wdiff rfc7967.original rfc7967.txt

CoRE
Independent Submission A. Bhattacharyya
Internet Draft
Request for Comments: 7967 S. Bandyopadhyay
Intended status:
Category: Informational A. Pal
Expires: November 2016
ISSN: 2070-1721 T. Bose
Tata Consultancy Services Ltd.
May 12,
August 2016

CoAP option

Constrained Application Protocol (CoAP) Option for no server-response
draft-tcs-coap-no-response-option-17 No Server Response

Abstract

There can be M2M machine-to-machine (M2M) scenarios where responses from a server against
requests from
responses to client requests are redundant. This kind of open-loop
exchange (with no response path from the server to the client) may be
desired to minimize resource consumption in constrained systems while
updating a bulk of many resources simultaneously, simultaneously or updating a resource
with a very high frequency. performing high-frequency
updates. CoAP already provides Non-confirmable (NON) messages that
are not acknowledged by the recipient. However, the request/response
semantics still require the server to respond with a status code
indicating "the result of the attempt to understand and satisfy the request".
request", per RFC 7252.

This specification introduces a CoAP option called 'No-Response'.
Using this option option, the client can explicitly express to the server
its disinterest in all responses against the particular request.
This option also provides granular control to enable expression of
disinterest to a particular class of response class or a combination of
response-classes.
response classes. The server MAY decide to suppress the response by
not transmitting it back to the client according to the value of No-
Response the
No-Response option in the request. This option may be effective for
both unicast and multicast requests. This document also discusses a
few exemplary examples of applications which that benefit from this option.

Status of this This Memo

This Internet-Draft document is submitted in full conformance with not an Internet Standards Track specification; it is
published for informational purposes.

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provisions of BCP 78 and BCP 79.

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Table of Contents

1. Introduction...................................................3 Introduction ....................................................3
1.1. Potential Benefits........................................3 Benefits .........................................4
1.2. Terminology...............................................4 Terminology ................................................4
2. Option Definition..............................................4 Definition ...............................................5
2.1. Granular Control over Response Suppression................5 Suppression .................5
2.2. Method-specific Method-Specific Applicability Consideration...............7 Considerations ...............8
3. Miscellaneous Aspects..........................................8 Aspects ...........................................9
3.1. Re-using Tokens...........................................9 Reusing Tokens .............................................9
3.2. Taking Care of Congestion Control and Server-side Server-Side
Flow
Control.......................................................10 Control ..............................................10
3.3. Considerations Regarding regarding Caching of Responses............11 Responses .............11
3.4. Handling the No-Response Option for a HTTP-to-CoAP
Reverse Proxy
..............................................................11 .............................................11
4. Exemplary Application Scenarios...............................11 Scenarios ..........................................12
4.1. Frequent Update of Geo-location Geolocation from Vehicles to
Backend
Server........................................................11 Server ............................................12
4.1.1. Using No-Response with PUT..........................13 PUT .........................13
4.1.2. Using No-Response with POST.........................13 POST ........................14
4.1.2.1. POST updating Updating a fixed target resource..........13 Fixed Target Resource .....14
4.1.2.2. POST updating Updating through query-string.............14 Query String ........15
4.2. Multicasting Actuation Command from a Handheld Device
to a Group of Appliances...........................................15 Appliances ..................................15
4.2.1. Using Granular Response Suppression.................16 Suppression ................16
5. IANA Considerations...........................................16 Considerations ............................................16
6. Security Considerations.......................................16 Considerations ........................................16
7. Acknowledgments...............................................16
8. References....................................................16
8.1. References .....................................................16
7.1. Normative References.....................................16
8.2. References ......................................16
7.2. Informative References...................................17 References ....................................17
Acknowledgments ...................................................18
Authors' Addresses ................................................18

1. Introduction

This specification defines a new option for the Constrained
Application Protocol (CoAP) [RFC7252] called 'No-Response'. This
option enables clients to explicitly express their disinterests disinterest in
receiving responses back from the server. The disinterest can be
expressed at the granularity of response classes (e.g., 2.xx 2.xx) or the a
combination of classes (e.g., 2.xx and 5.xx). By default default, this
option indicates interest in all response classes. The server MAY
decide to suppress the response by not transmitting it back to the
client according to the value of the No-Response option in the
request.

Along with the technical details details, this document presents some
practical application scenarios which bring out that highlight the usefulness of this
option.

Wherever, in [ITS-LIGHT] and [CoAP-ADAPT] contain the background research
for this document.

In this document, when it is mentioned that a request from a client
is with No-Response No-Response, the intended meaning is that the client
expresses its disinterest for all or some selected classes of
responses.

1.1. Potential Benefits

Use

The use of the No-Response option should be driven by typical
application
requirement requirements and, particularly, characteristics of the
information to be updated. If this option is opportunistically used
in a fitting M2M application application, then the concerned system may benefit
in the following aspects (however, it is to be noted, aspects. (However, note that this option is
elective
elective, and servers can simply ignore the preference expressed by
the client): client.)

* Reduction in network congestion due to effective reduction of
the overall traffic.

* Reduction in server-side load by relieving the server from
responding to each request when requests for which responses are not necessary.

* Reduction in battery consumption at the constrained end-
point(s).
endpoint(s).

* Reduction in overall communication cost.

1.2. Terminology

The terms used in this document are in conformance with those defined
in [RFC7252].

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119. [RFC2119].

2. Option Definition

The properties of the No-Response option are given in Table 1. In
this table, the C, U, N, and R columns indicate the properties
Critical, Unsafe, NoCacheKey, and Repeatable, respectively.

+--------+---+---+---+---+-------------+--------+--------+---------+
| Number | C | U | N | R | Name | Format | Length | Default |
+--------+---+---+---+---+-------------+--------+--------+---------+
| 258 | | X | - | | No-Response | uint | 0-1 | 0 |
+--------+---+---+---+---+-------------+--------+--------+---------+

Table 1: Option Properties

This option is a request option. It is Elective elective and Non-Repeatable. not repeatable.
This option is Unsafe-to-forward Unsafe-to-Forward, as the intermediary MUST know how
to interpret this option. Otherwise Otherwise, the intermediary, without intermediary (without
knowledge about the special unidirectional nature of the request, request)
would wait for responses.

Note: Since CoAP maintains a clear separation between the
request/response and the message sub-layer, this option does not
have any dependency on the type of message (Confirmable/Non-
confirmable).
(Confirmable/Non-confirmable). So, even the absence of a message
sub-layer (ex.
CoAP-over-TCP [I-D.ietf-core-coap-tcp-tls-01]) (e.g., CoAP over TCP [CoAP-TCP-TLS]) should have no
effect on the interpretation of this option. However, considering
the CoAP-over-UDP scenario [RFC7252], NON type of messages are best fitting with suited
to this option, considering option because of the expected benefits
out of it. benefits. Using
No-Response with NON messages gets rid of any kind of reverse traffic
traffic, and the interaction becomes completely
open-loop. open loop.

Using this option with CON type of requests may not serve the desired
purpose if piggybacked responses are triggered. But, in
case if the
server responds with a separate response (which, perhaps, the
client does not care about) about), then this option can be useful.
Suppressing the separate response reduces traffic by one
additional CoAP message in this case.

This option contains values to indicate disinterest in all or a
particular class or combination of classes of responses as described
in the next sub-section. Section 2.1.

2.1. Granular Control over Response Suppression

This option enables granular control over response suppression by
allowing the client to express its disinterest in a typical class or
combination of classes of responses. For example, a client may
explicitly tell the receiver that no response is required unless
something 'bad' happens and a response of class 4.xx or 5.xx is to be
fed back to the client. No response of the class 2.xx is required in
such case.

Note: Section 2.7 of [RFC7390] describes a scheme where a server in
the multicast group may decide on its own to suppress responses
for group communication with granular control. The client does
not have any knowledge about that. However, on the other hand,
the 'No-Response' No-Response option enables the clients client to explicitly inform the
servers about its disinterest in responses. Such explicit control
on the client side may be helpful for debugging network resources.
An example scenario is described in Section 4.2.1.

The server MUST send back responses of the classes for which the
client has not expressed any dis-interest. disinterest. There may be instances
where a server, on its own, decides to suppress responses. An
example is suppression of responses by multicast servers as described
in Section 2.7 of [RFC7390]. If such a server receives a request
with a No-Response option showing 'interest' in specific response
classes (i.e., not expressing disinterest for these options), then
any default behaviour behavior of suppressing response, responses, if present, MUST be
overridden to deliver those responses which that are of interest to the
client.

So, for example, suppose a multicast server suppresses all responses
by default and receives a request with a No-Response option
expressing disinterest in 2.xx (success) responses only. Note that
the option value naturally expresses interest in error responses
4.xx/5.xx 4.xx
and 5.xx in this case. Then Thus, the server must send back a response if
the concerned request caused an error.

The option value is defined as a bit-map bit map (Table 2) to achieve
granular suppression. Its length can be 0 byte (empty value) bytes (empty) or 1 byte.

+-------+-----------------------+---------------------------------+

+-------+-----------------------+-----------------------------------+
| Value | Binary Representation | Description |
+-------+-----------------------+---------------------------------+
+-------+-----------------------+-----------------------------------+
| 0 | <empty> | Interested in all responses. |
+-------+-----------------------+---------------------------------+
+-------+-----------------------+-----------------------------------+
| 2 | 00000010 | Not interested in 2.xx |
| | | responses. |
+-------+-----------------------+---------------------------------+
+-------+-----------------------+-----------------------------------+
| 8 | 00001000 | Not interested in 4.xx |
| | | responses. |
+-------+-----------------------+---------------------------------+
+-------+-----------------------+-----------------------------------+
| 16 | 00010000 | Not interested in 5.xx |
| | | responses. |
+-------+-----------------------+---------------------------------+
+-------+-----------------------+-----------------------------------+

Table 2: Option values Values
The conventions used in deciding the option values are:

1. To suppress an individual class: Set bit number (n-1) starting
from the LSB least significant bit (bit number 0) to suppress all
responses belonging to class n.xx. So,

option value to suppress n.xx class = 2**(n-1). 2**(n-1)

2. To suppress a combination of classes: Set each corresponding bit
according to point 1 above. Example: The option value will be 18
(binary: 00010010) to suppress both 2.xx and 5.xx responses.
This is essentially bitwise OR of the corresponding individual
values for suppressing 2.xx and 5.xx. The "CoAP Response Codes"
registry (Ref. (see Section 12.1.2 of [RFC7252]) defines 2.xx, 4.xx 4.xx,
and 5.xx responses. So, an option value of 26 (binary: 00011010)
will request to suppress all response codes defined in [RFC7252].

Note: When No-Response is used with value 26 in a request request, the client
end-point
endpoint SHOULD cease listening to response(s) against to the particular
request. On the other hand, showing interest in at least one
class of response means that the client end-point endpoint can no longer
completely cease listening activity and must be configured to
listen up to during some application specific time-out period for the
particular request. The client end-point endpoint never knows whether the
present request will be a success or a failure. Thus, for
example, if the client decides to open up the response for errors
(4.xx and 5.xx) 5.xx), then it has to wait for the entire time-out
period -- even for the instances where the request is successful
(and the server is not supposed to send back a response). A point to be noted Note
that in this context is that there may be situations when the response on to
errors might get lost. In such a situation situation, the client would wait up to
during the time-out period but
will would not receive any response. But
However, this should not lead to the
impression to give the client the impression that the
request was necessarily successful. In other words, in this case case,
the client cannot distinguish between response suppression and
message loss. The application designer needs to tackle such this
situation. For example, while performing frequent updates, the
client may strategically interweave requests without No-Response
option into a series of requests with No-Response to check time to time if
periodically that things are fine at the server end and the server
is actively responding.

2.2. Method-specific Method-Specific Applicability Consideration Considerations

The following table provides a ready-reference ready reference on the possible
applicability of this option for all the with four REST methods. This table is prepared in view of
for the type of possible interactions foreseen at the time of
preparing this specification. Capitalization of The key words like from RFC 2119 such as
"SHOULD NOT", etc. etc., deliberately have not been deliberately used in this table as this table is
because it only suggestive. contains suggestions.

+-------------+----------------------------------------------------+
| Method Name | Remarks on applicability Applicability |
+-------------+----------------------------------------------------+
| | This should not be used with a conventional GET |
| | request when the client requests the contents |
| | of a resource. However, this option may be useful |
| | for exceptional cases where GET requests has have side |
| GET | effects. For instance, the proactive 'cancellation'| cancellation |
| | procedure for observing a request [RFC7641] requires |
| | requires a client to issue a GET request with Observe option| the |
| | Observe option set to 1 ('deregister'). In case If it is more |
| | more efficient to use this deregistration instead of |
| | of reactive cancellation (rejecting the next |
| | notification with RST), the client MAY express its |
| | disinterest in the response to such a GET request. |
+-------------+----------------------------------------------------+
| | Suitable for frequent updates (particularly in NON |
| | messages) on existing resources. Might not be |
| | useful when PUT is used to create a new resource as| resource, |
| | as it may be important for the client to know that |
| PUT | the resource creation was actually successful in |
| | order to carry out future actions. Also, it may be | be|
| | important to ensure that a resource was actually |
| | created rather than updating an existing resource. |
+-------------+----------------------------------------------------+
| | If POST is used to update a target resource resource, |
| | then No-Response can be used in the same manner as |
| | in PUT. This option may also be useful while |
| POST | updating through query strings rather than updating|
| | a fixed target resource (see Section 4.1.2.2 for an|
| | example). |
+-------------+----------------------------------------------------+
| | Deletion is usually a permanent action and if action. If the |
| DELETE | client likes wants to ensure that the deletion request |
| | was properly executed executed, then this option should not |
| | be used with the request. |
+-------------+----------------------------------------------------+

Table 3: Suggested applicability Applicability of No-Response for different with REST
methods Methods

3. Miscellaneous Aspects

This section further describes important implementation aspects worth
considering while using the No-Response option. The following
discussion contains guidelines and requirements (derived by combining
[RFC7252], [RFC7390] [RFC7390], and [RFC5405]) for the application developer.

3.1. Re-using Reusing Tokens

Tokens provide a matching criteria between a request and the
corresponding response. The life of a Token starts when it is
assigned to a request and ends when the final matching response is
received. Then Then, the Token can again be re-used. reused. However, a request
with No-Response typically does not have any guaranteed response
path. So, the client has to decide on its own about when it can
retire a Token which that has been used in an earlier request so that the
Token can be reused in a future request. Since the No-Response
option is 'elective', a server which that has not implemented this option
will respond back. This leads to the following two scenarios:

The first scenario is, is when the client is never going to care about
any response coming back or about relating the response to the
original request. In that case case, it MAY reuse the Token value at
liberty.

However, as a second scenario, let us consider that the client sends
two requests where the first request is with No-Response and the
second request, with request (with the same Token, Token) is without No-Response. In this
case
case, a delayed response to the first one can be interpreted as a
response to the second request (client needs a response in the second
case) if the time interval between using the same Token is not long
enough. This creates a problem in the request-response semantics.

The most ideal solution would be to always use a unique Token for
requests with No-Response. But if a client wants to reuse a Token Token,
then in most practical cases the client implementation SHOULD
implement an application specific application-specific reuse time after which it can reuse
the Token. A minimum reuse time for Tokens with a similar expression
as in Section 2.5 of [RFC7390] SHOULD be used:

TOKEN_REUSE_TIME = NON_LIFETIME + MAX_SERVER_RESPONSE_DELAY +
MAX_LATENCY.
MAX_LATENCY

NON_LIFETIME and MAX_LATENCY are defined in Section 4.8.2 of
[RFC7252]. MAX_SERVER_RESPONSE_DELAY has the same interpretation as
in Section 2.5 of [RFC7390] for a multicast request. For a unicast
request, since the message is sent to only one server,
MAX_SERVER_RESPONSE_DELAY means the expected maximum response delay
from the particular server to
which that client that sent the request. For
multicast requests, MAX_SERVER_RESPONSE_DELAY has the same
interpretation as in Section 2.5 of [RFC7390]. So, for multicast it
is the expected maximum server response delay "over all servers that
the client can send a multicast request to". to", per [RFC7390]. This
response delay for a given server includes its specific Leisure
period; where Leisure is defined in Section 8.2 of [RFC7252]. In
general, the Leisure for a server may not be known to the client. A
lower bound for Leisure, lb_Leisure, is defined in [RFC7252], but not
an upper bound as is needed in this case. Therefore Therefore, the upper bound
can be estimated by taking N (N>>1) times the lower bound lb_Leisure:

lb_Leisure = S * G / R

where
S = estimated response size; R = data transfer rate; size
G = group size
estimate) estimate
R = data transfer rate

Any estimate of MAX_SERVER_RESPONSE_DELAY MUST be larger than
DEFAULT_LEISURE
DEFAULT_LEISURE, as defined in [RFC7252].

Note: If it is not possible for the client to get a reasonable
estimate of the MAX_SERVER_RESPONSE_DELAY MAX_SERVER_RESPONSE_DELAY, then the client, to be
safe, SHOULD use a unique Token for each stream of message. messages.

3.2. Taking Care of Congestion Control and Server-side Server-Side Flow Control

This section provides guidelines for basic congestion control.
Better congestion control mechanisms can be designed as future work.

If this option is used with NON messages messages, then the interaction
becomes completely open-loop. Absence open loop. The absence of any feedback from the
server-end affects congestion-control mechanism. mechanisms. In this case case, the
communication pattern maps to the scenario where the application
cannot maintain an RTT estimate as described in Section 3.1.2 of
[RFC5405].Hence, following
[RFC5405]. Hence, per [RFC5405], a 3 seconds 3-second interval is suggested as
the minimum interval between successive updates updates, and it is suggested
to use an even less aggressive rate when possible. However, in case
of more
frequent update rates a higher rate of updates, the application MUST have some knowledge
about the channel channel, and an application developer MUST interweave
occasional closed-loop exchanges (e.g. (e.g., NON messages without No-Response
No-Response, or CON messages) to get an RTT estimate between the
endpoints.

Interweaving requests without No-Response is a MUST in case of an
aggressive request rate for applications where server-side flow
control is necessary. For example, as proposed in [I-D.koster-core-
coap-pubsub], [CoAP-PUBSUB], a
broker MAY return "4.29 Too 4.29 (Too Many Requests" Requests) in order to request a
client to slow down the request rate. Interweaving requests without
No-Response allows the client to listen to such a response.

3.3. Considerations Regarding regarding Caching of Responses

The cacheability of CoAP responses does not depend on the request
method, but it depends on the Response Code. The No-Response option
does not lead to any impact on cacheability of responses. If a
request containing No-Response triggers a cacheable response response, then
the response MUST be cached. However, the response MAY not be
transmitted considering the value of the No-Response option in the
request.

For example, if a request with No-Response triggers a cacheable
response of 4.xx class with Max-Age !=0 not equal to 0, then the response
must be cached. The cache will return the response to subsequent
similar requests without No-Response as long as the Max-Age is has not
elapsed.

3.4. Handling the No-Response Option for a HTTP-to-CoAP Reverse Proxy

A HTTP-to-CoAP reverse proxy MAY translate an incoming HTTP request
to a corresponding CoAP request indicating that no response is
required (showing disinterest in all classes of responses) based on
some application specific application-specific requirement. In this case case, it is
RECOMMENDED that the reverse proxy generates generate an HTTP response with
status code 204 (No Content) when such response is allowed. The
generated response is sent after the proxy has successfully sent out
the CoAP request.

In case

If the reverse proxy applies No-Response for particular
class(es) one or more classes of response(s)
responses, it will wait for responses up to an
application specific application-specific
maximum time (T_max) before responding back to the HTTP-side. HTTP side. If a
response of a desired class is received within
T_max T_max, then the
response gets translated to HTTP as defined in [I-
D.ietf-core-http-mapping]. However [HTTP-to-CoAP].
However, if the proxy does not receive any response within T_max, it
is RECOMMENDED that the reverse Proxy
sends send an HTTP response with
status code 204 (No Content) when allowed for the specific HTTP
request method.

4. Exemplary Application Scenarios

This section describes some exemplary examples of application scenarios which that
may potentially benefit from the use of the No-Response option.

4.1. Frequent Update of Geo-location Geolocation from Vehicles to Backend Server

Let us consider an intelligent traffic system (ITS) consisting of
vehicles equipped with a sensor-gateway sensor gateway comprising sensors like GPS
and Accelerometer. accelerometer sensors. The sensor-gateway sensor gateway acts as a CoAP client.
It connects to the Internet using a low-bandwidth cellular (e.g. GPRS)
connection. connection
(e.g., General Packet Radio Service (GPRS)). The GPS co-ordinates coordinates of
the vehicle are periodically updated to the backend server.

While performing frequent location update, updates, retransmitting (through
the CoAP CON mechanism) a location co-ordinate which coordinate that the vehicle has
already left in the meantime is not efficient as it adds redundant traffic to the
network. Therefore, the updates are done using NON messages.
However, given the huge number of vehicles updating frequently, the
NON exchange will also trigger a huge number of responses from the
backend. Thus Thus, the cumulative load on the network will be quite
significant. Also, the client in this case may not be interested in
getting responses against to location update request requests for
the a location it has
already crossed in the meantime passed and a when the next location update is imminent.

On the contrary, if the client end-points endpoints on the vehicles explicitly
declare that they do not need any status response back from the
server
server, then load will be reduced significantly. The assumption is
that, since
that the update high rate is high, of updates will compensate for the stray losses in geo-location
reports will be compensated with the large update rate.
geolocation reports.

Note: It may be argued that the above example application can also be
implemented using the Observe option ([RFC7641]) [RFC7641] with NON
notifications. But, in practice, implementing with Observe would
require lot of book-keeping bookkeeping at the data-collection end-point data collection endpoint at the
backend (observer). The observer needs to maintain all the
observe relationships with each vehicle. The data collection end-
point
endpoint may be unable to know all its data sources beforehand.
The client end-points endpoints at vehicles may go offline or come back
online randomly. In the case of Observe Observe, the onus is always on
the data collection end-point endpoint to establish an observe relationship
with each data-source. data source. On the other hand, implementation will be
much simpler if the initiative initiating is left on to the data-source data source to carry out
updates using the No-Response option. Another way of looking at
it
is, is that the implementation choice depends on the perspective of where there is
interest to initiate the update. In an Observe scenario scenario, the
interest is expressed by the data-consumer. On the contrary, data consumer. In contrast, the
classic update case applies when the interest is from the data- data
producer. The 'No-Response' No-Response option enables to make makes classic updates further consume
even less resource consuming.

Following resources.

The following subsections illustrate some exemplary sample exchanges based on
the application described above.

4.1.1. Using No-Response with PUT

Each vehicle is assigned a dedicated resource "vehicle-stat-<n>",
where <n> can be any string uniquely identifying the vehicle. The
update requests are sent over using NON type of messages. The No-Response option
causes the server not to respond back.

Figure 1: Exemplary unreliable update Example of Unreliable Update with No-Response option using
PUT. Option
Using PUT

4.1.2. Using No-Response with POST

4.1.2.1. POST updating Updating a fixed target resource Fixed Target Resource

In this case case, POST acts the same way as PUT. The exchanges are the
same as above. The updated values are carried as payload of POST as
shown in Figure 2.

Figure 2: Exemplary unreliable update Example of Unreliable Update with No-Response option using Option
Using POST as the update-method. Update Method

4.1.2.2. POST updating Updating through query-string Query String

It may be possible that the backend infrastructure deploys a
dedicated database to store the location updates. In such a case case,
the client can update through a POST by sending a query string in the
URI. The query-string query string contains the name/value pairs for each update.
'No-Response'
No-Response can be used in the same manner as for updating fixed
resources. The scenario is depicted in Figure 3.

Figure 3: Exemplary unreliable update Example of Unreliable Update with No-Response option using Option
Using POST with a query-string to insert update information Query String to backend
database. Insert Update Information
into the Backend Database

4.2. Multicasting Actuation Command from a Handheld Device to a Group
of Appliances

A handheld device (e.g. (e.g., a smart phone) may be programmed to act as
an IP enabled IP-enabled switch to remotely operate on a single one or group of IP
enabled more IP-enabled
appliances. For example, a multicast request to switch on/
off on/off all
the lights of a building can be sent. In this case case, the IP switch
application can use the No-Response option in a NON request message
to reduce the traffic generated due to simultaneous CoAP responses
from all the lights.

Thus

Thus, No-Response helps in reducing overall communication cost and
the probability of network congestion in this case.

4.2.1. Using Granular Response Suppression

The IP switch application may optionally use granular response
suppression such that the error responses are not suppressed. In
that case case, the lights which that could not execute the request would
respond back and be readily identified. Thus, explicit suppression
of option classes by the multicast client may be useful to debug the
network and the application.

5. IANA Considerations

The IANA has had previously assigned number 284 to this option in the
CoAP
"CoAP Option Numbers Registry. Numbers" registry. IANA is requested to change has updated this as shown
below:

+--------+--------------+----------------------------+

+--------+--------------+-------------+
| Number | Name | Reference |
+--------+--------------+----------------------------+
+--------+--------------+-------------+
| 258 | No-Response | Section 2 of this document RFC 7967 |
+--------+--------------+----------------------------+
+--------+--------------+-------------+

6. Security Considerations

The No-Response option defined in this document presents no security
considerations beyond those in Section 11 of the base CoAP
specification [RFC7252].

7. Acknowledgments

Thanks to Carsten Bormann, Matthias Kovatsch, Esko Dijk, Bert
Greevenbosch, Akbar Rahman and Klaus Hartke for their valuable
inputs.

8. References

8.1.

7.1. 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,
<http://www.rfc-editor.org/info/rfc2119>.

[RFC7252] Shelby, Z., Hartke, K. K., and C. Bormann, C.,"Constrained "The Constrained
Application Protocol (CoAP)", RFC 7252, June, 2014

8.2.
DOI 10.17487/RFC7252, June 2014,
<http://www.rfc-editor.org/info/rfc7252>.

7.2. Informative References

[RFC7641]

Hartke, K.," Observing Resources in the Constrained Application
Protocol (CoAP)", RFC 7641, September, 2015

[RFC7390]

Rahman, A. and Dijk, E.,"Group Communication for CoAP", RFC 7390,
October, 2014

[RFC5405]

Eggert, L. and Fairhurst, G.," Unicast UDP Usage Guidelines for
Application Designers", RFC 5405, November, 2008

[I-D.ietf-core-http-mapping]

Castellani,

[CoAP-ADAPT]
Bandyopadhyay, S., Bhattacharyya, A., et al., "Guidelines and A. Pal,
"Adapting protocol characteristics of CoAP using sensed
indication for HTTP-CoAP Mapping
Implementations", draft-ietf-core-http-mapping-09, April 6, 2016

[I-D.koster-core-coap-pubsub] vehicular analytics", 11th ACM Conference
on Embedded Networked Sensor Systems (SenSys '13),
DOI 10.1145/2517351.2517422, November 2013.

[CoAP-PUBSUB]
Koster, M., et al., "Publish-Subscribe Keranen, A., and J. Jimenez, "Publish-
Subscribe Broker for the Constrained Application Protocol
(CoAP)", draft-koster-core-coap-pubsub-04,
November 5, 2015

[I-D.ietf-core-coap-tcp-tls-01] Work in Progress, draft-koster-core-coap-
pubsub-05, July 2016.

[CoAP-TCP-TLS]
Bormann, C., et al., "A TCP Lemay, S., Tschofenig, H., Hartke, K.,
Silverajan, B., and B. Raymor, Ed., "CoAP (Constrained
Application Protocol) over TCP, TLS, and WebSockets", Work
in Progress, draft-ietf-core-coap-tcp-tls-04, August 2016.

[HTTP-to-CoAP]
Castellani, A., Loreto, S., Rahman, A., Fossati, T., and TLS Transport
E. Dijk, "Guidelines for the Constrained
Application Protocol (CoAP)", draft-ietf-core-coap-tcp-tls-01,
November 19, 2015

[Mobiquitous 2013] HTTP-to-CoAP Mapping
Implementations", Work in Progress, draft-ietf-core-http-
mapping-13, July 2016.

[ITS-LIGHT]
Bhattacharyya, A., Bandyopadhyay, S. S., and A. Pal, A.,
"ITS-light: Adaptive lightweight scheme to resource
optimize intelligent transportation tracking system (ITS)-Customizing (ITS)
- Customizing CoAP for opportunistic optimization", 10th
International Conference on Mobile and Ubiquitous Systems:
Computing, Networking and Services
(Mobiquitous (MobiQuitous 2013), December,
DOI 10.1007/978-3-319-11569-6_58, December 2013.

[Sensys 2013]

Bandyopadhyay, S., Bhattacharyya, A.

[RFC5405] Eggert, L. and Pal, G. Fairhurst, "Unicast UDP Usage Guidelines
for Application Designers", BCP 145, RFC 5405,
DOI 10.17487/RFC5405, November 2008,
<http://www.rfc-editor.org/info/rfc5405>.

[RFC7390] Rahman, A., "Adapting protocol
characteristics of CoAP using sensed indication Ed., and E. Dijk, Ed., "Group Communication
for vehicular
analytics", 11th ACM Conference on Embedded Networked Sensor Systems
(Sensys 2013), November, 2013. the Constrained Application Protocol (CoAP)", RFC
7390, DOI 10.17487/RFC7390, October 2014,
<http://www.rfc-editor.org/info/rfc7390>.

[RFC7641] Hartke, K., "Observing Resources in the Constrained
Application Protocol (CoAP)", RFC 7641,
DOI 10.17487/RFC7641, September 2015,
<http://www.rfc-editor.org/info/rfc7641>.

Acknowledgments

Thanks to Carsten Bormann, Matthias Kovatsch, Esko Dijk, Bert
Greevenbosch, Akbar Rahman, and Klaus Hartke for their valuable
input.

Authors' Addresses

Abhijan Bhattacharyya
Tata Consultancy Services Ltd.
Kolkata, India

Email: abhijan.bhattacharyya@tcs.com

Soma Bandyopadhyay
Tata Consultancy Services Ltd.
Kolkata, India

Email: soma.bandyopadhyay@tcs.com

Arpan Pal
Tata Consultancy Services Ltd.
Kolkata, India

Email: arpan.pal@tcs.com

Tulika Bose
Tata Consultancy Services Ltd.
Kolkata, India

Email: tulika.bose@tcs.com