Network Working Group                                     D. Purkayastha
Internet-Draft                                                 A. Rahman
Intended status: Informational          InterDigital Communications, LLC
Expires: August 12, 2019                                      D. Trossen
                                                InterDigital Europe, Ltd
                                                               T. Eckert
                                                        February 8, 2019

Applicability of BIER Multicast Overlay for Adaptive Streaming Services


   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.  IP multicast is commonly used for IPTV
   services.  DVB and BBF is also developing a reference architecture
   for IP Multicast service.  A few problems with IPMC, such as waste of
   transmission bandwidth, increase in signaling when there are few
   users are described.  Realization over BIER, through a BIER Multicast
   Overlay Layer, is described.  How BIER Multicast Overlay operation
   improves over IP Multicast, such as reduction in signaling, dynamic
   creation of multicast groups to reduce signaling and bandwidth
   wastage is described.  We conclude with few next steps.

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).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at

   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."

   This Internet-Draft will expire on August 12, 2019.

Purkayastha, et al.      Expires August 12, 2019                [Page 1]

Internet-Draft   Applicability of BIER Multicast Overlay   February 2019

Copyright Notice

   Copyright (c) 2019 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
   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   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.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Realization over IP Multicast . . . . . . . . . . . . . . . .   6
     5.1.  Mapping to Requirements . . . . . . . . . . . . . . . . .   7
     5.2.  Problems  . . . . . . . . . . . . . . . . . . . . . . . .   8
   6.  Realization over BIER . . . . . . . . . . . . . . . . . . . .   8
     6.1.  Description of a "BIER Multicast Overlay" to support HTTP
           Multicast . . . . . . . . . . . . . . . . . . . . . . . .   9
       6.1.1.  BIER Multicast Overlay Components . . . . . . . . . .   9
       6.1.2.  BIER Multicast Overlay Operations . . . . . . . . . .  10
     6.2.  Achieving Multicast Responses . . . . . . . . . . . . . .  12
     6.3.  BIER multicast Overlay Traffic Management . . . . . . . .  13
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   9.  Informative References  . . . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

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

Purkayastha, et al.      Expires August 12, 2019                [Page 2]

Internet-Draft   Applicability of BIER Multicast Overlay   February 2019

   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 "BIER Multicast overlay" layer, i.e.,
   the methods by which the sending BIER router knows how to send other
   application packets.  The requirements for BIER Multicast overlay
   layer is described in this document.  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 the PATH ID (represents the path between 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.

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.

Purkayastha, et al.      Expires August 12, 2019                [Page 3]

Internet-Draft   Applicability of BIER Multicast Overlay   February 2019

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

    [SH : 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 SH (Service Handler) and PCE (Path
   Computation Element) elements shown in the figure.  When
   interconnecting with a non-BIER enabled IP routed peering network, a
   special SH, 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 includes the BFIR
   function and SH.  SNAP is responsible for aggregating the relevant

Purkayastha, et al.      Expires August 12, 2019                [Page 4]

Internet-Draft   Applicability of BIER Multicast Overlay   February 2019

   HTTP Requests and sending one or more BIER Multicast HTTP response to
   multiple clients who requested the same content.

   The SH function is assumed to be collocated with BFIR / BFER.  The
   BFIR and BFER is assumed to be normal router boxes in the network.
   If the additional function of SH cannot be added to normal routers,
   then SH can be deployed as a separate function outside the routers.
   In such scenario an interface between SH and BFIR or BFER needs to be

   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.

Purkayastha, et al.      Expires August 12, 2019                [Page 5]

Internet-Draft   Applicability of BIER Multicast Overlay   February 2019

   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
   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.  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

5.  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.

Purkayastha, et al.      Expires August 12, 2019                [Page 6]

Internet-Draft   Applicability of BIER Multicast Overlay   February 2019

   DVB released reference architecture [DVB_REF_ARCH] for an end-to-end
   system to deliver linear content over IP networks in a scalable and
   standards-compliant manner.  It focuses on delivering Adaptive Bit
   Rate unicast content over a IP multicast network.

   A Multicast gateway is deployed in a CPE, Upstream Network Edge
   device or Terminal and provides multicast to unicast conversion
   facilities for several homes.  All in-scope traffic on the access
   network between the Multicast Gateway (e.g. network edge device) and
   the Terminal or home gateway device is unicast.  The individual media
   files are encapsulated into other protocols, so that they can be
   recovered as discrete files, when they exit the multicast pipe, which
   is terminated at Multicast Gateway.  Interface "L" between Multicast
   server and Content playback supports fetching of all specified types
   of Content, Conditional request, Range request, Caching etc.  BBF
   also started similar work in October 2016, called WT-399.  This work
   is now coordinated with DVB.  BBF focuses on developing the device
   management model.

   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.

5.1.  Mapping to Requirements

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

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

Purkayastha, et al.      Expires August 12, 2019                [Page 7]

Internet-Draft   Applicability of BIER Multicast Overlay   February 2019

   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

5.2.  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.

6.  Realization over BIER

Purkayastha, et al.      Expires August 12, 2019                [Page 8]

Internet-Draft   Applicability of BIER Multicast Overlay   February 2019

6.1.  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 an
   IP address.  In the example illustration, other layers such as TCP,
   IP has been terminated at the egress point.  Outside BIER domain we
   terminate TCP/IP session to extract the URI.  The URI is processed by
   the "multicast overlay" layer to generate PATH IDENTIFIER , which is
   used as BIER header.

   Path Identifier or PATH ID, is used in path-based approach, which
   utilizes path information provided by the source of the packet for
   forwarding said packet in the network.  This is similar to segment
   routing albeit differing in the type of information provided for such
   source-based forwarding.

   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.  We assume TCP friendly transport, which can
   assure reliable delivery.

6.1.1.  BIER Multicast Overlay Components

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

Purkayastha, et al.      Expires August 12, 2019                [Page 9]

Internet-Draft   Applicability of BIER Multicast Overlay   February 2019

   o  Service Handler (SH): The Service handler terminates transport
      level protocols, such as TCP, and extracts the URI.  It processes
      the URI in order to determine the PATH ID by contacting the PCE
      for a suitable path resolution, which in turn is used to send the
      HTTP Request.

   o  Optional PCE : Path Computation Element keeps track of all service
      execution end points through a registration process.  SH interacts
      with the PCE to obtain PATH information by resolving the FQDN from
      the incoming URI at the ingress SH to a suitable PATH ID.

   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

6.1.2.  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 SH
   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 SHs to invalidate
   previous path identifiers to the specific URL that might exist.  This
   may result in an a renewed 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.  Otherwise, a previously
   resolved PATH ID for the URI determined at the ingress SH is being
   used instead, removing any resolution latency to an SH-local lookup
   of the PATH ID.

Purkayastha, et al.      Expires August 12, 2019               [Page 10]

Internet-Draft   Applicability of BIER Multicast Overlay   February 2019

   +-------+    +------+----+   +--------+                  +----+-----+
   |Apps   |    |Apps---->  |   | PCE    |                  |    | APP |
   |layer  |--->|layer | SH |   +---/\---+                  | SH-->    |
   |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 SH, the HTTP request is terminated at the TCP
   level at a local HTTP proxy.  The server side SH at the egress
   terminates any transport protocol on the outgoing (server) side.
   These terminating functions are assumed to be part of the client/
   server SH.  As a consequence, the SH obtains the destination "Service
   Name" from the received HTTP request.

   If no local BIER forwarding information exists at the client side SH,
   the path computation entity (PCE) is consulted, which calculates a
   unicast path from the BFIR to which the client SH is connected to the
   BFER to which the server SH is connected.  The PCE provides the
   forwarding information (Path ID) to the client SH, which in turn
   caches the result.  The Client SH 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 SH towards the server-
   facing SH via the local BFIR.  We assume a (TCP-friendly) transport
   protocol being used for the transmission between client and server
   SH.  The possibility of sending one HTTP response to several CNAPs
   makes this a reliable multicast transport protocol.  The exact nature

Purkayastha, et al.      Expires August 12, 2019               [Page 11]

Internet-Draft   Applicability of BIER Multicast Overlay   February 2019

   of this transport protocol is left for further studies.  A suitable
   transport or Layer 2 encapsulation, as supported by BIER layer, is
   added to the above payload.

                |             |             |              |
                | 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 SH, it forwards the
   HTTP request as a well-formed HTTP request locally to the server,
   awaiting an HTTP response for the reverse direction.

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

6.2.  Achieving Multicast Responses

   Upon arrival of any further client SH request at the server SH 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 SH, the server SH
   consults its internal request table for any outstanding HTTP requests
   to the same request.  The server SH retrieves the stored BIER
   forwarding information for the reverse direction for all outstanding
   HTTP requests and determines the path information to all client SHs
   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.

   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.

Purkayastha, et al.      Expires August 12, 2019               [Page 12]

Internet-Draft   Applicability of BIER Multicast Overlay   February 2019

   This completely eliminates any dynamic multicast signaling between
   CNAP and SNAP.  It also avoids 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.

6.3.  BIER multicast Overlay Traffic Management

   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
   Engineering for BIER packets via explicit hop-by-hop and/or loose hop
   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 SH function in the CNAP and SNAP
   communicates with BIER TE controller.  SH 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.

7.  IANA Considerations

   This document requests no IANA actions.

8.  Security Considerations

   The operations in Section 6 consider the forwarding of HTTP packets
   between ingress and egress points based on information derived from
   the HTTP request.  The support for HTTPS is foreseen to ensure
   suitable encryption capability of such exchanges.  Future updates to
   this draft will outline the support for such HTTPS-based exchanges.

Purkayastha, et al.      Expires August 12, 2019               [Page 13]

Internet-Draft   Applicability of BIER Multicast Overlay   February 2019

9.  Informative References

              DVB, "Adaptive media streaming over IP multicast", DVB
              Document A176, March 2018,

              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-09
              (work in progress), January 2019.

              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-04 (work in progress), September 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, <

Purkayastha, et al.      Expires August 12, 2019               [Page 14]

Internet-Draft   Applicability of BIER Multicast Overlay   February 2019

Authors' Addresses

   Debashish Purkayastha
   InterDigital Communications, LLC
   1001 E Hector St
   Conshohocken  19428


   Akbar Rahman
   InterDigital Communications, LLC
   1000 Sherbrooke Street West
   Montreal  H3A 3G4


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


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


Purkayastha, et al.      Expires August 12, 2019               [Page 15]