Network Working Group N. Kumar Internet-Draft R. Asati Intended status: Informational Cisco Expires: March 14, 2021 M. Chen X. Xu Huawei A. Dolganow Nokia T. Przygienda Juniper Networks A. Gulko Thomson Reuters D. Robinson id3as-company Ltd V. Arya DirecTV Inc C. Bestler Nexenta September 10, 2020 BIER Use Cases draft-ietf-bier-use-cases-12.txt Abstract Bit Index Explicit Replication (BIER) is an architecture that provides optimal multicast forwarding through a "BIER domain" without requiring intermediate routers to maintain any multicast related per- flow state. BIER also does not require any explicit tree-building protocol for its operation. A multicast data packet enters a BIER domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the BIER domain at one or more "Bit-Forwarding Egress Routers" (BFERs). The BFIR router adds a BIER header to the packet. The BIER header contains a bit-string in which each bit represents exactly one BFER to forward the packet to. The set of BFERs to which the multicast packet needs to be forwarded is expressed by setting the bits that correspond to those routers in the BIER header. This document describes some of the use cases for BIER. 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 Kumar, et al. Expires March 14, 2021 [Page 1] Internet-Draft BIER Use Cases September 2020 working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. 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 March 14, 2021. Copyright Notice Copyright (c) 2020 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 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 . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Specification of Requirements . . . . . . . . . . . . . . . . 3 3. BIER Use Cases . . . . . . . . . . . . . . . . . . . . . . . 3 3.1. Multicast in L3VPN Networks . . . . . . . . . . . . . . . 3 3.2. Broadcast, Unknown unicast and Multicast (BUM) in EVPN . 4 3.3. IPTV and OTT Services . . . . . . . . . . . . . . . . . . 5 3.4. Multi-Service, Converged L3VPN Network . . . . . . . . . 6 3.5. Control-Plane Simplification and SDN-Controlled Networks 7 3.6. Data Center Virtualization/Overlay . . . . . . . . . . . 8 3.7. Financial Services . . . . . . . . . . . . . . . . . . . 8 3.8. 4K Broadcast Video Services . . . . . . . . . . . . . . . 9 3.9. Distributed Storage Cluster . . . . . . . . . . . . . . . 10 3.10. Hyper Text Transfer Protocol (HTTP) Level Multicast . . . 11 4. Security Considerations . . . . . . . . . . . . . . . . . . . 13 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 7. Contributing Authors . . . . . . . . . . . . . . . . . . . . 14 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 8.1. Normative References . . . . . . . . . . . . . . . . . . 14 8.2. Informative References . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 Kumar, et al. Expires March 14, 2021 [Page 2] Internet-Draft BIER Use Cases September 2020 1. Introduction Bit Index Explicit Replication (BIER) [RFC8279] is an architecture that provides optimal multicast forwarding through a "BIER domain" without requiring intermediate routers to maintain any multicast related per-flow state. BIER also does not require any explicit tree-building protocol for its operation. A multicast data packet enters a BIER domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the BIER domain at one or more "Bit-Forwarding Egress Routers" (BFERs). The BFIR router adds a BIER header to the packet. The BIER header contains a bit-string in which each bit represents exactly one BFER to forward the packet to. The set of BFERs to which the multicast packet needs to be forwarded is expressed by setting the bits that correspond to those routers in the BIER header. The obvious advantage of BIER is that there is no per flow multicast state in the core of the network and there is no tree building protocol that sets up tree on demand based on users joining a multicast flow. In that sense, BIER is potentially applicable to many services where multicast is used and not limited to the examples described in this draft. In this document we are describing a few use cases where BIER could provide benefit over using existing mechanisms. 2. Specification of Requirements The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119] RFC 8174 [RFC8174] when and only when, they appear in all capitals, as shown here. 3. BIER Use Cases 3.1. Multicast in L3VPN Networks The Multicast L3VPN architecture [RFC6513] describes many different profiles in order to transport L3 multicast across a provider's network. Each profile has its own different tradeoffs (see section 2.1 [RFC6513]). When using "Multidirectional Inclusive" "Provider Multicast Service Interface" (MI-PMSI) an efficient tree is built per VPN, but causes flooding of egress PEs that are part of the VPN, but have not joined a particular C-multicast flow. This problem can be solved with the "Selective" PMSI (S-PMSI) by building a special tree for only those PEs that have joined the C-multicast flow for that specific VPN. The more S-PMSI's, the less bandwidth is wasted due to flooding, but causes more state to be created in the provider's network. This is a typical problem network operators are faced with Kumar, et al. Expires March 14, 2021 [Page 3] Internet-Draft BIER Use Cases September 2020 by finding the right balance between the amount of state carried in the network and how much flooding (waste of bandwidth) is acceptable. Some of the complexity with L3VPN's comes due to providing different profiles to accommodate these trade-offs. With BIER there is no trade-off between State and Flooding. Since the receiver information is explicitly carried within the packet, there is no need to build S-PMSI's to deliver multicast to a sub-set of the VPN egress PEs. Due to that behaviour, there is no need for S-PMSI's. MI-PMSI's and S-PMSI's are also used to provide the VPN context to the egress PE router that receives the multicast packet. Also, in some MVPN profiles it is also required to know which Ingress PE forwarded the packet. Based on the PMSI the packet is received from, the target VPN is determined. This also means there is a requirement to have at least a PMSI per VPN or per VPN/ingress PE. This means the amount of state created in the network is proportional to the VPN and ingress PEs. Creating PMSI state per VPN can be prevented by applying the procedures as documented in [RFC5331]. This however has not been very much adopted/implemented due to the excessive flooding it would cause to egress PEs since *all* VPN multicast packets are forwarded to *all* PEs that have one or more VPNs attached to it. With BIER, the destination PEs are identified in the multicast packet, so there is no flooding concern when implementing [RFC5331]. For that reason there is no need to create multiple BIER domains per VPN, the VPN context can be carry in the multicast packet using the procedures as defined in [RFC5331]. Also see [RFC8556] for more information. With BIER only a few MVPN profiles will remain relevant, simplifying the operational cost and making it easier to be interoperable among different vendors. 3.2. Broadcast, Unknown unicast and Multicast (BUM) in EVPN The current widespread adoption of L2VPN services [RFC4664], especially the upcoming EVPN solution [RFC7432] which transgresses many limitations of Virtual Private LAN Service (VPLS), introduces the need for an efficient mechanism to replicate broadcast, unknown unicast and multicast (BUM) traffic towards the PEs that participate in the same EVPN instances (EVIs). As simplest deployable mechanism, ingress replication is used but poses accordingly a high burden on the ingress node as well as saturating the underlying links with many copies of the same frame headed to different PEs. Fortunately enough, EVPN signals internally PMSI attribute [RFC6513] to establish transport for BUM frames and with that allows to deploy a plethora of Kumar, et al. Expires March 14, 2021 [Page 4] Internet-Draft BIER Use Cases September 2020 multicast replication services that the underlying network layer can provide. It is therefore relatively simple to deploy BIER P-Tunnels for EVPN and with that distribute BUM traffic without creating P-router states in the core that are required by Protocol Independent Multicast (PIM), Multipoint LDP (mLDP) or comparable solutions. Specifically, the same I-PMSI attribute suggested for mVPN can be used easily in EVPN, and given that EVPN can multiplex and disassociate BUM frames on p2mp and mp2mp trees using upstream assigned labels, BIER P-Tunnel will support BUM flooding for any number of EVIs over a single sub-domain for maximum scalability but allow at the other extreme of the spectrum to use a single BIER sub- domain per EVI if such a deployment is necessary. Multiplexing EVIs onto the same PMSI forces the PMSI to span more than the necessary number of PEs normally, i.e. the union of all PEs participating in the EVIs multiplexed on the PMSI. Given the properties of BIER it is however possible to encode in the receiver bitmask only the PEs that participate in the EVI that the BUM frame targets. In a sense, BIER is an inclusive as well as a selective tree and can allow delivering the frame to only the set of receivers interested in a frame even though many others participate in the same PMSI. As another significant advantage, it is imaginable that the same BIER tunnel needed for BUM frames can optimize the delivery of the multicast frames though the signaling of group memberships for the PEs involved, but has not been specified as of date. 3.3. IPTV and OTT Services IPTV is a service, well known for its characteristics of allowing both live and on-demand delivery of media traffic over an end-to-end managed IP network. Over The Top (OTT) is a similar service, well known for its characteristics of allowing live and on-demand delivery of media traffic between IP domains, where the source is often on an external network relative to the receivers. Content Delivery Networks (CDN) operators provide layer 4 applications, and often some degree of managed layer 3 IP networks, that enable media to be securely and reliably delivered to many receivers. In some models they may place applications within third party networks, or they may place those applications at the edges of their own managed network peerings and similar inter-domain connections. CDNs provide capabilities to help publishers scale to meet large audience demand. Their applications are not limited to Kumar, et al. Expires March 14, 2021 [Page 5] Internet-Draft BIER Use Cases September 2020 audio and video delivery, but may include static and dynamic web content, or optimized delivery for Massive Multiplayer Gaming and similar. Most publishers will use a CDN for public Internet delivery, and some publishers will use a CDN internally within their IPTV networks to resolve layer 4 complexity. In a typical IPTV environment the egress routers connecting to the receivers will build the tree towards the ingress router connecting to the IPTV servers. The egress routers would rely on IGMP/MLD (static or dynamic) to learn about the receivers interest in one or more multicast groups/channels. Interestingly, BIER could allow provisioning any new multicast group/channel by only modifying the channel mapping on ingress routers. This is deemed beneficial for the linear IPTV video broadcasting in which all receivers behind all egress PE routers would receive the IPTV video traffic. With BIER in an IPTV environment, there is no need for tree building from egress to ingress. Further, any addition of new channels or new egress routers can be directly controlled from the ingress router. When a new channel is included, the multicast group is mapped to a bit string that includes all egress routers. Ingress router would start sending the new channel and deliver it to all egress routers. As it can be observed, there is no need for static IGMP provisioning in each egress router whenever a new group/channel is added. Instead, it can be controlled from ingress router itself by configuring the new group to bit mask mapping on ingress router. With BIER in OTT environment, the edge routers in CDN domain terminating the OTT user session connect to the ingress BIER routers connecting content provider domains or a local cache server and leverage the scalability benefit that BIER could provide. This may rely on Multi-Protocol BGP (MP-BGP) interoperation (or similar) between the egress of one domain and the ingress of the next domain, or some other SDN control plane may prove a more effective and simpler way to deploy BIER. For a single CDN operator this could be well managed in the layer 4 applications that they provide and it may be that the initial receiver in a remote domain is actually an application operated by the CDN which in turn acts as a source for the ingress BIER router in that remote domain, and by doing so keeps the BIER domains discrete. 3.4. Multi-Service, Converged L3VPN Network Increasingly operators deploy single networks for multiple services. For example a single metro core network could be deployed to provide residential IPTV retail service, residential IPTV wholesale service, and business L3VPN service with multicast. It may often be desired by an operator to use a single architecture to deliver multicast for Kumar, et al. Expires March 14, 2021 [Page 6] Internet-Draft BIER Use Cases September 2020 all of those services. In some cases, governing regulations may additionally require same service capabilities for both wholesale and retail multicast services. To meet those requirements, some operators use the multicast architecture as defined in [RFC5331]. However, the need to support many L3VPNs, with some of those L3VPNs scaling to hundreds of egress PEs and thousands of C-multicast flows, make scaling/efficiency issues defined in earlier sections of this document even more prevalent. Additionally support for tens of millions of BGP multicast A-D and join routes alone could be required in such networks with all of the consequences that such a scale brings. With BIER, again there is no need of tree building from egress to ingress for each L3VPN or individual or group of c-multicast flows. As described earlier, any addition of a new IPTV channel or new egress router can be directly controlled from ingress router and there is no flooding concern when implementing [RFC5331]. 3.5. Control-Plane Simplification and SDN-Controlled Networks With the advent of Software Defined Networking, some operators are looking at various ways to reduce the overall cost of providing networking services including multicast delivery. Some of the alternatives being considered include minimizing capex cost through deployment of network elements with a simplified control plane function, minimizing operational cost by reducing control protocols required to achieve a particular service, etc. Segment routing as described in [RFC8402] provides a solution that could be used to provide simplified control plane architecture for unicast traffic. With Segment routing deployed for unicast, a solution that simplifies control plane for multicast would thus also be required, or operational and capex cost reductions will not be achieved to their full potential. With BIER, there is no longer a need to run control protocols required to build a distribution tree. If L3VPN with multicast, for example, is deployed using [RFC5331] with MPLS in P-instance, the MPLS control plane would no longer be required. BIER also allows migration of C-multicast flows from non-BIER to BIER-based architecture, which simplifies the operation of transitioning the control plane. Finally, for operators, who desire a centralized, offloaded control plane, multicast overlay as well as BIER forwarding could be used with controller-based programming. Kumar, et al. Expires March 14, 2021 [Page 7] Internet-Draft BIER Use Cases September 2020 3.6. Data Center Virtualization/Overlay Virtual eXtensible Local Area Network (VXLAN) [RFC7348] is a kind of network virtualization overlay technology which is intended for multi-tenancy data center networks. To emulate a layer 2 flooding domain across the layer 3 underlay, it requires a 1:1 or n:1 mapping between the VXLAN Virtual Network Instance (VNI) and the corresponding IP multicast group. In other words, it requires enabling the multicast capability in the underlay. For instance, it requires enabling PIM-SM [RFC7761] or PIM-BIDIR [RFC5015] multicast routing protocol in the underlay. VXLAN is designed to support 16M VNIs at maximum. In the mapping ratio of 1:1, it would require 16M multicast groups in the underlay which would become a significant challenge to both the control plane and the data plane of the data center switches. In the mapping ratio of n:1, it would result in inefficiency bandwidth utilization which is not optimal in data center networks. More importantly, it is recognized by many data center operators as an undesireable burden to run multicast in data center networks from the perspective of network operation and maintenance. As a result, many VXLAN implementations claim to support the ingress replication capability since ingress replication eliminates the burden of running multicast in the underlay. Ingress replication is an acceptable choice in small-sized networks where the average number of receivers per multicast flow is not too large. However, in multi-tenant data center networks, especially those in which the Network Virtualization Edge (NVE)functionality is enabled on a large number of physical servers, the average number of NVEs per VN instance would be very large. As a result, the ingress replication scheme would result in a serious bandwidth waste in the underlay and a significant replication burden on ingress NVEs. With BIER, there is no need for maintaining that huge amount of multicast state in the underlay anymore while the delivery efficiency of overlay BUM traffic is the same as if any kind of stateful multicast protocols such as PIM-SM or PIM-BIDIR is enabled in the underlay. 3.7. Financial Services Financial services extensively rely on IP multicast to deliver stock market data and its derivatives, and critically require optimal latency path (from publisher to subscribers), deterministic convergence (so as to deliver market data derivatives fairly to each client) and secured delivery. Current multicast solutions, e.g. PIM, mLDP, etc., however, don't sufficiently address the above requirements. The reason is that the current solutions are primarily subscriber driven, i.e. multicast Kumar, et al. Expires March 14, 2021 [Page 8] Internet-Draft BIER Use Cases September 2020 tree is setup using reverse path forwarding techniques, and as a result, the chosen path for market data may not be latency optimal from publisher to the (market data) subscribers. As the number of multicast flows grows, the convergence time might increase and make it somewhat nondeterministic from the first to the last flow depending on platforms/implementations. Also, by having more protocols in the network, the variability to ensure secured delivery of multicast data increases, thereby undermining the overall security aspect. BIER enables setting up the most optimal path from publisher to subscribers by leveraging unicast routing relevant for the subscribers. With BIER, the multicast convergence is as fast as unicast, uniform and deterministic regardless of number of multicast flows. This makes BIER a perfect multicast technology to achieve fairness for market derivatives per each subscriber. 3.8. 4K Broadcast Video Services In a broadcast network environment, the media content is sourced from various content providers across different locations. The 4k broadcast video is an evolving service placing enormous demand on network infrastructure in terms of low latency, faster convergence, high throughput, and high bandwidth. In a typical broadcast satellite network environment, the receivers are the satellite terminal nodes which will receive the content from various sources and feed the data to the satellite. Typically a multicast group address is assigned for each source. Currently the receivers can join the sources using either PIM-SM [RFC7761] or PIM- SSM [RFC4607]. In such network scenarios, normally PIM will be the multicast routing protocol used to establish the tree between ingress connecting the content media sources to egress routers connecting the receivers. In PIM-SM mode, the receivers relies on shared tree to learn the source address and build source tree while in PIM-SSM mode, IGMPv3 is used by receiver to signal the source address to the egress router. In either case, as the number of sources increases, the number of multicast trees in the core also increases resulting in more multicast state entries in the core and increasing the convergence time. With BIER in 4k broadcast satellite network environment, there is no need to run PIM in the core and no need to maintain any multicast state. The obvious advantage with BIER is the low multicast state maintained in the core and the faster convergence (which is typically Kumar, et al. Expires March 14, 2021 [Page 9] Internet-Draft BIER Use Cases September 2020 at par with the unicast convergence). The edge router at the content source facility can act as BIFR router and the edge router at the receiver facility can act as BFER routers. Any addition of a new content source or new satellite Terminal nodes can be added seamlessly in to the BEIR domain. The group membership from the receivers to the sources can be provisioned either by Border Gateway Protocol (BGP) or an SDN controller. 3.9. Distributed Storage Cluster Distributed Storage Clusters can benefit from dynamically targeted multicast messaging both for dynamic load-balancing negotiations and efficient concurrent replication of content to multiple targets. For example, in the NexentaEdge storage cluster (by Nexenta Systems) a Chunk Put transaction is accomplished with the following steps: o The Client multicasts a 'Chunk Put Request' to a multicast group known as a Negotiating Group. This group holds a small number of storage targets that are collectively responsible for providing storage for a stable subset of the chunks to be stored. In NexentaEdge this is based upon a cryptographic hash of the Object Name or the Chunk payload. o Each recipient of the 'Chunk Put Request' unicasts a 'Chunk Put Response' to the Client indicating when it could accept a transfer of the Chunk. o The Client selects a different multicast group (a Rendezvous Group) which will target the set storage targets selected to hold the Chunk. This is a subset of the Negotiation Group, presumably selected so as to complete the transfer as early as possible. o The Client multicasts a 'Chunk Put Accept' message to inform the Negotiation Group of what storage targets have been selected, when the transfer will occur and over what multicast group. o The client performs the multicast transfer over the Rendezvous Group at the agreed upon time. o Each recipient sends a 'Chunk Put Ack' to positively or negatively acknowledge the chunk transfer. o The client will retry the entire transaction as needed if there are not yet sufficient replicas of the Chunk. Chunks are retrieved by multicasting a 'Chunk Get Request' to the same Negotiating Group, collecting 'Chunk Get Responses', picking one Kumar, et al. Expires March 14, 2021 [Page 10] Internet-Draft BIER Use Cases September 2020 source from those responses, sending a 'Chunk Get Accept' message to identify the selected source and having the selected storage server unicast the chunk to the source. Chunks are found by the Object Name or by having the payload cryptographic hash of payload chunks be recorded in a "chunk reference" in a metadata chunk. The metadata chunks are found using the Object Name. The general pattern in use here, which should apply to other cluster applications, is that multicast messages are sent amongst a dynamically selected subset of the entire cluster, which may result in exchanging further messages over a smaller subset even more dynamically selected. Currently the distributed storage application discussed use of Multicast Listener Discovery (MLD) [RFC3810] managed IPV6 multicast groups. This in turn requires either a push-based mechanism for dynamically configuring Rendezvous Groups or pre-provisioning a very large number of potential Rendezvous Groups and dynamically selecting the multicast group that will deliver to the selected set of storage targets. BIER would eliminate the need for a vast number of multicast groups. The entire cluster can be represented as a single BIER domain using only the default sub-domain. Each Negotiating Group is simply a subset of the whole that is deterministically selected by the Cryptographic Hash of the Object Name or Chunk Payload. Each Rendezvous Group is a further subset of the Negotiating Group. In a simple mapping of the MLD managed multicast groups, each Negotiating Group could be represented by a short bit string selected by a Set Identifier. The Set Identier effectively becomes the Negotiating Group. To address the entire Negotiating Group the bit string is set to all ones. To later address a subset of the group a subset bit string is used. This allows a short fixed size BIER header to multicast to a very large storage cluster. 3.10. Hyper Text Transfer Protocol (HTTP) Level Multicast Scenarios where a number of HTTP [RFC7231] clients are quasi- synchronously accessing the same HTTP-level resource can benefit from the dynamic multicast group formation enabled by BIER. For example, in the FLIPS (Flexible IP Services) solution by InterDigital, network attachment points (NAPs) provide a protocol Kumar, et al. Expires March 14, 2021 [Page 11] Internet-Draft BIER Use Cases September 2020 mapping from HTTP to an efficient BIER-compliant transfer along a bit-indexed path between an ingress (here the NAP to which the clients connect) and an egress (here the NAP to which the HTTP-level server connects). This is accomplished with the following steps: o at the client NAP, the HTTP request is terminated at the HTTP level at a local HTTP proxy. o the HTTP request is published by the client NAP towards the Fully Qualified Domain Names (FQDN) of the server defined in the HTTP request * if no local BIER forwarding information exists to the server (NAP), a path computation entity (PCE) is consulted, which calculates a unicast path to the egress NAP (here the server NAP). The PCE provides the forwarding information to the client NAP, which in turn caches the result. + if the local BIER forwarding information exists in the NAP- local cache, it is used instead. o Upon arrival of a client NAP request at the server NAP, the server NAP proxy forwards the HTTP request as a well-formed HTTP request locally to the server. * If no client NAP forwarding information exists for the reverse direction, this information is requested from the PCE. Upon arrival of such reverse direction forwarding information, it is stored in a local table for future use. o Upon arrival of any further client NAP request at the server NAP to an HTTP request whose response is still outstanding, the client NAP is added to an internal request table and the request is suppressed from being sent to the server. * If no client NAP forwarding information exists for the reverse direction, this information is requested from the PCE. Upon arrival of such reverse direction forwarding information, it is stored in a local table for future use. o Upon arrival of an HTTP response at the server NAP, the server NAP consults its internal request table for any outstanding HTTP requests to the same request the server NAP retrieves the stored BIER forwarding information for the reverse direction for all outstanding HTTP requests found above and determines the path information to all client NAPs through a binary OR over all BIER forwarding identifiers Kumar, et al. Expires March 14, 2021 [Page 12] Internet-Draft BIER Use Cases September 2020 with the same SI field. This newly formed joint BIER multicast response identifier is used to send the HTTP response across the network, while the procedure is executed until all requests have been served. o Upon arrival of the HTTP response at a client NAP, it will be sent by the client NAP proxy to the locally connected client. A number of solutions exist to manage necessary updates in locally stored BIER forwarding information for cases of client/server mobility as well as for resilience purposes. Applications for HTTP-level multicast are manifold. Examples are HTTP-level streaming (HLS) services, provided as an OTT offering, either at the level of end user clients (connected to BIER-enabled NAPs) or site-level clients. Others are corporate intranet storage cluster solutions that utilize HTTP- level synchronization. In multi-tenant data centre scenarios such as outlined in Section 3.6., the aforementioned solution can satisfy HTTP-level requests to popular services and content in a multicast delivery manner. BIER enables such solution through the bitfield representation of forwarding information, which is in turn used for ad-hoc multicast group formation at the HTTP request level. While such solution works well in SDN-enabled intra- domain scenarios, BIER would enable the realization of such scenarios in multi-domain scenarios over legacy transport networks without relying on SDN-controlled infrastructure. Also see [I-D.ietf-bier-multicast-http-response] for more information. 4. Security Considerations There are no security issues introduced by this draft. 5. IANA Considerations There are no IANA consideration introduced by this draft. 6. Acknowledgments The authors would like to thank IJsbrand Wijnands, Greg Shepherd and Christian Martin for their contribution. The authors would also like to thank Anoop Ghanwani and Suneesh Babu for the thorough review and comments. Kumar, et al. Expires March 14, 2021 [Page 13] Internet-Draft BIER Use Cases September 2020 7. Contributing Authors Dirk Trossen InterDigital Inc Email: dirk.trossen@interdigital.com 8. References 8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., Przygienda, T., and S. Aldrin, "Multicast Using Bit Index Explicit Replication (BIER)", RFC 8279, DOI 10.17487/RFC8279, November 2017, . [RFC8556] Rosen, E., Ed., Sivakumar, M., Przygienda, T., Aldrin, S., and A. Dolganow, "Multicast VPN Using Bit Index Explicit Replication (BIER)", RFC 8556, DOI 10.17487/RFC8556, April 2019, . 8.2. Informative References [I-D.ietf-bier-multicast-http-response] Trossen, D., Rahman, A., Wang, C., and T. Eckert, "Applicability of BIER Multicast Overlay for Adaptive Streaming Services", draft-ietf-bier-multicast-http- response-04 (work in progress), July 2020. [RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener Discovery Version 2 (MLDv2) for IPv6", RFC 3810, DOI 10.17487/RFC3810, June 2004, . [RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for IP", RFC 4607, DOI 10.17487/RFC4607, August 2006, . Kumar, et al. Expires March 14, 2021 [Page 14] Internet-Draft BIER Use Cases September 2020 [RFC4664] Andersson, L., Ed. and E. Rosen, Ed., "Framework for Layer 2 Virtual Private Networks (L2VPNs)", RFC 4664, DOI 10.17487/RFC4664, September 2006, . [RFC5015] Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano, "Bidirectional Protocol Independent Multicast (BIDIR- PIM)", RFC 5015, DOI 10.17487/RFC5015, October 2007, . [RFC5331] Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream Label Assignment and Context-Specific Label Space", RFC 5331, DOI 10.17487/RFC5331, August 2008, . [RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/ BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February 2012, . [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content", RFC 7231, DOI 10.17487/RFC7231, June 2014, . [RFC7348] Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger, L., Sridhar, T., Bursell, M., and C. Wright, "Virtual eXtensible Local Area Network (VXLAN): A Framework for Overlaying Virtualized Layer 2 Networks over Layer 3 Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014, . [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February 2015, . [RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I., Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March 2016, . [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, July 2018, . Kumar, et al. Expires March 14, 2021 [Page 15] Internet-Draft BIER Use Cases September 2020 Authors' Addresses Nagendra Kumar Cisco 7200 Kit Creek Road Research Triangle Park, NC 27709 US Email: naikumar@cisco.com Rajiv Asati Cisco 7200 Kit Creek Road Research Triangle Park, NC 27709 US Email: rajiva@cisco.com Mach(Guoyi) Chen Huawei Email: mach.chen@huawei.com Xiaohu Xu Huawei Email: xuxiaohu@huawei.com Andrew Dolganow Nokia 750D Chai Chee Rd 06-06 Viva Business Park 469004 Singapore Email: andrew.dolganow@nokia.com Tony Przygienda Juniper Networks 1194 N. Mathilda Ave Sunnyvale, CA 95089 USA Email: prz@juniper.net Kumar, et al. Expires March 14, 2021 [Page 16] Internet-Draft BIER Use Cases September 2020 Arkadiy Gulko Thomson Reuters 195 Broadway New York NY 10007 USA Email: arkadiy.gulko@thomsonreuters.com Dom Robinson id3as-company Ltd UK Email: Dom@id3as.co.uk Vishal Arya DirecTV Inc 2230 E Imperial Hwy CA 90245 USA Email: varya@directv.com Caitlin Bestler Nexenta Systems 451 El Camino Real Santa Clara, CA US Email: caitlin.bestler@nexenta.com Kumar, et al. Expires March 14, 2021 [Page 17]