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IETF RFC 1246
Experience with the OSPF Protocol
Last modified on Friday, August 9th, 1991
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Network Working Group J. Moy, Editor
Request for Comments: 1246 July 1991
Experience with the OSPF protocol
 Status of this Memo
This memo provides information for the Internet community. It does not
specify any Internet standard. Distribution of this memo is unlimited.
Abstract
This is the second of two reports on the OSPF protocol. These reports
are required by the IAB/IESG in order for an Internet routing protocol
to advance to Draft Standard Status. OSPF is a TCP/IP routing protocol,
designed to be used internal to an Autonomous System (in other words,
OSPF is an Interior Gateway Protocol).
OSPF is currently designated as a Proposed Standard. Version 1 of the
OSPF protocol was published in RFC 1131. Since then OSPF version 2 has
been developed. Version 2 has been documented in RFC 1247. The changes
between version 1 and version 2 of the OSPF protocol are explained in
Appendix F of RFC 1247. It is OSPF Version 2 that is the subject of this
report.
This report documents experience with OSPF V2. This includes reports on
interoperability testing, field experience, simulations and the current
state of OSPF implementations. It also presents a summary of the OSPF
Management Information Base (MIB), and a summary of OSPF authentication
mechanism.
Please send comments to ospf@trantor.umd.edu.
1.0 Introduction
This document addresses, for OSPF V2, the requirements set forth by the
IAB/IESG for an Internet routing protocol to advance to Draft Standard
state. This requirements are briefly summarized below. The remaining
sections of this report document how OSPF V2 satisfies these
requirements:
[Moy] PAGE 1 
RFC 1246 Experience with OSPF July 1991
o The specification for the routing protocol must be well written such
that independent, interoperable implementations can be developed
solely based on the specification. For example, it should be possible
to develop an interoperable implementation without consulting the
original developers of the routing protocol.
o A Management Information Base (MIB) must be written for the protocol.
The MIB must be in the standardization process, but does not need to
be at the same level of standardization as the routing protocol.
o The security architecture of the protocol must be set forth
explicitly. The security architecture must include mechanisms for
authenticating routing messages and may include other forms of
protection.
o Two or more interoperable implementations must exist. At least two
must be written independently.
o There must be evidence that all features of the protocol have been
tested, running between at least two implementations. This must
include that all of the security features have been demonstrated to
operate, and that the mechanisms defined in the protocol actually
provide the intended protection.
o There must be significant operational experience. This must include
running in a moderate number routers configured in a moderately
complex topology, and must be part of the operational Internet. All
significant features of the protocol must be exercised. In the case
of an Interior Gateway Protocol (IGP), both interior and exterior
routes must be carried (unless another mechanism is provided for the
exterior routes). In the case of a Exterior Gateway Protocol (EGP),
it must carry the full complement of exterior routes.
This report is a compilation of information obtained from many people.
The reader is referred to specific people when more information on a
subject is available. People references are gathered into Section 10.0,
in a format similar to that used in [4].
1.1 Acknowledgments
The OSPF protocol has been developed by the OSPF Working Group of the
Internet Engineering Task Force. Many people have contributed to this
report. They are listed in Section 10.0 of this report.
[Moy] PAGE 2
RFC 1246 Experience with OSPF July 1991
2.0 Documentation
Version 1 of the OSPF protocol is documented in RFC 1131 [1]. OSPF
Version 2, which supersedes Version 1, has been documented in RFC 1247
[2]. The differences between OSPF Version 1 and Version 2 are relatively
minor, and are listed in Appendix F of RFC 1247 [2]. All information
presented in this report concerns OSPF V2 unless explicitly mentioned
otherwise.
The OSPF protocol was developed by the OSPF Working Group of the
Internet Engineering Task Force. This Working Group has a mailing list,
ospf@trantor.umd.edu, where discussions of protocol features and
operation are held. The OSPF Working Group also meets during the
quarterly Internet Engineering Task Force conferences. Reports of these
meeting are published in the IETF's Proceedings. In addition, two
reports on the OSPF protocol have been presented to the IETF plenary
(see "Everything You Ever Wanted to Know about OSPFIGP" in [5] and "OSPF
Update" in [6]).
The OSPF protocol began undergoing field trials in Spring of 1990. A
mailing list, ospf-tests@seka.cso.uiuc.edu, was formed to discuss how
the field trials were proceeding. This mailing list is maintained by
Ross Veach of the University of Illinois [rrv]. Archives of this list
are also available. There has been quite a bit of discussion on the list
concerning OSPF/RIP/EGP interaction.
A OSPF V2 Management Information Base has also been developed and
published in [3]. For more information, see Section 3.0 of this report.
There is a free implementation of OSPF available from the University of
Maryland. This implementation was written by Rob Coltun [rcoltun].
Contact Rob for details.
3.0 MIB
An OSPF Management Information Base has been published in RFC 1248 [3].
The MIB was written by Rob Coltun [rcoltun] and Fred Baker [fbaker]. The
OSPF MIB appears on the mgmt subtree as SMI standard-mib 13.
The OSPF MIB was originally developed by Rob Coltun of the University of
Maryland, under contract to Advanced Computer Communications. A subset
of his proposal was implemented to facilitate their development, and
represents operational experience of a sort.
The MIB consists of a general variables group and ten tables:
TABLE 1. OSPF MIB Organization
[Moy] PAGE 3
RFC 1246 Experience with OSPF July 1991
Group Name Description
________________________________________________________________
ospfGeneralGroup General Global Variables
ospfAreaTable Area Descriptions
ospfStubAreaTable Default Metrics, by Type of Service
ospfLsdbTable Link State Database
ospfAreaRangeTable Address Range Specifications
ospfHostTable Directly connected Hosts
ospfIfTable OSPF Interface Variables
ospfIfMetricTable Interface Metrics, by Type of Service
ospfVirtIfTable Virtual Links
ospfNbrTable (Non-virtual) OSPF Neighbors
ospfVirtNbrTable Virtual OSPF Neighbors
As MIBs go, the OSPF MIB is quite large; 105 objects. The following are
some statistics describing the distribution of the MIB's variables:
o 11 define the above Group and Tables
o 10 define the Entry in a Table
o 7 are Counters
o 6 are Gauges
o 68 objects mandated by the OSPF Version 2 Specification
Section D.2 of the OSPF V2 specification [2] lists a set of required
statistics that an implementation must maintain. These statistics have
been incorporated into the OSPF MIB. The MIB's thirteen Counters and
Gauges enable evaluation of the OSPF protocol's performance in an
operational environment. Most of the remainder of the MIB's variables
parameterize the many features that OSPF provides the network
administrator.
For more information on the MIB contact Fred Baker [fbaker].
4.0 Security architecture
In OSPF, all protocol packet exchanges are authenticated. The OSPF
packet header (which is common to all OSPF packets) contains a 16-bit
Authentication type field, and 64-bits of Authentication data. Each
particular OSPF area must run a single authentication scheme, as
indicated by the Authentication type field. However, authentication keys
can be configured by the system administrator on a per-network basis.
[Moy] PAGE 4
RFC 1246 Experience with OSPF July 1991
When an OSPF packet is received from a network, the OSPF router first
verifies that it indicates the correct Authentication type. The router
then authenticates the packet, running a verification algorithm using
the configured authentication key, the 64-bits of Authentication data
and the rest of the OSPF packet data as input. The precise algorithm
used is dictated by the Authentication type. Packets failing the
authentication algorithm are dropped, and the authentication failure is
noted in a MIB-accessible variable (see [3]).
There are currently few Authentication types in use. The current
assignments are:
TABLE 2. Current OSPF Authentication types.
Type code Algorithm
____________________________________________________________________
0 No authentication performed.
1 Simple (clear) password.
2-255 Reserved for assignment by the IANA (iana@isi.edu)
> 255 Available for local (per-AS) definition.
For more information on OSPF's authentication procedures, see Sections
8.1, 8.2, and Appendix E of [2].
5.0 Implementations
The are multiple, interoperable implementations of OSPF currently
available. This section gives a brief overview of the five
implementations that have participated in at least one round of
interoperability testing. (For a detailed discussion of OSPF
interoperability testing, see Section 7.0 of this report.) Other
implementations do exist, but because of commercial realities (e.g., the
product is not yet announced) they unfortunately cannot be listed here.
The five implementations that have participated in the OSPF
interoperability testing are (listed in alphabetical order):
o 3com. This implementation was wholly developed by 3com. It has
participated in all three rounds of interoperability testing. It is
also the only implementation of OSPF's TOS routing.. The 3com
implementation consists of approximately 9000 lines of C code,
including comments but excluding user interface and MIB code.
Consult Dino Farinacci [dino] for more details.
[Moy] PAGE 5
RFC 1246 Experience with OSPF July 1991
o ACC. This implementation is based on the University of Maryland code.
It participated in the last two rounds of interoperability testing.
It also contains the only implementation of (a precursor to) the OSPF
MIB (see Section 3.0 for details), which it uses for monitoring and
configuration. The ACC implementation consists of approximately
24,000 lines of C code, including its OSPF MIB code. Consult Fred
Baker [fbaker] for more details.
o Proteon. This implementation was wholly developed by Proteon. It has
participated in all three rounds of interoperability testing. It is
also the only implementation that has a significant amount of field
experience (see Section 6.0 for details). The Proteon implementation
consists of approximately 9500 lines of C code, including comments
but excluding user interface code. Consult John Moy [jmoy] for more
details.
o Wellfleet. This implementation has participated in all three rounds
of interoperability testing. Consult Jonathan Hsu [jhsu] for more
details.
o University of Maryland. This implementation was developed wholly by
Rob Coltun at the University of Maryland. It has formed the basis for
a number of commercial OSPF implementations, and also participated in
the latest round of interoperability testing. The University of
Maryland implementation consists of approximately 10,000 lines of C
code. Consult Rob Coltun [rcoltun] for more details.
Note that, as required by the IAB/IESG for Draft Standard status, there
are multiple interoperable independent implementations, namely those
from 3com, Proteon and the University of Maryland.
6.0 Operational experience
This section discusses operational experience with the OSPF protocol.
Version 1 of the OSPF protocol began to be deployed in the Internet in
Spring of 1990. The results of this original deployment were reported to
the mailing list ospf-tests@seka.cso.uiuc.edu. (Archives of this mailing
list are available from Ross Veach [rrv].) No protocol bugs were found
in this first deployment, although several additional features were
found to be desirable. These new features were added to the protocol in
OSPF Version 2.
The OSPF protocol is now deployed in a number of places in the Internet.
In this section we focus on three highly visible systems, namely the
NASA Sciences Internet, BARRNet and OARnet. The dimensions of these
three OSPF systems is summarized in the following table:
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RFC 1246 Experience with OSPF July 1991
TABLE 3. Three operational OSPF deployments
Name Version 1 date Version 2 date # routers
_____________________________________________________
NSI 4/13/90 1/1/91 15
BARRNet 4/90 11/90 14
OARnet 10/15/90 not yet 13
All the above deployments are using the Proteon OSPF implementation.
There is one other deployment worth mentioning in this context. 3com has
started to deploy OSPF on their corporate network. They have 8 of their
routers running OSPF (the 3com implementation), and are planning on
cutting over the remaining routers (20 in all). Currently they have two
operational routers running OSPF and RIP simultaneously. One converts
OSPF data to RIP data, and the other RIP data to OSPF data. For more
details, contact Dino Farinacci [dino].
6.1 NSI
The NASA Science Internet (NSI) is a multiprotocol network, currently
supporting both DECnet and TCP/IP protocols. NSI's mission is to provide
reliable high-speed communications to the NASA science community. The
NASA Science Internet connects with other national networks including
the National Science Foundation's NSFNET, the Department of Energy's
ESnet and the Department of Defense's MILNET. NSI also has
international connections to Japan, Australia, New Zealand, Chile and
several European countries.
For more information on NSI, contact Jeffrey Burgan [jeff] or Milo Medin
[medin].
6.1.1 NSI's OSPF system
NSI was one of the initial deployment sites for OSPF Version 1, having
deployed the protocol in April 1990. NSI has been running OSPF V2 since
1/1/91. They currently have 15 routers in their OSPF system. This
system is pictured in Figure 1. It consists of a nationwide collection
of serial lines, with ethernets at hub sites. The numbers associated to
interfaces/links in Figure1 are the associated OSPF costs. Note that
certain links have been weighted so that they are less preferable than
others.
Many of NSI's OSPF routers are speaking either RIP and/or EGP as well as
OSPF. Routes from these other routing protocols are selectively imported
[Moy] PAGE 7
RFC 1246 Experience with OSPF July 1991
into their OSPF system as externals. The current number of imported
externals is 496.
All NSI externals are imported as OSPF type 2 metrics. In addition, NSI
uses the OSPF external route tag to manage the readvertisement of
external routes. For example, a route learned at one edge of the NSI
system via EGP can be tagged with the number of the AS from which it was
learned. Then, as the OSPF external LSA describing this route is flooded
through the OSPF system, this tagging information is distributed to all
the other AS boundary routers. A router on the other edge of the NSI can
then say that it wants to readvertise (via EGP) routes learned from one
particular AS but not routes learned from another AS. This allows NSI to
implement transit policies at the granularity of Autonomous Systems,
instead of network numbers, which greatly reduces the network's
configuration burden.
NSI has also experimented with OSPF stub areas, in order to support
routers having a small amount of memory.
6.1.2 NSI - Deployment analysis
NSI ran a couple of experiments after OSPF's deployment to test OSPF's
convergence time in the face of network failures, and to compare the
level of routing traffic in OSPF with the level of routing traffic in
RIP. These experiments were included in NSI status reports to the OSPF
plenary.
The first experiment consisted of running a continuous ICMP ping, and
then bringing down one of the links in the ping packet's path. They then
timed how long it took OSPF to find an alternate path, by noticing when
the pings resumed. The result of this experiment is contained in Milo
Medin's "NASA Sciences Internet Report" in [8]. It shows that the
interrupted ping resumed in three seconds.
The second experiment consisted in analyzing the amount of routing
protocol traffic that flow over an NSI link. One of the NSI links was
installed, but did not have any active users yet. For this reason, all
traffic that flowed over the link was routing protocol traffic. The link
was instrumented to continuously measure the amount of bandwidth
consumed, first in the case where RIP was running, and then in the case
of where OSPF was running. The result is shown graphically in Jeffrey
Burgan's "NASA Sciences Internet" report in [9]. It shows that OSPF
consumes many times less network bandwidth than RIP.
[Moy] PAGE 8
RFC 1246 Experience with OSPF July 1991
6.2 BARRNet
BARRNet is the NSFNet regional network in Northern California. At the
present time, it serves approximately 80 member sites in an area
stretching from Sacramento in the north-east to Monterey in the in the
south-west. Sites are connected to the network at speeds from 9.6Kbps to
full T1 using Proteon and cisco routers as well as a Xylogics terminal
server. The membership is composed of a mix of university, government,
and commercial organizations. BARRNet has interconnections to the NSFNet
(peering with both T1 and T3 backbones at Stanford University), ESNet
(peering at LLNL, with additional multi-homed sites at LBL, SLAC, and
NASA Ames), and DDN national networks (peering at the FIX network at
NASA Ames), and to the statewide networks of the University of
California (peering at U.C. Berkeley) and the California State
University system (peering at San Francisco State and Sacramento State).
Topologically, the network consists of fourteen OSPF-speaking Proteon
routers, which as a "core", with six of these redundantly connected into
a ring. All "core" sites are interconnected via full T1 circuits. Other
member sites attach as "stub" connections to the "core" sites. The bulk
of these are connected in a "star" configuration at Stanford University,
with lesser numbers at other "core" sites.
Contact Vince Fuller [vaf] for more information on BARRNet.
6.2.1 BARRNet's OSPF system
BARRNet was also one of the initial deployment sites for OSPF Version 1,
having deployed the protocol in April 1990. BARRNet has been running
OSPF V2 since November 1990. They currently have 14 routers in their
OSPF system. The BARRNet OSPF system is pictured in Figure 2. It
consists of a collection of T1 serial lines, with ethernets at hub
sites.
Most of BARRNet's OSPF routers are speaking either RIP and/or EGP as
well as OSPF. Routes from these other routing protocols are selectively
imported into their OSPF system as externals. A large number of external
routes are imported; the current number is1816. The bulk of these are
the T1 NSFNet routes, followed by several hundred NSN routes, around
60-80 BARRNet routes from the non-OSPF system, and several dozen from
ESNet.
All external routes are imported into the BARRNet system as external
type 1 metrics. In addition, BARRnet, like NSI, uses the OSPF's external
route tagging feature to help manage the readvertisement of external
routes via EGP.
[Moy] PAGE 9
RFC 1246 Experience with OSPF July 1991
BARRnet is also using four stub OSPF areas in order to collapse subnet
information. These stub areas all consist of a single LAN. They do not
contain any OSPF routers in their interiors.
6.2.2 BARRNet - Deployment analysis
Initial deployment of OSPF Version 1 in BARRNet pointed to the need for
two new protocol features that were added to OSPF V2, namely:
o Addition of the forwarding address to OSPF external LSAs. This
eliminated the extra hops that were being taken in BARRNet when only
routers BR5 and BR6 were exchanging EGP information with the NSS (see
Figure 2). Without the forwarding address feature, that meant that
NSFNet traffic handled by routers BR10, BR16 and BR28 was taking an
extra hop to get to the NSS.
o Addition of stub areas. This was an attempt to get OSPF running on
some of the BARRNet routers that had insufficient memory to deal with
all of BARRNet's external routes.
6.3 OARnet
OARnet, the Ohio Academic Resources Network, is the regional network for
the state of Ohio. It serves the entire higher education community,
providing Ohio schools access to colleagues worldwide. The Ohio
Supercomputer Center and the NSF Supercomputer Centers are reached
through OARnet. Libraries, databases, national and international
laboratories and research centers are accessible to faculty, helping
make Ohio schools competitive.
OARnet was established in 1987 to provide state-wide access to the CRAY
at the Ohio Supercomputer Center in Columbus, Ohio. Since then it has
evolved into a network supporting all aspects of higher education within
Ohio. A primary goal of OARnet is to facilitate collaborative projects
and sharing of resources between institutions, including those outside
the state. OARnet connections are available to Ohio academic
institutions and corporations engaged in research, product development,
or instruction. Colleges, universities, and industries currently use
OARnet connections to communicate within the state and with colleagues
around the country.
OARnet uses the Internet (TCP/IP) and DECNET protocols. OARnet
participants using TP/IP protocols are connected to the worldwide
Internet, which includes all the major networks open to non-classified
research. OARnet is also connected to NSFNet, the national research and
[Moy] PAGE 10
RFC 1246 Experience with OSPF July 1991
education network sponsored by the National Science Foundation. It has
gateways to BITNET, CSNET, CICNet (a network connecting the Big Ten
universities), and the NASA Science Internet.
For more information on OARnet, contact Kannan Varadhan [kannan].
6.3.1 OARnet's OSPF system
OARnet has been running OSPF Version 1 since October 15, 1990. They
currently have 14 routers in their OSPF system. The OARnet OSPF system
is pictured in Figure 3.
There are 29 sites connected directly to the OARnet backbone. All 13 of
OARnet's OSPF routers act as ASBRs. There are 40 OSPF internal routes on
OARnet's network, and they import about 120 routes from RIP. OARnet
runs EGP on the DMZnet at Columbus, which connects them to CICNet. The
router connecting OARnet to DMZnet (OAR1 in Figure 3) runs EGP on the
DMZnet side, and OSPF and RIP on the OARnet backbone. No EGP routes are
imported into the OSPF system. The OAR1 router is configured to generate
a default when EGP routes are available. The OAR1 router is the keystone
for routing on OARnet's network, in that it acts as an intermediary for
all of OARnet's RIP centric routers.
OARnet uses the Event Logging System on its Proteon routers to generate
traps for "interesting" events related to routing. They have these traps
sent to an SNMP management station, where the logs are collected for
later perusal.
6.3.2 OARnet - Deployment analysis
OARnet is monitoring their OSPF system via collection of traps on their
SNMP management station. The following is a report on their
observations. It has been edited slightly to conform better with the
other text and maps presented in this report. For more information,
contact Kannan Varadhan [kannan]:
3 of our 10 DS1 circuits are on digital microwave, and these tend to
flap occasionally. Our observations indicate that the routers bring up
links, and adjacencies, on average, in about 2 seconds. Routes fallback
to alternate backup paths instantly. Whole blocks of routes cut over the
instant the adjacencies are formed.
In contrast to this, our RIP routes would take about 3-6 minutes to
cutover, and, on occasion, would not cut back to the preferred paths.
This was our prime motivation in switching to OSPF.
[Moy] PAGE 11
RFC 1246 Experience with OSPF July 1991
We attempted to duplicate Milo Medin's ping test to dramatically
illustrate the performance of RIP over OSPF. To do this, we selected a
host on the farthest point from our workstation, and ran a continuous
ping to it. We would then bring down a primary DS1 circuit, and watch
the time it took to switch to the fallback route. Following this, we
would bring the circuit back up, and study the time it took to re-sync
to the new path. With RIP, we were unable to fully complete the
experiment, because the farthest point was exactly equal to the new (and
preferred) primary path, and therefore, RIP would never choose it on
it's own, until the path it was currently using failed. With OSPF, it
took about 2 seconds to synchronize over a new, much slower 56kb path,
and less than a second when the DS1 circuit came back up.
Here are some more observations of the OARnet OSPF system's behavior:
o 131.187.36.0 is the 56kb line to Kent State University. Kent also has
a DS1 circuit leading into ASP, the Akron Pop. Likewise, UAkron.edu
has a similar configuration. A roundabout backup path exists when
traffic heads up to Cleveland over a couple of DS1 circuits, and then
down a 56kb backup path used by another school in the Cleveland area.
Some statistical information:
1. 09:55:17: SPF.37: new route to Net 131.187.36.5,
type SPF cost 32
2. 09:55:18: SPF.37: new route to Net 131.187.36.6,
type SPF cost 22
3. 09:55:20: SPF.21: State Change, nbr 131.187.27.6,
new state <Full>, event 9
4. 09:55:21: SPF.37: new route to Net 131.187.36.5,
type SPF cost 31
5. 09:55:22: SPF.37: new route to Net 131.187.36.6,
type SPF cost 21
6. 09:55:28: SPF.21: State Change, nbr 131.187.21.5,
new state <Full>, event 9
7. 09:55:29: SPF.21: State Change, nbr 131.187.51.6,
new state <Full>, event 9
8. 09:55:31: SPF.37: new route to Net 131.187.36.5,
type SPF cost 22
9. 09:55:33: SPF.37: new route to Net 131.187.36.5,
type SPF cost 11
The Akron router restarts, and has to re-sync with all the lines.
This restart is confirmed when one looks at the traps from gwCSP1.
Traps from gwASP1 still do not get through to us, because traps are
[Moy] PAGE 12
RFC 1246 Experience with OSPF July 1991
sent via UDP, and gwASP1's routing tables are not fully configured
yet.
Events 1 and 2 are route changes routing traffic via Cleveland,
across 2 DS1 circuits and a 56kb line.
When the DS1 circuit to UAkron came up, routes instantly cut over to
use this as a better least cost path. This is shown in events 3, 4
and 5.
In a few seconds, the line to Columbus is the next one up. This is
event 6. Event 8 relates to this cutover, and is the best path yet.
When the DS1 circuit to Kent is up, the link is used instantly.
We are able to make such a definitive conclusion of these traps on
the basis of the topological information that we have about the
network and the means used to monitor them.
o To illustrate the time required to fully synchronize a database, we
piece together a few adjacency forming traces...
Please bear in mind that these time stamps are the time stamps on the
management station, and are not to be taken as the absolute truth.
Things we haven't taken into account are transit times of
messages, ordering of events (SNMP traps are sent using UDP),
loss of event reports (recall that an entire synchronization sequence
of gwASP1 on the ASP-CSP link is missing), etc.
The trace below corresponds to the Akron router, gwASP1 bring up the
link in the previous section. This is as observed on the other end of
the line, gwCSP1.
REPORT DATE: 02/26/91 ROUTER: gwcsp1
09:55:06: SPF.15: State Change, ifc 131.187.22.6,
new state <Point-To-Point>, event 1
09:55:06: GW.xxx: Link Up Trap: 09:55:07: SPF.37:
new route to Net 131.187.22.5, type SPF cost 1
09:55:07: SPF.21: State Change, nbr 131.187.22.5,
new state <Init>, event 1
09:55:09: SPF.37: new route to Net 131.187.27.5,
type SPF cost 22
09:55:11: SPF.21: State Change, nbr 131.187.22.5,
new state <ExStart>, event 14
09:55:11: SPF.21: State Change, nbr 131.187.22.5,
new state <2-Way>, event 3
09:55:12: SPF.21: State Change, nbr 131.187.22.5,
new state <Exchange>, event 5
[Moy] PAGE 13
RFC 1246 Experience with OSPF July 1991
09:55:12: SPF.21: State Change, nbr 131.187.22.5,
new state <Full>, event 9
09:55:12: SPF.21: State Change, nbr 131.187.22.5,
new state <Loading>, event 6
Below, is another trace of the same router restart sequence, where
the router is proceeding to bring up other DS1 circuits. Bringing up
the first adjacency took about 5 seconds. Subsequent adjacencies take
the router less than a second as seen below.
REPORT DATE: 02/26/91 ROUTER: gwasp1
09:55:20: SPF.15: State Change, ifc 131.187.27.5,
new state <Point-To-Point>, event 1
09:55:20: GW.xxx: Link Up Trap: 09:55:20: SPF.21:
State Change, nbr 131.187.27.6, new state <Init>, event 1
09:55:20: SPF.21: State Change, nbr 131.187.27.6,
new state <ExStart>, event 14
09:55:20: SPF.21: State Change, nbr 131.187.27.6,
new state <Exchange>, event 5
09:55:20: SPF.21: State Change, nbr 131.187.27.6,
new state <Full>, event 9
09:55:21: SPF.21: State Change, nbr 131.187.27.6,
new state <Loading>, event 6
09:55:24: SPF.21: State Change, nbr 131.187.51.6,
new state <Init>, event 1
09:55:24: SPF.21: State Change, nbr 131.187.21.5,
new state <Init>, event 1
09:55:25: SPF.37: new route to Net 131.187.21.6, type SPF cost 13
09:55:25: SPF.37: new route to Net 131.187.51.5, type SPF cost 22
09:55:28: SPF.21: State Change, nbr 131.187.21.5,
new state <ExStart>, event 14
09:55:28: SPF.21: State Change, nbr 131.187.21.5,
new state <2-Way>, event 3
09:55:28: SPF.21: State Change, nbr 131.187.21.5,
new state <Exchange>, event 5
09:55:28: SPF.21: State Change, nbr 131.187.21.5,
new state <Full>, event 9
09:55:28: SPF.21: State Change, nbr 131.187.21.5,
new state <Loading>, event 6
09:55:29: SPF.37: new route to Net 131.187.51.6, type SPF cost 1
09:55:29: SPF.37: new route to Net 131.187.21.5, type SPF cost 1
09:55:29: SPF.21: State Change, nbr 131.187.51.6,
new state <Exchange>, event 5
09:55:29: SPF.21: State Change, nbr 131.187.51.6,
new state <ExStart>, event 14
09:55:29: SPF.21: State Change, nbr 131.187.51.6,
new state <2-Way>, event 3
09:55:29: SPF.21: State Change, nbr 131.187.51.6,
[Moy] PAGE 14
RFC 1246 Experience with OSPF July 1991
new state <Full>, event 9
09:55:29: SPF.21: State Change, nbr 131.187.51.6,
new state <Loading>, event 6
A transient fault on a DS1 circuit, causes the line to flap. All
routers quickly reroute around the flap, and the router itself takes
about 2 seconds to bring up the adjacency once more.
REPORT DATE: 02/26/91 ROUTER: gwasp1
14:33:43: GW.xxx: Link Up Trap:
14:34:19: SPF.15: State Change, ifc 131.187.22.5,
new state <Down>, event 7
14:34:19: GW.xxx: Link Failure Trap:
14:34:19: SPF.47: Net 131.187.22.6 now unreachable
14:34:36: SPF.15: State Change, ifc 131.187.22.5,
new state <Point-To-Point>, event 1
14:34:36: GW.xxx: Link Up Trap:
14:34:37: SPF.37: new route to Net 131.187.22.6, type SPF cost 1
14:34:45: SPF.21: State Change, nbr 131.187.22.6,
new state <2-Way>, event 3
14:34:45: SPF.21: State Change, nbr 131.187.22.6,
new state <Init>, event 1
14:34:46: SPF.21: State Change, nbr 131.187.22.6,
new state <ExStart>, event 14
14:34:46: SPF.21: State Change, nbr 131.187.22.6,
new state <Exchange>, event 5
14:34:47: SPF.21: State Change, nbr 131.187.22.6,
new state <Full>, event 9
14:34:47: SPF.21: State Change, nbr 131.187.22.6,
new state <Loading>, event 6
o On the amount of time it takes for a router to restart, and become
fully synchronized. Taking the logs in the previous instance, we
notice that the CSP-ASP link comes up at 9:55:06. The last link is
observed to be up at 9:55:29, which is less than a minute.
o On the RIP equivalent of the tests, it took us 3 minutes to cutover
to the slower speed fallback route, and we lost countless many
packets. The routes never cutover to the higher speed paths when
available, and we waited well over 30 minutes watching this,
wondering why. Unfortu- nately, at this point, we seem to have lost
the RIP statistics.
On the OSPF version, we have...
{nisca danw 51}
ping 131.187.25.6 PING 131.187.25.6 (131.187.25.6):
[Moy] PAGE 15
RFC 1246 Experience with OSPF July 1991
56 data bytes 64 bytes from 131.187.25.6:
icmp seq=0 ttl(255-ttl)=54(201). time=20 ms
[...]
icmp seq=10 ttl(255-ttl)=54(201). time=20 ms
|| T1 down
icmp seq=14 ttl(255-ttl)=54(201). time=180 ms
icmp seq=15 ttl(255-ttl)=54(201). time=60 ms
[...]
icmp seq=38 ttl(255-ttl)=8(247). time=1300 ms
icmp seq=39 ttl(255-ttl)=54(201). time=820 ms
|| Tl Up
icmp seq=40 ttl(255-ttl)=54(201). time=20 ms
icmp seq=41 ttl(255-ttl)=54(201). time=20 ms
131.187.25.6 PING Statistics
51 packets transmitted, 48 packets received, 5% packet loss
round-trip (ms) min/avg/max = 20/277/1300
6.4 Features exercised during operational deployment
In operational environments, all basic mechanisms of the OSPF protocol
have been exercised. These mechanisms include:
o Designated Router election. There have been operational deployments
have as many as 8 OSPF routers attached to a single broadcast
network.
o Database synchronization. This includes OSPF's adjacency bringup and
reliable flooding procedures. Large operational OSPF link state
databases (e.g., BARRNet) have provided a thorough test of these
mechanisms.
o Flushing advertisements. The procedure for flushing old or
unreachable advertisements (the MaxAge procedure) has been tested
operationally. It is interesting to note that flushing of
advertisements does occur more during interoperability testing
(because of the constant restart- ing of routers) that it does
operationally. For example, in a week of BARRNet statistics, 9650
advertisements were flushed, while 688,278 new advertisements were
flooded.
o Import of external routes. All options of external LSAs have been
tested operationally: type 1 metrics, type 2 metrics, forwarding
addresses and the external route tag.
o Authentication. The OSPF authentication procedure has been tested
operationally.
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RFC 1246 Experience with OSPF July 1991
o Equal-cost multipath. Operational deployments have included
topologies with equal-cost, redundant paths.
o Stub areas. These have been deployed both in BARRNet and NSI.
6.5 Limitations of operational deployments
The following things have not been tested in an operational environment:
o Multi-vendor deployments. So far all deployments have used a single
implementation. However, extensive interoperability testing of OSPF
has been done (see Section 7.0 of this report).
o Regular OSPF areas. These have however been tested in all three
rounds of the OSPF interoperability testing.
o Virtual links. These have however been tested in OSPF's
interoperability testing.
o Non-broadcast networks. However, OSPF interoperability testing has
been performed over X.25 networks.
o TOS routing. However, this has been tested in OSPF's interoperability
testing.
6.6 Conclusions
All basic features of the OSPF protocol have been exercised. Very large
OSPF link state databases (e.g., BARRNet's OSPF system) have been
deployed, providing a thorough test of OSPF's database synchronization
mechanisms. No OSPF protocol problems have been found in operational
deployments.
Most of the hassles in operation deployments has to do with the OSPF/RIP
interchange. Many of these issues have been ironed out on the ospf-tests
mailing list (see Section 2.0). However, the interaction between OSPF,
RIP, and EGP continues to be an active area of research.
7.0 Interoperability Testing
There have been three separate OSPF V2 interoperability testing
sessions. Five separate implementations have participated in at least
one session: implementations from the companies 3com, ACC, Proteon and
Wellfleet, and the publicly available implementation from the University
of Maryland.
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RFC 1246 Experience with OSPF July 1991
Each of the testing sessions is described in a succeeding section. For
each session, the participants are identified, and the testing
topologies are described along with the particular protocol features
that were exercised. Any protocol problems that were encountered during
the testing are also described. In addition, for the second and third
rounds testing reports were sent to the ospf mailing lists. These
reports are reproduced in this document.
There is quite a bit of commonality in the features that have been
tested from session to session. There are several reasons for this
commonality. First, in each testing session an attempt has been made to
increase the size of the OSPF system under test. For example, the number
of external routes imported has doubled each session. Secondly, the
interoperability sessions have been debugging sessions as well as
protocol sessions. Many things tested in the third round were to ver-
ify that implementations had successfully fixed problems found in
earlier sessions. A brief overview of the testing session is presented
in the following table:
TABLE 4. OSPF interoperability testing at a glance.
Site Week Routers Externals Implementations
_____________________________________________________________________________
Proteon 9/25/90 6 20-30 3com, Proteon, Wellfleet
SURAnet 12/17/90 10 96 3com, ACC, Proteon, Wellfleet
3com 2/4/91 16 400 3com, ACC, Proteon, Wellfleet, UMD
For more information on the interoperability testing, the following
people can be contacted: Fred Baker [fbaker], Rob Coltun [rcoltun], Dino
Farinacci [dino], Jonathan Hsu [jhsu], John Moy [jmoy], and William
Streilein [bstreile].
7.1 Testing methodology
In the interoperability tests, the routers have been interconnected
using ethernet, serial lines (PPP and proprietary), X.25 and 802.5 token
ring. Monitoring of the routers has been done through connecting
terminals (either directly or via telnet) to the router consoles. Each
implementation has a different user interface, which makes monitoring
somewhat difficult. As explained earlier in this document, there is now
an OSPF MIB, which in the future will enable a common monitoring
interface to all implementations.
In general, each implementation has an error logging capability, and
this is often how problems are discovered. LAN protocol analyzers are
[Moy] PAGE 18
RFC 1246 Experience with OSPF July 1991
also used to capture OSPF protocol packet exchanges that are causing
problems. These packet traces are available for analysis either during
of after the testing sessions.
Verification of routing was done through visual inspection of
implementations' routing table and link state databases (via the console
interface), and through network debugging tools such as "ping" and
"traceroute".
7.2 First round (Proteon, 9/25/90 - 9/29/90)
The first round of OSPF protocol testing took place at Proteon Inc.'s
Westborough facility, the week of September 25, 1990. Three
implementations participated, from the vendors 3com, Proteon and
Wellfleet.
There were two 3com routers, two Wellfleet routers and two Proteon
routers available for testing. These routers were interconnected with
ethernets and serial lines. External routes were imported from the
Proteon company internet. In addition, during off hours we were able to
connect the routers under test to the Proteon company internet, forming
one fairly large OSPF system.
The testing at Proteon proceeded as follows:
o All routers were connected to a single ethernet. Then, as routers
were taken up and down, the Designated Router election algorithm and
the Database Description process were tested. Also OSPF's reliable
flooding algorithm was tested in this configuration.
o Twenty to thirty external routes were imported into the OSPF system
by a Proteon router (which was simultaneously running RIP). It was
then verified that these external routes were installed into the
router's routing tables.
o One of the 3com routers was configured to originate an OSPF default
route. This tested OSPF default route processing, and also tested the
behavior of the system when multiple routers were importing external
routes.
o The OSPF system was split into areas. Both regular OSPF areas (non-
stub) and stub areas were tested.
o The six routers under test were connected to the Proteon company
internet (which was also running OSPF), forming an OSPF system of
eighteen routers. This configuration was shortlived, due to a
disagreement between the 3com and Proteon routers concerning how to
[Moy] PAGE 19
RFC 1246 Experience with OSPF July 1991
represent an OSPF default route.
Unfortunately, incomplete records were kept of this testing, so that no
maps of the testing configurations can be reproduced for this document.
7.2.1 Problems found in the First round testing
A couple of OSPF protocol/specification problems were uncovered in the
first round of testing. First, it was noticed that there was a window
in the Database Description process where concurrently flooded MaxAge
advertisements could prevent database synchronization from completing.
This required a change in the specification's handling of MaxAge LSAs.
Secondly, it was found that the OSPF specification did not specify how
the Network Mask field should be set in external LSAs that were
advertising the DefaultDestination. This was a minor problem, but caused
difficulties because of assumptions made in one implementation on how
the mask should be set.
7.3 Second round (SURAnet, 12/17/90 - 12/21/90)
The second round of OSPF protocol testing took place at SURAnet's
College Park facility, the week of December 12, 1990. Four
implementations participated, from the vendors 3com, ACC, Proteon and
Wellfleet.
There were two 3com routers, two ACC routers, two Wellfleet routers and
four Proteon routers available for testing. These routers were
interconnected with ethernets, serial lines and token rings. External
routes were imported from SURAnet by one of the Proteon routers.
The testing at SURAnet proceeded as follows. Initially nine routers were
configured as a single backbone area, with six of the routers connected
to a single ethernet. This is pictured in Figure 4. In this
configuration, the Designated Router transition and database
synchronization process were tested. Ninety-six external routes were
imported from SURAnet to stress the flooding algorithm. By restarting
the router that was importing the routes, the flushing of advertisements
from the routing domain was tested. Additionally, variable-length
subnets and OSPF's optional TOS routing capability were tested in this
configuration.
Next the routers were configured into four separate OSPF areas, with
each area directly connected to the OSPF backbone (which was a single
ethernet). There were no virtual links in this configuration. Inter-
[Moy] PAGE 20
RFC 1246 Experience with OSPF July 1991
area routing was tested, including having AS boundary routers internal
to a non-backbone area. Also tested was the case where a single router
was both an area border router and an AS boundary router.
For more details of the testing, see the "Official report of the Second
Round Testing" listed below.
7.3.1 Official report of the Second round testing
The following report was sent to the ospf, ospf-tests, and router-
requirements mailing lists after the second round of interoperability
tests:
The second round of OSPF multi-vendor testing was done in College Park,
Maryland the week of 12/17/90. The facilities were provided by SURAnet.
Four major router vendors were present, Advanced Computer Communications
(ACC), Proteon, 3Com, and Wellfleet. A press conference and presentation
was provided for 3 different data communication magazine
representatives.
Each vendor provided at least 2 routers. Each vendor had a device
connected to a common Ethernet. This Ethernet was configured as the OSPF
backbone area. The rest of the routers were attached to the various
backbone routers via Ethernet, Token Ring, proprietary serial line, PPP
serial line, and X.25 type media. The following test scenarios were
performed and completed in the following order:
o Intra-area routing. All routers were configured to reside in the
backbone area. Designated Router election was performed various
number of times so each vendor could be designated router for a
period of time. Packet data was captured on a Sniffer for later
observation.
o Variable Length Subnet Masks. Some of the serial lines in the
configuration were configured to be on the same IP network but with
different subnet masks. It was observed that all routers stored
routes for the different length subnets.
o Import SURAnet routes. The Proteon router was listening for RIP
routes generated by the SURAnet routers. These routes were imported
into our OSPF test system. 96 external link state advertisements were
generated as a result. Many scaling type implementation problems
surfaced for each vendor during this exercise.
o Type of Service generation. While the test setup was still configured
as a single area, the 3Com router generated Type of Service link
[Moy] PAGE 21
RFC 1246 Experience with OSPF July 1991
state advertisements. It was observed how the other vendor
implementations reacted to it. Some problems were found.
o Inter-area routing. Multiple areas were configured. Common non-
backbone areas were shared by Proteon and Wellfleet and by ACC and
3Com. It was observed that the correct Intra-area and Inter-area
routes appeared in each router's routing table. At this point in the
test setup, the Proteon router regenerated the 96 SURAnet routes into
the configuration. It was observed that the routes were learned and
propagated over area boundaries. Some problems occur at this point.
More emphasis on this scenario will occur at the next round of
testing.
o OSPF over X.25. A point-to-point link was connected between the
Proteon router and the 3Com router. The X.25 packet level was
configured to run over the link. OSPF was enabled over the link to
verify that multi-vendor OSPF over X.25 was performed. Both of these
routers were in the same area.
o MaxAge advertisements. Link state advertisements were flushed from
the routing domain using the MaxAge procedure. We verified that all
routers removed the advertisements from their databases, after they
were properly acknowledged by the flooding procedure. Some problems
were found in this test, although not nearly as many as in the first
round of testing.
Each vendor agreed that this sort of testing was extremely valuable and
that it should occur again. 3Com has offered for the third round of
testing to occur in Santa Clara sometime in February. 3Com will
encourage other OSPF implementations to join in the testing. Items that
will be tested are:
o Intra-area routing with loops (as well as equal-cost multipath).
o Inter-area testing including Stub and Transit area support, with both
Intra-area and Inter-area loops.
o Virtual link testing in the looped Inter-area configuration.
o RIP/OSPF route interchange including testing forwarding address
capability in external link state advertisements.
o EGP/OSPF router interchange including the use of the route tag field
in external link state advertisements.
o More than two routers connected to an X.25 network. We would like to
test OSPF's non-broadcast multi-access capabilities by attaching more
than two vendor's routers to an X.25 packet switch.
[Moy] PAGE 22
RFC 1246 Experience with OSPF July 1991
o Several vendors running OSPF and RIP simultaneously. This will
further test the OSPF/RIP interactions.
o Test processing of links with cost LSInfinity. These links should be
treated as unreachable.
Furthermore, we hope that in future rounds of testing an OSPF MIB would
allow us to also use a network management station to gather test data.
In summary, the stability of implementations were better this time more
so than the first round of testing. No problems with the protocol design
were encountered. The exchange of ideas and the cooperation among
implementors that occurred during this test effort, continues the spirit
that OSPF is truly an open protocol.
7.3.2 Problems found in the Second round testing
No problems were found in the OSPF protocol during the second round of
testing.
7.4 Third round (3com, 2/4/91 - 2/8/91)
The third round of OSPF protocol testing took place at 3com's Santa
Clara facility, the week of February 4, 1991. Five implementations
participated, from the vendors 3com, ACC, Proteon and Wellfleet and the
publicly available University of Maryland implementation (running on a
SUN workstation).
There were five 3com routers, four ACC routers, three Wellfleet routers,
three Proteon routers and the UMD Sun workstation available for testing
(giving a total of 16 routers available). These routers were
interconnected with ethernets, serial lines and X.25. External routes
were imported from BARRNet by one of the 3com routers.
The initial testing configuration is shown in Figure 5. Three areas were
configured, along with a non-contiguous backbone. The backbone was then
joined by configuring two virtual links. In this configuration the
following OSPF functionality was tested: inter-area routing and virtual
links.
The system was then reconfigured so that twelve of the routers were
connected to a single ethernet. This configuration is pictured in Figure
6. By bringing routers up and down, this configuration tested Designated
Router election, database synchronization and reliable flooding. To see
how this functionality, and also the implementations, scale, 400
[Moy] PAGE 23
RFC 1246 Experience with OSPF July 1991
external routes were imported from BARRNet.
7.4.1 Official report of the Third round testing
The following report was sent to the ospf, ospf-tests, and router-
requirements mailing lists after the third round of interoperability
tests:
The third round of OSPF interoperability testing was held at 3com
Corporation in Santa Clara the week of February 4-8. Four router vendors
came to the testing: 3com, ACC, Proteon and Wellfleet. In addition, Rob
Coltun brought the University of Maryland implementation, which was run
on a Sun Workstation.
Testing was performed over ethernet, point-to-point networks (using PPP)
and X.25. In all we had 16 routers available: five 3com routers, four
ACC routers, three Proteon routers, three Wellfleet routers and Rob's
SUN. We also were able to import external routes from BARRNet.
Specific tests performed included the following:
o Initially we configured the routers into three separate areas and a
physically disconnected backbone. The backbone was then reconnected
through configuration of several virtual links. These tests verified
the generation and processing of summary link advertisements, as well
as the operation of virtual links.
o We connected multiple routers to an X.25 packet switch, testing
OSPF's non-broadcast network capability. OSPF was successfully run
over the X.25 network, using routers that were both DR eligible and
DR ineligible. Some problems were encountered, but they all involved
running IP over X.25 (i.e., they were not X.25 specific).
o We also connected a 3com router, Proteon router, and Rob's SUN to an
ethernet, and then treated the ethernet as a non-broadcast network.
This allowed us to connect Rob's SUN into the rest of the routing
domain without installing the IP multicast modifications to the SUN
kernel. It also further tested the OSPF's non-broadcast network
capability.
o We then reconfigured the OSPF system so that all but three of the
routers were connected to a single ethernet. This tested the
Designated Router functionality (12 routers were synchronizing with
the DR). We then also tested the DR election algorithm, by
selectively restarting the DR, or sometimes both the DR and the
Backup DR. This also tested OSPF's Database Description process.
[Moy] PAGE 24
RFC 1246 Experience with OSPF July 1991
o In this configuration, we then imported 400 external routes from
BARRNet (one of the 3com routers ran both OSPF and EGP). Some
problems were encountered in implementations' buffer allocation
strategies, and problems were also found in the way implementations
avoid IP fragmentation. But overall, this system was fairly stable.
The following problems we found in the OSPF specification:
o The specification should say that the "Network mask" field should not
be verified in OSPF Hellos received over virtual links.
o The specification should say that on multi-access networks neighbors
are identified by their IP address, and on point-to-point networks
and virtual links by their OSPF Router ID. This eliminates confusion
when, for example, a router is restarted and comes up with the same
IP address but a different Router ID.
Thanks to 3com for providing the testing facility, cables. terminals,
X.25 switch. etc. Also thanks to Vince Fuller of BARRNet for helping us
import the BARRNet routes.
7.4.2 Problems found in the Third round testing
A couple of specification/protocol problems were found in the third
round of interoperability testing. First, it was noticed that the
specification did not specify the setting of the Network Mask field in
Hellos sent over virtual links. This caused some initial difficulty in
bringing up virtual links between routers belonging to different
vendors. Secondly, it was noticed that the specification was not strict
enough in defining how OSPF neighbors are identified on multi-access
networks. This caused difficulties in one implementation when another
vendor's router was restarted with the same IP address but a different
OSPF Router ID. This is discussed more fully in the above "Official
Report of the Third Round Testing".
7.5 Overall: Features tested
All significant protocol features and mechanisms have been tested in the
three rounds of interoperability testing. In particular, the following
basic pieces of the protocol have been tested:
o Designated Router election. With as many as thirteen routers attached
to a single LAN, the election of Backup Designated Router and
Designated router was verified by bringing routers up and down,
[Moy] PAGE 25
RFC 1246 Experience with OSPF July 1991
singly and in pairs.
o Adjacency bringup. The Database Description process was verified,
with databases having over 400 LSAs. Adjacency bringup was also
verified in times when flooding was taking place simultaneously.
o Reliable flooding. It was verified that OSPF's flooding algorithm
maintains database synchronization, both in the presence of loops in
the topology, and with large databases (over 400 LSAs).
o Flushing advertisements from routing domain. OSPF's procedure for
flushing old or unreachable LSAs from the routing domain was
verified, both in the presence of topology loops and with many LSAs
being flushed at once. This is also referred to as OSPF's MaxAge
procedure.
o OSPF routing hierarchy. The OSPF four level routing hierarchy:
intra-area, inter-area. type 1 externals and type 2 externals was
tested.
o Import of external routing information. The importing of external
routes has been tested, with as many as 400 imported at once. Also,
the varying options in external LSAs has been tested: type 1 or type
2 metrics and forwarding addresses.escribe all options. In addition,
test setups were utilized having AS boundary routers both internal to
non-backbone areas and also being simultaneously area border routers.
o Running protocol over various network types. In the test setups, OSPF
has been run over ethernet, point-to-point serial lines (both PPP and
proprietary), 802.5 token ring and X.25.
o Non-broadcast, multi-access networks. OSPF has been tested over X.25.
Some testing was also done treating ethernet as a non-broadcast
network. Two separate situations were tested: when all routers
attached to the non-broadcast network were DR-eligible, and when only
some of them were.
o Authentication. OSPF's authentication procedure was tested for the
two current authentication types.
o Equal-cost multipath. Much of the testing was done in configurations
with redundant paths, and equal-cost multipath was verified through
examination of implementations' routing tables.
o Variable-length subnet masks. It was verified that implementations
paid attention to the network mask field present in OSPF LSAs.
[Moy] PAGE 26
RFC 1246 Experience with OSPF July 1991
Testing was also performed on the following pieces of OSPF's Area
functionality:
o Extent of advertisements. It was verified that all advertisements
except external LSAs were flooded throughout a single area only.
o Inter-area routing. The generation and processing of summary link
LSAs was tested. Also tested were configurations having multiple area
border routers attaching to a single area.
o Virtual links.
The following OSPF options were also tested:
o TOS routing. The interplay between TOS-capable and non-TOS-capable
routers was tested, by configuring TOS-specific metrics in the only
implementation (3com) supporting TOS routing.
o Stub areas. OSPF's stub area functionality was verified.
7.6 Testing conclusions
The interoperability testing has proven to be very valuable. Many bugs
were found (and fixed) in the implementations. Some protocol problems
were found (and fixed), and gray areas of the specification were cleared
up. Implementations have also been "bullet-proofed" in order to deal
with the unexpected behavior of other implementations. All participants
in the testing now understand the maxim "be conservative in what you
generate, and liberal in what you accept" (if they didn't already).
7.7 Future work
The one thing that has gone mostly untested at the interoperability
sessions is the interaction between OSPF and other routing protocols
(such as RIP and EGP). Each interoperability session generally had a
router running multiple routing protocols in order to import external
routing information into the OSPF system. However, simultaneously
running multiple routing protocols between different vendors' routers
has not been tested.
Each vendor has developed a slightly different architecture for the
exchange of routing information between differing routing protocols. As
the OSPF field testing has also shown, this exchange of routing
information is an area of ongoing work and a candidate for future
standardization.
[Moy] PAGE 27
RFC 1246 Experience with OSPF July 1991
8.0 Simulation
The OSPF protocol has been simulated by the Distributed Systems Research
Group at the University of Maryland Baltimore County (UMBC). The two
principal investigators for the OSPF simulation project are Dr.
Deepinder P. Sidhu of UMBC and Rob Coltun. They have been aided by three
graduate students: S. Abdallah, T. Fu and R. Nair. This section
attempts to summarize their simulation setup and results. For more
information, contact the Distributed Systems Research Group at the
following address:
Dr. Deepinder P. Sidhu
Department of Computer Science
University of Maryland Baltimore County
Baltimore, MD 21228
email: sidhu@umbc3.umbc.edu
A demo was given of their OSPF simulation at the March 4-8, 1991 IETF in
St. Louis. Details of the demo should be available in the IETF
proceedings.
8.1 Simulator setup
The Distributed System Research Group uses a significantly enhanced
version of the MIT network simulator. The simulator is event driven, and
contains support for both point-to-point networks and ethernet links. It
can simulate characteristics of both packet switches and hosts, and can
simulate internet behavior under various types of data traffic load
(e.g., Poisson, normal, exponential and uniform distributions). This
latter ability could be used, for example, to simulate how a routing
protocol works in a congested internet. Specific network topologies can
be input into the simulator, or pseudo-random network topologies can be
generated. Packet loss rates can also be simulated.
To simulate OSPF, Rob Coltun's OSPF implementation was incorporated into
the simulator, essentially unchanged.
The output of the simulator can be displayed in a graphical manner (it
uses X windows). Any variable in the implementation under test can be
monitored. In addition, statistical reports can later be produced from
logging files produced during the simulation runs.
[Moy] PAGE 28
RFC 1246 Experience with OSPF July 1991
8.2 Simulation results
The OSPF simulation has been run using the following topologies:
o The two sample topologies in the OSPF specification (Figure 2 and
Figure 6 in [2]). The first of these topologies shows an Autonomous
System without areas, the second the same AS with three areas and a
virtual link configured.
o The 19-node hub topology from [7].
o A large network of over 50 nodes, all attached to a single ethernet.
o A large network of over 50 nodes, containing both ethernets and
serial lines, pseudo randomly generated.
In these topologies, the correctness of the OSPF database
synchronization was verified. This was done through examination of the
nodes' OSPF link state databases and the nodes' routing tables. The
implementation of multiple OSPF areas was also tested. Also, database
convergence time was analyzed as a function of the network components'
link speeds.
Also, some formal analysis of the OSPF protocol was undertaken. The
neighbor and interface state machines were analyzed. In addition, the
Designated Router election algorithm was verified for certain sets of
initial conditions.
9.0 Reference Documents
The following documents have been referenced by this report:
[1] Moy, J., "The OSPF Specification", RFC 1131, October 1989.
[2] Moy, J., "OSPF Version 2", RFC 1247, July 1991.
[3] Coltun, R. and Baker, F., "OSPF Version 2 Management Information
Base", RFC 1248, July 1991.
[4] Reynolds, J. and Postel, J., "Assigned Numbers', RFC 1060, March
1990.
[5] Corporation for National Research Initiatives, "Proceedings of the
Thirteenth Internet Engineering Task Force", Cocoa Beach, Florida,
April 11-14, 1989.
[Moy] PAGE 29
RFC 1246 Experience with OSPF July 1991
[6] Corporation for National Research Initiatives, "Proceedings of the
Sixteenth Internet Engineering Task Force", Florida State
University, February 6-9, 1990.
[7] Gardner, M., et al., "Type-of-service routing: modeling and
simulation," Report 6364, BBN Communications Corporation, January
1987.
[8] Corporation for National Research Initiatives, "Proceedings of the
Seventeenth Internet Engineering Task Force", Pittsburgh
Supercomputing Center, May 1-4, 1990.
[9] Corporation for National Research Initiatives, "Proceedings of the
Eighteenth Internet Engineering Task Force", University of British
Columbia, July 30-August 3, 1990.
10.0 People
The following people have contributed information to this report and can
be contacted for further information:
TABLE 5. People references in this report
Tag Name Affiliation email
__________________________________________________________________________________
bstreile William Streilein Wellfleet bstreile@wellfleet.com
dino Dino Farinacci 3com dino@buckeye.esd.3com.com
fbaker Fred Baker ACC fbaker@acc.com
jeff Jeffrey Burgan Sterling Software jeff@nsipo.nasa.gov
jhsu Jonathan Hsu Wellfleet jhsu@wellfleet.com
jmoy John Moy Proteon jmoy@proteon.com
kannan Kannan Varadhan OARnet kannan@oar.net
medin Milo Medin Sterling Software medin@nsipo.nasa.gov
rcoltun Rob Coltun U. of Maryland rcoltun@umd5.umd.edu
rrv Ross Veach U. of Illinois rrv@seka.cso.uiuc.edu
vaf Vince Fuller BARRNet vaf@valinor.stanford.edu
[Moy] PAGE 30
RFC 1246 Experience with OSPF July 1991
Security Considerations
The OSPF protocol's security architecture is described in Section 4.0.
Author's Address
John Moy
Proteon Inc.
2 Technology Drive
Westborough, MA 01581
Phone: (508) 898-2800
Email: jmoy@proteon.com
[Moy] PAGE 31
Experience with the OSPF Protocol
RFC TOTAL SIZE: 70441 bytes
PUBLICATION DATE: Friday, August 9th, 1991
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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