Manufacturer Usage Description SpecificationCisco SystemsRichtistrasse 7WallisellenCH-8304Switzerland+41 44 878 9200lear@cisco.comGoogle355 Main St., 5th FloorCambridge+1 978 376 3731rdroms@gmail.com+972 54 5555347dromasca@gmail.comInternet-DraftThis memo specifies a component-based architecture for manufacturer
usage descriptions (MUD). The goal of MUD is to provide a means for
end devices to signal to the network what sort of access and network
functionality they require to properly function. The initial focus is
on access control. Later work can delve into other aspects.This memo specifies two YANG modules, IPv4 and IPv6 DHCP options, an
LLDP TLV, a URL, an X.509 certificate extension and a means to sign
and verify the descriptions.The Internet has largely been constructed for general purpose
computers, those devices that may be used for a purpose that is
specified by those who own the device. presumed that an
end device would be most capable of protecting itself. This made
sense when the typical device was a workstation or a mainframe, and it
continues to make sense for general purpose computing devices today,
including laptops, smart phones, and tablets. discusses design patterns for, and poses questions about,
smart objects. Let us then posit a group of objects that are
specifically not intended to be used for general purpose computing
tasks. These devices, which this memo refers to as Things, have a
specific purpose. By definition, therefore, all other uses are not
intended. If a small number of communication patterns follows from
those small number of uses, the combination of these two statements
can be restated as a manufacturer usage description (MUD) that can be
applied at various points within a network. MUD primarily addresses
threats to the device rather than the device as a threat. In some
circumstances, however, MUD may offer some protection in the latter
case, depending on the MUD-URL is communicated, and how devices and
their communications are authenticated.We use the notion of “manufacturer” loosely in this context to refer
to the entity or organization that will state how a device is intended
to be used. For example, in the context of a lightbulb, this might
indeed be the lightbulb manufacturer. In the context of a smarter
device that has a built in Linux stack, it might be an integrator of
that device. The key points are that the device itself is assumed to
serve a limited purpose, and that there exists an organization in
the supply chain of that device that will take responsibility for
informing the network about that purpose.The intent of MUD is to provide the following:Substantially reduce the threat surface on a device to those
communications intended by the manufacturer.Provide a means to scale network policies to the ever-increasing
number of types of devices in the network.Provide a means to address at least some vulnerabilities in a way
that is faster than the time it might take to update systems. This will be
particularly true for systems that are no longer supported.Keep the cost of implementation of such a system to the bare minimum.Provide a means of extensibility for manufacturers to express other
device capabilities or requirements.MUD consists of three architectural building blocks:A URL that can be used to locate a description;The description itself, including how it is interpreted, and;A means for local network management systems to retrieve the description.MUD is most effective when the network is able to identify in some way
the remote endpoints that Things will talk to.In this specification we describe each of these building blocks and how
they are intended to be used together. However, they may also be used
separately, independent of this specification, by local deployments
for their own purposes.MUD is not intended to address network authorization of general
purpose computers, as their manufacturers cannot envision a specific
communication pattern to describe. In addition, even those devices
that have a single or small number of uses might have very broad
communication patterns. MUD on its own is not for them either.Although MUD can provide network administrators with some additional
protection when device vulnerabilities exist, it will never replace the
need for manufacturers to patch vulnerabilities.Finally, no matter what the manufacturer specifies in a MUD file,
these are not directives, but suggestions. How they are instantiated
locally will depend on many factors and will be ultimately up to the
local network administrator, who must decide what is appropriate in
a given circumstances.A light bulb is intended to light a room. It may be remotely
controlled through the network, and it may make use of a rendezvous
service of some form that an application on a smart phone. What we can
say about that light bulb, then, is that all other network access is
unwanted. It will not contact a news service, nor speak to the
refrigerator, and it has no need of a printer or other devices. It
has no social networking friends. Therefore, an access list applied
to it that states that it will only connect to the single rendezvous
service will not impede the light bulb in performing its function,
while at the same time allowing the network to provide both it and
other devices an additional layer of protection.
manufacturer usage description.
a file containing YANG-based JSON that describes a Thing and associated suggested specific network behavior.
a web server that hosts a MUD file.
the system that requests and receives the MUD file from the MUD
server. After it has processed a MUD file, it may direct changes to
relevant network elements.
a synonym that has been used in the past for MUD manager.
a URL that can be used by the MUD manager to receive the MUD file.
the device emitting a MUD URL.
the entity that configures the Thing to emit the MUD URL and the one
who asserts a recommendation in a MUD file. The manufacturer
might not always be the entity that constructs a Thing. It could,
for instance, be a systems integrator, or even a component provider.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 when, and only when, they
appear in all capitals, as shown here.The notion of intended use is in itself not new. Network
administrators apply access lists every day to allow for only such
use. This notion of white listing was well described by Chapman and
Zwicky in . Profiling systems that make use of heuristics
to identify types of systems have existed for years as well.A Thing could just as easily tell the network what sort of access it
requires without going into what sort of system it is. This would, in
effect, be the converse of . In seeking a general
solution, however, we assume that a device will implement
functionality necessary to fulfill its limited purpose. This is basic
economic constraint. Unless the network would refuse access to such a
device, its developers would have no reason to provide the network any
information. To date, such an assertion has held true.Our work begins with the device emitting a Universal
Resource Locator (URL) . This URL serves both to
classify the device type and to provide a means to locate a policy
file.MUD URLs MUST use the HTTPS scheme .In this memo three means are defined to emit the MUD URL, as follows:A DHCP option, that the DHCP client uses to inform
the DHCP server. The DHCP server may take further actions, such as
act as the MUD manager or otherwise pass it along to the MUD manager.An X.509 constraint. The IEEE has developed that
provides a certificate-based approach to communicate device characteristics,
which itself relies on . The MUD URL extension is
non-critical, as required by IEEE 802.1AR. Various means may be used
to communicate that certificate, including Tunnel Extensible
Authentication Protocol (TEAP) .Finally, a Link Layer Discovery Protocol (LLDP) frame is defined .It is possible that there may be other means for a MUD URL to be
learned by a network. For instance, some devices may already be
fielded or have very limited ability to communicate a MUD URL, and yet
can be identified through some means, such as a serial number or a
public key. In these cases, manufacturers may be able to map those
identifiers to particular MUD URLs (or even the files themselves).
Similarly, there may be alternative resolution mechanisms available
for situations where Internet connectivity is limited or does not
exist. Such mechanisms are not described in this memo, but are
possible. Implementors are encouraged to allow for this sort of
flexibility of how MUD URLs may be learned.MUD managers that are able to do so SHOULD retrieve MUD URLs and
signature files as per , using the GET method .
They MUST validate the certificate using the rules in ,
Section 3.1.Requests for MUD URLs SHOULD include an “Accept” header (,
Section 5.3.2) containing “application/mud+json”, an “Accept-Language”
header field (, Section 5.3.5), and a “User-Agent” header
(, Section 5.5.3).MUD managers SHOULD automatically process 3xx response status codes.If a MUD manager is not able to fetch a MUD URL, other means MAY
be used to import MUD files and associated signature files. So long
as the signature of the file can be validated, the file can be used.
In such environments, controllers SHOULD warn administrators when
cache-validity expiry is approaching so that they may check for new
files.It may not be possible for a MUD manager to retrieve a MUD file at any
given time. Should a MUD manager fail to retrieve a MUD file, it
SHOULD consider the existing one safe to use, at least for a time.
After some period, it SHOULD log that it has been unable to retrieve
the file. There may be very good reasons for such failures, including
the possibility that the MUD manager is in an off-line environment,
the local Internet connection has failed, or the remote Internet
connection has failed. It is also possible that an attacker is
attempting to interfere with the deployment of a device. It is a
local decision as to how to handle such circumstances.When the MUD URL is resolved, the MUD manager retrieves a file that
describes what sort of communications a device is designed to have.
The manufacturer may specify either specific hosts for cloud based
services or certain classes for access within an operational network.
An example of a class might be “devices of a specified manufacturer
type”, where the manufacturer type itself is indicated simply by the
authority component (e.g, the domain name) of the MUD URL. Another
example might be to allow or disallow local access. Just like other
policies, these may be combined. For example:Allow access to devices of the same manufacturerAllow access to and from controllers via Constrained Application
Protocol (COAP)Allow access to local DNS/NTPDeny all other accessA printer might have a description that states:Allow access for port IPP or port LPDAllow local access for port HTTPDeny all other accessIn this way anyone can print to the printer, but local access would
be required for the management interface.The files that are retrieved are intended to be closely aligned to
existing network architectures so that they are easy to deploy. We
make use of YANG because it provides accurate and adequate
models for use by network devices. JSON is used as a serialization
format for compactness and readability, relative to XML. Other formats may
be chosen with later versions of MUD.While the policy examples given here focus on access control, this is
not intended to be the sole focus. By structuring the model described
in this document with clear extension points, other
descriptions could be included. One that often comes to mind is
quality of service.The YANG modules specified here are extensions of
. The extensions to this model allow for
a manufacturer to express classes of systems that a manufacturer would
find necessary for the proper function of the device. Two modules are
specified. The first module specifies a means for domain names to be
used in ACLs so that devices that have their controllers in the cloud
may be appropriately authorized with domain names, where the mapping
of those names to addresses may rapidly change.The other module abstracts away IP addresses into certain classes that
are instantiated into actual IP addresses through local processing.
Through these classes, manufacturers can specify how the device is
designed to communicate, so that network elements can be configured by
local systems that have local topological knowledge. That is, the
deployment populates the classes that the manufacturer specifies. The
abstractions below map to zero or more hosts, as follows:
A device made by a particular manufacturer, as identified by the authority
component of its MUD URL
Devices that have the same authority component of their MUD URL.
Devices that the local network administrator admits to the particular class.
Devices intended to serve as controllers for the MUD-URL that the Thing emitted.
The class of IP addresses that are scoped within some administrative boundary.
By default it is suggested that this be the local subnet.The “manufacturer” classes can be easily specified by the
manufacturer, whereas controller classes are initially envisioned to
be specified by the administrator.Because manufacturers do not know who will be using their devices, it
is important for functionality referenced in usage descriptions to be
relatively ubiquitous and mature. For these reasons the YANG-based
configuration in a MUD file is limited to either the modules specified
or referenced in this document, or those specified in documented
extensions.With these components laid out we now have the basis for an
architecture. This leads us to ASCII art.In the above diagram, the switch or router collects MUD URLs and
forwards them to the MUD manager (a network management system) for
processing. This happens in different ways, depending on how the URL
is communicated. For instance, in the case of DHCP, the DHCP server
might receive the URL and then process it. In the case of IEEE 802.1X
, the switch would carry the URL via a certificate to the
authentication server via EAP over Radius, which would then
process it. One method to do this is TEAP, described in .
The certificate extension is described below.The information returned by the MUD file server is valid for as long
as the Thing is connected. There is no expiry. However, if the MUD
manager has detected that the MUD file for a Thing has changed, it
SHOULD update the policy expeditiously, taking into account whatever
approval flow is required in a deployment. In this way, new
recommendations from the manufacturer can be processed in a timely
fashion.The information returned by the MUD file server (a web server) is
valid for the duration of the Thing’s connection, or as specified in
the description. Thus if the Thing is disconnected, any associated
configuration in the switch can be removed. Similarly, from time to
time the description may be refreshed, based on new capabilities or
communication patterns or vulnerabilities.The web server is typically run by or on behalf of the manufacturer.
Its domain name is that of the authority found in the MUD URL. For
legacy cases where Things cannot emit a URL, if the switch is able to
determine the appropriate URL, it may proxy it. In the trivial case
it may hardcode MUD-URL on a switch port or a map from some
available identifier such as an L2 address or certificate hash to a
MUD-URL.The role of the MUD manager in this environment is to do the
following:receive MUD URLs,fetch MUD files,translate abstractions in the MUD files to specific network element
configuration,maintain and update any required mappings of the abstractions, andupdate network elements with appropriate configuration.A MUD manager may be a component of a AAA or network management
system. Communication within those systems and from those systems to
network elements is beyond the scope of this memo.As mentioned above, MUD contains architectural building blocks, and so
order of operation may vary. However, here is one clear intended
example:Thing emits URL.That URL is forwarded to a MUD manager by the nearest switch
(how this happens depends on the way in which the MUD URL is emitted).The MUD manager retrieves the MUD file and signature from the MUD file
server, assuming it doesn’t already have copies. After validating
the signature, it may test the
URL against a web or domain reputation service, and it may test any hosts within
the file against those reputation services, as it deems fit.The MUD manager may query the administrator for permission to
add the Thing and associated policy. If the Thing is known or
the Thing type is known, it may skip this step.The MUD manager instantiates local configuration based on
the abstractions defined in this document.The MUD manager configures the switch nearest the Thing.
Other systems may be configured as well.When the Thing disconnects, policy is removed.A MUD file consists of a YANG model instance that has been serialized in JSON
. For purposes of MUD, the nodes that can be modified are
access lists as augmented by this model. The MUD file is limited to
the serialization of only the following YANG schema:ietf-access-control-list ietf-mud (this document)ietf-acldns (this document)Extensions may be used to add additional schema. This is described
further on.To provide the widest possible deployment, publishers of MUD files
SHOULD make use of the abstractions in this memo and avoid the use of
IP addresses. A MUD manager SHOULD NOT automatically implement any
MUD file that contains IP addresses, especially those that might have
local significance. The addressing of one side of an access list is
implicit, based on whether it is applied as to-device-policy or
from-device-policy.With the exceptions of “name” of the ACL, “type”, “name” of the ACE, and TCP
and UDP source and destination port information, publishers of MUD
files SHOULD limit the use of ACL model leaf nodes expressed to those
found in this specification. Absent any extensions, MUD files are
assumed to implement only the following ACL model features:match-on-ipv4, match-on-ipv6, match-on-tcp,
match-on-udp, match-on-icmpFurthermore, only “accept” or “drop” actions SHOULD be included. A
MUD manager MAY choose to interpret “reject” as “drop”. A MUD
manager SHOULD ignore all other actions. This is because
manufacturers do not have sufficient context within a local deployment
to know whether reject is appropriate. That is a decision that should
be left to a network administrator.Given that MUD does not deal with interfaces, the support of the
“ietf-interfaces” module is not required. Specifically,
the support of interface-related features and branches (e.g.,
interface-attachment and interface-stats) of the ACL YANG module is
not required.In fact, MUD managers MAY ignore any particular component of a
description or MAY ignore the description in its entirety, and SHOULD
carefully inspect all MUD descriptions. Publishers of MUD files MUST
NOT include other nodes except as described in . See
that section for more information.This module is structured into three parts:The first component, the “mud” container, holds information that is
relevant to retrieval and validity of the MUD file itself, as well
as policy intended to and from the Thing.The second component augments the matching container of the ACL
model to add several nodes that are relevant to the MUD URL, or
otherwise abstracted for use within a local environment.The third component augments the tcp-acl container of the ACL
model to add the ability to match on the direction of initiation of a
TCP connection.A valid MUD file will contain two root objects, a “mud” container and
an “acls” container. Extensions may add additional root
objects as required. As a reminder, when parsing acls,
elements within a “match” block are logically ANDed. In general, a
single abstraction in a match statement should be used. For instance,
it makes little sense to match both “my-controller” and “controller”
with an argument, since they are highly unlikely to be the same value.A simplified graphical representation of the data models is used in
this document. The meaning of the symbols in these diagrams is
explained in .This node specifies the integer version of the MUD specification. This memo
specifies version 1.This URL identifies the MUD file. This is useful when the file and
associated signature are manually uploaded, say, in an offline mode. describes access-lists. In the case of
MUD, a MUD file must be explicit in describing the communication
pattern of a Thing, and that includes indicating what is to be
permitted or denied in either direction of communication. Hence each
of these containers indicates the appropriate direction of a flow in
association with a particular Thing. They contain references to
specific access-lists.This is a date-and-time value of when the MUD file was
generated. This is akin to a version number. Its form is taken from
which, for those keeping score, in turn was taken from
Section 5.6 of , which was taken from .This uint8 is the period of time in hours that a network management
station MUST wait since its last retrieval before checking for an
update. It is RECOMMENDED that this value be no less than 24 and MUST
NOT be more than 168 for any Thing that is supported. This period
SHOULD be no shorter than any period determined through HTTP caching
directives (e.g., “cache-control” or “Expires”). N.B., expiring of
this timer does not require the MUD manager to discard the MUD
file, nor terminate access to a Thing. See for more
information.This boolean is an indication from the manufacturer to the network
administrator as to whether or not the Thing is supported. In this
context a Thing is said to not be supported if the manufacturer
intends never to issue a firmware or software update to the Thing or
never update the MUD file. A MUD manager MAY still periodically check
for updates.This is a textual UTF-8 description of the Thing
to be connected. The intent is for administrators to be able to see a
brief displayable description of the Thing. It SHOULD NOT exceed 60
characters worth of display space.These optional fields are filled in as specified by
. Note that firmware-rev and software-rev
MUST NOT be populated in a MUD file if the device can be upgraded but
the MUD-URL cannot be. This would be the case, for instance, with
MUD-URLs that are contained in 802.1AR certificates.This optional leaf-list names MUD extensions that are used in the MUD
file. Note that MUD extensions MUST NOT be used in a MUD file without
the extensions being declared. Implementations MUST ignore any node
in this file that they do not understand.Note that extensions can either extend the MUD file as described in
the previous paragraph, or they might reference other work. An
extension example can be found in .Note that in this section, when we use the term “match” we are
referring to the ACL model “matches” node.This node consists of a hostname that would be matched against the
authority component of another Thing’s MUD URL. In its simplest form
“manufacturer” and “same-manufacturer” may be implemented as
access-lists. In more complex forms, additional network capabilities
may be used. For example, if one saw the line
“manufacturer” : “flobbidy.example.com”, then all Things that
registered with a MUD URL that contained flobbity.example.com in its
authority section would match.This null-valued node is an equivalent for when the manufacturer
element is used to indicate the authority that is found in another
Thing’s MUD URL matches that of the authority found in this Thing’s
MUD URL. For example, if the Thing’s MUD URL were
https://b1.example.com/ThingV1, then all devices
that had MUD URL with an authority section of b1.example.com would
match.This URI consists of a URL that points to documentation relating to
the device and the MUD file. This can prove particularly useful when
the “controller” class is used, so that its use can be explained.This string matches the entire MUD URL, thus covering the model that
is unique within the context of the authority. It may contain not
only model information, but versioning information as well, and any
other information that the manufacturer wishes to add. The intended
use is for devices of this precise class to match, to permit or
deny communication between one another.This null-valued node expands to include local networks. Its
default expansion is that packets must not traverse toward a default
route that is received from the router. However, administrators may
expand the expression as is appropriate in their deployments.This URI specifies a value that a controller will register with the
MUD manager. The node then is expanded to the set
of hosts that are so registered. This node may also be a URN. In
this case, the URN describes a well known service, such as DNS or
NTP, that has been standardized. Both of those URNs may be found in
.When “my-controller” is used, it is possible that the administrator
will be prompted to populate that class for each and every model. Use
of “controller” with a named class allows the user to populate that
class only once for many different models that a manufacturer may
produce.Controller URIs MAY take the form of a URL (e.g. “http[s]://”).
However, MUD managers MUST NOT resolve and retrieve such files, and
it is RECOMMENDED that there be no such file at this time, as their
form and function may be defined at a point in the future. For now,
URLs should serve simply as class names and may be populated by the
local deployment administrator.Great care should be taken by MUD managers when invoking the
controller class in the form of URLs. For one thing, it requires some
understanding by the administrator as to when it is appropriate.
Pre-registration in such classes by controllers with the MUD server is
encouraged. The mechanism to do that is beyond the scope of this
work.This null-valued node signals to the MUD manager to use whatever
mapping it has for this MUD URL to a particular group of hosts. This may
require prompting the administrator for class members. Future work
should seek to automate membership management.This MUST only be applied to TCP. This matches the direction in which
a TCP connection is initiated. When direction initiated is
“from-device”, packets that are transmitted in the direction of a
thing MUST be dropped unless the thing has first initiated a TCP
connection. By way of example, this node may be implemented in its
simplest form by looking at naked SYN bits, but may also be
implemented through more stateful mechanisms.When applied this matches packets when the flow was initiated in the
corresponding direction. specifies IPv6 guidance best
practices. While that document is scoped specifically to IPv6, its
contents are applicable for IPv4 as well.To keep things relatively simple in addition to whatever definitions
exist, we also apply two additional default behaviors:Anything not explicitly permitted is denied.Local DNS and NTP are, by default, permitted to and from the
Thing.An explicit description of the defaults can be found in .
These are applied AFTER all other explicit rules. Thus, a default
behavior can be changed with a “drop” action.MUD URLs are required to use the HTTPS scheme, in order to establish the
MUD file server’s identity and assure integrity of the MUD file.Any “https://” URL can be a MUD URL. For example:A manufacturer may construct a MUD URL in any way, so long as it makes
use of the “https” schema.This module specifies an extension to IETF-ACL model such that domain
names may be referenced by augmenting the “matches” node.
Different implementations may deploy differing methods to maintain the
mapping between IP address and domain name, if indeed any are needed.
However, the intent is that resources that are referred to using a
name should be authorized (or not) within an access list.The structure of the change is as follows:The choice of these particular points in the access-list model is
based on the assumption that we are in some way referring to
IP-related resources, as that is what the DNS returns. A domain name
in our context is defined in . The augmentations are
replicated across IPv4 and IPv6 to allow MUD file authors the ability
to control the IP version that the Thing may utilize.The following node are defined.The argument corresponds to a domain name of a source as specified by
inet:host. A number of means may be used to resolve hosts. What is
important is that such resolutions be consistent with ACLs required by
Things to properly operate.The argument corresponds to a domain name of a destination as
specified by inet:host See the previous section relating to
resolution.Note when using either of these with a MUD file, because access is
associated with a particular Thing, MUD files MUST NOT contain either
a src-dnsname in an ACL associated with from-device-policy or
a dst-dnsname associated with to-device-policy.This example contains two access lists that are intended to provide
outbound access to a cloud service on TCP port 443.In this example, two policies are declared, one from the Thing and
the other to the Thing. Each policy names an access list that
applies to the Thing, and one that applies from. Within each access
list, access is permitted to packets flowing to or from the Thing
that can be mapped to the domain name of “service.bms.example.com”.
For each access list, the enforcement point should expect that the
Thing initiated the connection.The IPv4 MUD URL client option has the following format:Code OPTION_MUD_URL_V4 (161) is assigned by IANA. len is a single
octet that indicates the length of MUD string in octets. The MUD
string is defined as follows:The entire option MUST NOT exceed 255 octets. If a space follows the
MUD URL, a reserved string that will be defined in future
specifications follows. MUD managers that do not understand this
field MUST ignore it.The IPv6 MUD URL client option has the following format:OPTION_MUD_URL_V6 (112; assigned by IANA).option-length contains the length of the MUDstring, as defined above,
in octets.The intent of this option is to provide both a new Thing classifier
to the network as well as some recommended configuration to the
routers that implement policy. However, it is entirely the purview of
the network system as managed by the network administrator to decide
what to do with this information. The key function of this option is
simply to identify the type of Thing to the network in a structured
way such that the policy can be easily found with existing toolsets.A DHCPv4 client MAY emit a DHCPv4 option and a DHCPv6 client MAY emit
DHCPv6 option. These options are singletons, as specified in
. Because clients are intended to have at most one MUD URL
associated with them, they may emit at most one MUD URL option via
DHCPv4 and one MUD URL option via DHCPv6. In the case where both v4
and v6 DHCP options are emitted, the same URL MUST be used.A DHCP server may ignore these options or take action based on receipt
of these options. When a server consumes this option, it will either
forward the URL and relevant client information (such as the gateway
address or giaddr and requested IP address, and lease length) to a
network management system, or it will retrieve the usage description
itself by resolving the URL.DHCP servers may implement MUD functionality themselves or they may
pass along appropriate information to a network management system or
MUD manager. A DHCP server that does process the MUD URL MUST adhere
to the process specified in and to validate
the TLS certificate of the web server hosting the MUD file. Those
servers will retrieve the file, process it, create and install the
necessary configuration on the relevant network element. Servers
SHOULD monitor the gateway for state changes on a given interface. A
DHCP server that does not provide MUD functionality and has forwarded
a MUD URL to a MUD manager MUST notify the MUD manager
of any corresponding change to the DHCP state of the client
(such as expiration or explicit release of a network address lease).Should the DHCP server fail, in the case when it implements the MUD
manager functionality, any backup mechanisms SHOULD include the MUD
state, and the server SHOULD resolve the status of clients upon its
restart, similar to what it would do, absent MUD manager
functionality. In the case where the DHCP server forwards information
to the MUD manager, the MUD manager will either make use of
redundant DHCP servers for information, or otherwise clear state based
on other network information, such as monitoring port status on a
switch via SNMP, Radius accounting, or similar mechanisms.There are no additional requirements for relays.This section defines an X.509 non-critical certificate extension that
contains a single Uniform Resource Locator (URL) that points to an
on-line Manufacturer Usage Description concerning the certificate
subject. URI must be represented as described in Section 7.4 of .Any Internationalized Resource Identifiers (IRIs) MUST be mapped to
URIs as specified in Section 3.1 of before they are placed
in the certificate extension.The semantics of the URL are defined of this document.The choice of id-pe is based on guidance found in Section 4.2.2 of
:The MUD URL is precisely that: online information about the particular subject.In addition, a separate new element is defined as id-pe-mudsigner.
This contains the subject field of the signing certificate of the MUD
file. When this element is present, the MUD manager MUST process it.
The signature is said to be valid if the certificate chain is
otherwise validated AND the id-pe-mudsigner field in the device
manufacturer certificate is equal to that of that of the subject of
the certificate used to sign the MUD file. If id-pe-mudsigner
is not present, the MUD manager SHOULD generate an exception and
inform the administrator prior to further processing.The purpose of this signature is to make a claim that the MUD file
found on the server is valid for a given device, independent of any
other factors. There are several security considerations below in
.A new content-type id-ct-mud is also defined. While signatures are
detached today, should a MUD file be transmitted as part of a CMS
message, this content-type SHOULD be used.The new extension is identified as follows:While this extension can appear in either an 802.AR manufacturer
certificate (IDevID) or deployment certificate (LDevID), of course it
is not guaranteed in either, nor is it guaranteed to be carried over.
It is RECOMMENDED that MUD manager implementations maintain a table
that maps a Thing to its MUD URL based on IDevIDs.The IEEE802.1AB Link Layer Discovery Protocol (LLDP) is a
one hop vendor-neutral link layer protocol used by end hosts network
Things for advertising their identity, capabilities, and neighbors on
an IEEE 802 local area network. Its Type-Length-Value (TLV) design
allows for ‘vendor-specific’ extensions to be defined. IANA has a
registered IEEE 802 organizationally unique identifier (OUI) defined
as documented in . The MUD LLDP extension uses a subtype
defined in this document to carry the MUD URL.The LLDP vendor specific frame has the following format:where:TLV Type = 127 indicates a vendor-specific TLVlen – indicates the TLV string lengthOUI = 00 00 5E is the organizationally unique identifier of IANAsubtype = 1 (to be assigned by IANA for the MUD URL)MUD URL – the length MUST NOT exceed 255 octetsThe intent of this extension is to provide both a new Thing
classifier to the network as well as some recommended configuration to
the routers that implement policy. However, it is entirely the
purview of the network system as managed by the network administrator
to decide what to do with this information. The key function of this
extension is simply to identify the type of Thing to the network in a
structured way such that the policy can be easily found with existing
toolsets.Hosts, routers, or other network elements that implement this option
are intended to have at most one MUD URL associated with them, so they
may transmit at most one MUD URL value.Hosts, routers, or other network elements that implement this option may
ignore these options or take action based on receipt of these options.
For example they may fill in information in the respective extensions
of the LLDP Management Information Base (LLDP MIB). LLDP operates in a
one-way direction. LLDPDUs are not exchanged as information requests
by one Thing and response sent by another Thing. The other Things do
not acknowledge LLDP information received from a Thing. No specific
network behavior is guaranteed. When a Thing consumes this extension,
it may either forward the URL and relevant remote Thing information to
a MUD manager, or it will retrieve the usage description by
resolving the URL in accordance with normal HTTP semantics.Because MUD files contain information that may be used to configure
network access lists, they are sensitive. To ensure that they have
not been tampered with, it is important that they be signed. We make
use of DER-encoded Cryptographic Message Syntax (CMS) for
this purpose.A MUD file MUST be signed using CMS as an opaque binary object. In
order to make successful verification more likely, intermediate
certificates SHOULD be included. The signature is stored at the
location specified in the MUD file. Signatures are
transferred using content-type “application/pkcs7-signature”.For example:Note: A MUD file may need to be re-signed if the signature expires.Prior to processing the rest of a MUD file the MUD manager MUST
retrieve the MUD signature file by retrieving the value of
“mud-signature” and validating the signature across the MUD file. The
Key Usage Extension in the MUD file signature MUST have the bit
digitalSignature(0) set. A MUD manager MUST cease processing of that
file it cannot validate the chain of trust to a known trust anchor or
if it cannot validate the id-pe-mudsigner field until an administrator
has given approval.The purpose of the signature on the file is to assign accountability
to an entity, whose reputation can be used to guide administrators on
whether or not to accept a given MUD file. It is already common place
to check web reputation on the location of a server on which a file
resides. While it is likely that the manufacturer will be the signer
of the file, this is not strictly necessary, and may not be desirable.
For one thing, in some environments, integrators may install their own
certificates. For another, what is more important is the
accountability of the recommendation, and not just the relationship
between the Thing and the file.An example:Note the additional step of verifying the common trust root.One of our design goals is to see that MUD files are able to be
understood by as broad a cross-section of systems as is possible.
Coupled with the fact that we have also chosen to leverage existing
mechanisms, we are left with no ability to negotiate extensions and a
limited desire for those extensions in any event. A such, a
two-tier extensibility framework is employed, as follows:At a coarse grain, a protocol version is included in a MUD URL.
This memo specifies MUD version 1. Any and all changes are
entertained when this version is bumped. Transition approaches
between versions would be a matter for discussion in future versions.At a finer grain, only extensions that would not incur additional
risk to the Thing are permitted. Specifically, adding nodes to the
mud container is permitted with the understanding that such additions
will be ignored by unaware implementations. Any such extensions
SHALL be standardized through the IETF process, and MUST be named in
the “extensions” list. MUD managers MUST ignore YANG nodes they
do not understand and SHOULD create an exception to be resolved by an
administrator, so as to avoid any policy inconsistencies.Because MUD consists of a number of architectural building blocks, it
is possible to assemble different deployment scenarios. One key
aspect is where to place policy enforcement. In order to protect the
Thing from other Things within a local deployment, policy can be
enforced on the nearest switch or access point. In order to limit
unwanted traffic within a network, it may also be advisable to enforce
policy as close to the Internet as possible. In some circumstances,
policy enforcement may not be available at the closest hop. At that
point, the risk of lateral infection (infection of devices that reside
near one another) is increased to the number of Things that are able
to communicate without protection.A caution about some of the classes: admission of a Thing into the
“manufacturer” and “same-manufacturer” class may have impact on access
of other Things. Put another way, the admission may grow the
access-list on switches connected to other Things, depending on how
access is managed. Some care should be given on managing that
access-list growth. Alternative methods such as additional
network segmentation can be used to keep that growth within reason.Because as of this writing MUD is a new concept, one can expect a
great many devices to not have implemented it. It remains a local
deployment decision as to whether a device that is first connected
should be allowed broad or limited access. Furthermore, as mentioned
in the introduction, a deployment may choose to ignore a MUD policy in
its entirety, but simply taken into account the MUD URL as a
classifier to be used as part of a local policy decision.Finally, please see directly below regarding device lifetimes and use
of domain names.Based on how a MUD URL is emitted, a Thing may be able to lie about
what it is, thus gaining additional network access. This happens when
a device emits a MUD URL using DHCP or LLDP, and is either
inappropriately admitted to a class such as “same-manufacturer” or
given access to a device such as “my-controller”, where such access
would otherwise be disallowed. Whether that is the case will depend
on the deployment. Implementations SHOULD be configurable to disallow
additive access for devices using MUD-URLs that not emitted in a
secure fashion such as in a certificate. Similarly, implementations
SHOULD NOT grant elevated permissions (beyond those of devices
presenting no MUD policy) to devices which do not strongly bind their
identity to their L2/L3 transmissions. When insecure methods are used
by the MUD Manager, the classes SHOULD NOT contain devices that use
both insecure and secure methods, in order to prevent privilege
escalation attacks, and MUST NOT contain devices with the same MUD-URL
that are derived from both strong and weak authentication methods.Devices may forge source (L2/L3) information. Deployments should
apply appropriate protections to bind communications to the
authentication that has taken place. For 802.1X authentication, IEEE
802.1AE (MACsec) is one means by which this may happen.
A similar approach can be used with 802.11i (WPA2) .
Other means are available with other lower layer technologies.
Implementations using session-oriented access that is not
cryptographically bound should take care to remove state when any form
of break in the session is detected.A rogue CA may sign a certificate that contains the same subject name
as is listed in the MUDsigner field in the manufacturer certificate,
thus seemingly permitting a substitute MUD file for a device. There
are two mitigations available: first, if the signer changes, this may
be flagged as an exception by the MUD manager. If the MUD file also
changes, the MUD manager SHOULD seek administrator approval (it should
do this in any case). In all circumstances, the MUD manager MUST
maintain a cache of trusted CAs for this purpose. When such a rogue
is discovered, it SHOULD be removed.Additional mitigations are described below.When certificates are not present, Things claiming to be of a certain
manufacturer SHOULD NOT be included in that manufacturer grouping
without additional validation of some form. This will be relevant
when it makes use of primitives such as “manufacturer” for the purpose
of accessing Things of a particular type. Similarly, network
management systems may be able to fingerprint the Thing. In such
cases, the MUD URL can act as a classifier that can be proven or
disproven. Fingerprinting may have other advantages as well: when
802.1AR certificates are used, because they themselves cannot change,
fingerprinting offers the opportunity to add artifacts to the MUD
string in the form of the reserved field discussed in .
The meaning of such artifacts is left as future work.MUD managers SHOULD NOT accept a usage description for a Thing with
the same MAC address that has indicated a change of the URL authority
without some additional validation (such as review by a network
administrator). New Things that present some form of unauthenticated
MUD URL SHOULD be validated by some external means when they would be
be given increased network access.It may be possible for a rogue manufacturer to inappropriately
exercise the MUD file parser, in order to exploit a vulnerability.
There are three recommended approaches to address this threat. The
first is to validate that the signer of the MUD file is known to and
trusted by the MUD manager. The second is to have a system do a
primary scan of the file to ensure that it is both parseable and
believable at some level. MUD files will likely be relatively small,
to start with. The number of ACEs used by any given Thing should be
relatively small as well. It may also be useful to limit retrieval of
MUD URLs to only those sites that are known to have decent web or
domain reputations.Use of a URL necessitates the use of domain names. If a domain name
changes ownership, the new owner of that domain may be able to provide
MUD files that MUD managers would consider valid. There are a few
approaches that can mitigate this attack. First, MUD managers
SHOULD cache certificates used by the MUD file server. When a new
certificate is retrieved for whatever reason, the MUD manager
should check to see if ownership of the domain has changed. A fair
programmatic approximation of this is when the name servers for the
domain have changed. If the actual MUD file has changed, the
MUD manager MAY check the WHOIS database to see if registration
ownership of a domain has changed. If a change has occurred, or if for
some reason it is not possible to determine whether ownership has
changed, further review may be warranted. Note, this remediation does
not take into account the case of a Thing that was produced long ago
and only recently fielded, or the case where a new MUD manager has
been installed.The release of a MUD URL by a Thing reveals what the Thing is, and
provides an attacker with guidance on what vulnerabilities may be
present.While the MUD URL itself is not intended to be unique to a specific
Thing, the release of the URL may aid an observer in identifying
individuals when combined with other information. This is a privacy
consideration.In addressing both of these concerns, implementors should take into
account what other information they are advertising through mechanisms
such as mDNS, how a Thing might otherwise be identified,
perhaps through how it behaves when it is connected to the network,
whether a Thing is intended to be used by individuals or carry
personal identifying information, and then apply appropriate data
minimization techniques. One approach is to make use of TEAP
as the means to share information with authorized
components in the network. Network elements may also assist in
limiting access to the MUD URL through the use of mechanisms such as
DHCPv6-Shield .There is the risk of the MUD manager itself being spied on to
determine what things are connected to the network. To address this
risk, MUD managers may choose to make use of TLS proxies that they
trust that would aggregate other information.Please note that the security considerations mentioned in Section 4.7
of are not applicable in this case
because the YANG serialization is not intended to be accessed via
NETCONF. However, for those who try to instantiate this model in a
network element via NETCONF, all objects in each model in this draft
exhibit similar security characteristics as
. The basic purpose of MUD is to
configure access, and so by its very nature can be disruptive if used
by unauthorized parties.[ There was originally a registry entry for .well-known suffixes.
This has been removed from the draft and may be marked as deprecated
in the registry. RFC Editor: please remove this comment. ]The following YANG modules are requested to be registered in the “IANA
Module Names” registry:The ietf-mud module:Name: ietf-mudURN: urn:ietf:params:xml:ns:yang:ietf-mudPrefix: ietf-mudRegistrant conact: The IESGReference: [RFCXXXX]The ietf-acldns module:Name: ietf-acldnsURI: urn:ietf:params:xml:ns:yang:ietf-acldnsPrefix: ietf-acldnsRegistrant: the IESGReference: [RFCXXXX]The IANA has allocated option 161 in the Dynamic Host Configuration
Protocol (DHCP) and Bootstrap Protocol (BOOTP) Parameters registry for
the MUD DHCPv4 option, and option 112 for DHCPv6, as described in .IANA is kindly requested to make the following assignments for:o The MUDURLExtnModule-2016 ASN.1 module in the “SMI Security for
PKIX Module Identifier” registry (1.3.6.1.5.5.7.0).o id-pe-mud-url object identifier from the “SMI Security for PKIX
Certificate Extension” registry (1.3.6.1.5.5.7.1).o id-pe-mudsigner object identifier from the “SMI Security for
PKIX Certificate Extension” registry (TBD).o id-ct-mud object identifier from the “SMI Security for S/MIME CMS
Content Type” registry.The use of these values is specified in .The following media-type is defined for transfer of MUD file:IANA is requested to create a new registry for IANA Link Layer
Discovery Protocol (LLDP) TLV subtype values. The recommended policy
for this registry is Expert Review. The maximum number of entries in
the registry is 256.IANA is required to populate the initial registry with the value:LLDP subtype value = 1
(All the other 255 values should be initially marked as ‘Unassigned’.)Description = the Manufacturer Usage Description (MUD) Uniform Resource Locator (URL)Reference = < this document >The following parameter registry is requested to be added in
accordance with The following entries should be added to the “urn:ietf:params:mud” name space:“urn:ietf:params:mud:dns” refers to the service specified by .
“urn:ietf:params:mud:ntp” refers to the service specified by .The IANA is requested to establish a registry of extensions as follows:Each extension MUST follow the rules specified in this specification.
As is usual, the IANA issues early allocations based in accordance
with .The authors would like to thank Einar Nilsen-Nygaard, who
singlehandedly updated the model to match the updated ACL model,
Bernie Volz, Tom Gindin, Brian Weis, Sandeep Kumar, Thorsten Dahm,
John Bashinski, Steve Rich, Jim Bieda, Dan Wing, Joe Clarke, Henk
Birkholz, Adam Montville, Jim Schaad, and Robert Sparks for their
valuable advice and reviews. Russ Housley entirely rewrote
to be a complete module. Adrian Farrel provided the basis
for privacy considerations text. Kent Watsen provided a thorough
review of the architecture and the YANG model. The remaining errors
in this work are entirely the responsibility of the authors.Requirements for Internet Hosts - Application and SupportThis RFC is an official specification for the Internet community. It incorporates by reference, amends, corrects, and supplements the primary protocol standards documents relating to hosts. [STANDARDS-TRACK]Key words for use in RFCs to Indicate Requirement LevelsIn many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.HTTP Over TLSThis memo describes how to use Transport Layer Security (TLS) to secure Hypertext Transfer Protocol (HTTP) connections over the Internet. This memo provides information for the Internet community.UTF-8, a transformation format of ISO 10646ISO/IEC 10646-1 defines a large character set called the Universal Character Set (UCS) which encompasses most of the world's writing systems. The originally proposed encodings of the UCS, however, were not compatible with many current applications and protocols, and this has led to the development of UTF-8, the object of this memo. UTF-8 has the characteristic of preserving the full US-ASCII range, providing compatibility with file systems, parsers and other software that rely on US-ASCII values but are transparent to other values. This memo obsoletes and replaces RFC 2279.Extensible Authentication Protocol (EAP)This document defines the Extensible Authentication Protocol (EAP), an authentication framework which supports multiple authentication methods. EAP typically runs directly over data link layers such as Point-to-Point Protocol (PPP) or IEEE 802, without requiring IP. EAP provides its own support for duplicate elimination and retransmission, but is reliant on lower layer ordering guarantees. Fragmentation is not supported within EAP itself; however, individual EAP methods may support this. This document obsoletes RFC 2284. A summary of the changes between this document and RFC 2284 is available in Appendix A. [STANDARDS-TRACK]Uniform Resource Identifier (URI): Generic SyntaxA Uniform Resource Identifier (URI) is a compact sequence of characters that identifies an abstract or physical resource. This specification defines the generic URI syntax and a process for resolving URI references that might be in relative form, along with guidelines and security considerations for the use of URIs on the Internet. The URI syntax defines a grammar that is a superset of all valid URIs, allowing an implementation to parse the common components of a URI reference without knowing the scheme-specific requirements of every possible identifier. This specification does not define a generative grammar for URIs; that task is performed by the individual specifications of each URI scheme. [STANDARDS-TRACK]Internationalized Resource Identifiers (IRIs)This document defines a new protocol element, the Internationalized Resource Identifier (IRI), as a complement of the Uniform Resource Identifier (URI). An IRI is a sequence of characters from the Universal Character Set (Unicode/ISO 10646). A mapping from IRIs to URIs is defined, which means that IRIs can be used instead of URIs, where appropriate, to identify resources. The approach of defining a new protocol element was chosen instead of extending or changing the definition of URIs. This was done in order to allow a clear distinction and to avoid incompatibilities with existing software. Guidelines are provided for the use and deployment of IRIs in various protocols, formats, and software components that currently deal with URIs.Network Access Control List (ACL) YANG Data ModelThis document defines a data model for Access Control List (ACL). An ACL is a user-ordered set of rules, used to configure the forwarding behavior in device. Each rule is used to find a match on a packet, and define actions that will be performed on the packet.Network Time Protocol Version 4: Protocol and Algorithms SpecificationThe Network Time Protocol (NTP) is widely used to synchronize computer clocks in the Internet. This document describes NTP version 4 (NTPv4), which is backwards compatible with NTP version 3 (NTPv3), described in RFC 1305, as well as previous versions of the protocol. NTPv4 includes a modified protocol header to accommodate the Internet Protocol version 6 address family. NTPv4 includes fundamental improvements in the mitigation and discipline algorithms that extend the potential accuracy to the tens of microseconds with modern workstations and fast LANs. It includes a dynamic server discovery scheme, so that in many cases, specific server configuration is not required. It corrects certain errors in the NTPv3 design and implementation and includes an optional extension mechanism. [STANDARDS-TRACK]Common YANG Data TypesThis document introduces a collection of common data types to be used with the YANG data modeling language. This document obsoletes RFC 6021.Dynamic Host Configuration ProtocolThe Dynamic Host Configuration Protocol (DHCP) provides a framework for passing configuration information to hosts on a TCPIP network. DHCP is based on the Bootstrap Protocol (BOOTP), adding the capability of automatic allocation of reusable network addresses and additional configuration options. [STANDARDS-TRACK]Dynamic Host Configuration Protocol for IPv6 (DHCPv6)Guidelines for Creating New DHCPv6 OptionsThis document provides guidance to prospective DHCPv6 option developers to help them create option formats that are easily adoptable by existing DHCPv6 software. It also provides guidelines for expert reviewers to evaluate new registrations. This document updates RFC 3315.Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and RoutingThe Hypertext Transfer Protocol (HTTP) is a stateless application-level protocol for distributed, collaborative, hypertext information systems. This document provides an overview of HTTP architecture and its associated terminology, defines the "http" and "https" Uniform Resource Identifier (URI) schemes, defines the HTTP/1.1 message syntax and parsing requirements, and describes related security concerns for implementations.DHCPv6-Shield: Protecting against Rogue DHCPv6 ServersThis document specifies a mechanism for protecting hosts connected to a switched network against rogue DHCPv6 servers. It is based on DHCPv6 packet filtering at the layer 2 device at which the packets are received. A similar mechanism has been widely deployed in IPv4 networks ('DHCP snooping'); hence, it is desirable that similar functionality be provided for IPv6 networks. This document specifies a Best Current Practice for the implementation of DHCPv6-Shield.The YANG 1.1 Data Modeling LanguageYANG is a data modeling language used to model configuration data, state data, Remote Procedure Calls, and notifications for network management protocols. This document describes the syntax and semantics of version 1.1 of the YANG language. YANG version 1.1 is a maintenance release of the YANG language, addressing ambiguities and defects in the original specification. There are a small number of backward incompatibilities from YANG version 1. This document also specifies the YANG mappings to the Network Configuration Protocol (NETCONF).JSON Encoding of Data Modeled with YANGThis document defines encoding rules for representing configuration data, state data, parameters of Remote Procedure Call (RPC) operations or actions, and notifications defined using YANG as JavaScript Object Notation (JSON) text.Early IANA Allocation of Standards Track Code PointsThis memo describes the process for early allocation of code points by IANA from registries for which "Specification Required", "RFC Required", "IETF Review", or "Standards Action" policies apply. This process can be used to alleviate the problem where code point allocation is needed to facilitate desired or required implementation and deployment experience prior to publication of an RFC, which would normally trigger code point allocation. The procedures in this document are intended to apply only to IETF Stream documents.Augmented BNF for Syntax Specifications: ABNFInternet technical specifications often need to define a formal syntax. Over the years, a modified version of Backus-Naur Form (BNF), called Augmented BNF (ABNF), has been popular among many Internet specifications. The current specification documents ABNF. It balances compactness and simplicity with reasonable representational power. The differences between standard BNF and ABNF involve naming rules, repetition, alternatives, order-independence, and value ranges. This specification also supplies additional rule definitions and encoding for a core lexical analyzer of the type common to several Internet specifications. [STANDARDS-TRACK]Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) ProfileThis memo profiles the X.509 v3 certificate and X.509 v2 certificate revocation list (CRL) for use in the Internet. An overview of this approach and model is provided as an introduction. The X.509 v3 certificate format is described in detail, with additional information regarding the format and semantics of Internet name forms. Standard certificate extensions are described and two Internet-specific extensions are defined. A set of required certificate extensions is specified. The X.509 v2 CRL format is described in detail along with standard and Internet-specific extensions. An algorithm for X.509 certification path validation is described. An ASN.1 module and examples are provided in the appendices. [STANDARDS-TRACK]Cryptographic Message Syntax (CMS)This document describes the Cryptographic Message Syntax (CMS). This syntax is used to digitally sign, digest, authenticate, or encrypt arbitrary message content. [STANDARDS-TRACK]New ASN.1 Modules for Cryptographic Message Syntax (CMS) and S/MIMEThe Cryptographic Message Syntax (CMS) format, and many associated formats, are expressed using ASN.1. The current ASN.1 modules conform to the 1988 version of ASN.1. This document updates those ASN.1 modules to conform to the 2002 version of ASN.1. There are no bits-on-the-wire changes to any of the formats; this is simply a change to the syntax. This document is not an Internet Standards Track specification; it is published for informational purposes.New ASN.1 Modules for the Public Key Infrastructure Using X.509 (PKIX)The Public Key Infrastructure using X.509 (PKIX) certificate format, and many associated formats, are expressed using ASN.1. The current ASN.1 modules conform to the 1988 version of ASN.1. This document updates those ASN.1 modules to conform to the 2002 version of ASN.1. There are no bits-on-the-wire changes to any of the formats; this is simply a change to the syntax. This document is not an Internet Standards Track specification; it is published for informational purposes.Internet Assigned Numbers Authority (IANA) Procedures for the Management of the Service Name and Transport Protocol Port Number RegistryThis document defines the procedures that the Internet Assigned Numbers Authority (IANA) uses when handling assignment and other requests related to the Service Name and Transport Protocol Port Number registry. It also discusses the rationale and principles behind these procedures and how they facilitate the long-term sustainability of the registry.This document updates IANA's procedures by obsoleting the previous UDP and TCP port assignment procedures defined in Sections 8 and 9.1 of the IANA Allocation Guidelines, and it updates the IANA service name and port assignment procedures for UDP-Lite, the Datagram Congestion Control Protocol (DCCP), and the Stream Control Transmission Protocol (SCTP). It also updates the DNS SRV specification to clarify what a service name is and how it is registered. This memo documents an Internet Best Current Practice.Ambiguity of Uppercase vs Lowercase in RFC 2119 Key WordsRFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.The JavaScript Object Notation (JSON) Data Interchange FormatJavaScript Object Notation (JSON) is a lightweight, text-based, language-independent data interchange format. It was derived from the ECMAScript Programming Language Standard. JSON defines a small set of formatting rules for the portable representation of structured data.This document removes inconsistencies with other specifications of JSON, repairs specification errors, and offers experience-based interoperability guidance.YANG Tree DiagramsThis document captures the current syntax used in YANG module tree diagrams. The purpose of this document is to provide a single location for this definition. This syntax may be updated from time to time based on the evolution of the YANG language.A YANG Data Model for Hardware ManagementThis document defines a YANG data model for the management of hardware on a single server.IEEE Standard for Local and Metropolitan Area Networks-- Station and Media Access Control Connectivity DiscoveryInstitute for Electrical and Electronics EngineersHypertext Transfer Protocol (HTTP/1.1): Semantics and ContentThe Hypertext Transfer Protocol (HTTP) is a stateless \%application- level protocol for distributed, collaborative, hypertext information systems. This document defines the semantics of HTTP/1.1 messages, as expressed by request methods, request header fields, response status codes, and response header fields, along with the payload of messages (metadata and body content) and mechanisms for content negotiation.IAB and IESG Statement on Cryptographic Technology and the InternetIABIESGThe Internet Architecture Board (IAB) and the Internet Engineering Steering Group (IESG), the bodies which oversee architecture and standards for the Internet, are concerned by the need for increased protection of international commercial transactions on the Internet, and by the need to offer all Internet users an adequate degree of privacy. This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind.Date and Time on the Internet: TimestampsAn IETF URN Sub-namespace for Registered Protocol ParametersThis document describes a new sub-delegation for the 'ietf' URN namespace for registered protocol items. The 'ietf' URN namespace is defined in RFC 2648 as a root for persistent URIs that refer to IETF- defined resources. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.Recommended Simple Security Capabilities in Customer Premises Equipment (CPE) for Providing Residential IPv6 Internet ServiceThis document identifies a set of recommendations for the makers of devices and describes how to provide for "simple security" capabilities at the perimeter of local-area IPv6 networks in Internet-enabled homes and small offices. This document is not an Internet Standards Track specification; it is published for informational purposes.The Common Log Format (CLF) for the Session Initiation Protocol (SIP): Framework and Information ModelWell-known web servers such as Apache and web proxies like Squid support event logging using a common log format. The logs produced using these de facto standard formats are invaluable to system administrators for troubleshooting a server and tool writers to craft tools that mine the log files and produce reports and trends. Furthermore, these log files can also be used to train anomaly detection systems and feed events into a security event management system. The Session Initiation Protocol (SIP) does not have a common log format, and, as a result, each server supports a distinct log format that makes it unnecessarily complex to produce tools to do trend analysis and security detection. This document describes a framework, including requirements and analysis of existing approaches, and specifies an information model for development of a SIP common log file format that can be used uniformly by user agents, proxies, registrars, and redirect servers as well as back-to-back user agents.IANA Considerations and IETF Protocol and Documentation Usage for IEEE 802 ParametersSome IETF protocols make use of Ethernet frame formats and IEEE 802 parameters. This document discusses several uses of such parameters in IETF protocols, specifies IANA considerations for assignment of points under the IANA OUI (Organizationally Unique Identifier), and provides some values for use in documentation. This document obsoletes RFC 5342.Tunnel Extensible Authentication Protocol (TEAP) Version 1This document defines the Tunnel Extensible Authentication Protocol (TEAP) version 1. TEAP is a tunnel-based EAP method that enables secure communication between a peer and a server by using the Transport Layer Security (TLS) protocol to establish a mutually authenticated tunnel. Within the tunnel, TLV objects are used to convey authentication-related data between the EAP peer and the EAP server.Architectural Considerations in Smart Object NetworkingThe term "Internet of Things" (IoT) denotes a trend where a large number of embedded devices employ communication services offered by Internet protocols. Many of these devices, often called "smart objects", are not directly operated by humans but exist as components in buildings or vehicles, or are spread out in the environment. Following the theme "Everything that can be connected will be connected", engineers and researchers designing smart object networks need to decide how to achieve this in practice.This document offers guidance to engineers designing Internet- connected smart objects.Port Control Protocol (PCP) Server SelectionThis document specifies the behavior to be followed by a Port Control Protocol (PCP) client to contact its PCP server(s) when one or several PCP server IP addresses are configured.This document updates RFC 6887.A YANG Data Model for Interface ManagementThis document defines a YANG data model for the management of network interfaces. It is expected that interface-type-specific data models augment the generic interfaces data model defined in this document. The data model includes definitions for configuration and system state (status information and counters for the collection of statistics).The YANG data model in this document conforms to the Network Management Datastore Architecture (NMDA) defined in RFC 8342.This document obsoletes RFC 7223.The Constrained Application Protocol (CoAP)The Constrained Application Protocol (CoAP) is a specialized web transfer protocol for use with constrained nodes and constrained (e.g., low-power, lossy) networks. The nodes often have 8-bit microcontrollers with small amounts of ROM and RAM, while constrained networks such as IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs) often have high packet error rates and a typical throughput of 10s of kbit/s. The protocol is designed for machine- to-machine (M2M) applications such as smart energy and building automation.CoAP provides a request/response interaction model between application endpoints, supports built-in discovery of services and resources, and includes key concepts of the Web such as URIs and Internet media types. CoAP is designed to easily interface with HTTP for integration with the Web while meeting specialized requirements such as multicast support, very low overhead, and simplicity for constrained environments.Data elements and interchange formats - Information interchange - Representation of dates and timesInternational Organization for StandardizationGuidelines for Authors and Reviewers of YANG Data Model DocumentsThis memo provides guidelines for authors and reviewers of specifications containing YANG data model modules. Recommendations and procedures are defined, which are intended to increase interoperability and usability of Network Configuration Protocol (NETCONF) and RESTCONF protocol implementations that utilize YANG data model modules. This document obsoletes RFC 6087.Secure Device IdentityInstitute for Electrical and Electronics EngineersIEEE Standard for Local and metropolitan area networks--Port-Based Network Access ControlInstitute for Electrical and Electronics EngineersIEEE Standard for Local and Metropolitan Area Networks- Media Access Control (MAC) SecurityInstitute for Electrical and Electronics EngineersIEEE Standard for information technology-Telecommunications and information exchange between systems-Local and metropolitan area networks-Specific requirements-Part 11- Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications- Amendment 6- Medium Access Control (MAC) Security EnhancementsInstitute for Electrical and Electronics EngineersBuilding Internet FirewallsRFC Editor to remove this section prior to publication.Draft -19:
* Edits after discussion with apps area to address reserved
field for the future.
* Correct systeminfo to be utf8.
* Remove “hardware-rev” from list.Draft -18:
* Correct an error in the augment statement
* Changes to the ACL model re ports.Draft -17:One editorial.Draft -16add mud-signature element based on review commentsredo mud-urlmake clear that systeminfo uses UTF8Draft -13 to -14:Final WGLC comments and review commentsMove version from MUD-URL to ModelHave MUD-URL in modelUpdate based on update to draft-ietf-netmod-acl-modelPoint to tree diagram draft instead of 6087bis.Draft -12 to -13:Additional WGLC commentsDraft -10 to -12:These are based on WGLC comments:Correct examples based on ACL model changes.Change ordering nodes.Additional explanatory text around systeminfo.Change ordering in examples.Make it VERY VERY VERY VERY clear that these are recommendations,
not mandates.DHCP -> NTP in some of the intro text.Remove masa-server“Things” to “network elements” in a few key places.Reference to JSON YANG RFC added.Draft -10 to -11:Example correctionsTypoFix two lists.Addition of ‘any-acl’ and ‘mud-acl’ in the list of allowed features.Clarification of what should be in a MUD file.Draft -09 to -10:AD input.Correct dates.Add compliance sentence as to which ACL module features are implemented.Draft -08 to -09:Resolution of Security Area review, IoT directorate review,
GenART review, YANG doctors review.change of YANG structure to address mandatory nodes.Terminology cleanup.specify out extra portion of MUD-URL.consistency changes.improved YANG descriptions.Remove extra revisions.Track ACL model changes.Additional cautions on use of ACL model; further clarifications
on extensions.Draft -07 to -08:a number of editorials corrected.definition of MUD file tweaked.Draft -06 to -07:Examples updated.Additional clarification for direction-initiated.Additional implementation guidance given.Draft -06 to -07:Update models to match new ACL modelextract directionality from the ACL, introducing a new device container.Draft -05 to -06:Make clear that this is a component architecture (Polk and Watson)Add order of operations (Watson)Add extensions leaf-list (Pritikin)Remove previous-mud-file (Watson)Modify text in last-update (Watson)Clarify local networks (Weis, Watson)Fix contact info (Watson)Terminology clarification (Weis)Advice on how to handle LDevIDs (Watson)Add deployment considerations (Watson)Add some additional text about fingerprinting (Watson)Appropriate references to 6087bis (Watson)Change systeminfo to a URL to be referenced (Lear)Draft -04 to -05:
* syntax error correctionDraft -03 to -04:
* Re-add my-controllerDraft -02 to -03:
* Additional IANA updates
* Format correction in YANG.
* Add reference to TEAP.Draft -01 to -02:
* Update IANA considerations
* Accept Russ Housley rewrite of X.509 text
* Include privacy considerations text
* Redo the URL limit. Still 255 bytes, but now stated in the URL definition.
* Change URI registration to be under urn:ietf:paramsDraft -00 to -01:
* Fix cert trust text.
* change supportInformation to meta-info
* Add an informational element in.
* add urn registry and create first entry
* add default elementsWhat follows is the portion of a MUD file that permits DNS traffic to
a controller that is registered with the URN “urn:ietf:params:mud:dns”
and traffic NTP to a controller that is registered
“urn:ietf:params:mud:ntp”. This is considered the default behavior
and the ACEs are in effect appended to whatever other “ace” entries
that a MUD file contains. To block DNS or NTP one repeats the
matching statement but replaces the “forwarding” action “accept” with
“drop”. Because ACEs are processed in the order they are received,
the defaults would not be reached. A MUD manager might further
decide to optimize to simply not include the defaults when they are
overridden.Four “acl” list entries that implement default MUD nodes are listed
below. Two are for IPv4 and two are for IPv6 (one in each direction
for both versions of IP). Note that neither access-list name nor ace
name need be retained or used in any way by local implementations, but
are simply there for completeness’ sake.In this sample extension we augment the core MUD model to indicate
whether the device implements DETNET. If a device claims not to use
NETNET, but then later attempts to do so, a notification or exception
might be generated. Note that this example is intended only for
illustrative purposes.This extension augments the MUD model to include a single node,
using the following sample module that has the following tree
structure:The model is defined as follows:Using the previous example, we now show how the extension would be
expressed: