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Versions: 00 01 draft-ietf-bier-multicast-http-response

Network Working Group                                     D. Purkayastha
Internet-Draft                                                 A. Rahman
Intended status: Informational                                D. Trossen
Expires: December 31, 2018              InterDigital Communications, LLC
                                                               T. Eckert
                                                           June 29, 2018

                BIER Multicast Overlay for HTTP Respone


   HTTP Level multicast, using BIER, is described as a use case in BIER
   Use cases document.  HTTP Level Multicast is used in today's video
   streaming and delivery services such as HLS, AR/VR etc., generally
   realized over IP Multicast.  A realization of "HTTP Multicast" over
   "IP Multicast" is described and few problems are identified.
   Realization over BIER, through a BIER Multicast Overlay Layer, is
   described.  How BIER Multicast Overlay operation improves over IP
   Multicast is also discussed.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on December 31, 2018.

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 to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of

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   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Reference Deployment  . . . . . . . . . . . . . . . . . .   3
   2.  Conventions used in this document . . . . . . . . . . . . . .   5
   3.  Use cases . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Realization over IP Multicast . . . . . . . . . . . . . . . .   6
     4.1.  Mapping to Requirements . . . . . . . . . . . . . . . . .   6
     4.2.  Problems  . . . . . . . . . . . . . . . . . . . . . . . .   7
   5.  Realization over BIER . . . . . . . . . . . . . . . . . . . .   8
     5.1.  Description of a "BIER Multicast Overlay" to support HTTP
           Multicast . . . . . . . . . . . . . . . . . . . . . . . .   8
       5.1.1.  BIER Multicast Overlay Componentst  . . . . . . . . .   8
       5.1.2.  BIER Multicast Overlay Operations . . . . . . . . . .   9
     5.2.  Achieving Multicast Responses . . . . . . . . . . . . . .  11
     5.3.  BIER Traffic Enginnering  . . . . . . . . . . . . . . . .  11
   6.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .  12
   7.  Next Steps  . . . . . . . . . . . . . . . . . . . . . . . . .  12
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   10. Informative References  . . . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   BIER Use Cases document [I-D.ietf-bier-use-cases] describes an "HTTP
   Level Multicast" scenario, where HTTP Responses are carried over a
   BIER multicast infrastructure to multiple clients.  Especially rate-
   adaptive HTTP solutions can benefit from the dynamic multicast group
   membership changes enabled by BIER.  For this, the "server side NAP
   (Network Attachment Point), creates a list of outstanding client side
   NAP (Network Attachment Point) requests for the same HTTP resource.
   When the response is available, the list of NAPs with outstanding
   client requests are converted into the BIER or BIER-TE bitstring and
   used to send the HTTP response.

   In this draft, we describe how this class of use cases can be
   realized over IP Multicast and how the operation of the use case can
   be improved if realized over BIER.  The realization over BIER is
   achieved through what is called in BIER "BIER Multicast overlay"
   layer: The methods by which the sending BIER router knows what . The

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   requirements for BIER Multicast overlay layer is described.  It also
   describes the necessary functions that form the BIER multicast
   overlay and the operations that enable the desired "HTTP Level
   Multicast" behavior.  One such operation is generating PATH ID
   (represents the BFIR and BFER) based on named service relationship
   and translating it to appropriate BIER header.  We describe a list of
   protocols needed for the realization of the individual operations.

   We conclude with future steps and seek input from the WG.

1.1.  Reference Deployment

   Let us formulate the architecture of the BIER multicast overlay for
   the scenario outlined in [I-D.ietf-bier-use-cases].  This overlay is
   shown in Figure 1 below.

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    +---------+   +------------+
    |         |   |            |/
    +IP only  +---+  SR + BFER +-----|
    |receiver |   |  (CNAP)    |\    |
    |UE       |   +----/\------+     |
    +---------+        ||            |
                       ||       +----------+   +---------+
                       ||       |          |   |         |
                |--------       |  BFR     |---|  BFR    |------|
                |               |          |   |         |      |
                |               +----------+   +---------+      |
            +---------+                                     +-------+
            |         |------------------------------------>| BFIR  |
            + BIER TE +                                     |  +    |
            |  PCE    |         +---------+    +-------+    |  SR   |
            |         |--||     |         |----| BFR   |----|(SNAP) |
            +---------+  ||     |   BFR   |    +-------+    |       |
                         ||     |         |                 +-------+
                         ||     +---------+                    /|\
    +---------+   +------\/----+      |                         |
    |         |   |            |/     |                         |
    +IP only  +---+  SR + BFER +------|                   +----------+
    |receiver |   |   (CNAP)   |\                         | IP only  |
    +---------+   +------------+                          | Sender   |
                                                          |(Server)  |

    [SR : Service Handler, CNAP : Client Network Attachment Point]
    [SNAP : Server Network Attachment Point]
    [PCE : Path Computation Element]

                      Figure 1: Deployment over BIER

   The multicast overlay is formed by the BFIR and BFER of the BIER
   layer and the additional SR (Service Handler) and PCE (Path
   Computation Element) elements shown in the figure.  When connecting
   to a standard IP routed peering network, a special SR, such as Border
   Gateway may be used

   The Service Handler and BFER can be assumed to be collocated and can
   be viewed as Client Network Attachment Point (CNAP).  Clients sends
   and receives HTTP transactions through CNAP.

   On the server side, the Service handling function can be part of the
   Server Network Attachment Point (SNAP).  It also includes the BFIR
   function.  SNAP is responsible for aggregating all HTTP Request and

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   sending BIER Multicasted HTTP response to multiple clients who
   requested the same content.

   As part of POINT/RIFE EU Horizon 2020 project, HTTP Level Multicast
   use case has been executed on SDN based and ICN based underlay
   network, as described in the [I-D.irtf-icnrg-deployment-guidelines].

   "HTTP multicast" demonstrated benefits in HTTP-level streaming video
   delivery, when deployed on POINT test bed with 80+ nodes.  This draft
   [I-D.irtf-icnrg-deployment-guidelines] also describes protocol
   requirements to enable HTTP multicast to work on ICN underlay.

2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

3.  Use cases

   With the extensive use of "web technology", "distributed services"
   and availability of heterogeneous network, HTTP has effectively
   transitioned into the common transport or session layer for E2E and
   multi-hop communication across the web that is also called Service
   signaling.  Multi-hop when using a sequence of HTTP instance such as
   HTTP caches.  The draft "On the use of HTTP as a Substrate"
   [I-D.ietf-httpbis-bcp56bis], describes how HTTP is commonly used
   among service instances to communicate with each other, thus
   abstracting the lower layer details to application developers.

   Referring to the BIER Use Cases [I-D.ietf-bier-use-cases], multicast
   is used to scale out HLS (HTTP live streaming) to a large number of
   receivers that use HTTP.  This is used today in solutions like DOCSIS
   hybrid streaming [TR_IPMC_ABR].  Multicast can speed up both live and
   high-demand VoD streaming.  Adaptive Bit Rate IPMC [TR_IPMC_ABR]
   describes use of IP multicast towards the CMTS or a box beside it,
   where the content is converted to HTTP/TCP to stream to the receivers
   (e.g., homes).  A server hosting the HLS content is shown as "NAP
   Server".  The gateways acting as receivers for the multicast from the
   server are shown as "Client-NAP" (CNAP).  Each CNAP can serve
   multiple clients.

   HTTP request and response used in media streaming services like HLS,
   use HTTP response for delivery of content.  In such scenarios, where
   semi-synchronous access to the same resource occurs (such as watching
   prominent videos over Netflix or similar platforms or live TV over
   HTTP), traffic grows linearly with the number of viewers since the
   HTTP-based server will provide an HTTP response to each individual

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   viewer.  This poses a significant burden on operators in terms of
   costs and on users in terms of likely degradation of quality.

   This solution is not limited to traditional TV broadcasting.
   Consider a virtual reality use case where several users are joining a
   VR session at the same time, e.g., centered around a joint event.
   Hence, due to the temporal correlation of the VR sessions, we can
   assume that multiple requests are sent for the same content at any
   point, particularly when viewing angles of VR clients are similar or
   the same.  Due to availability of virtual functions and cloud
   technology, the actual end point from where content is delivered may

4.  Realization over IP Multicast

   IPTV or Internet video distribution in CDNs, uses HTTP Level
   Multicast and realized over IP Multicast (IPMC).  Many features of
   the IPTV service uses IPMC Group dependent state.  Besides popular
   features like PIM, Mldp, in a variable bit rate encoded content
   source, content consumption also depends on group state.

   Assume clients that are consuming the same content (such as a TV
   program) and that this content has for each block (typically segments
   worth 2 seconds of content) a set of outstanding requests from its
   clients.  When IP Multicast is used in the domain, such as in
   aforementioned pre-existing solutions like in Cablelabs/DOCSIS
   [TR_IPMC_ABR], all possible blocks of the content have to be mapped
   to some IP multicast group, and the CNAP will need to know the
   mapping of block to groups.  For example, a live stream may have 11
   different bitrates available.  In the most simple Block to IP
   multicast group mapping scheme, there could be 11 multicast groups,
   one for all the blocks of one bitrate (note that this is not
   necessarily done in deployments of this solution, but we consider it
   here for the purpose of explanation).

   If the multicast domain and especially the links into the CNAP has
   enough bandwidth, this solution work well with IP multicast.  As soon
   as there is at least one Client connected to a CNAP for one
   particular content, the CNAP would join all 11 multicast groups for
   this content.

4.1.  Mapping to Requirements

   To realize "HTTP Level Multicast" over "IP Multicast", some
   additional functions needs to be supported in an intermediate
   (overlay) layer.

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   Support of mapping between FQDN based end points, Multicast Address.
   Creating multicast group from FQDN based end points.

   Control mechanism related to time when to start sending response as
   the multicast group is created.  It is required that the source
   should not send response immediately to the Multicast address.  Wait
   for some time to build the group sufficiently and then send response.

   Support of IGMP signaling between User device, NAPs and Multicast

4.2.  Problems

   If the number of clients on a CNAP for a particular program is large,
   the approach will work fairly well, because the likelihood that each
   of the 11 bitrates of a content is necessary for at least one Client
   is then fairly high.

   When the number of receivers is not very large, IP multicast runs
   into two issues.  If all the bitrates for the content are sent across
   the same group, then many of the bitrates may not be required and
   would have to be received unnecessarily and dropped by the CNAP.  If
   each bitrate was sent on a different IP multicast group, the CNAP
   could dynamically join/leave each multicast group based on the known
   receivers, but that would create an extremely high and undesirable
   amount of IP multicast signaling protocol activity (PIM/IGMP) that is
   easily overloading the network

   For efficiency reasons, the CNAP would need to dynamically join to
   only those bitrate steams where it does have outstanding requests,
   therefore achieving the best efficiency.  This would mean in the
   worst case that a CNAP would need to send for each new block, aka.:
   every two second for every client one IGMP/PIM leave and one IGMP/PIM
   join towards the upstream router to get a block for an appropriate
   bitrate (or changed content) whenever bitrate or content on a client
   have changed.  This high rate of control-plane signaling between CNAP
   and routers, and even between routers inside the multicast Domain is
   a major pain point and may easily prohibit deployment of these
   solutions because in many network devices, the performance of PIM/
   IGMP is not scaled for continuous change in forwarding.  Even worse,
   the limit may not simply be the CPU performance of the routers
   control plane, but a limitation in the number of changes in
   forwarding that the forwarding plane units (NPU/ASICs) can support.

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5.  Realization over BIER

5.1.  Description of a "BIER Multicast Overlay" to support HTTP

   The Service Handler (as in Figure 1) in BIER Multicast Overlay,
   process the FQDN in the service request.  At the service level, e.g.
   HTTP service, the fixed relationship among consumer and providers may
   be abstracted using "Service Names", and the changing relationship at
   the Service execution endpoints can be managed at the "multicast
   overlay" level, handing out the exact locations where service request
   or response needs to be sent to BIER layer.

          +-------------+        +-----------+       +-----------+
          |             |        |           |       | PATH ID   |
          | Service name|        | Multicast |       | translates|
          | [producer,  |------->| Overlay   |------>| to BIER   |
          |  consumer]  |        | Layer     |       | header    |
          |             |        |           |       |           |
          +-------------+        +-----------+       +-----------+

               Figure 2: Service name to Path ID translation

   We illustrate this using HTTP URI as service names.  It should be
   noted, other identifiers can also be used as service name, such as IP
   address.  In the example illustration, other layers such as TCP, IP
   has been abstracted.  Outside BIER domain we terminate TCP/IP session
   to extract the URI.  URI is processed by the "multicast overlay"
   layer to generate PATH IDENTIFIER, which is used as BIER header.
   Once the BIER header is determined and added at the BFIR, the rest of
   the transport layers is assumed to be any underlay technology as
   supported by BIER.

5.1.1.  BIER Multicast Overlay Componentst

   With reference to Figure 1, the following components are part of BIER
   Multicast Overlay Layer.

   o  SR : The Service handler terminates application level protocols,
      extracts the URI.  It processes the URI in order to determine the
      PATH ID, which is used to send the HTTP Request.

   o  Optional PCE : Path Computation Element keeps track of all service
      execution end points and how to reach them.  SR may interact with
      PCE to obtain PATH information

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   o  Interface functions to BFIR where the PATH ID is mapped to BIER
      header.  An Interface to the BFER is likely not required because
      the BFER will only receive the traffic that they need and should
      be able to derive from the BIER payload which subset of its
      receivers need to get an HTTP encapsulated version of a particular

5.1.2.  BIER Multicast Overlay Operations

   As shown in Figure 3, the "Multicast overlay function" includes a
   function called PCE (Path Computation Element function), which is
   responsible for selecting the correct multicast end point and
   possibly realizing path policy enforcement.  The result of the
   selection is a BIER path identifier, which is delivered to the SR
   upon initial path computation request (or provided to the ingress
   router BFIR to be added as BIER header ) (i.e., when sending a
   request to or response for a specific URL for the first time).  The
   path identifier is utilized for any future request for a given URL-
   based request.

   All service end points indicate availability to the PCE through a
   registration procedure, the PCE will instruct all SRs to invalidate
   previous path identifiers to the specific URL.  This may result in an
   initial path computation request at the next service request
   forwarding.  Through this, the newly registered service endpoint
   might be utilized if the policy-governed path computation selects
   said service instance.

   +-------+    +------+----+   +--------+                  +----+-----+
   |Apps   |    |Apps---->  |   | PCE    |                  |    | APP |
   |layer  |--->|layer | SR |   +---/\---+                  | SR-->    |
   |prot   |    |prot  |    |       ||                      |    | LYR |
   +-------+    +------+----+   +---------+   +---------+   +----+-----+
   |   L2  |    |      L2   |-->|Forwarder|-->|Forwarder|-->|    L2    |
   +-------+    +------+----+   +---------+   +---------+   +----------+
                              |--------BIER DOMAIN -------|

              Figure 3: Protocol for Multicast Overlay Layer

   In the diagram shown above, an HTTP request is sent by an IP-based
   device towards the FQDN of the server defined in the HTTP request.

   At the client facing SR, the HTTP request is terminated at the HTTP
   level at a local HTTP proxy.  We assume termination on the client
   side at Layer 3 and above protocols, such as TCP.  Server side SR at

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   the egress, terminates any transport protocol on the outgoing
   (server) side.  These terminating functions are assumed to be part of
   the client/server SR.  The SR obtains the destination "Service Name"
   from the received HTTP request.

   If no local BIER forwarding information exists to the client side SR,
   a path computation entity (PCE) is consulted, which calculates a
   unicast path from the BFIR to which the client SR is connected to the
   BFER to which the server SR is connected.  The PCE provides the
   forwarding information (Path ID) to the client SR, which in turn
   caches the result.  The Client SR may forward the Path ID to BFIR,
   which creates the BIER header.

                       |             |              |
                       | BIER HEADER | HTTP REQUEST |
                       |             | [ENCODED IN  |
                       |             | TEXT]        |
                       |             |              |

                Figure 4: Encapsulation of Service Request

   Ultimately, the "HTTP Request" encapsulated by BIER header, as shown
   in above diagram, is forwarded by the client SR towards the server-
   facing SR via the local BFIR.  We assume a (TCP-friendly) transport
   protocol being used for the transmission between client and server SR
   while not mandating the use of TCP for this transmission.  A suitable
   transport or Layer 2 encapsulation, as supported by BIER layer, is
   added to the above payload as shown in the following diagram.

                |             |             |              |
                | Transport L2| BIER HEADER | HTTP REQUEST |
                |   HEADER    |             | [ENCODED IN  |
                |             |             | TEXT]        |
                |             |             |              |

             Figure 5: Transport Encapsulation of BIER payload

   Upon arrival of an HTTP request at the server SR, it forwards the
   HTTP request as a well-formed HTTP request locally to the server.

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   If no BIER forwarding information exists for the reverse direction
   towards the requesting client SR, this information is requested from
   the PCE, similar to the operation in forward direction.

   Upon arrival of any further client SR request at the server SR to an
   HTTP request whose response is still outstanding, the client SR is
   added to an internal request table.  Optionally, the request is
   suppressed from being sent to the server.

   Upon arrival of an HTTP response at the server SR, the server SR
   consults its internal request table for any outstanding HTTP requests
   to the same request.  The server SR retrieves the stored BIER
   forwarding information for the reverse direction for all outstanding
   HTTP requests and determines the path information to all client SRs
   through a binary OR over all BIER forwarding identifiers with the
   same SI field.  This newly formed joint BIER multicast response
   identifier is used to send the HTTP response across the network.

5.2.  Achieving Multicast Responses

   BIER makes the solution scalable.  Instead of IP multicast with IGMP/
   PIM, BIER is being used between Server NAP (SNAP) and CNAP, the SNAP
   simply coalesces the forwarded HTTP requests from the CNAP, and
   determines for every requested block the set of CNAPs requesting it.
   A set of CNAPs corresponds to a set of bits in the BIER-bitstring,
   one bit per CNAP.  The SNAP then sends the block into BIER with the
   appropriate bitstring set.

   This completely eliminates any dynamic multicast signaling between
   CNAP and SNAP.  It also avoid sending of any unnecessary data block,
   which in the IP multicast solution is pretty much unavoidable.

   Furthermore, using the approach with BIER, the SNAP can also easily
   control how long to delay sending of blocks.  For example, it may
   wait for some percentage of the time of a block (e.g, 50% = 1
   second), therefore ensuring that it is coalescing as many requests
   into one BIER multicast answer as possible.

5.3.  BIER Traffic Enginnering

   BIER-TE (BIER Traffic Engineering [I-D.ietf-bier-te-arch]) forwards
   and replicates packets like BIER based on a BitString in the packet
   header.  Where BIER forwards and replicates its packets on shortest
   paths towards BFER, BIER-TE allows (and requires) to also use bits in
   the bitstring to indicate the paths in the BIER domain across which
   the BIER-TE packets are to be sent.  This is done to support Traffic
   Engineeringfor BIER packets via explicit hop-by-hop and/or loose hop

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   forwarding of BIER-TE packets.  A BIER-TE controller calculates
   explicit paths for this packet forwarding.

   The Multicast Flow Overlay operates as in BIER.  Instead of
   interacting with the BIER layer, it interacts with the BIER-TE

   In this draft, "Name-based" service forwarding over BIER, is
   described to handle changes in service execution end points and
   manage adhoc relationship in a multicast group.  BIER-TE is another
   way of doing this, while integrated with BIER architecture.  The PCE
   function described earlier in the BIER Multicast Overlay, may become
   part of BIER-TE Controller.  The SR function in the CNAP and SNAP
   communicates with BIER TE controller.  SR sends the service name to
   the controller, which process the request using the PCE function and
   returns the "bitstring" to be used as BIER header for delivery of the
   HTTP response to multiple clients.

6.  Requirements

   A realization for the "HTTP multicast" use case may have the
   following requirements:

   o  MUST support multiple FQDN-based service endpoints to exist in the

   o  MUST send FQDN-based service requests at the network level to a
      suitable FQDN-based service endpoint via policy-based selection of
      appropriate path information

   o  MUST allow for multicast delivery of HTTP response to same HTTP
      request URI

   o  MUST provide direct path mobility, where the path between the
      egress and ingress Service Routers(SR) can be determined as being
      optimal (e.g., shortest path or direct path to a selected
      instance), is needed to avoid the use of anchor points and further
      reduce service-level latency

7.  Next Steps

   This Applicability Statement document describes how name based
   service forwarding can be realized over BIER.  Name based service
   forwarding helps in handling the change of service execution end
   points.  This document describes the functionalities in the multicast
   overlay layer to enable the name based forwarding.  We would like to
   get feedback from the WG if this is relevant and would like to get
   support to continue this work.  We will like to elaborate further on

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   the functions of the overlay layer and list the involved protocols by
   the next IETF after Montreal.  We also plan to implement in our H2020

8.  IANA Considerations

   This document requests no IANA actions.

9.  Security Considerations


10.  Informative References

              Eckert, T., Cauchie, G., Braun, W., and M. Menth, "Traffic
              Engineering for Bit Index Explicit Replication (BIER-TE)",
              draft-ietf-bier-te-arch-00 (work in progress), January

              Kumar, N., Asati, R., Chen, M., Xu, X., Dolganow, A.,
              Przygienda, T., Gulko, A., Robinson, D., Arya, V., and C.
              Bestler, "BIER Use Cases", draft-ietf-bier-use-cases-06
              (work in progress), January 2018.

              Nottingham, M., "On the use of HTTP as a Substrate",
              draft-ietf-httpbis-bcp56bis-05 (work in progress), May

              Rahman, A., Trossen, D., Kutscher, D., and R. Ravindran,
              "Deployment Considerations for Information-Centric
              Networking (ICN)", draft-irtf-icnrg-deployment-
              guidelines-03 (work in progress), June 2018.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

              CableLabs, "IP Multicast Adaptive Bit Rate Architecture
              Technical Report", OC-TR-IP-MULTI-ARCH-V01-141112 C01,
              October 2016, <https://community.cablelabs.com/wiki/plugin

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Internet-Draft  BIER Multicast Overlay for HTTP Response       June 2018

Authors' Addresses

   Debashish Purkayastha
   InterDigital Communications, LLC

   Email: Debashish.Purkayastha@InterDigital.com

   Akbar Rahman
   InterDigital Communications, LLC

   Email: Akbar.Rahman@InterDigital.com

   Dirk Trossen
   InterDigital Communications, LLC
   64 Great Eastern Street, 1st Floor
   London  EC2A 3QR
   United Kingdom

   Email: Dirk.Trossen@InterDigital.com
   URI:   http://www.InterDigital.com/

   Toerless Eckert
   Huawei USA - Futurewei Technologies Inc.
   2330 Central Expy
   Santa Clara  95050

   Email: tte+ietf@cs.fau.de

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