Adaptive RESTful Real-time Live Streaming for Things (A-REaLiST)
draft-bhattacharyya-core-a-realist-01
The information below is for an old version of the document.
| Document | Type |
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|---|---|---|---|
| Authors | Abhijan Bhattacharyya , Suvrat Agrawal , Hemant Kumar Rath , Arpan Pal | ||
| Last updated | 2019-02-04 | ||
| RFC stream | (None) | ||
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draft-bhattacharyya-core-a-realist-01
CoRE A. Bhattacharyya
Internet Draft S. Agrawal
Intended status: Standards Track H. Rath
Expires: August 2019 A. Pal
B. Purushothaman
TATA CONSULTANCY SERVICES LTD.
February 4, 2019
Adaptive RESTful Real-time Live Streaming for Things (A-REaLiST)
draft-bhattacharyya-core-a-realist-01
Abstract
This draft presents extensions to Constrained Application Protocol (CoAP) to
enable RESTful Real-time Live Streaming for improving the Quality of Experience
(QoE) for delay-sensitive Internet of Things (IoT) applications. The overall
architecture is termed ''Adaptive RESTful Real-time Live Streaming for Things (A-
REaLiST)''. It is particularly designed for applications which rely on real-time
augmented vision through live First Person View (FPV) feed from constrained remote
agents like Unmanned Aerial Vehicle (UAV), etc. These extensions provide the
necessary hooks to help solution designers ensure low-latency transfer of streams
and, for contents like video, a quick recovery from freeze and corruption without
incurring undue lag. A-REaLiST is an attempt to provide an integrated approach to
maintain the balance amongst QoE, resource-efficiency and loss resilience. It
provides the necessary hooks to optimize system performance by leveraging
contextual intelligence inferred from instantaneous information segments in
flight. These extensions equip CoAP with a standard for efficient RESTful
streaming for Internet of Things (IoT) contrary to HTTP-streaming in conventional
Internet.
Status of this Memo
This Internet-Draft is submitted in full conformance with the provisions of BCP 78
and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Task Force
(IETF), its areas, and its working groups. Note that other groups may also
distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months and may be
updated, replaced, or obsoleted by other documents at any time. It is
inappropriate to use Internet-Drafts as reference material or to cite them other
than as "work in progress."
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Internet-Drafts are working documents of the Internet Engineering Task Force
(IETF), its areas, and its working groups. Note that other groups may also
distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months and may be
updated, replaced, or obsoleted by other documents at any time. It is
inappropriate to use Internet-Drafts as reference material or to cite them other
than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
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http://www.ietf.org/shadow.html
This Internet-Draft will expire on August 4, 2019.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the document authors.
All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating
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warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction ..................................................... 3
2. Revisiting CoAP................................................... 4
2.1. Some Interesting Aspects of CoAP ................................ 4
2.2. The Prevalent Approaches for Streaming over Internet ............... 5
2.3. CoAP as the Best of Two Worlds ................................. 5
3. The Approach behind A-REaLiST ....................................... 5
3.1. Optional Context Aware Semantic Switch ........................... 5
4. The Options Introduced ............................................. 6
5. The Handshake and Exchange Semantics ................................. 8
5.1. Initial Negotiation........................................... 8
5.2. Renegotiation............................................... 10
6. Some Design Guidelines ............................................ 12
6.1. Implicit Congestion Avoidance ................................. 12
6.2. Considerations for Consumer-side Rendering ...................... 12
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7. IANA Considerations .............................................. 13
8. Security Considerations ........................................... 13
9. References ...................................................... 13
9.1. Normative References ......................................... 13
9.2. Informative References ....................................... 14
1. Introduction
IoT emerged to facilitate exchange of frequent-but-small sensory information
amongst numerous constrained sensors [IOT-ISOC][RFC7452]. However, recent trends
in industry and research community realize the importance of live visual data as
important sensory information. There are many discourses available to support this
observation [Murphy]. Live First Person View (FPV) from Unmanned Aerial Vehicles
(UAV) and dumb robot terminals are being used for futuristic remote control and
actuation applications for Augmented Reality (AR), Visual Simultaneous
Localization and Mapping (VSLAM), UAV based surveillance, etc. Efficacy of these
applications depends on resource-efficient, low-latency, yet high QoE transfer of
the FPV over the Internet (or IP networks in general). Contrary to the traditional
video streaming applications, the UAV-like end-points (henceforth referred as
'video producer') that capture and transmit the FPV are resource constrained
devices. Moreover, the producer may work in a lossy environment marred with
fluctuating radio connectivity and disruptions due network congestion.
The QoE considerations of the video rendering unit (henceforth referred as 'video
consumer') for these applications are quite different from traditional
applications. For example, in case of highly delay sensitive AR applications, a
human brain may not tolerate a noticeable video freeze or delayed reception, which
might have been overlooked for usual content delivery service like a YouTube
video. Such delay may result in wrong actuation. For example, delayed FPV from a
UAV may lead to wrong control commands leading to catastrophic consequences. In
addition, the communication should be as light-weight as possible to optimize the
usage of on-board computing and energy resources of the UAV. So, real-time video
transmissions for IoT applications require special treatment [Pereira]. However,
as revealed through a detail analysis of the state-of-the-art in the next section,
the existing solutions do not address such special requirements. This draft
attempts to bridge this important gap by extending CoAP [RFC7252].
To realize its purpose, the A-REaLiST architecture relies on [RFC7967] and adds
few new header options which, taken together, can be conceived to form a
conceptual 'Stream' extension on CoAP (Fig. 1).
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+----------------------+
| Application |
+----------------------+ ----
| Stream | \
|----------------------| \ |CoAP
| Requests/Responses | | |extended
|----------------------| | CoAP |for
| Messages | | / A-REaLiST
+----------------------+ / ----
+----------------------+
| UDP |
+----------------------+
Figure 1: Abstract extended layering of CoAP for A-REaLiST with the conceptual
layer for streaming.
Though primarily designed for video streaming, these extensions can also be used
to allow streaming of time-series information on CoAP.
Note: Block-wise transfer [RFC7959] is a standardized extension to CoAP for
transferring large application data. The cited use case for this is to perform
firmware upgrade for a large number of constrained devices. Block-wise
transfer is primarily concerned with reliable delivery of information. It
works in synchronized manner. If a message remains unacknowledged despite
retransmissions then the whole exchange is cancelled. So, it is not suitable
for real-time delivery [GIoTS] which is requirement for many time-series
information streams including video.
2. Revisiting CoAP
2.1. Some Interesting Aspects of CoAP
( i) CoAP allows both confirmable (CON) and non-confirmable (NON) messaging.
( ii) CON mode enables CoAP with an option for reliable RESTful delivery like HTTP
[RFC2616]on TCP. On the other hand, intelligent use of No-Response option
[RFC7967] along with NON mode can create an RTP like best-effort messaging on
UDP.
(iii) Context based switching between the reliable and best-effort semantics can
be executed from the end-application level. This way an optimum balance
between reliability delay-performance can be maintained to improve the overall
Quality of Experience (QoE).
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( iv) The base CoAP specification is inherently designed for resource constrained
devices. Hence, a streaming protocol using the stateless RESTful semantics on
CoAP makes the solution inherently lightweight. So, unlike conventional
approach the designers can use a single stack that is equally efficient for
sending the small data out of sensors, as well as, infinite visual stream.
2.2. The Prevalent Approaches for Streaming over Internet
The two prevalent approaches for streaming over the Internet are as below.
First approach is to send the information segment over HTTP which uses the
reliability feature of the underlying Transmission Control Protocol (TCP)
transport. In this case TCP state-machine puts more emphasis on reliable delivery
of segments rather than maintaining the real-time deadlines. However, this is
right now the prevalent approach as it treats video and other streams as general
Internet traffic. So, streaming can seamlessly co-exist with the existing Internet
architecture. Also, since TCP takes care of ordered delivery, the end-application
does not need to worry about these matters.
The other approach is to use a specialized protocol like Real-time Transport
Protocol (RTP) [RFC3550]. It treats video and other real-time streams as a special
type of traffic. To ensure real-time delivery, the data is delivered in best-
effort manner on top of UDP. So, reliable delivery is undermined.
2.3. CoAP as the Best of Two Worlds
It can be conjectured, tallying the above with previous section, that CoAP
inherently imbibes the functional features from HTTP-on-TCP (reliable delivery)
and RTP-on-UDP (best-effort delivery). Further CoAP allows the switching between
these two seamlessly just by maneuvering the header options.
3. The Approach behind A-REaLiST
The design stems from the principles of ''progressive download'' on top of the
RESTful request/response semantics of CoAP. The ''producer'' chunks the continuous
information stream into segments as per the agreed maximum payload size suggested
in [RFC7252]. Each chunk is transmitted as a CoAP request to a given resource at
the ''consumer''. This draft provides the necessary header extensions that enable
the ''consumer'' to maintain the sequence of the information segments in time and
space.
3.1. Optional Context Aware Semantic Switch
Before forming the CoAP message for each segment, the streaming application may
use a real-time analytics module (henceforth referred as 'analytics module') which
may provide inference to the ''Stream'' layer to decide the exchange semantics for
the current segment. The message is sent reliably (CON message) or as best-effort
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(NON message with No-Response option) based on the segment's information
criticality. Criticality is measured in terms of importance of the segment-content
in reconstruction of the frames at the consumer. However, determination of
criticality can be done on many aspects involving several application features
like the source encoding type, the rendering logic at the consumer, etc. This way
the over-all balance between QoE and resource-consumption may be maintained. Fig.
2 explains the idea with conceptual blocks. The overall concept and its efficacy
has been explained with experimental results in [Wi-UAV-Globecom]
+----------------------+
| Application | Information segment ---------
+----------------------+ ====================> |Real-time|
| Stream | <==================== |Analytics|
|----------------------| Reliable/ ---------
| Requests/Responses | Best-effort?
|----------------------|
| Messages |
+----------------------+
Figure 2: Illustrating the concept for context aware switching
Some examples are:
Example-1: Temporally compressed videos like MPEG consist of Group of Pictures
(GoP) which comprises I-frames (Intra-frames) or key-frames, P-frames
(Predicted frames) and B-frames (Bidirectional frames). Out of these 3 types
of frames I-frames are most critical in terms of synchronizing with the GoP at
the receiver end for successful rendering. So, an analytics module at the
''video producer'' end may infer each information segments of I-frames as
critical and send those segments reliably. The segments corresponding to P and
B frames may be transferred as best-effort requests.
Example-2: Let us consider a Motion JPEG (MJPEG) stream. In this case all the
frames are independent JPEG frames and there is no temporal compression. The
analytics module may treat the segments containing MJPEG meta-data for each
frame as critical segments and transfer them through reliable messaging. Rest
of the segments may be transferred as best-effort requests. An intelligent
rendering engine at the ''consumer'' application may compensate for / conceal
any possible loss of non-meta-data (non-critical) segments using the reliably
received meta-data and rest of the non-meta-data segments received through
best-effort. This way high QoE can be ensured despite reduced resource usage.
4. The Options Introduced
To achieve the purpose of the Stream layer, three new protocol header options have
been proposed as below:
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1) Stream_info: Consumes one unsigned byte. It maintains the stream identity and
indicates the present phase of exchange. It is both a request and response
option. It has two fields. The 3-LSBs indicate the state of exchange
(Stream_state) and 5-MSBs indicate an identifier (Stream_id) for the stream.
The identifier remains unchanged for the entire stream. So,
Stream_id = Stream_info >> 3;
Stream_ state = Stream_info & 0x7.
Interpretation of Stream_state bits are :
000=> stream initiation (always with request);
001=> initiation accepted (always with response);
010=> initiation rejected (always with response);
011=> stream re-negotiation (with request or response);
100=> stream ongoing.
2) Time-stamp: It consumes 32-bit unsigned integer. It is a request option. It
relates a particular application information segment to the corresponding
frame in the play sequence.
3) Position: It consumes 16-bit unsigned integer. It is a request option and MUST
be accompanied with the Time-stamp option. It is a combination of two fields.
The 15-MSBs indicate the ''offset'' at which the present segment is placed in
the frame corresponding to the given timestamp. The LSB indicates if the
current segment is the last segment of the frame corresponding to the given
timestamp. Hence,
Last_segment = Position &0x01 ? True : False;
Offset = (Position >> 1).
+-----+---+---+---+---+--------------+--------+--------+---------+
| No. | C | U | N | R | Name | Format | Length | Default |
+-----+---+---+---+---+--------------+--------+--------+---------+
| TBD | X | | - | | Stream-info | uint | 1 | (none) |
+-----+---+---+---+---+--------------+--------+--------+---------+
| TBD | X | | - | | Time-stamp | uint | 4 | (none) |
+-----+---+---+---+---+--------------+--------+--------+---------+
| TBD | X | | - | | Position | uint | 2 | (none) |
+-----+---+---+---+---+--------------+--------+--------+---------+
Table 1: Option Properties
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5. The Handshake and Exchange Semantics
As per the design considerations in view of the scenarios conceived at present,
video transfer is initiated by the ''producer'' which acts as the client.
Note: The design considerations are driven by the experiences drawn from the
applications where live video feeds are transmitted from battery operated
constrained ''video producers'' like UAVs and dumb robotic terminals, etc. For
example, while a fixed infrastructure system is using streamed FPV feed from UAVs,
there may be situations where each time a UAV is low on resources (energy and
computation, a new UAV with better state of resources (fresh battery, etc.) is
commissioned. The overall operation becomes simple if the newly commissioned UAV
readily starts its job by streaming to the same resource at the fixed
infrastructure. It can be easily configured to determine whether the consumer is
up and watching by observing the responses to the CON requests. In case the
exchange is initiated by the consumer then whenever a new UAV is commissioned, the
consumer has to re-initiate the request again.
Each segment is transmitted to the ''video consumer'' as a POST request. The Time-
stamp and Position options help sequential ordering of the segments at the
consumer.
5.1. Initial Negotiation
Initial negotiations for frame rate, video type, encoding details, etc., are
performed by exchanging configuration scripts (cbor or json) over POST request.
Exact format of the script is application dependent and is not part of this draft.
Fig. 3 illustrates the exemplary exchanges related to handshakes for connection
initiation.
Note: All reliable transfers are in blocking mode. So, the producer MUST wait to
send any further segment (critical/ on-critical) till the response is received for
the critical segment. Please refer to Section 6 for suggested behavior in case a
reliable transfer fails.
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Client (Producer) Server (Consumer)
| |
| POST: CON; |
| URI=/video; |
| Stream-info = <5-bit ID>000; |
| Payload= CBOR or JSON |\
+------------------------------------------------->| |
| | |Stream
| ACK; | |negotiation
| Response = 2.04 CHANGED | |
| Steam-info = <5-bit ID>001 | |
|<-------------------------------------------------|/
: :
: :
|(First segment of an MJPEG frame. Contains |
| meta-data. Critical segment needs reliable |
| delivery.) |
| |
| POST: CON; |
| URI=/video; |
| Stream-info = <5-bit ID>100; |
| Time-stamp = <time_stamp_of_this_frame>; |
| Position = 0; |
| Payload= <Bytes_in_1st segment> |\
+------------------------------------------------->| |
| | |
| ACK; | |
| Response = 2.04 CHANGED | |
| Steam-info = <5-bit ID>100 | |
|<-------------------------------------------------| |
|(Second segment of an MJPEG frame. Contains | |
| non-meta-data. Non-critical segment- best effort | |
| transfer.) | |
| | | Stream
| POST: NON; | | ongoing
| URI=/video; No-response = 127 | |
| Stream-info = <5-bit ID>100; | |
| Time-stamp = <time_stamp_of_this_frame>; | |
| Position = 1024; | |
| Payload= <Bytes_in 2nd _segment> | |
+------------------------------------------------->| |
| | |
: : |
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Figure 3: Example showing successful negotiation of streaming parameters followed
by transmission of video information and control. It is assumed that the segment
size negotiated as 1024 at the initiation. So, the position of the 2nd block is
1024. Note the use of No-response option with NON request for the non-critical
segment.
5.2. Renegotiation
The renegotiation phase may occur when the ''consumer'' does not agree to
parameters proposed by the producer and proposes a modified set. This may happen
when the consumer application may need a less frame-rate than what is proposed by
the producer. So, the ''consumer'' may request a lower frame-rate and thereby avoid
unnecessary traffic in the network. The reduction may also be driven by the
processing load on the producer which is anyway a constrained device. So, if a
consumer requests more frame-rate than what is initially proposed by the producer,
then the producer may insist on the lower frame-rate. Renegotiation may also occur
if, during a stream, the producer senses a change in the end-to-end channel
condition and proposes a new set of best possible parameters that can be served
to the consumer.
Note that, that the consumer is never allowed to exceed the limits advertised by
the producer.
Fig. 4 illustrates exemplary exchanges for re-negotiation.
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Client (Producer) Server (Consumer)
| |
| POST: CON; |
| URI=/video; |
| Stream-info = <5-bit ID>000; |
| Payload= CBOR or JSON |\ Initial
+------------------------------------------------->| |negotiation
| | |followed by
| ACK; | |renegotiation
| Response = 2.04 CHANGED | |request with
| Steam-info = <5-bit ID>010 | |revised
| Payload= CBOR or JSON | |params.
|<-------------------------------------------------|/
| |
| POST: CON; |
| URI=/video; |
| Stream-info = <5-bit ID>010; |
| Payload= CBOR or JSON |\ Successful
+------------------------------------------------->| |renegotiation
| | |as the
| ACK; | |consumer
| Response = 2.04 CHANGED | |agrees to the
| Steam-info = <5-bit ID>001 | |revised
|<-------------------------------------------------|/ proposal.
: :
: (Streaming starts) :
Figure 4: Example showing successful renegotiation of streaming parameters. Note
the maneuvering of the Stream-info bit patterns.
Fig. 5 illustrates exemplary exchanges when a stream negotiation is unsuccessful.
The accompanied script may provide hints to the reason for unsuccessful
negotiations. A simple case of unsuccessful attempt may be observed if the
resource on the ''consumer'' side is not ready. The exact formatting of the script
is not in the scope of this draft.
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Client (Producer) Server (Consumer)
| |
| POST: CON; |
| URI=/video; |
| Stream-info = <5-bit ID>000; |
| Payload= CBOR or JSON |\ Unsuccessful
+------------------------------------------------->| |negotiation.
| | |The request
| ACK; | |is successful.
| Response = 2.04 CHANGED | |But consumer
| Steam-info = <5-bit ID>011 | |may reject
| Payload= CBOR or JSON | |for some
|<-------------------------------------------------|/ reason
| | mentioned in
Script.
Figure 5: Example showing unsuccessful renegotiation despite successful response
code against the initiation request.
6. Some Design Guidelines
6.1. Implicit Congestion Avoidance
The throughput and resource optimization for A-REaLiST depends largely on the
best-effort delivery on UDP. Despite that the application designer can make A-
REaLiST implicitly congestion aware and proactively avoid congestion. CoAP has a
basic congestion avoidance mechanism which uses exponential back off to increase
the timeout for retransmissions. However, that works only for CON messages.
The implicit congestion avoidance works like this: In case the producer fails to
successfully transfer a critical segment of a frame within the MAX_TRANSMIT_SPAN
as well as within MAX_RETRANSMIT [RFC7252] attempts, the producer drops
transmission of rest of the segments in that frame and waits for the next frame to
be ready. The rationale is, since the critical segment is not delivered, the
consumer will fail to reconstruct this frame anyway. So, there is no point in
clogging the network with rest of the segments.
6.2. Considerations for Consumer-side Rendering
While the critical segments are delivered reliably in a sequential manner, non-
critical are delivered with best-effort in an open-loop exchange. Also, the whole
frame can be dropped to avoid congestion. Hence, the application at the
''consumer'' end-point (server) needs to deal with issues like out-of-order
delivery, frame/segment loss, asynchronous segment arrival.
The issues mentioned above have been discussed in literatures [Perkins]. So the
basic approach should be: Buffer till a critical time to iron out the jittery,
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out-of-order arrival of the segments, play out from the appropriate buffer at a
constant rate determined by the frame-rate of the video. There may be intelligent
algorithms to play-out with high QoE despite non-arrival of non-critical segments
within the play-out deadline. This draft provides the hooks to create such
designs. Reference architecture of the play-out mechanism is provided in [Wi-UAV-
Globecom]. The play-out architecture leverages on the design assumption about the
'less-constrained' nature of the consumer in terms of memory and processor.
6.3. Determining the segment size
Size of the information segment in a CoAP message should be limited by the least
possible MTU for the end-to-end channel. This is to ensure that there is no
undesired conversation state at the lower layers of the protocol stack due to
uncontrolled fragmentation leading to undesired explosion of traffic in the
network. For IPV6 network, the MTU can be determined using Path MTU Discovery
(PMTUD) [RFC8201] which bestows the responsibility of determining the path MTU on
the end-points itself.
The size of the segment should be guided by the recommendations as specified in
Section 4.6 of [RFC7252].
7. IANA Considerations
The IANA is requested to assign numbers to the three options introduced in this
draft for inclusion in the ''CoAP Option Numbers" registry as shown below.
+--------+--------------+-------------+
| Number | Name | Reference |
+--------+--------------+-------------+
| TBD | Stream-info | Section 4 |
+--------+--------------+-------------+
| TBD | Time-stamp | Section 4 |
+--------+--------------+-------------+
| TBD | Position | Section 4 |
+--------+--------------+-------------+
8. Security Considerations
This draft presents no security considerations beyond those in Section 11 of the
base CoAP specification [RFC7252].
9. References
9.1. Normative References
[RFC7252]
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Shelby, Z., Hartke, K. and Bormann, C.,"Constrained Application Protocol (CoAP)",
RFC 7252, June, 2014.
[RFC7967]
Bhattacharyya, A., Bandyopadhyay, S., Pal, A., Bose, T., ''Constrained Application
Protocol (CoAP) Option for No Server Response'', RFC 7967, August, 2016.
[RFC8201]
McCann, J., et al., ''Path MTU Discovery for IP version 6'', RFC 8201, July, 2017.
9.2. Informative References
[IOT-ISOC]
Rose, K., Eldridge, S., Chapin, L., ''The Internet of Things: an overview'',
Internet Society, pp.1-50, October, 2015.
[RFC7452]
Tschofenig, H., Arkko, J., McPherson, D., "Architectural Considerations in Smart
Object Networking", RFC 7452, March, 2015.
[Murphy]
Murphy, C., ''Internet of Things: Are you underestimating video?'', Available
online:
http://www.informationweek.com/bigdata/bigdataanalytics/internetofthingsareyouunde
restimatingvideo/a/d-id/1269508, June, 2014.
[Pereira]
Pereira, R., Pereira, E. G., ''Video Streaming Considerations for Internet of
Things'', International Conference on Future Internet of Things and Cloud, pp. 48-
52, August, 2014.
[RFC7959]
Bormann, C., Shelby, Z., ''Block-Wise Transfers in the Constrained Application
Protocol (CoAP)'', RFC 7959, August, 2016.
[GIoTS]
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Dey, S., Bhattacharyya, A., Mukherjee, A., "Semantic data exchange between
collaborative robots in fog environment: Can CoAP be a choice?", Global IoTS, pp.
1-6, June, 2017.
[RFC2616]
Fielding, R., Irvine, U.C., Gettys, J., Mogul, J., Frystyk, H., Masinter, L.,
Leach, P., Berners-Lee, T., ''Hypertext Transfer Protocol -- HTTP/1.1'', RFC 2616,
June, 1999.
[RFC3550]
Schulzrinne, H., Casner, S., Frederick, R., Jacobson, V., ''RTP: A Transport
Protocol for Real-Time Applications'', RFC 3550, July, 2003.
[Wi-UAV-Globecom]
Bhattacharyya, A., Agrawal, S., Rath, H., Pal, A., ''Improving Live-streaming
Experience for Delay-sensitive IoT Applications : A RESTful Approach'', accepted in
Globecom (Wi-UAV workshop), Dec., 2018.
[Perkins]
Perkins, C., ''RTP: Audio and Video for the Internet'', Addison-Wesley, 2003.
Bhattacharyya, et al. Expires August 4, 2019 [Page 15]
Internet-Draft draft-bhattacharyya-core-a-realist-01 February 2019
Authors' Addresses
Abhijan Bhattacharyya
Tata Consultancy Services Ltd.
Kolkata, India
Email: abhijan.bhattacharyya@tcs.com
Suvrat Agrawal
Tata Consultancy Services Ltd.
Bangalore, India
Email: suvrat.a@tcs.com
Hemant Rath
Tata Consultancy Services Ltd.
Bhubaneswar, India
Email: hemant.rath@tcs.com
Arpan Pal
Tata Consultancy Services Ltd.
Kolkata, India
Email: arpan.pal@tcs.com
Balamurali Purushothaman
Tata Consultancy Services Ltd.
Bangalore, India
Email: arpan.pal@tcs.com
Bhattacharyya, et al. Expires August 4, 2019 [Page 16]