Internet DRAFT - draft-ietf-opsawg-mud-acceptable-urls
draft-ietf-opsawg-mud-acceptable-urls
OPSAWG Working Group M. Richardson
Internet-Draft Sandelman Software Works
Updates: 8520 (if approved) W. Pan
Intended status: Standards Track Huawei Technologies
Expires: 2 September 2024 E. Lear
Cisco Systems
1 March 2024
Authorized update to MUD URLs
draft-ietf-opsawg-mud-acceptable-urls-11
Abstract
This document provides a way for an RFC8520 Manufacturer Usage
Description (MUD) definitions to declare what are acceptable
replacement MUD URLs for a device.
RFCEDITOR-please-remove: this document is being worked on at:
https://github.com/mcr/iot-mud-acceptable-urls
Status of This Memo
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provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on 2 September 2024.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Please review these documents carefully, as they describe your rights
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extracted from this document must include Revised BSD License text as
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Possible issues with updating the MUD files in place . . . . 3
3.1. Adding capabilities . . . . . . . . . . . . . . . . . . . 4
3.2. Removing capabilities . . . . . . . . . . . . . . . . . . 4
3.3. Significant changes to protocols . . . . . . . . . . . . 5
3.4. Motivation for updating MUD URLs . . . . . . . . . . . . 5
4. Updating the MUD URLs . . . . . . . . . . . . . . . . . . . . 5
4.1. Leveraging the manufacturer signature . . . . . . . . . . 6
4.2. Concerns about same-signer mechanism . . . . . . . . . . 7
5. Proposed mechanism for updating MUD URLs . . . . . . . . . . 7
5.1. Small Changes to the MUD URL . . . . . . . . . . . . . . 8
5.2. Big Changes to the MUD URL . . . . . . . . . . . . . . . 9
5.3. Merger, Acquisitions and Key Changes . . . . . . . . . . 9
5.3.1. Changing file structure . . . . . . . . . . . . . . . 9
5.3.2. Changing hosting URLs . . . . . . . . . . . . . . . . 10
5.3.3. Changing Signing Authority . . . . . . . . . . . . . 10
6. Polling for changes in MUD files . . . . . . . . . . . . . . 11
7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 11
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
9. Security Considerations . . . . . . . . . . . . . . . . . . . 12
9.1. Updating files vs Updating MUD URLs . . . . . . . . . . . 13
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
10.1. Normative References . . . . . . . . . . . . . . . . . . 13
10.2. Informative References . . . . . . . . . . . . . . . . . 13
Appendix A. Appendices . . . . . . . . . . . . . . . . . . . . . 15
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction
[RFC8520] provides a standardized way to describe how a specific
purpose device makes use of Internet resources and associated
suggested network behavior. The behaviors are described in a MUD
file hosted in its manufacturer's server. The device provides a MUD
URL to the MUD controller, which can locate this MUD file and
determine the required network authorization of the device.
In some cases, e.g., the firmware update, the network behaviors of
the device may change, and the description in the original MUD file
will no longer apply. To solve this problem, there are two common
ways which the manufacturer can use.
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One is to change what is in the MUD file, i.e., update the MUD file
in place, whenever the behavior of the firmware changes. Section 3
discusses three scenarios for updating the MUD file and the
corresponding potential issues.
The other is to change which MUD file is processed by changing the
MUD URL. Section 4 describes the common sources of MUD URLs and the
problems and threats faced by each type of source when updating the
MUD URL. This document proposes an enhanced mechanism of how to
securely update the MUD URL in Section 5.
There are also some assumptions and prerequisites in this document.
While MUD files may include signatures, [RFC8520] does not mandate
checking them, and there is not a clear way to connect the entity
which signed the MUD file to the device itself. This document limits
itself to situations in which the MUD file is signed, and that the
MUD controller has been configured to always check the signatures,
rejecting files whose signatures do not match.
[RFC8520] does not specify how MUD controllers establish their trust
in the manufacturers' signing key: there are many possible solutions
from manual configuration of trust anchors, some kind of automatic
configuration during onboarding, or a Trust on First Use (TOFU)
mechanism that accepts the signer on first use. How this initial
trust is established is not important for this document, it is
sufficient that some satisfactory initial trust is established.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Possible issues with updating the MUD files in place
Three scenarios for updating the MUD file and the corresponding
potential issues are discussed below.
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3.1. Adding capabilities
For situations where new capabilities are added to the firmware, the
MUD file will detail the new access that the new firmware requires.
This may involve new incoming or outgoing connections that should be
authorized. Devices that have been upgraded to the new firmware will
make use of the new features. Devices that have not been upgraded to
the new firmware may have new connections that are authorized, but
which the device does not use (outgoing connections), or which the
device is not prepared to respond to (new incoming connections).
It is possible that older versions of the firmware have
vulnerabilities that were not easily exploitable due to the MUD file
preventing particular kinds of access. For example, an older
firmware could have no credentials required (or default credentials)
access via telnet on port 23 or HTTP on port 80. The MUD file
protected the device such that it could either not be accessed at
all, or access was restricted to connections from a controller only.
Useful and needed upgrades to the firmware could add credentials to
that service, allowing it to be opened up for more general access.
The new MUD file would provide for such access, but when combined
with the weak security of the old firmware, it results in a
compromised device.
While there is an argument that old firmware was insecure and should
be replaced, it is often the case that the upgrade process involves
downtime, or can introduce risks due to needed evaluations not having
been completed yet. As an example: moving vehicles (cars, airplanes,
etc.) should not perform upgrades while in motion! It is probably
undesirable to perform any upgrade to an airplane outside the service
facility. A vehicle owner may desire only to perform software
upgrades when they are at their residence. Should there be a
problem, they could make alternate arrangements for transportation.
This contrasts with an alternative situation where the vehicle is
parked at, for instance, a remote cabin, and where an upgrade failure
could cause a much greater inconvenience.
The situation for upgrades of medical devices has even more
considerations involving regulatory compliance.
3.2. Removing capabilities
For situations where existing capabilities prove to be a problem and
are to be turned off or removed in subsequent versions of the
firmware, the MUD file will be updated to disallow connections that
previously were allowed.
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In this case, the new MUD file will forbid some connections, which
the old firmware still expects to do. As explained in the previous
section, upgrades may not always occur immediately upon releasing the
new firmware.
In this case, the old device will be performing unwanted connections,
and the MUD controller will be alerting the network owner that the
device is misbehaving rather than not being upgraded. This causes a
false-positive situation (see [boycrieswolf]), leading to real
security issues being ignored. This is a serious issue as documented
also in [boywolfinfosec], and [falsemalware].
3.3. Significant changes to protocols
[I-D.ietf-opsawg-mud-tls] suggests MUD definitions to allow
examination of TLS protocol details. Such a profile may be very
specific to the TLS library which is shipped in a device. Changes to
the library (including bug fixes) may cause significant changes to
the profile, requiring changes to the profile described in the MUD
file. Such changes are likely neither forward nor backward
compatible with other versions, and in place updates to MUD files are
therefore not advised.
3.4. Motivation for updating MUD URLs
While many small tweaks to a MUD file can be done in place, the
situation described above, particularly when it comes to removing
capabilities will suggest that changes to the MUD URL are in order.
A strategy for doing this securely is needed, and the rest of this
document provides a mechanism to do this securely.
4. Updating the MUD URLs
MUD URLs can come from a number of sources:
* IDevID Extensions
* DHCP option
* LLDP TLV
* [I-D.richardson-mud-qrcode] proposes to scan them from QRcodes.
The IDevID mechanism provides a URL that is asserted
cryptographically by a manufacturer. However, it is difficult for
manufacturers to update the IDevID of a device which is already in a
box.
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The DHCP and LLDP mechanisms are not signed, but are asserted by the
device. A firmware update may update what MUD URL is emitted.
Sufficiently well targeted malware would also be able to change the
MUD URL that is emitted.
The QRcode mechanism is usually done via paper/stickers, and is
typically not under the control of the device itself at all.
However, being applied by a human and not easily changed, a MUD URL
obtained in this fashion is likely as trustworthy as the rest of the
vendors packaging. (It may not, due to mixups in labeling represent
the correct device, but this is a human coordination issue, and is
out of scope for this document.)
The manufacturer can use all the four mechanisms above when
manufacturing the device. But when considering updating the
firmware, it seems like only the DHCP and LLDP mechanisms are
sufficiently easy to send the new MUD URL. Because of that
sensitivity, they may also be easily changed by malware!
There are mitigating mechanisms which may be enough to deal with this
problem when MUD files are signed by the manufacturer.
[RFC8520], Section 13.2 explains how to verify MUD File Signatures.
That document does not define a way for a MUD controller to determine
who should sign the MUD file for a particular device.
[RFC8520] leaves this for a local policy. This document establishes
one such local policy. There are a number of other processes that
could be used, it is expected that many such industrial vertical will
work out supply chain arrangements or other heuristics to supply
appropriate anchors.
4.1. Leveraging the manufacturer signature
The first time a signature of the MUD file related to a particular
device-type is verified by the MUD controller, the identity of the
signing authority is recorded. That it, the signing authority is
pinned. This policy means that subsequent MUD files must be signed
by the same entity in order to be accepted.
The trust and acceptance of the first signer may come from many
sources. The first signature could be from a manually configured
trust anchor in the MUD controller. The first signature could be
Trust on First Use (TOFU), with the URL coming from a trusted IDevID
certificate.
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Based upon this process, an update to the MUD URL would be valid if
the new MUD file was signed by the same entity that signed the
previous entry. This mechanism permits a replacement URL to be any
URL that the same manufacturer can provide.
4.2. Concerns about same-signer mechanism
There is still a potential threat: a manufacturer which has many
products may have a MUD definition for another product that has the
privileges that the malware desires.
The malware could simply change the expressed MUD URL to that of the
other product, and it will be accepted by the MUD controller as
valid.
This works as long as manufacturers use a single key to sign all
products. Some manufacturers could sign each product with a
different key. Such manufacturers would probably then collect all
the signing keys into a certificate infrastructure (PKI), with a
single manufacturer CA key.
In this case, the question then becomes whether the MUD controller
should pin the End-Entity (EE) certificate, or the CA certificate.
Pinning the End-Entity (EE) certificate defends against malware that
changes the product type, but prevents the manufacturer from being
able to cycle the validity of the End-Entity certificate for
cryptographic hygiene reasons.
Pinning the CA certificate allows the EE certificate to change, but
may not defend against product type changes.
It is possible to invent policy mechanisms that would link the EE
certificate to a value that is in the MUD file. This could be a
policy OID, or could involve some content in a subjectAltName.
Future work could go in that direction. This document proposes a
simpler solution.
5. Proposed mechanism for updating MUD URLs
The document proposes to limit what MUD URLs are considered valid
from the device, limiting new MUD URLs to be variations of the
initial (presumed to be secure) URL.
The first MUD file which is defined for a device can come from an
IDevID (which is considered more secure), or via Trust on First Use
with DHCP or LLDP or other mechanisms. This first, initially
trusted, MUD file will be called the "root" MUD file.
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A MUD file contains a self-referential MUD-URL attribute that points
to the MUD file itself located on the vendor's website. While the
IDevID, DHCP and LLDP mechanisms only transmit a URL, there are some
newer, not yet standardized proposals that would fetch an entire MUD
file from the device, such as [I-D.jimenez-t2trg-mud-coap].
The MUD-URL MUST always be an Absolute URI: see [RFC3986] section
4.3.
The URL found in the MUD-URL attribute is to be called the canonical
MUD URL for the device.
The MUD-SIGNATURE attribute in the MUD file SHOULD be a relative URI
(see [RFC3986] section 4.2) with the (hierarchical) base URI for this
reference being the MUD-URL attribute.
When pinning the signature, the MUD manager SHOULD pin the lowest
Certification Authority (CA) that was used in the validation of the
CMS structure, along with the chain of Subject Names leading to the
signature. The MUD manager may need additional trust anchors
(including previously pinned ones) in order to verify that CA
certificate.
5.1. Small Changes to the MUD URL
Subsequent MUD files are considered valid if:
* they have the same initial Base-URI as the MUD-URL, but may have a
different final part
* they are signed by an equivalent End Entity (same trusted CA and
same Subject Name) as the "root" MUD file.
Section 5.2 of [RFC3986] details many cases for calculating the Base-
URI.
Section 3.3 of [RFC3986] explains how the different parts of the URL
are described. As explained in that section, a _path_ component
consists of a series of _segment_ seperated by slash ("/")
characters. The new URL is considered acceptable if it contains the
same series of segments in its path, excepting that the last segment
may be different.
For a simple example, if the canonical MUD-URL is
http://example.com/hello/there/file.json then any URL that starts
with http://example.com/hello/there/ would be acceptable, such as
http://example.com/hello/there/revision2.json.
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One problem with these small changes is that malware could still
express a MUD file that was previously valid, but which should no
longer considered accurate. This is a rollback attack. This might
result in the malware being able to reach destinations that turned
out to be a mistake; a security fault. In order to combat this, MUD
managers SHOULD keep track of the list of MUD-URLs that they have
successfully retrieved, and if a device ever suggests a URL that was
previously used, then the MUD manager should suspect that is a
rollback attack. MUD managers are not typically resource
constrained, and while the list of URLs could grow without bound, it
is unlikely to be a burden. A site with thousands of similar devices
could keep a common list of URLs.
5.2. Big Changes to the MUD URL
Once a new MUD file is accepted, either by reloading an existing file
from the same URL, or via the Small Changes mechanism described
above, then the MUD-URL attribute in this file becomes the new
canonical MUD file. The contained MUD-URL attribute in the file need
not be related in any way to the existing MUD-URL.
As a result, any subsequent updates MUST be relative to the new MUD-
URL in this file.
This rule enables the location of the MUD file to change over time
based upon the needs of the organization.
5.3. Merger, Acquisitions and Key Changes
The above process allows for a manufacturer to rework its file
structure. They can change web server host names, so long as they
retain the old structure long enough for all devices to upgrade at
least once.
The process also allows a manufacturer to change the EE certificate
and Certification Authority used for signing.
5.3.1. Changing file structure
A manufacturer has been hosting a MUD file at
https://example.com/household/products/mudfiles/toaster.json and
wishes to move it to https://example.com/mudfiles/toasters/model1945/
mud.json
The manufacturer creates a new MUD file at the new location.
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Then the manufacturer changes the MUD-URL contained with the files at
the old location to have a value of
https://example.com/mudfiles/toasters/model1945/mud.json. Note that
in order for MUD controllers to reload the old file, it MUST have
been served with an appropriate ETag, and appropriate Expires or
Cache Control headers [RFC9111], Section 5.3. If control over
caching is not possible for the manufacturer, then they need to do
this in two steps, with the first step creating a new MUD file at an
acceptable location (in the above example, perhaps:
https://example.com/household/products/mudfiles/toaster0.json ). The
device then will have to do two firmware updates: one to switch to
the intermediate URL, and a second one to switch to the desired final
URL.
The manufacturer must continue to serve the files from the old
location for some time, or to return an HTTP 301 (Moved Permanently)
redirecting to the new location.
5.3.2. Changing hosting URLs
A manufacturer has been hosting a MUD file at
https://example.com/household/products/mudfiles/toaster.json and
wishes to move it to https://mud.example/hosthold/products/mudfiles/
toaster.json
The scenario is much the same as for Section 5.3.1, and can be
handled in the same fashion. This situation is likely to occur when
one company acquires another.
Note, however, that a 301 Redirect that changed the hostname SHOULD
NOT be accepted by MUD controllers.
5.3.3. Changing Signing Authority
A manufacturer has been signing MUD files using an EE Certificate
with subjectAltName foo.example, issued by an internal Certification
Authority BAZ.
The manufacturer wishes to begin signing with an EE Certificate with
subjectAltname foo.example, but now signed by a public CA (call it:
Fluffy).
The manufacturer first creates a new MUD file with a new detached
signature file. Within this signature file, the manufacturer places
a certificate chain: Internal-CA BAZ->Fluffy, and then the Fluffy
Certificate, and then the foo.example certificate issued from Fluffy.
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This supports changing certification authorities, but it does not
support changing the Subject Name of the signing entity.
6. Polling for changes in MUD files
The MUD file update mechanisms described in Section 3 requires that
the MUD controller poll for updates. The MUD controller will receive
no signal about a change from the device because the URL will not
have changed.
The manufacturer SHOULD serve MUD files from a source for which ETag
Section 2.3 of [RFC7232] may be generated. Static files on disk
satisfy this requirement. MUD files generated from a database
process might not. The use of ETag allows a MUD controller to more
efficiently poll for changes in the file.
A manufacturer should also serve MUD files with an HTTP Max-Age
header as per Section 5.2.2.8 of [RFC7234].
The MUD controller should take the Max-Age as an indication of when
to next poll for updates to the MUD file. Values of less than 1
hour, or more than 1 month should be considered out of range, and
clamped into the range (1 hour, 1 month).
MUD controllers SHOULD add some random jitter to the timing of their
requests. MUD controllers MAY use a single HTTP(S)/1.1 connection to
retrieve all resources at the same destination.
7. Privacy Considerations
The MUD URL could contain sensitive information such as the model
number and even firmware revision numbers. Thus, the MUD URL may
identify the make, model and revision of a device.
[RFC8520] already identifies this privacy concern, and suggests use
of TLS so that the HTTP requests that retrieve the MUD file do not
divulge that level of detail.
The requirement for the MUD controller to poll for changes to MUD
files results in multiple interactions between the MUD controller and
the manufacturer whereas a more naive implementation might only
interact once. Even if HTTPS used, an observer of the traffic to
that manufacturer will be revealing, and [RFC8520] goes on to suggest
use of a proxy as well.
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8. IANA Considerations
This document makes no requests to IANA.
9. Security Considerations
Prior to the standardization of the process in this document, if a
device was infiltrated by malware, and said malware wished to make
accesses beyond what the current MUD file allowed, the malware would
have to:
1. arrange for an equivalent MUD file to be visible somewhere on the
Internet
2. depend upon the MUD controller either not checking signatures, or
3. somehow get the manufacturer to sign the alternate MUD file
4. announce this new URL via DHCP or LLDP, updating the MUD
controller with the new permissions.
One way to accomplish (3) is to leverage the existence of MUD files
created by the manufacturer for different classes of devices. Such
files would already be signed by the same manufacturer, eliminating
the need to spoof a signature.
With the standardization of the process in this document, then the
attacker can no longer point to arbitrary MUD files in step 4, but
can only make use of MUD files that the manufacturer has already
provided for this device.
Manufacturers are advised to maintain an orderly layout of MUD files
in their web servers, with each unique product having its own
directory/pathname.
The process described updates only MUD controllers and the processes
that manufacturers use to manage the location of their MUD files.
A manufacturer which has not managed their MUD files in the way
described here can deploy new directories of per-product MUD files,
and then can update the existing MUD files in place to point to the
new URLs using the MUD-URL attribute.
There is therefore no significant flag day: MUD controllers may
implement the new policy without significant concern about backwards
compatibility.
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9.1. Updating files vs Updating MUD URLs
Device developers need to consider whether to make a change by
updating a MUD file, or updating the MUD URL.
MUD URLs can only be updated by shipping a new firmware. It is
reasonable to update the MUD URL whenever a new firmware release
causes new connectivity to be required. The updated mechanism
defined in this document makes this a secure operation, and there is
no practical limitation on the number of files that a web server can
hold.
In place updates to a MUD file should be restricted to cases where it
turns out that the description was inaccurate: a missing connection,
an inadvertent one authorized, or just incorrect information.
Developers should be aware that many enterprise websites use
outsourced content distribution networks, and MUD controllers are
likely to cache files for some time. Changes to MUD files will take
some time to propagate through the various caches. An updated MUD
URL will however, not experience any cache issues, but can not be
deployed with a firmware update.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8520] Lear, E., Droms, R., and D. Romascanu, "Manufacturer Usage
Description Specification", RFC 8520,
DOI 10.17487/RFC8520, March 2019,
<https://www.rfc-editor.org/info/rfc8520>.
10.2. Informative References
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[boycrieswolf]
"The Boy Who Cried Wolf", 18 January 2020,
<https://fablesofaesop.com/the-boy-who-cried-wolf.html>.
[boywolfinfosec]
"Security Alerts - A Case of the Boy Who Cried Wolf?", 18
January 2020, <https://www.infosecurity-
magazine.com/opinions/security-alerts-boy-cried-wolf/>.
[falsemalware]
"False malware alerts cost organizations $1.27M annually,
report says", 18 January 2020,
<https://www.scmagazine.com/home/security-news/false-
malware-alerts-cost-organizations-1-27m-annually-report-
says/ and http://go.cyphort.com/Ponemon-Report-Page.html>.
[I-D.ietf-opsawg-mud-tls]
Reddy.K, T., Wing, D., and B. Anderson, "Manufacturer
Usage Description (MUD) (D)TLS Profiles for IoT Devices",
Work in Progress, Internet-Draft, draft-ietf-opsawg-mud-
tls-13, 23 January 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-opsawg-
mud-tls-13>.
[I-D.jimenez-t2trg-mud-coap]
Jimenez, J., "Using MUD on CoAP environments", Work in
Progress, Internet-Draft, draft-jimenez-t2trg-mud-coap-00,
9 March 2020, <https://datatracker.ietf.org/doc/html/
draft-jimenez-t2trg-mud-coap-00>.
[I-D.richardson-mud-qrcode]
Richardson, M., Latour, J., and H. H. Gharakheili,
"Loading Manufacturer Usage Description (MUD) URLs from QR
Codes", Work in Progress, Internet-Draft, draft-
richardson-mud-qrcode-07, 21 March 2022,
<https://datatracker.ietf.org/doc/html/draft-richardson-
mud-qrcode-07>.
[RFC7232] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Conditional Requests", RFC 7232,
DOI 10.17487/RFC7232, June 2014,
<https://www.rfc-editor.org/info/rfc7232>.
[RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
RFC 7234, DOI 10.17487/RFC7234, June 2014,
<https://www.rfc-editor.org/info/rfc7234>.
Richardson, et al. Expires 2 September 2024 [Page 14]
Internet-Draft mud-acceptable-urls March 2024
[RFC9111] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Caching", STD 98, RFC 9111,
DOI 10.17487/RFC9111, June 2022,
<https://www.rfc-editor.org/info/rfc9111>.
Appendix A. Appendices
Contributors
Jie Yang
Email: jay.yang@huawei.com
Tianqing Tang
Email: tangtianqing@huawei.com
Authors' Addresses
Michael Richardson
Sandelman Software Works
Email: mcr+ietf@sandelman.ca
Wei Pan
Huawei Technologies
Email: william.panwei@huawei.com
Eliot Lear
Cisco Systems
Email: lear@cisco.com
Richardson, et al. Expires 2 September 2024 [Page 15]
