Network Working Group Y. Jiang Internet-Draft N. Finn Intended status: Standards Track Huawei J. Ryoo ETRI B. Varga Ericsson L. Geng China Mobile Expires: January 2019 July 2, 2018 Deterministic Networking Application in Ring Topologies draft-jiang-detnet-ring-01 Abstract Deterministic Networking (DetNet) provides a capability to carry data flows for real-time applications with extremely low data loss rates and bounded latency. This document describes how DetNet can be used in ring topologies to support Point-to-Point (P2P) and Point-to-Multipoint (P2MP) real-time services. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on January 2, 2019. Jiang and et al Expires January 2, 2019 [Page 1] Internet-Draft DetNet Ring July 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 (http://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 1.1. Conventions used in this document ....................... 3 1.2. Terminology ............................................. 4 2. P2P DetNet Ring ............................................ 4 2.1. DetNet applications on a single ring for P2P traffic .... 4 2.2. Implementation implications of a DetNet ring for P2P traffic ...................................................... 5 3. P2MP DetNet Ring ........................................... 5 3.1. DetNet applications on a single ring for P2MP traffic ... 5 3.2. Section LSPs as underlay (Service layer replication) .... 6 3.3. P2MP LSP tunnels as underlay (LSP layer replication) .... 7 4. DetNet Ring Interconnections ............................... 8 4.1. Single node interconnection ............................. 9 4.2. Dual node interconnection ............................... 9 4.2.1. Dual node interconnection for P2P traffic ............ 9 4.2.2. Dual node interconnection for P2MP traffic using section LSP ................................................. 10 4.2.3. Dual node interconnection for P2MP traffic using P2MP LSP 11 5. Resource reservation ...................................... 11 6. Security Considerations ................................... 11 7. IANA Considerations ....................................... 12 8. References ................................................ 12 8.1. Normative References ................................... 12 8.2. Informative References ................................. 12 9. Acknowledgments ........................................... 13 Jiang and et al Expires January 2, 2019 [Page 2] Internet-Draft DetNet Ring July 2018 1. Introduction An overview of Deterministic Networking (DetNet) architecture is given in [I-D.ietf-detnet-architecture], and DetNet data plane encapsulations are specified in [I-D.ietf-detnet-dp-sol]. But there is not any discussion on a ring topology in [I-D.ietf-detnet- architecture] yet. Furthermore, [I-D.ietf-detnet-use-cases] outlines several Detnet use cases where multicast capability is needed. If a multicast service replicates all of its packets from the source (as a traditional Virtual Private LAN Service (VPLS) does), the requirements of deterministic delay and high availability for all these replicated packets will pose a great challenge to the Detnet network. In fact, ring topologies have been very popular and widely deployed in network arrangements for various transport networks, such as Synchronous Digital Hierarchy, Synchronous Optical Network, Optical Transport Network, and Ethernet. The IETF has done some work on ring protection in Multi-Protocol Label Switching - Transport Profile (MPLS-TP), such as [RFC6974] and [RFC8227]. All these works, except Ethernet ring protection, typically use swapping or steering as the protection mechanism. As ring topologies are widely deployed for transport networks, it is also necessary for DetNet to support ring topologies (currently, there is not any discussion on a ring topology in [I-D.ietf-detnet-architecture] yet). This draft demonstrates how DetNet can be used in a ring topology. Specifically, DetNet ring supports for Point-to-Point (P2P) and Point-to-Multipoint (P2MP, for multicast services) are discussed in details. This document assumes that MPLS encapsulation for DetNet is supported as specified in [I-D.ietf-detnet-dp-sol-mpls] and all nodes in a ring network can support the Multi-Protocol Label Switching (MPLS) functionalities. It should be noted that it is more convenient for DetNet to support a ring topology with the intrinsic duplication and elimination mechanism, as there is no need of swapping or steering operations (consequently, its Operations, Administration and Maintenance (OAM) can also be simplified) for any service protection. 1.1. Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. Jiang and et al Expires January 2, 2019 [Page 3] Internet-Draft DetNet Ring July 2018 1.2. Terminology DetNet Deterministic Networking LSP Label Switched Path MPLS Multi-Protocol Label Switching MPLS-TP Multi-Protocol Label Switching - Transport Profile P2MP Point-to-Point P2P Point-to-Multipoint PEF Packet Elimination Function PRF Packet Replication Function PW Pseudowire 2. P2P DetNet Ring 2.1. DetNet applications on a single ring for P2P traffic Figure 1 depicts an example of the DetNet ring for P2P real time traffic. Nodes A and C are DetNet aware devices, and P2P DetNet traffic is transported from node A to node C. A clockwise and a counter clockwise Pseudowire (PW) and Label Switched Path (LSP) tunnel are configured from node A to node C respectively. The DetNet traffic is replicated by a Packet Replication Function (PRF) in node A, encapsulated with the specific PW and LSP labels, and transported on both LSP paths towards node C. Upon reception of the traffic, node C terminates the LSP and is aware of the DetNet traffic by inspection of the PW label carried in each packet. A Packet Elimination Function (PEF) in node C guarantees that only one copy of the DetNet service exits on egress with the help of the DetNet sequence number. Jiang and et al Expires January 2, 2019 [Page 4] Internet-Draft DetNet Ring July 2018 +---+#############+---+ | B |-------------| C | +-- DetNet +---+ +---+ egress #/ *\ #/ *\ #/ *\ +---+ +---+ DetNet--+ | A | | D | ingress +---+ +---+ \* */ \* */ \* */ +---+*************+---+ | F |-------------| E | +---+ +---+ ----- Physical Links ##### Clockwise_ ***** Counter Clockwise Figure 1: DetNet Ring for P2P traffic 2.2. Implementation implications of a DetNet ring for P2P traffic In a DetNet ring for P2P traffic, one path may be far longer than the other path for the DetNet (this is a DetNet issue more general than a ring). The buffer needs to be large enough to accommodate for the sequence number difference between these two paths. Otherwise, some packets may get lost when a link fault causes traffic switching from a path to another path. 3. P2MP DetNet Ring 3.1. DetNet applications on a single ring for P2MP traffic Figure 2 further depicts an example of the DetNet ring for P2MP real time traffic. Nodes A, B, C, E and F are DetNet aware devices, and P2MP DetNet traffic is transported from head-end node A to multiple tail-end nodes C, E and F. Jiang and et al Expires January 2, 2019 [Page 5] Internet-Draft DetNet Ring July 2018 Two approaches are described in Section 3.2 and 3.3 for P2MP traffic. +---+#############+---+ | B |-------------| C | +-- DetNet +---+*************+---+ egress #/ *\# #/ *\# #/ *\# +---+ +---+ DetNet--+ | A | | D | ingress +---+ +---+ \* */# \* */# \* */# +---+*************+---+ DetNet--+ | F |-------------| E |+-- DetNet egress +---+#############+---+ egress ----- Physical Links ##### Clockwise traffic ***** Counter Clockwise traffic Figure 2: DetNet Ring for P2MP traffic 3.2. Section LSPs as underlay (Service layer replication) If section LSPs are used as an underlay for DetNet services, a bidirectional section LSP tunnel is set up between each pair of neighboring nodes in the ring (e.g., node A and node B, ..., node F and node A). In this case, DetNet PW layer replicates the DetNet packets from one tail-end to another neighboring tail-end. The DetNet head-end (i.e., node A) in the ring needs to support DetNet replication function. Upon reception on node A, the DetNet traffic is replicated in node A, encapsulated with the specific PW and section LSP labels, and then transported on both section LSPs (i.e., A-B and A-F) originated from the head-end. All intermediate nodes (non tail-ends) on the ring SHOULD transparently forward the DetNet traffic with a specific PW to the next hop on the ring in the same direction. All DetNet tail-ends except the penultimate node (egress nodes such as nodes C and E in the clockwise, and node F, E and C in the counter clockwise) on the ring MUST support both DetNet PRF and PEF Jiang and et al Expires January 2, 2019 [Page 6] Internet-Draft DetNet Ring July 2018 functions. For example, upon reception of the clockwise traffic, node C terminates the section LSP and is aware of the DetNet traffic by inspection of the PW label in the packet. Firstly, node C needs to transparently forward the DetNet traffic with a specific PW to the next hop on the ring in the same direction. Secondly, DetNet traffic is directed to a DetNet PEF associated with a specific PW, only one copy of the DetNet service exits on egress by inspection of the DetNet sequence number. If multiple endpoints are attached to a tail-end node, a multicast module can be used to forward the filtered DetNet traffic to all these endpoints. To avoid a loop of DetNet service, the penultimate node in the ring (such as node B on the counter clock-wise LSP) needs to terminate the DetNet flow. For example, upon reception of the clockwise DetNet traffic, node F terminates the DetNet traffic by inspection of the PW label in the packet. As an alternative, the last DetNet tail-end (such as node C on the counter clock-wise LSP) may terminate the DetNet flow, so that the bandwidth from this node to the penultimate node can be saved. 3.3. P2MP LSP tunnels as underlay (LSP layer replication) If P2MP LSPs are used as an underlay for the DetNet service, a P2MP unidirectional LSP tunnel in clockwise is set up from head-end (ingress node A) to all the tail-ends (egress nodes C, E and F) for the ring, and another P2MP unidirectional LSP tunnel in counter clockwise is set up from head-end (ingress node A) to all the tail- ends (egress nodes F, E and C) for the ring. Thus, a PRF in LSP layer replicates the DetNet packets from one tail-end to another neighboring tail-end. The DetNet head-end (i.e., node A) in the ring needs to support DetNet PRF function. Upon reception on node A, the DetNet traffic is replicated, encapsulated with the specific PW and P2MP LSP labels, and transported on both P2MP LSP tunnels in the ring. All DetNet tail-ends (egress nodes such as node C, E and F in Figure 2) on the ring need to support the DetNet PEF function. For example, upon reception of the traffic, node C pops the P2MP LSP label and is aware of the DetNet traffic by inspection of the PW label in the label stack. Traffic from both directions with the same PW is directed to the same PEF so that only one copy of the Jiang and et al Expires January 2, 2019 [Page 7] Internet-Draft DetNet Ring July 2018 DetNet service exits on egress by inspection of the DetNet sequence number. If multiple endpoints are attached to a tail-end node, a multicast module can be used to forward the filtered DetNet traffic to all these endpoints. 4. DetNet Ring Interconnections Two DetNet rings can be connected via one or more interconnection nodes. Figures 3(a) and 3(b) show the ring interconnection scenarios with a single node and dual nodes respectively. In the interconnected rings, each ring operates in the same way as described in Sections 2 and 3 except the node or nodes that are used to interconnect two rings. In this section, we describe the behavior of interconnection nodes with the traffic going from Ring L to Ring R. Symmetrical description is assumed for the traffic in the other direction (i.e., from Ring R to Ring L). S T B C S T O---O O---O O---O / \ / \ / \ B I1/ \ / \ / \ O---O Ring R O U A O Ring L O Ring R O U / \ / \ /I\ / / \ / \ / \ / A O Ring L O---O O---O O---O \ /I2 V F E W V \ / O---O F E (a) (b) Figure 3: DetNet ring interconnection with: (a) single node (node I), and (b) dual nodes (nodes I1 and I2). Jiang and et al Expires January 2, 2019 [Page 8] Internet-Draft DetNet Ring July 2018 4.1. Single node interconnection In the case of the single node interconnection, as shown in Figure 3(a), both P2P and P2MP DetNet traffic that needs to be transported between Ring L and Ring R uses a single interconnection node between two rings. Thus, the interconnection node acts as a DetNet relay node, which provides both PRF and PEF functions. For P2P DetNet traffic going from Ring L to Ring R, interconnection node I receives the same Detnet flow traffic from both node C and node E (i.e., clockwise and counter-clockwise), a PEF in node I performs packet elimination, and a PRF in node I replicates the packet, node I then sends one copy to node S and another copy to node W. For P2MP DetNet traffic going from Ring L to Ring R, interconnection node I performs the same packet elimination and replication functions as described above. In addition, node I further transparently forwards the P2MP DetNet traffic on Ring L in the same direction if it is not the last tail-end node. 4.2. Dual node interconnection In order to prevent a single point of failure, two interconnection nodes can be used as shown in Figure 3(b). To provide high availability for DetNet services, dual node interconnection is recommended. Two interconnection nodes act as DetNet relay nodes, each provides both packet replication and elimination functions. 4.2.1. Dual node interconnection for P2P traffic For the P2P DetNet traffic that flows from Ring L to Ring R, the operation of interconnection nodes I1 and I2 follows the description on relay nodes shown in Figure 1 of Section 3.2.4 in [I-D.ietf-detnet-architecture]. In the following, the operation is explained with Figure 3(a). When interconnection node I1 receives clockwise traffic from node B, it replicates the traffic and sends one copy to interconnection node I2 and another copy to a PEF in node I1. When interconnection node I1 receives counter-clockwise traffic from interconnection node I2, it also forwards the traffic to the PEF of I1. At the PEF of I1, duplicate elimination is performed for the clockwise traffic from node B and the counter-clockwise traffic Jiang and et al Expires January 2, 2019 [Page 9] Internet-Draft DetNet Ring July 2018 from interconnection node I2, and only one copy is sent to the clockwise direction of Ring R (i.e., sent towards node S). When interconnection node I2 receives counter-clockwise traffic from node E, it replicates the traffic and sends one copy to interconnection node I1 and another copy to a PEF in node I2. When interconnection node I2 receives clockwise traffic from interconnection node I1, it also forwards the traffic to the PEF of I2. At the PEF of I2, duplicate elimination is performed for the counter-clockwise traffic from node E and the clockwise traffic from interconnection node I1, and only one copy is sent to the counter-clockwise direction of Ring R (i.e., sent towards node V). 4.2.2.Dual node interconnection for P2MP traffic using section LSP For the P2MP traffic that flows from Ring L to Ring R, each ring is configured and operated as described in Section 3.2 except the interconnection nodes, whose operations are described below. When interconnection node I1 receives clockwise traffic from node B, its PRF replicates the traffic and sends one copy to interconnection node I2 and another copy to node I1's PEF. When interconnection node I1 receives the counter-clockwise traffic from interconnection node I2, its PRF replicates the traffic and sends one copy to node B and another copy to node I1's PEF unless interconnection node I1 is the penultimate node for the counter- clockwise traffic on Ring L. In the case that interconnection node I1 is the penultimate node for the counter-clockwise traffic on Ring L, the counter-clockwise traffic from interconnection node I2 is only forwarded to node I1's PEF. At node I1's PEF, duplicate elimination is performed for the clockwise traffic from node B and the counter-clockwise traffic from interconnection node I2, and only one copy is sent to the clockwise direction of Ring R (i.e., sent towards node S). When interconnection node I2 receives the counter-clockwise traffic from node E, its PRF replicates the traffic and sends one copy to interconnection node I1 and another copy to node I2's PEF. Jiang and et al Expires January 2, 2019 [Page 10] Internet-Draft DetNet Ring July 2018 When interconnection node I2 receives the clockwise traffic from interconnection node I1, its PRF replicates the traffic and sends one copy to node E and another copy to node I2's PEF unless interconnection node I2 is the penultimate node for the clockwise traffic in Ring L. In the case that interconnection node I2 is the penultimate node for the clockwise traffic in Ring L, the clockwise traffic from interconnection node I1 is only forwarded to node I2's PEF. At node I2's PEF, duplicate elimination is performed for the counter-clockwise traffic from node E and the clockwise traffic from interconnection node I1, and only one copy is sent to the counter-clockwise direction of Ring R (i.e., sent towards node V). 4.2.3.Dual node interconnection for P2MP traffic using P2MP LSP If P2MP LSPs are used in the interconnected rings, two P2MP unidirectional LSP tunnels are used on each ring for the clockwise and counter-clockwise directions. When the P2MP traffic is forwarded from one ring to another ring, for example from Ring L to Ring R in Figure 3(b), each P2MP LSP in Ring L MUST include interconnection nodes I1 and I2 as its tail- ends. For Ring R, one P2MP LSP is set up from interconnection node I1 to all the tail-ends in the clockwise direction on Ring R, and the other P2MP LSP is set up from interconnection node I2 to all the tail-ends in the counter-clockwise direction on Ring R. Therefore, an interconnection node acts as a tail-end for one ring and a head-end for another ring in one direction, and performs the same operation of tail-end and head-end as specified in Section 3.3. 5. Resource reservation In order to guarantee that DetNet flows don't suffer from network congestion, resource reservation considerations as outlined in Section 4.3.2 of [I-D.ietf-detnet-architecture] apply here. 6. Security Considerations This document describes the application of DetNet on general ring topologies. Thus the security considerations as described in [I- D.ietf-detnet-dp-sol] also apply to this document. Jiang and et al Expires January 2, 2019 [Page 11] Internet-Draft DetNet Ring July 2018 7. IANA Considerations There are no IANA actions required by this document. 8. References 8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997 [I-D.ietf-detnet-architecture] Finn, N., Thubert, P., Varga, B., and J. Farkas, "Deterministic Networking Architecture", draft-ietf-detnet-architecture (work in progress), June 2018 [I-D.ietf-detnet-dp-sol-mpls] Korhonen, J., Varga, B., "DetNet MPLS Data Plane Encapsulation", draft-ietf-detnet-dp-sol-mpls (work in progress), June 2018 8.2. Informative References [I-D.ietf-detnet-dp-sol] Korhonen, J., Andersson, L., Jiang, Y., and etc., "DetNet Data Plane Encapsulation", draft-ietf- detnet-dp-sol (work in progress), March 2018 [I-D.ietf-detnet-use-cases] Grossman, E., and etc., "Deterministic Networking Use Cases", draft-ietf-detnet-use-cases (work in progress), June 2018 [RFC6974] Weingarten, Y., Bryant, S., and etc., "Applicability of MPLS Transport Profile for Ring Topologies", RFC 6974, July 2013 [RFC8227] Cheng, W., Wang, L., and etc., "MPLS-TP Shared-Ring Protection (MSRP) Mechanism for Ring Topology", RFC 8227, August 2017 Jiang and et al Expires January 2, 2019 [Page 12] Internet-Draft DetNet Ring July 2018 9. Acknowledgments TBD Authors' Addresses Yuanlong Jiang Huawei Technologies Co., Ltd. Bantian, Longgang district Shenzhen 518129, China Phone: +86-18926415311 Email: jiangyuanlong@huawei.com Norman Finn Huawei Technologies Co. Ltd 3755 Avocado Blvd, California 91941, USA Phone: +1 925 980 6430 Email: norman.finn@mail01.huawei.com Jeong-dong Ryoo ETRI 218 Gajeongno Yuseong-gu, Daejeon 305-700, South Korea Phone: +82-42-860-5384 Email: ryoo@etri.re.kr Balazs Varga Ericsson Konyves Kalman krt. 11/B Budapest 1097 Hungary Email: balazs.a.varga@ericsson.com Liang Geng China Mobile Beijing, China Email: gengliang@chinamobile.com Jiang and et al Expires January 2, 2019 [Page 13]