [2] by performing an
administrative shutdown of the interface.
5. Measure Rate-Derived Convergence Time [2] as DUT detects the
link down event and converges all IGP routes and traffic over
the Next-Best Egress Interface.
6. Restore SONET on DUT's Local Interface by administratively
enabling the interface.
7. Measure Restoration Convergence Time [2] as DUT detects the link
up event and converges all IGP routes and traffic back to the
Preferred Egress Interface.
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Results
The measured IGP Convergence time is influenced by the Local
SONET indication, SPF delay, SPF Holdtime, SPF Execution
Time, Tree Build Time, and Hardware Update Time.
4.1.2 Convergence Due to Neighbor Interface Failure
Objective
To obtain the IGP Route Convergence due to a local link
failure event at the Tester's Neighbor Interface.
Procedure
1. Advertise matching IGP routes from Tester to DUT on
Preferred Egress Interface [2] and Next-Best Egress Interface
[2] using the topology shown in Figure 1. Set the cost of
the routes so that the Preferred Egress Interface is the
preferred next-hop.
2. Send traffic at maximum forwarding rate to destinations
matching all IGP routes from Tester to DUT on Ingress
Interface [2].
3. Verify traffic routed over Preferred Egress Interface.
4. Remove SONET on Tester's Neighbor Interface [2] connected to
DUT' s Preferred Egress Interface.
5. Measure Rate-Derived Convergence Time [2] as DUT detects the
link down event and converges all IGP routes and traffic over
the Next-Best Egress Interface.
6. Restore SONET on Tester's Neighbor Interface connected to
DUT's Preferred Egress Interface.
7. Measure Restoration Convergence Time [2] as DUT detects the
link up event and converges all IGP routes and traffic back to
the Preferred Egress Interface.
Results
The measured IGP Convergence time is influenced by the Local
SONET indication, SPF delay, SPF Holdtime, SPF Execution
Time, Tree Build Time, and Hardware Update Time.
4.1.3 Convergence Due to Remote Interface Failure
Objective
To obtain the IGP Route Convergence due to a Remote
Interface failure event.
Procedure
1. Advertise matching IGP routes from Tester to SUT on
Preferred Egress Interface [2] and Next-Best Egress Interface
[2] using the topology shown in Figure 2. Set the cost of the
routes so that the Preferred Egress Interface is the preferred
next-hop.
2. Send traffic at maximum forwarding rate to destinations
matching all IGP routes from Tester to DUT on Ingress Interface
[2].
3. Verify traffic is routed over Preferred Egress Interface.
4. Remove SONET on Tester's Neighbor Interface [2] connected to
SUT' s Preferred Egress Interface.
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5. Measure Rate-Derived Convergence Time [2] as SUT detects
the link down event and converges all IGP routes and traffic
over the Next-Best Egress Interface.
6. Restore SONET on Tester's Neighbor Interface connected to
SUT's Preferred Egress Interface.
7. Measure Restoration Convergence Time [2] as SUT detects the
link up event and converges all IGP routes and traffic over
the Preferred Egress Interface.
Results
The measured IGP Convergence time is influenced by the
SONET failure indication, LSA/LSP Flood Packet Pacing,
LSA/LSP Retransmission Packet Pacing, LSA/LSP Generation
time, SPF delay, SPF Holdtime, SPF Execution Time, Tree
Build Time, and Hardware Update Time. The additional
convergence time contributed by LSP Propagation can be
obtained by subtracting the Rate-Derived Convergence Time
measured in 4.1.2 (Convergence Due to Neighbor Interface
Failure) from the Rate-Derived Convergence Time measured in
this test case.
4.2 Convergence Due to PPP Session Failure
Objective
To obtain the IGP Route Convergence due to a Local PPP Session
failure event.
Procedure
1. Advertise matching IGP routes from Tester to DUT on
Preferred Egress Interface [2] and Next-Best Egress Interface
[2] using the topology shown in Figure 1. Set the cost of
the routes so that the IGP routes along the Preferred Egress
Interface is the preferred next-hop.
2. Send traffic at maximum forwarding rate to destinations
matching all IGP routes from Tester to DUT on Ingress
Interface [2].
3. Verify traffic routed over Preferred Egress Interface.
4. Remove PPP session from Tester's Neighbor Interface [2]
connected to Preferred Egress Interface.
5. Measure Rate-Derived Convergence Time [2] as DUT detects the
PPP session down event and converges all IGP routes and
traffic over the Next-Best Egress Interface.
6. Restore PPP session on DUT's Preferred Egress Interface.
7. Measure Restoration Convergence Time [2] as DUT detects the
session up event and converges all IGP routes and traffic over
the Preferred Egress Interface.
Results
The measured IGP Convergence time is influenced by the PPP
failure indication, SPF delay, SPF Holdtime, SPF Execution
Time, Tree Build Time, and Hardware Update Time.
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IGP Data Plane Route Convergence
4.3 Convergence Due to IGP Adjacency Failure
Objective
To obtain the IGP Route Convergence due to a Local IGP Adjacency
failure event.
Procedure
1. Advertise matching IGP routes from Tester to DUT on
Preferred Egress Interface [2] and Next-Best Egress Interface
[2] using the topology shown in Figure 1. Set the cost of
the routes so that the Preferred Egress Interface is the
preferred next-hop.
2. Send traffic at maximum forwarding rate to destinations
matching all IGP routes from Tester to DUT on Ingress
Interface [2].
3. Verify traffic routed over Preferred Egress Interface.
4. Remove IGP adjacency from Tester's Neighbor Interface [2]
connected to Preferred Egress Interface.
5. Measure Rate-Derived Convergence Time [2] as DUT detects the
IGP session failure event and converges all IGP routes and
traffic over the Next-Best Egress Interface.
6. Restore IGP session on DUT's Preferred Egress Interface.
7. Measure Restoration Convergence Time [2] as DUT detects the
session up event and converges all IGP routes and traffic over
the Preferred Egress Interface.
Results
The measured IGP Convergence time is influenced by the IGP
Hello Interval, IGP Dead Interval, SPF delay, SPF Holdtime,
SPF Execution Time, Tree Build Time, and Hardware Update
Time.
4.4 Convergence Due to Route Withdrawal
Objective
To obtain the IGP Route Convergence due to Route Withdrawal.
Procedure
1. Advertise matching IGP routes from Tester to DUT on
Preferred Egress Interface [2] and Next-Best Egress Interface
[2] using the topology shown in Figure 1. Set the cost of
the routes so that the Preferred Egress Interface is the
preferred next-hop.
2. Send traffic at maximum forwarding rate to destinations
matching all IGP routes from Tester to DUT on Ingress
Interface [2].
3. Verify traffic routed over Preferred Egress Interface.
4. Tester withdraws all IGP routes from DUT's Local Interface
on Preferred Egress Interface.
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IGP Data Plane Route Convergence
6. Re-advertise IGP routes to DUT's Preferred Egress Interface.
7. Measure Restoration Convergence Time [2] as DUT converges all
IGP routes and traffic over the Preferred Egress Interface.
Results
The measured IGP Convergence time is the SPF Processing and FIB
Update time as influenced by the SPF delay, SPF Holdtime,
SPF Execution Time, Tree Build Time, and Hardware Update Time.
4.5 Convergence Due to Cost Change
Objective
To obtain the IGP Route Convergence due to route cost change.
Procedure
1. Advertise matching IGP routes from Tester to DUT on
Preferred Egress Interface [2] and Next-Best Egress Interface
[2] using the topology shown in Figure 1. Set the cost of
the routes so that the Preferred Egress Interface is the
preferred next-hop.
2. Send traffic at maximum forwarding rate to destinations
matching all IGP routes from Tester to DUT on Ingress
Interface [2].
3. Verify traffic routed over Preferred Egress Interface.
4. Tester increases cost for all IGP routes at DUT's Preferred
Egress Interface so that the Next-Best Egress Interface
has lower cost and becomes preferred path.
5. Measure Rate-Derived Convergence Time [2] as DUT detects the
cost change event and converges all IGP routes and traffic
over the Next-Best Egress Interface.
6. Re-advertise IGP routes to DUT's Preferred Egress Interface
with original lower cost metric.
7. Measure Restoration Convergence Time [2] as DUT converges all
IGP routes and traffic over the Preferred Egress Interface.
Results
There should be no measured packet loss for this case.
4.6 Convergence Due to ECMP Member Interface Failure
Objective
To obtain the IGP Route Convergence due to a local link
failure event of an ECMP Member.
Procedure
1. Configure ECMP Set as shown in Figure 3.
2. Advertise matching IGP routes from Tester to DUT on
each ECMP member.
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IGP Data Plane Route Convergence
3. Send traffic at maximum forwarding rate to destinations
matching all IGP routes from Tester to DUT on Ingress
Interface [2].
4. Verify traffic routed over all members of ECMP Set.
5. Remove SONET on Tester's Neighbor Interface [2] connected to
one of the DUT's ECMP member interfaces.
6. Measure Rate-Derived Convergence Time [2] as DUT detects the
link down event and converges all IGP routes and traffic
over the other ECMP members.
7. Restore SONET on Tester's Neighbor Interface connected to
DUT's ECMP member interface.
8. Measure Restoration Convergence Time [2] as DUT detects the
link up event and converges IGP routes and some distribution
of traffic over the restored ECMP member.
Results
The measured IGP Convergence time is influenced by the Local
SONET indication, Tree Build Time, and Hardware Update Time.
4.7 Convergence Due to Parallel Link Interface Failure
Objective
To obtain the IGP Route Convergence due to a local link
failure event for a Member of a Parallel Link.
Procedure
1. Configure Parallel Link as shown in Figure 4.
2. Advertise matching IGP routes from Tester to DUT on
each Parallel Link member.
3. Send traffic at maximum forwarding rate to destinations
matching all IGP routes from Tester to DUT on Ingress
Interface [2].
4. Verify traffic routed over all members of Parallel Link.
5. Remove SONET on Tester's Neighbor Interface [2] connected to
one of the DUT's Parallel Link member interfaces.
6. Measure Rate-Derived Convergence Time [2] as DUT detects the
link down event and converges all IGP routes and traffic over
the other Parallel Link members.
7. Restore SONET on Tester's Neighbor Interface connected to
DUT's Parallel Link member interface.
8. Measure Restoration Convergence Time [2] as DUT detects the
link up event and converges IGP routes and some distribution
of traffic over the restored Parallel Link member.
Results
The measured IGP Convergence time is influenced by the Local
SONET indication, Tree Build Time, and Hardware Update Time.
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IGP Data Plane Route Convergence
5. Security Considerations
Documents of this type do not directly affect the security of
the Internet or corporate networks as long as benchmarking
is not performed on devices or systems connected to operating
networks.
6. References
[1] Poretsky, S., "Benchmarking Applicability for IGP
Convergence", draft-ietf-bmwg-igp-dataplane-conv-app-02, work
in progress, January 2004.
[2] Poretsky, S., Imhoff, B., "Benchmarking Terminology for IGP
Convergence", draft-ietf-bmwg-igp-dataplane-conv-term-02, work
in progress, January 2004
[3] Callon, R., "Use of OSI IS-IS for Routing in TCP/IP and Dual
Environments", RFC 1195, December 1990.
[4] Moy, J., "OSPF Version 2", RFC 2328, IETF, April 1998.
7. Author's Address
Scott Poretsky
Quarry Technologies
8 New England Executive Park
Burlington, MA 01803
USA
Phone: + 1 781 395 5090
EMail: sporetsky@quarrytech.com
Brent Imhoff
WilTel Communications
3180 Rider Trail South
Bridgeton, MO 63045
USA
Phone: +1 314 595 6853
EMail: brent.imhoff@wcg.com
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8. Full Copyright Statement
Copyright (C) The Internet Society (1998). All Rights
Reserved.
This document and translations of it may be copied and
furnished to others, and derivative works that comment on or
otherwise explain it or assist in its implementation may be
prepared, copied, published and distributed, in whole or in
part, without restriction of any kind, provided that the above
copyright notice and this paragraph are included on all such
copies and derivative works. However, this document itself may
not be modified in any way, such as by removing the copyright
notice or references to the Internet Society or other Internet
organizations, except as needed for the purpose of developing
Internet standards in which case the procedures for copyrights
defined in the Internet Standards process must be followed, or
as required to translate it into languages other than English.
The limited permissions granted above are perpetual and will
not be revoked by the Internet Society or its successors or
assigns. This document and the information contained herein is
provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE
INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY
THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY
RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR PURPOSE.
Poretsky, Imhoff [Page 13] Network Working Group
INTERNET-DRAFT
Expires in: July 2004
Scott Poretsky
Quarry Technologies
January 2004
Benchmarking Applicability for
IGP Data Plane Route Convergence
<draft-ietf-bmwg-igp-dataplane-conv-app-02.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
ABSTRACT
This draft describes the applicability of IGP Route Convergence
benchmarking methodology [1] and IGP Route Convergence benchmarking
terminology [2]. The methodology and terminology is to be used
for benchmarking route convergence and can be applied to any
link-state IGP such as ISIS [3] and OSPF [4]. The data plane is
measured to obtain the convergence benchmarking metrics described
in [1].
Table of Contents
1. Introduction ...............................................2
2. Existing definitions .......................................2
3. Factors for IGP Route Convergence Time......................2
4. Network Events that Cause Route Convergence.................3
5. Use of Data Traffic for IGP Route Convergence Benchmarking..3
6. Security Considerations.....................................4
7. Acknowledgements............................................4
8. References..................................................4
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IGP Data Plane Route Convergence
9. Author's Address............................................5
10. Full Copyright Statement...................................5
1. Introduction
IGP Convergence is a critical performance parameter. Customers
of Service Providers use packet loss due to IGP Convergence as a
key metric of their network service quality. Service Providers
use IGP Convergence time as a key metric of router design and
architecture. Fast network convergence can be optimally achieved
through deployment of fast converging routers. The fundamental
basis by which network users and operators benchmark convergence
is packet loss, which is an externally observable event having
direct impact on their application performance.
IGP Route Convergence is a Direct Measure of Quality (DMOQ) when
benchmarking the data plane. For this reason it is important to
develop a standard router benchmarking methodology and terminology
for measuring IGP convergence that uses the data plane as described
in [1] and [2]. This document describes all of the factors that
influence a convergence measurement and how a purely black box test
can be designed to account for all of these factors. This enables
accurate benchmarking and evaluation for route convergence time.
2. Existing definitions
For the sake of clarity and continuity this RFC adopts the template
for definitions set out in Section 2 of RFC 1242. Definitions are
indexed and grouped together in sections for ease of reference.
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.
3. Factors for IGP Route Convergence Time
There are four major categories of factors contributing to the
measured Router IGP Convergence Time. As discussed in [5], [6],
[7], [8] and [9], these categories are Event Detection, SPF
Processing, IGP Advertisement, and FIB Update. These have numerous
components that influence the convergence time. These are listed
as follow:
-Event Detection-
SONET failure indication time
PPP failure indication time
IGP Hello Dead Interval
-SPF Processing-
SPF Delay Time
SPF Hold time
SPF Execution time
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-IGP Advertisement-
LSA/LSP Flood Packet Pacing
LSA/LSP Retransmission Packet Pacing
LSA/LSP Generation time
-FIB Update-
Tree Build time
Hardware Update time
The contribution of each of these factors listed above will vary
with each router vendors' architecture and IGP implementation.
It is therefore necessary to design a convergence test that
considers all of these components, not just one or a few of these
components. The additional benefit of designing a test for all
components is that it enables black-box testing in which knowledge
of the routers' internal implementations is not required. It is
then possible to make valid use of the convergence benchmarking
metrics when comparing routers from different vendors.
4. Network Events that Cause Convergence
There are different types of network events that can cause IGP
convergence. These network events are administrative link
removal, unplanned link failure, line card failure, and route
changes such as withdrawal, flap, next-hop change, and cost change.
When benchmarking a router it is important to measure the
convergence time for local and remote occurrence of these network
events. The convergence time measured will vary whether the network
event occurred locally or remotely due to varying combinations of
factors listed in the previous sections. This behavior makes it
possible to design purely black-box tests that isolate
measurements for each of the components of convergence time.
5. Use of Data Plane for IGP Route Convergence Benchmarking
Customers of service providers use packet loss as the metric to
calculate convergence time. Packet loss is an externally observable
event having direct impact on customers' application performance.
For this reason it is important to develop a standard router
benchmarking methodology and terminology that is a Direct Measure
of Quality (DMOQ)for measuring IGP convergence. Such a
methodology uses the data plane as described in [1] and [2].
An additional benefit of using packet loss for calculation of
IGP Route Convergence time is that it enables black-box tests to
be designed. Data traffic can be offered to the
device under test (DUT), an emulated network event can be forced
to occur, and packet loss can be externally measured to calculate
the convergence time. Knowledge of the DUT architecture and IGP
implementation is not required. There is no need to rely on the
DUT to produce the test results. There is no need to build
intrusive test harnesses for the DUT.
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IGP Data Plane Route Convergence
Use of data traffic and measurement of packet loss on the data
plane also enables Route Convergence methodology test cases that
consider the time for the Route Controller to update the FIB on
the forwarding engine of the hardware. A router is not fully
converged until all components are updated and traffic is
rerouted to the correct egress interface. As long as there is
packet loss, routes have not converged. It is possible to send
diverse traffic flows to destinations matching every route in the
FIB so that the time it takes for the router to converge an entire
route table can be benchmarked.
6. Security Considerations
Documents of this type do not directly effect the security of
the Internet or of corporate networks as long as benchmarking
is not performed on devices or systems connected to operating
networks.
7. Acknowledgements
Thanks to Curtis Villamizar for sharing so much of his
knowledge and experience through the years. Also, special
thanks to the many Network Engineers and Network Architects
at the Service Providers who are always eager to discuss
Route Convergence.
8. References
[1] Poretsky, S., "Benchmarking Methodology for IGP Data Plane
Route Convergence", draft-ietf-bmwg-igp-dataplane-conv-meth-01,
work in progress, October 2004.
[2] Poretsky, S., "Benchmarking Terminology for IGP Data Plane
Route Convergence", draft-ietf-bmwg-igp-dataplane-conv-term-01,
work in progress, October 2004.
[3] Callon, R., "Use of OSI IS-IS for Routing in TCP/IP and Dual
Environments", RFC 1195, December 1990.
[4] Moy, J., "OSPF Version 2", RFC 2328, IETF, April 1998.
[5] Villamizar, C., "Convergence and Restoration Techniques for
ISP Interior Routing", NANOG 25, October 2002.
[6] Katz, D., "Why are we Scared of SPF? IGP Scaling and
Stability", NANOG 25, October 2002.
[7] Filsfils, C., "Deploying Tight-SLA Services on an Internet
Backbone: ISIS Fast Convergence and Differentiated Services
Design (tutorial)", NANOG 25, October 2002.
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[8] Alaettinoglu, C. and Casner, S., "ISIS Routing on the Qwest
Backbone: a Recipe for Subsecond ISIS Convergence", NANOG 24,
October 2002.
[9] Alaettinoglu, C., Jacobson, V., and Yu, H., "Towards
Millisecond IGP Convergence", NANOG 20, October 2000.
9. Author's Address
Scott Poretsky
Quarry Technologies
8 New England Executive Park
Burlington, MA 01803
USA
Phone: + 1 781 395 5090
EMail: sporetsky@quarrytech.com
10. Full Copyright Statement
Copyright (C) The Internet Society (1998). All Rights
Reserved.
This document and translations of it may be copied and
furnished to others, and derivative works that comment on or
otherwise explain it or assist in its implementation may be
prepared, copied, published and distributed, in whole or in
part, without restriction of any kind, provided that the above
copyright notice and this paragraph are included on all such
copies and derivative works. However, this document itself may
not be modified in any way, such as by removing the copyright
notice or references to the Internet Society or other Internet
organizations, except as needed for the purpose of developing
Internet standards in which case the procedures for copyrights
defined in the Internet Standards process must be followed, or
as required to translate it into languages other than English.
The limited permissions granted above are perpetual and will
not be revoked by the Internet Society or its successors or
assigns. This document and the information contained herein is
provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE
INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY
THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY
RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR PURPOSE.
Poretsky [Page 5]
