Internet DRAFT - draft-ietf-teas-pcecc-use-cases
draft-ietf-teas-pcecc-use-cases
TEAS Working Group Z. Li
Internet-Draft D. Dhody
Intended status: Informational Huawei Technologies
Expires: 12 July 2023 Q. Zhao
Etheric Networks
K. He
Tencent Holdings Ltd.
B. Khasanov
Yandex LLC
8 January 2023
The Use Cases for Path Computation Element (PCE) as a Central Controller
(PCECC).
draft-ietf-teas-pcecc-use-cases-13
Abstract
The Path Computation Element (PCE) is a core component of a Software-
Defined Networking (SDN) systems. It can compute optimal paths for
traffic across a network and update paths to reflect changes in the
network or traffic demands. PCE was developed to derive paths for
MPLS Label Switched Paths (LSPs), which are supplied to the head end
of the LSP using the Path Computation Element Communication Protocol
(PCEP).
SDN has a much broader applicability than signal MPLS traffic-
engineered (TE) paths, and the PCE may be used to determine paths in
a range of use cases including static LSPs, Segment Routing (SR),
Service Function Chaining (SFC), and most forms of a routed or
switched network. It is, therefore, reasonable to consider PCEP as a
control protocol for use in these environments to allow the PCE to be
fully enabled as a central controller.
A PCE as a Central Controller (PCECC) can simplify the processing of
a distributed control plane by blending it with elements of SDN and
without necessarily completely replacing it. This document describes
general considerations for PCECC deployment and examines its
applicability and benefits, as well as its challenges and
limitations, through a number of use cases. PCEP extensions which
required for the PCECC use cases are covered in separate documents.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 12 July 2023.
Copyright Notice
Copyright (c) 2023 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
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. PCECC for Label Management . . . . . . . . . . . . . . . 5
3.2. PCECC and Segment Routing . . . . . . . . . . . . . . . . 7
3.2.1. PCECC SID Allocation . . . . . . . . . . . . . . . . 8
3.2.2. PCECC for SR Best Effort (BE) Path . . . . . . . . . 9
3.2.3. PCECC for SR-TE Path . . . . . . . . . . . . . . . . 9
3.2.4. PCECC for SRv6 . . . . . . . . . . . . . . . . . . . 12
3.3. PCECC for Static TE LSP . . . . . . . . . . . . . . . . . 13
3.4. PCECC for Load Balancing (LB) . . . . . . . . . . . . . . 15
3.5. PCECC and Inter-AS TE . . . . . . . . . . . . . . . . . . 18
3.6. PCECC for Multicast LSPs . . . . . . . . . . . . . . . . 21
3.6.1. PCECC for P2MP/MP2MP LSPs' Setup . . . . . . . . . . 21
3.6.2. PCECC for the End-to-End Protection of P2MP/MP2MP
LSPs . . . . . . . . . . . . . . . . . . . . . . . . 23
3.6.3. PCECC for the Local Protection of the P2MP/MP2MP
LSPs . . . . . . . . . . . . . . . . . . . . . . . . 24
3.7. PCECC for Traffic Classification . . . . . . . . . . . . 26
3.8. PCECC for SFC . . . . . . . . . . . . . . . . . . . . . . 26
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3.9. PCECC for Native IP . . . . . . . . . . . . . . . . . . . 27
3.10. PCECC for BIER . . . . . . . . . . . . . . . . . . . . . 28
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
5. Security Considerations . . . . . . . . . . . . . . . . . . . 29
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 29
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 29
7.1. Normative References . . . . . . . . . . . . . . . . . . 29
7.2. Informative References . . . . . . . . . . . . . . . . . 30
Appendix A. Other Use Cases of PCECC . . . . . . . . . . . . . . 37
A.1. PCECC for Network Migration . . . . . . . . . . . . . . . 37
A.2. PCECC for L3VPN and PWE3 . . . . . . . . . . . . . . . . 38
A.3. PCECC for Local Protection (RSVP-TE) . . . . . . . . . . 39
A.4. Using reliable P2MP TE based multicast delivery for
distributed computations (MapReduce-Hadoop) . . . . . . . 40
Appendix B. Contributor Addresses . . . . . . . . . . . . . . . 42
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 43
1. Introduction
The Path Computation Element (PCE) [RFC4655] was developed to offload
the path computation function from routers in an MPLS traffic-
engineered (TE) network. It can compute optimal paths for traffic
across a network and can also update the paths to reflect changes in
the network or traffic demands. The role and function of PCE have
grown to cover several other uses (such as GMPLS [RFC7025],
Multicast), and to allow delegated stateful control [RFC8231] and
PCE-initiated use of network resources [RFC8281].
According to [RFC7399], Software-Defined Networking (SDN) refers to a
separation between the control elements and the forwarding components
so that software running in a centralized system, called a
controller, can act to program the devices in the network to behave
in specific ways. A required element in an SDN architecture is a
component that plans how the network resources will be used and how
the devices will be programmed. It is possible to view this
component as performing specific computations to place traffic flows
within the network given knowledge of the availability of network
resources, how other forwarding devices are programmed, and the way
that other flows are routed. This is the function and purpose of a
PCE, and the way that a PCE integrates into a wider network control
system (including an SDN system) is presented in [RFC7491].
[RFC8283] introduces the architecture for the PCE as a central
controller as an extension to the architecture described in [RFC4655]
and assumes the continued use of PCEP as the protocol used between
the PCE and PCC. [RFC8283] further examines the motivations and
applicability of PCEP as a Southbound Interface (SBI) and introduces
the implications for the protocol.
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[RFC9050] introduces the procedures and extensions for PCEP to
support the PCECC architecture [RFC8283].
This document describes the various use cases for the PCECC
architecture.
2. Terminology
The following terminology is used in this document.
IGP: Interior Gateway Protocol. In the document we assume either
Open Shortest Path First (OSPF) [RFC2328][RFC5340] or Intermediate
System to Intermediate System (IS-IS) [RFC1195] as IGP.
PCC: Path Computation Client. As per [RFC4655], any client
application requesting a path computation to be performed by a Path
Computation Element.
PCE: Path Computation Element. As per [RFC4655], an entity
(component, application, or network node) that is capable of
computing a network path or route based on a network graph and
applying computational constraints.
PCECC: PCE as a central controller. Extension of PCE to support SDN
functions as per [RFC8283].
TE: Traffic Engineering [I-D.ietf-teas-rfc3272bis].
3. Use Cases
[RFC8283] describes various use cases for PCECC such as:
* Use of PCECC to set up Static TE LSPs. The PCEP extension for
this use case is in [RFC9050].
* Use of PCECC in Segment Routing [RFC8402].
* Use of PCECC to set up Multicast Point-to-Multipoint (P2MP) LSP.
* Use of PCECC to set up Service Function Chaining (SFC) [RFC7665].
* Use of PCECC in Optical Networks.
Section 3.1 describe the general case of PCECC being in charge of
managing MPLS label space which is a prerequisite for further use
cases. Further, various use cases (SR, Multicast etc) are described
in the following sections to showcase scenarios that can benefit from
the use of PCECC.
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3.1. PCECC for Label Management
As per [RFC8283], in some cases, the PCE-based controller can take
responsibility for managing some part of the MPLS label space for
each of the routers that it controls, and it may take wider
responsibility for partitioning the label space for each router and
allocating different parts for different uses, communicating the
ranges to the router using PCEP.
[RFC9050] describes a mode where LSPs are provisioned as explicit
label instructions at each hop on the end-to-end path. Each router
along the path must be told what label forwarding instructions to
program and what resources to reserve. The controller uses PCEP to
communicate with each router along the path of the end-to-end LSP.
For this to work, the PCE-based controller will take responsibility
for managing some part of the MPLS label space for each of the
routers that it controls. An extension to PCEP could be done to
allow a PCC to inform the PCE of such a label space to control. (See
[I-D.li-pce-controlled-id-space] for a possible PCEP extension to
support advertisement of the MPLS label space to the PCE to control.)
[RFC8664] specifies extensions to PCEP that allow a stateful PCE to
compute, update or initiate SR-TE paths.
[I-D.ietf-pce-pcep-extension-pce-controller-sr] describes the
mechanism for PCECC to allocate and provision the node/prefix/
adjacency label (Segment Routing Identifier (SID)) via PCEP. To make
such allocation PCE needs to be aware of the label space from Segment
Routing Global Block (SRGB) or Segment Routing Local Block (SRLB)
[RFC8402] of the node that it controls. A mechanism for a PCC to
inform the PCE of such a label space to control is needed within
PCEP. The full SRGB/SRLB of a node could be learned via existing IGP
or BGP-LS mechanisms too.
Further, there have been proposals for a global label range in MPLS,
the PCECC architecture could be used as means to learn the label
space of nodes, and could also be used to determine and provision the
global label range.
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+------------------------------+ +------------------------------+
| PCE DOMAIN 1 | | PCE DOMAIN 2 |
| +--------+ | | +--------+ |
| | | | | | | |
| | PCECC1 | ---------PCEP---------- | PCECC2 | |
| | | | | | | |
| | | | | | | |
| +--------+ | | +--------+ |
| ^ ^ | | ^ ^ |
| / \ PCEP | | PCEP / \ |
| V V | | V V |
| +--------+ +--------+ | | +--------+ +--------+ |
| |NODE 11 | | NODE 1n| | | |NODE 21 | | NODE 2n| |
| | | ...... | | | | | | ...... | | |
| | PCECC | | PCECC | | | | PCECC | |PCECC | |
| |Enabled | | Enabled| | |Enabled | |Enabled | |
| +--------+ +--------+ | | +--------+ +--------+ |
| | | |
+------------------------------+ +------------------------------+
Figure 1: PCECC for Label Management
* As shown in Figure 1, PCC will advertise the PCECC capability to
the PCE central controller (PCECC) [RFC9050].
* The PCECC could also learn the label range set aside by the PCC
([I-D.li-pce-controlled-id-space]).
* Optionally, the PCECC could determine the shared MPLS global label
range for the network.
- In the case that the shared global label range need to be
negotiated across multiple domains, the central controllers of
these domains will also need to negotiate a common global label
range across domains.
- The PCECC will need to set the shared global label range to all
PCC nodes in the network.
As per [RFC9050], PCECC could also rely on the PCC to make label
allocations initially and use PCEP to distribute it to where it is
needed.
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3.2. PCECC and Segment Routing
Segment Routing (SR) leverages the source routing paradigm. Using
SR, a source node steers a packet through a path without relying on
hop-by-hop signaling protocols such as LDP [RFC5036] or RSVP-TE
[RFC3209]. Each path is specified as an ordered list of instructions
called "segments". Each segment is an instruction to route the
packet to a specific place in the network, or to perform a specific
service on the packet. A database of segments can be distributed
through the network using a routing protocol (such as IS-IS or OSPF)
or by any other means. PCEP (and PCECC) could also be one of them.
[RFC8664] specifies the SR specific PCEP extensions. PCECC may
further use PCEP protocol for SR SIDs (Segment Identifiers)
distribution to the SR nodes (PCC) with some benefits. If the PCECC
allocates and maintains the SIDs in the network for the nodes and
adjacencies; and further distributes them to the SR nodes directly
via the PCEP session then it is more advantageous over the
configurations on each SR node and flooding them via IGP, especially
in a SDN environment.
When the PCECC is used for the distribution of the Node-SID and Adj-
SID, the Node-SID is allocated from the SRGB of the node. For the
allocation of Adj-SID, the allocation is from the SRLB of the node as
described in [I-D.ietf-pce-pcep-extension-pce-controller-sr].
[RFC8355] identifies various protection and resiliency usecases for
SR. Path protection lets the ingress node be in charge of the
failure recovery (used for SR-TE). Also protection can be performed
by the node adjacent to the failed component, commonly referred to as
local protection techniques or fast-reroute (FRR) techniques. In
case of PCECC, the protection paths can be pre-computed and setup by
the PCE.
The Figure 2 illustrates the use case where the Node-SID and Adj-SID
are allocated by the PCECC.
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192.0.2.1/32
+----------+
| R1(1001) |
+----------+
|
+----------+
| R2(1002) | 192.0.2.2/32
+----------+
* | * *
* | * *
*link1| * *
192.0.2.4/32 * | *link2 * 192.0.2.5/32
+-----------+ 9001| * +-----------+
| R4(1004) | | * | R5(1005) |
+-----------+ | * +-----------+
* | *9003 * +
* | * * +
* | * * +
+-----------+ +-----------+
192.0.2.3/32 | R3(1003) | |R6(1006) |192.0.2.6/32
+-----------+ +-----------+
|
+-----------+
| R8(1008) | 192.0.2.8/32
+-----------+
Figure 2: SR Topology
3.2.1. PCECC SID Allocation
Each node (PCC) is allocated a Node-SID by the PCECC. The PCECC
needs to update the label mapping of each node to all the other nodes
in the domain. After receiving the label mapping, each node (PCC)
uses the local routing information to determine the nexthop and
download the label forwarding instructions accordingly. The
forwarding behavior and the end result is the same as IGP shortest-
path SR forwarding based on Node-SID. Thus, from anywhere in the
domain, it enforces the ECMP-aware shortest-path forwarding of the
packet towards the related node.
For each adjacency in the network, a PCECC can allocate an Adj-SID.
The PCECC sends a PCInitiate message to update the label mapping of
each adjacency to the corresponding nodes in the domain. Each node
(PCC) downloads the label forwarding instructions accordingly. The
forwarding behavior and the end result are similar to IGP-based Adj-
SID allocation and usage in SR.
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These mechanisms are described in
[I-D.ietf-pce-pcep-extension-pce-controller-sr].
3.2.2. PCECC for SR Best Effort (BE) Path
In this use case, the PCECC just needs to allocate the Node-SID
(without calculating the explicit path for the SR path). The ingress
router of the forwarding path just needs to encapsulate the
destination Node-SID on top of the packet. All the intermediate
nodes will forward the packet based on the destination Node-SID. It
is similar to the LDP LSP.
R1 may send a packet to R8 simply by pushing an SR label with segment
{1008} (Node-SID for R8). The path will be based on the routing/
nexthop calculation on the routers.
3.2.3. PCECC for SR-TE Path
SR-TE paths may not follow an IGP SPT. Such paths may be chosen by a
PCECC and provisioned on the ingress node of the SR-TE path. The SR
header consists of a list of SIDs (or MPLS labels). The header has
all necessary information so that, the packets can be guided from the
ingress node to the egress node of the path; hence, there is no need
for any signalling protocol. For the case where strict traffic
engineering path is needed, all the Adj-SID are stacked, otherwise a
combination of node-SID or adj-SID can be used for the SR-TE paths.
R1 may send a packet to R8 by pushing an SR header with segment list
{1002, 9001, 1008}. Where, 1002 and 1008 are the Node-SID of R2 and
R8 respectively. 9001 is the Adj-SID for the link1. The path should
be: R1-R2-link1-R3-R8.
To achieve this, the PCECC first allocates and distribute SIDs as
described in Section 3.2.1. [RFC8664] describe the mechanism for a
PCE to compute, update, or initiate SR-TE paths.
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192.0.2.1/32
+----------+
| R1 (1001)|
+----------+
| |
90011 | |90012
link1 | |link2
+----------+
| R2 (1002)| 192.0.2.2/32
+----------+
link3 * | * * link4
90023 * | * * 90024
*link5| * *
192.0.2.4/32 *90025 | *link6 * 192.0.2.5/32
+-----------+ | *90026+-----------+
| R4 (1004) | | * | R5 (1005) |
+-----------+ | * +-----------+
* | * +
link10 * | * link7 +
* | * +
+-----------+ +-----------+
192.0.2.3/32 | R3 (1003) | |R6 (1006) |192.0.2.6/32
+-----------+ +-----------+
| |
|link8 |
| |----------|link9
+-----------+
| R8 (1008) | 192.0.2.8/32
+-----------+
Figure 3: PCECC TE LSP Setup Example
Refer Figure 3 for an example of TE topology, where, 100x - are Node-
SIDs and 900xx - are Adj-SIDs.
* The SID allocation and distribution are done by the PCECC with all
Node-SIDs (100x) and all Adj-SIDs (900xx).
* Based on path computation request/delegation or PCE initiation,
the PCECC receives a request with constraints and optimization
criteria from a PCC.
* PCECC will calculate the optimal path according to given
constrains (e.g. bandwidth).
* PCECC will provision SR-TE LSP (path R1-link1-R2-link6-R3-R8) at
the ingress node: {90011,1002,90026,1003,1008}
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* For the end-to-end protection, PCECC can provision the secondary
path (R1-link2-R2-link4-R5-R8): {90012,1002,90024,1005,1008}.
3.2.3.1. PCECC for SR Policy
[RFC8402] defines Segment Routing architecture, which uses an SR
Policy to steer packets from a node through an ordered list of
segments. The SR Policy could be configured on the headed or
instantiated by an SR controller. The SR architecture does not
restrict how the controller programs the network. In this case, the
focus is on PCEP as the protocol for SR Policy delivery from PCE to
PCC.
An SR Policy architecture is described in [RFC9256]. An SR Policy is
a framework that enables the instantiation of an ordered list of
segments on a node for implementing a source routing policy for the
steering of traffic for a specific purpose (e.g. for a specific SLA)
from that node.
An SR Policy is identified through the tuple <headend, color,
endpoint>.
Figure 3 is used as an example of PCECC application for SR Policy
instantiation, where, 100x - are Node-SIDs and 900xx - are Adj-SIDs.
Let's assume that R1 needs to have two disjoint SR Policies towards
R8 based on different bandwidth, the possible paths are:
POL1: {Headend R1, color 100, Endpoint R8; Candidate Path1:
Segment List 1: {90011,1002,90023,1004,1003,1008}}
POL2: {Headend R1, color 200, Endpoint R8; Candidate Path1:
Segment List 1: {90012,1002,90024,1005,1006,1008}}
Each SR Policy (including candidate path and segment list) will be
signaled to a headend (R1) via PCEP
[I-D.ietf-pce-segment-routing-policy-cp] with addition of an
ASSOCIATION object. Binding SID (BSID) [RFC8402] can be used for
traffic steering of labelled traffic into SR Policy, BSID can pe
provisioned from PCECC also via PCEP
[I-D.ietf-pce-binding-label-sid]. For non-labelled traffic steering
into the SR Policy POL1 or POL2 a per-destination traffic steering
will be used by means of BGP Color extended community [RFC9012]
The procedure:
PCECC allocates Node-SIDs and Adj-SIDs as described in Section 3.1
for all nodes and links.
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PCECC will calculate disjoint paths for POL1 and POL2 and create
Segment Lists for them:{90011,1002,90023,1004,1003,1008};{90012,10
02,90024,1005,1006,1008}.
PCECC will form both SR Policies POL1 and POL2.
PCECC will send both POL1 and POl2 to R1 via PCEP.
PCECC optionally can allocate BSIDs for the SR Policies.
The traffic from R1 to R8 which fits to color 100 will be steered
to POL1 and follows the path: R1-link1-R2-link3-R4-R3-R8. The
traffic from R1 to R8 which fits to color 200 will be steered to
POL2 and follows the path: R1-link2-R2-link4-R5-R6-R8. Due to the
possibility to have many Segment Lists in the same Candidate Path
of each POL1/POL2, PCECC could provision more paths towards R8 and
traffic will be balanced either as ECMP or as w/ECMP. This is the
advantage of SR Policy architecture.
3.2.4. PCECC for SRv6
As per [RFC8402], with Segment Routing (SR), a node steers a packet
through an ordered list of instructions, called segments. Segment
Routing can be applied to the IPv6 architecture with the Segment
Routing Header (SRH) [RFC8754]. A segment is encoded as an IPv6
address. An ordered list of segments is encoded as an ordered list
of IPv6 addresses in the routing header. The active segment is
indicated by the Destination Address of the packet. Upon completion
of a segment, a pointer in the new routing header is incremented and
indicates the next segment.
As per [RFC8754], an SRv6 Segment is a 128-bit value. "SRv6 SID" or
simply "SID" are often used as a shorter reference for "SRv6
Segment". Further details are in An illustration is provided in
[RFC8986] where SRv6 SID is represented as LOC:FUNCT.
[I-D.ietf-pce-segment-routing-ipv6] extends [RFC8664] to support SR
for IPv6 data plane. Further a PCECC could be extended to support
SRv6 SID allocation and distribution. PCECC PCEP extensions for SRv6
[I-D.dhody-pce-pcep-extension-pce-controller-srv6] will be used for
that.
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2001:db8::1
+----------+
| R1 |
+----------+
|
+----------+
| R2 | 2001:db8::2
+----------+
* | * *
* | * *
*link1| * *
2001:db8::4 * | *link2 * 2001:db8::5
+-----------+ | * +-----------+
| R4 | | * | R5 |
+-----------+ | * +-----------+
* | * * +
* | * * +
* | * * +
+-----------+ +-----------+
2001:db8::3 | R3 | |R6 |2001:db8::6
+-----------+ +-----------+
|
+-----------+
| R8 | 2001:db8::8
+-----------+
Figure 4: PCECC for SRv6
In the case, as shown in Figure 4, PCECC could assign the SRv6 SID
(in form of an IPv6 address) to be used for node and adjacency.
Later SRv6 path in form of a list of SRv6 SID could be used at the
ingress. Some examples -
* SRv6 SID-List={2001:db8::8} - The best path towards R8
* SRv6 SID-List={2001:db8::5, 2001:db8::8} - The path towards R8 via
R5
The rest of the procedures and mechanisms remain the same as SR-MPLS.
3.3. PCECC for Static TE LSP
As described in Section 3.1.2 of [RFC8283], PCECC architecture
support the provisioning of static TE LSP. To achieve this, the
existing PCEP can be used to communicate between the PCECC and nodes
along the path to provision explicit label instructions at each hop
on the end-to-end path. Each router along the path must be told what
label-forwarding instructions to program and what resources to
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reserve. The PCE-based controller keeps a view of the network and
determines the paths of the end-to-end LSPs, and the controller uses
PCEP to communicate with each router along the path of the end-to-end
LSP.
192.0.2.1/32
+----------+
| R1 |
+----------+
| |
|link1 |
| |link2
+----------+
| R2 | 192.0.2.2/32
+----------+
link3 * | * * link4
* | * *
*link5| * *
192.0.2.4/32 * | *link6 * 192.0.2.5/32
+-----------+ | * +-----------+
| R4 | | * | R5 |
+-----------+ | * +-----------+
* | * * +
link10 * | * *link7 +
* | * * +
+-----------+ +-----------+
192.0.2.3/32 | R3 | |R6 |192.0.2.6/32
+-----------+ +-----------+
| |
|link8 |
| |link9
+-----------+
| R8 | 192.0.2.8/32
+-----------+
Figure 5: PCECC TE LSP Setup Example
Refer Figure 5 for an example TE topology.
* Based on path computation request/delegation or PCE initiation,
the PCECC receives a request with constraints and optimization
criteria.
* PCECC will calculate the optimal path according to given
constrains (e.g. bandwidth).
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* PCECC will provision each node along the path and assign incoming
and outgoing labels from R1 to R8 with the path as
"R1-link1-R2-link3-R4-link10-R3-link8-R8":
- R1: Outgoing label 1001 on link 1
- R2: Incoming label 1001 on link 1
- R2: Outgoing label 2003 on link 3
- R4: Incoming label 2003 on link 3
- R4: Outgoing label 4010 on link 10
- R3: Incoming label 4010 on link 10
- R3: Outgoing label 3008 on link 8
- R8: Incoming label 3008 on link 8
* This can also be represented as {R1, link1, 1001}, {1001, R2,
link3, 2003], {2003, R4, link10, 4010}, {4010, R3, link8, 3008},
{3008, R8}.
* For the end to end protection, PCECC program each node along the
path from R1 to R8 with the secondary path: {R1, link2, 1002},
{1002, R2, link4, 2004], {2004, R5, link7, 5007}, {5007, R3,
link9, 3009}, {3009, R8}.
* It is also possible to have a bypass path for the local protection
setup by the PCECC. For example, the primary path as above, then
to protect the node R4 locally, PCECC can program the bypass path
like this: {R2, link5, 2005}, {2005, R3}. By doing this, the node
R4 is locally protected at R2.
3.4. PCECC for Load Balancing (LB)
Very often many service providers use TE tunnels for solving issues
with non-deterministic paths in their networks. One example of such
applications is usage of TEs in the mobile backhaul (MBH). Consider
the topology as shown in Figure 6 (AGG1...AGGN are Aggregation
Routers, Core 1...Core N are Core routers) -
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TE1 -------------->
+---------+ +--------+ +--------+ +--------+ +------+ +---+
| Access |----| Access |----| AGG 1 |----| AGG N-1|----|Core 1|--|SR1|
| SubNode1| | Node 1 | +--------+ +--------+ +------+ +---+
+---------+ +--------+ | | | ^ |
| Access | Access | AGG Ring 1 | | |
| SubRing 1 | Ring 1 | | | | |
+---------+ +--------+ +--------+ | | |
| Access | | Access | | AGG 2 | | | |
| SubNode2| | Node 2 | +--------+ | | |
+---------+ +--------+ | | | | |
| | | | | | |
| | | +----TE2----|-+ |
+---------+ +--------+ +--------+ +--------+ +------+ +---+
| Access | | Access |----| AGG 3 |----| AGG N |----|Core N|--|SRn|
| SubNodeN|----| Node N | +--------+ +--------+ +------+ +---+
+---------+ +--------+
Figure 6: PCECC Load Balancing (LB) Use Case
This MBH architecture uses L2 access rings and sub-rings. L3 starts
at the aggregation layer. For the sake of simplicity, the figure
shows only one access sub-ring. The access ring and aggregation ring
are connected by Nx10GE interfaces. The aggregation domain runs its
own IGP. There are two Egress routers (AGG N-1,AGG N) that are
connected to the Core domain (Core 1...Core N) via L2 interfaces.
Core also has connections to service routers, RSVP-TE or SR-TE is
used for MPLS transport inside the ring. There could be at least 2
tunnels (one way) from each AGG router to egress AGG routers. There
are also many L2 access rings connected to AGG routers.
Service deployment, made by means of Layer 2 Virtual Private Networks
(L2VPNs) (Virtual Private LAN Service (VPLS)), Layer 3 Virtual
Private Networks (L3VPNs) or Ethernet VPNs (EVPNs). Those services
use MPLS TE (or SR-TE) as transport towards egress AGG routers. TE
tunnels could be also used as transport towards service routers in
case of seamless MPLS ([I-D.ietf-mpls-seamless-mpls]) based
architecture.
There is a need to solve the following tasks:
* Perform automatic load-balance amongst TE tunnels according to
current traffic load.
* TE bandwidth (BW) management: Provide guaranteed BW for specific
services: High Speed Data Service (HSI)), IPTV, etc., provide
time-based BW reservation (BW on demand (BoD)) for other services.
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* Simplify the development of TE tunnels by automation without any
manual intervention.
* Provide flexibility for Service Router placement (anywhere in the
network by the creation of transport LSPs to them).
In this section, the focus is on load balancing (LB) task. LB task
could be solved by means of PCECC in the following way:
* Application or network service or operator can ask SDN controller
(PCECC) for LSP based load balancing between AGG X and AGG N/AGG
N-1 (egress AGG routers which have connections to core). Each of
these will have associated constrains (i.e. bandwidth, inclusion
or exclusion specific links or nodes, number of paths, objective
function (OF), need for disjoint LSP paths etc.);
* PCECC could calculate multiple (say N) LSPs according to given
constrains, calculation is based on results of Objective Function
(OF) [RFC5541], constraints, endpoints, same or different
bandwidth (BW) , different links (in case of disjoint paths) and
other constrains.
* Depending on given LSP Path setup type (PST), PCECC will download
instructions to the PCC. At this stage it is assumed the PCECC is
aware of the label space it controls and SID allocation and
distribution is already done in case of SR.
* PCECC will send PCInitiate message [RFC8281] towards ingress AGG X
router(PCC) for each of N LSPs and receives PCRpt PCEP message
[RFC8231] back from PCCs. If PST is PCECC-SR, the PCECC will
include a SID stack as per [RFC8664]. If PST is PCECC (basic),
then the PCECC will assign labels along the calculated path and
set up the path by sending central controller instructions in PCEP
message to each node along the path of the LSP as per [RFC9050]
and then send PCUpd message to the ingress AGG X router with
information about new LSP. AGG X(PCC) will respond with PCRpt
with LSP status.
* AGG X as ingress router now have N LSPs towards AGG N and AGG N-1
which are available for installing to router's forwarding table
and load-balance traffic between them. Traffic distribution
between those LSPs depends on particular realization of hash-
function on that router.
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* Since PCECC is aware of TEDB (TE state) and LSP-DB, it can manage
and prevent possible over-subscriptions and limit number of
available load-balance states. Via PCECC mechanism the control
can take quick actions into the network by directly provisioning
the central control instructions.
3.5. PCECC and Inter-AS TE
There are various signaling options for establishing Inter-AS TE LSP:
contiguous TE LSP [RFC5151], stitched TE LSP [RFC5150], and nested TE
LSP [RFC4206].
Requirements for PCE-based Inter-AS setup [RFC5376] describe the
approach and PCEP functionality that is needed for establishing
Inter-AS TE LSPs.
[RFC5376] also gives Inter- and Intra-AS PCE Reference Model (as
shown in Figure 7) that is provided below in shortened form for the
sake of simplicity.
Inter-AS Inter-AS
PCC <-->PCE1<--------->PCE2
:: :: ::
:: :: ::
R1----ASBR1====ASBR3---R3---ASBR5
| AS1 | | PCC |
| | | AS2 |
R2----ASBR2====ASBR4---R4---ASBR6
:: ::
:: ::
Intra-AS Intra-AS
PCE3 PCE4
Figure 7: Shortened form of Inter- and Intra-AS PCE Reference Model
The PCECC belonging to the different domains can co-operate to set up
inter-AS TE LSP. The stateful H-PCE [RFC8751] mechanism could also
be used to establish a per-domain PCECC LSP first. These could be
stitched together to form inter-AS TE LSP as described in
[I-D.ietf-pce-stateful-interdomain].
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For the sake of simplicity, here the focus is on a simplified Inter-
AS case when both AS1 and AS2 belong to the same service provider
administration. In that case, Inter and Intra-AS PCEs could be
combined in one single PCE if such combined PCE performance is enough
for handling the load. The PCE will require interfaces (PCEP and
BGP-LS) to both domains. PCECC redundancy mechanisms are described
in [RFC8283]. Thus routers (PCCs) in AS1 and AS2 can send PCEP
messages towards the same PCECC.
+----BGP-LS------+ +------BGP-LS-----+
| | | |
+-PCEP-|----++-+-------PCECC-----PCEP--++-+-|-------+
+-:------|----::-:-+ +--::-:-|-------:---+
| : | :: : | | :: : | : |
| : RR1 :: : | | :: : RR2 : |
| v v: : | LSP1 | :: v v |
| R1---------ASBR1=======================ASBR3--------R3 |
| | v : | | :v | |
| +----------ASBR2=======================ASBR4---------+ |
| | Region 1 : | | : Region 1 | |
|----------------:-| |--:-------------|--|
| | v | LSP2 | v | |
| +----------ASBR5=======================ASBR6---------+ |
| Region 2 | | Region 2 |
+------------------+ <--------------> +-------------------+
MPLS Domain 1 Inter-AS MPLS Domain 2
<=======AS1=======> <========AS2=======>
Figure 8: Particular case of Inter-AS PCE
In a case of PCECC Inter-AS TE scenario (as shown in Figure 8) where
service provider controls both domains (AS1 and AS2), each of them
have own IGP and MPLS transport. There is a need to setup Inter-AS
LSPs for transporting different services on top of them (Voice, L3VPN
etc.). Inter-AS links with different capacity exist in several
regions. The task is not only to provision those Inter-AS LSPs with
given constrains but also calculate the path and pre-setup the backup
Inter-AS LSPs that will be used if primary LSP fails.
As per the Figure 8, LSP1 from R1 to R3 goes via ASBR1 and ASBR3, and
it is the primary Inter-AS LSP. R1-R3 LSP2 that goes via ASBR5 and
ASBR6 is the backup one. In addition there could also be a bypass
LSP setup to protect against ASBR or inter-AS link failures.
After the addition of PCECC functionality to PCE (SDN controller),
PCECC-based Inter-AS TE model should follow the PCECC usecase for TE
LSP including requirements of [RFC5376] with the following details:
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* Since PCECC needs to know the topology of both domains AS1 and
AS2, PCECC can utilize the BGP-LS peering with routers (or RRs) in
both domains.
* PCECC needs to establish PCEP connectivity with all routers in
both domains (see also section 4 in [RFC5376]).
* After operator's application or service orchestrator will create
request for tunnel creation of specific service, PCECC will
receive that request via NBI (NBI type is implementation
dependent, could be NETCONF/Yang, REST etc.). Then PCECC will
calculate the optimal path based on Objective Function (OF) and
given constraints (i.e. path setup type, bandwidth etc.),
including those from [RFC5376]: priority, AS sequence, preferred
ASBR, disjoint paths, protection type. On this step we will have
two paths: R1-ASBR1-ASBR3-R3, R1-ASBR5-ASBR6-R3
* Depending on given LSP PST (PCECC or PCECC-SR), PCECC will use
central control download instructions to the PCC. At this stage
it is assumed the PCECC is aware of the label space it controls
and in case of SR the SID allocation and distribution is already
done.
* PCECC will send PCInitiate message [RFC8281] towards the ingress
router R1 (PCC) in AS1 and receives PCRpt PCEP message [RFC8231]
back from. If the PST is PCECC-SR, the PCECC will include the SID
stack as per [RFC8664]. Optionally, a binding SID or BGP Peering-
SID [RFC9087] can also be included on the AS boundary. The backup
SID stack can be installed at ingress R1 but more importantly each
node along the SR path could also do the local protection just
based on the top segment. If the PST is PCECC (basic), when the
PCECC will assign labels along the calculated paths
(R1-ASBR1-ASBR3-R3, R1-ASBR5-ASBR6-R3); and set up the path by
sending central controller instructions in PCEP message to each
node along the path of the LSPs as per [RFC9050]. Then PCECC will
send PCUpd message to the ingress R1 router with an information
about new LSPs and R1 will respond by PCRpt with LSP(s) status.
* After that step R1 now have primary and backup TEs (LSP1 and LSP2)
towards R3. It is up to router implementation how to make
switchover to backup LSP2 if LSP1 fails.
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3.6. PCECC for Multicast LSPs
The multicast LSPs can be setup via the RSVP-TE P2MP or Multipoint
LDP (mLDP) protocols. The setup of these LSPs may require manual
configurations and complex signaling when the protection is
considered. By using the PCECC solution, the multicast LSP can be
computed and setup through centralized controller which has the full
picture of the topology and bandwidth usage for each link. It not
only reduces the complex configurations comparing the distributed
RSVP-TE P2MP or mLDP signaling, but also it can compute the disjoint
primary path and secondary P2MP path efficiently.
3.6.1. PCECC for P2MP/MP2MP LSPs' Setup
It is assumed the PCECC is aware of the label space it controls for
all nodes and makes allocations accordingly.
+----------+
| R1 | Root node of the multicast LSP
+----------+
|9000 (L0)
+----------+
Transit Node | R2 |
branch +----------+
* | * *
9001* | * *9002
L1 * | * *L2
+-----------+ | * +-----------+
| R4 | | * | R5 | Transit Nodes
+-----------+ | * +-----------+
* | * * +
9003* | * * +9004
L3 * | * * +L4
+-----------+ +-----------+
| R3 | | R6 | Leaf Node
+-----------+ +-----------+
9005| L5
+-----------+
| R8 | Leaf Node
+-----------+
Figure 9: Using PCECC for P2MP/MP2MP LSPs' Setup
The P2MP examples (based on Figure 9) are explained here, where R1 is
the root and the router R8 and R6 are the leaves.
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* Based on the P2MP path computation request / delegation or PCE
initiation, the PCECC receives the request with constraints and
optimization criteria.
* PCECC will calculate the optimal P2MP path according to given
constrains (i.e.bandwidth).
* PCECC will provision each node along the path and assign incoming
and outgoing labels from R1 to {R6, R8} with the path as
"R1-L0-R2-L2-R5-L4-R6" and "R1-L0-R2-L1-R4-L3-R3-L5-R8":
- R1: Outgoing label 9000 on link L0
- R2: Incoming label 9000 on link L0
- R2: Outgoing label 9001 on link L1 (*)
- R2: Outgoing label 9002 on link L2 (*)
- R5: Incoming label 9002 on link L2
- R5: Outgoing label 9004 on link L4
- R6: Incoming label 9004 on link L4
- R4: Incoming label 9001 on link L1
- R4: Outgoing label 9003 on link L3
- R3: Incoming label 9003 on link L3
- R3: Outgoing label 9005 on link L5
- R8: Incoming label 9005 on link L5
* This can also be represented as : {R1, 6000}, {6000, R2,
{9001,9002}}, {9001, R4, 9003}, {9002, R5, 9004} {9003, R3, 9005},
{9004, R6}, {9005, R8}. The main difference (*) is in the branch
node instruction at R2 where two copies of packet are sent towards
R4 and R5 with 9001 and 9002 labels respectively.
The packet forwarding involves -
Step 1: R1 sends a packet to R2 simply by pushing the label of
9000 to the packet.
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Step 2: When R2 receives the packet with label 9000, it will
forward it to R4 by swapping label 9000 to 9001 and at the same
time, it will replicate the packet and swap label 9000 to 9002
and forward to R5
Step 3: When R4 receives the packet with label 9001, it will
forward it to R3 by swapping 9001 to 9003. When R5 receives the
packet with label 9002, it will forward it to R6 by swapping 9002
to 9004.
Step 4: When R3 receives the packet with label 9003, it will
forward it to R8 by swapping to 9005 and when R5 receives the
packet with label 9002, it will be swapped to 9004 and sent to R6.
Step 5: When R8 receives the packet with label 9005, it will pop
the label; when R6 receives the packet with label 9004, it will
pop the label.
3.6.2. PCECC for the End-to-End Protection of P2MP/MP2MP LSPs
In this section, the end-to-end managed path protection service as
well as the local protection with the operation management in the
PCECC network for the P2MP/MP2MP LSP.
An end-to-end protection principle can be applied for computing
backup P2MP or MP2MP LSPs. During computation of the primary
multicast trees, PCECC could also take the computation of a secondary
tree into consideration. A PCECC could compute the primary and
backup P2MP (or MP2MP) LSPs together or sequentially.
+----+ +----+
Root node of LSP | R1 |--| R11|
+----+ +----+
/ +
10/ +20
/ +
+----------+ +-----------+
Transit Node | R2 | | R3 |
+----------+ +-----------+
| \ + +
| \ + +
10| 10\ +20 20+
| \ + +
| \ +
| + \ +
+-----------+ +-----------+ Leaf Nodes
| R4 | | R5 | (Downstream LSR)
+-----------+ +-----------+
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Figure 10: PCECC for the End-to-End Protection of the P2MP/MP2MP LSPs
In the Figure 10, when the PCECC setups the primary multicast tree
from the root node R1 to the leaves, which is R1->R2->{R4, R5}, at
the same time, it can setup the backup tree, which is
R1->R11->R3->{R4, R5}. Both of them (primary forwarding tree and
secondary forwarding tree) will be downloaded to each router along
the primary path and the secondary path. The traffic will be
forwarded through the R1->R2->{R4, R5} path normally, but when a node
in the primary tree fails (say R2) the root node R1 will switch the
flow to the backup tree, which is R1->R11->R3->{R4, R5}. By using the
PCECC a path computation, label downloading and finally forwarding
can be done without complex signaling used in the P2MP RSVP-TE or
mLDP.
3.6.3. PCECC for the Local Protection of the P2MP/MP2MP LSPs
In this section we describe the local protection service in the PCECC
network for the P2MP/MP2MP LSP.
While the PCECC sets up the primary multicast tree, it can also build
the backup LSP between Point of Local Repair (PLR), the protected
node and Merge Points (MPs) (the downstream nodes of the protected
node). In the cases where the amount of downstream nodes is huge,
this mechanism can avoid unnecessary packet duplication on PLR and
protect the network from traffic congestion risk.
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+------------+
| R1 | Root Node
+------------+
.
.
.
+------------+ Point of Local Repair/
| R10 | Switchover Point
+------------+ (Upstream LSR)
/ +
10/ +20
/ +
+----------+ +-----------+
Protected Node | R20 | | R30 |
+----------+ +-----------+
| \ + +
| \ + +
10| 10\ +20 20+
| \ + +
| \ +
| + \ +
+-----------+ +-----------+ Merge Point
| R40 | | R50 | (Downstream LSR)
+-----------+ +-----------+
. .
. .
Figure 11: PCECC for the Local Protection of the P2MP/MP2MP LSPs
In Figure 11, when the PCECC setups the primary multicast path around
the PLR node R10 to protect node R20, which is R10->R20->{R40, R50},
at the same time, it can set up the backup path R10->R30->{R40, R50}.
Both the primary forwarding path and secondary bypass forwarding path
will be downloaded to each router along the primary path and the
secondary bypass path. The traffic will be forwarded through the
R10->R20->{R40, R50} path normally and when there is a node failure
for node R20, the PLR node R10 will switch the flow to the backup
path, which is R10->R30->{R40, R50}. By using the PCECC, path
computation, label downloading and finally forwarding can be done
without complex signaling used in the P2MP RSVP-TE or mLDP.
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3.7. PCECC for Traffic Classification
As described in [RFC8283], traffic classification is an important
part of traffic engineering. It is the process of looking into a
packet to determine how it should be treated while it is forwarded
through the network. It applies in many scenarios including MPLS
traffic engineering (where it determines what traffic is forwarded
into which LSPs); segment routing (where it is used to select which
set of forwarding instructions (SIDs) to add to a packet); SFC (where
it indicates how a packet should be forwarded across which service
function path ). In conjunction with traffic engineering, traffic
classification is an important enabler for load balancing. Traffic
classification is closely linked to the computational elements of
planning for the network functions because it determines how traffic
is balanced and distributed through the network. Therefore,
selecting what traffic classification mechanism should be performed
by a router is an important part of the work done by a PCECC.
Instructions can be passed from the controller to the routers using
PCEP. These instructions tell the routers how to map traffic to
paths or connections. Refer [RFC9168].
Along with traffic classification, there are few more questions that
needs to be considered after path setup:
* how to use it
* Whether it is a virtual link
* Whether to advertise it in the IGP as a virtual link
* What bits of this information to signal to the tail end
These are out of scope of this document.
3.8. PCECC for SFC
Service Function Chaining (SFC) is described in [RFC7665]. It is the
process of directing traffic in a network such that it passes through
specific hardware devices or virtual machines (known as service
function nodes) that can perform particular desired functions on the
traffic. The set of functions to be performed and the order in which
they are to be performed is known as a service function chain. The
chain is enhanced with the locations at which the service functions
are to be performed to derive a Service Function Path (SFP). Each
packet is marked as belonging to a specific SFP, and that marking
lets each successive service function node know which functions to
perform and to which service function node to send the packet next.
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To operate an SFC network, the service function nodes must be
configured to understand the packet markings, and the edge nodes must
be told how to mark packets entering the network. Additionally, it
may be necessary to establish tunnels between service function nodes
to carry the traffic. Planning an SFC network requires load
balancing between service function nodes and traffic engineering
across the network that connects them. As per [RFC8283], these are
operations that can be performed by a PCE-based controller, and that
controller can use PCEP to program the network and install the
service function chains and any required tunnels.
A possible mechanism could add support for SFC-based central control
instructions. PCECC will be able to instruct the each SFF along the
SFP.
* Service Path Identifier (SPI): Uniquely identifies a SFP.
* Service Index (SI): Provides location within the SFP.
* SFC Proxy handling
PCECC can play the role for setting the traffic classification rules
at the classifier to impose the Network Service Header (NSH) as well
as downloading the forwarding instructions to each SFFs along the way
so that they could process the NSH and forward accordingly.
Including instructions for the service classifier that handle the
context header, meta data etc.
It is also possible to support SFC with SR in conjunction with or
without NSH such as [I-D.ietf-spring-nsh-sr] and
[I-D.ietf-spring-sr-service-programming]. PCECC technique can also
be used for service function related segments and SR service
policies.
3.9. PCECC for Native IP
[RFC8735] describes the scenarios and simulation results for the
"Centrally Control Dynamic Routing (CCDR)" solution, which integrates
the advantage of using distributed protocols (IGP/BGP) and the power
of a centralized control technology (PCE/SDN), providing traffic
engineering for native IP networks. [RFC8821] defines the framework
for CCDR traffic engineering within Native IP network, using multiple
BGP sessions and a PCE as the centralized controller. PCEP protocol
will be used to transfer the key parameters between PCE and the
underlying network devices (PCC) using PCECC technique. The central
control instructions from PCECC to PCC will identify which prefix
should be advertised on which BGP session. There are PCEP extensions
defined in [I-D.ietf-pce-pcep-extension-native-ip] for it.
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+------+
+----------+ PCECC+-------+
| +------+ |
| |
PCEP | BGP Session 1(lo11/lo21)| PCEP
+-------------------------+
| |
| BGP Session 2(lo12/lo22)|
+-------------------------+
PF12 | | PF22
PF11 | | PF21
+---+ +-----+-----+ +-----+-----+ +---+
|SW1+---------+(lo11/lo12)+-------------+(lo21/lo22)+-----------+SW2|
+---+ | R1 +-------------+ R2 | +---+
+-----------+ +-----------+
Figure 12: PCECC for Native IP
In the case, as shown in Figure 12, PCECC will instruct both R1 and
R2 via PCEP how to form BGP sessions with each other and which IP
prefixes need to be advertised via which BGP session.
3.10. PCECC for BIER
Bit Index Explicit Replication (BIER) [RFC8279] defines an
architecture where all intended multicast receivers are encoded as a
bitmask in the multicast packet header within different
encapsulations. A router that receives such packet will forward that
packet based on the bit position in the packet header towards the
receiver(s) following a precomputed tree for each of the bits in the
packet. Each receiver is represented by a unique bit in the bitmask.
BIER-TE [RFC9262] shares architecture and packet formats with BIER.
BIER-TE forwards and replicates packets based on a BitString in the
packet header, but every BitPosition of the BitString of a BIER-TE
packet indicates one or more adjacencies. BIER-TE Path can be
derived from a PCE and used at the ingress as described in
[I-D.chen-pce-bier].
PCECC mechanism could be used for the allocation of bits for the BIER
router for BIER as well as for the adjacencies for BIER-TE. PCECC-
based controller can use PCEP to instruct the BIER capable routers
the meaning of the bits as well as other fields needed for BIER
encapsulation. The PCECC could be used to program the BIER router
with various parameters used in the BIER encapsulation such as BIER
subdomain-ID, BFR-ID, BIER Encapsulation etc. for both node and
adjacency.
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Detailed procedures of PCECC usage and extensions are described in
[I-D.chen-pce-pcep-extension-pce-controller-bier].
4. IANA Considerations
This document does not require any action from IANA.
5. Security Considerations
[RFC8283] describes how the security considerations for a PCE-based
controller are little different from those for any other PCE system.
PCECC operations relies heavily on the use and security of PCEP, so
due consideration should be given to the security features discussed
in [RFC5440] and the additional mechanisms described in [RFC8253].
It further lists the vulnerability of a central controller
architecture, such as a central point of failure, denial of service,
and a focus for interception and modification of messages sent to
individual Network Elements (NEs).
As per [RFC9050], the use of Transport Layer Security (TLS) in PCEP
is recommended, as it provides support for peer authentication,
message encryption, and integrity. It further provides mechanisms
for associating peer identities with different levels of access and/
or authoritativeness via an attribute in X.509 certificates or a
local policy with a specific accept-list of X.509 certificates. This
can be used to check the authority for the PCECC operations.
It is expected that each new document that is produced for a specific
use case will also include considerations of the security impacts of
the use of a PCE-based central controller on the network type and
services being managed.
6. Acknowledgments
Thanks to Adrian Farrel, Aijun Wang, Robert Tao, Changjiang Yan,
Tieying Huang, Sergio Belotti, Dieter Beller, Andrey Elperin and
Evgeniy Brodskiy for their useful comments and suggestions.
Thanks to Mach Chen for RTGDIR review.
7. References
7.1. Normative References
[RFC5440] Vasseur, JP., Ed., Le Roux, JL., Ed., and RFC Publisher,
"Path Computation Element (PCE) Communication Protocol
(PCEP)", RFC 5440, DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.
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[RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., Dhody, D., and
RFC Publisher, "PCEPS: Usage of TLS to Provide a Secure
Transport for the Path Computation Element Communication
Protocol (PCEP)", RFC 8253, DOI 10.17487/RFC8253, October
2017, <https://www.rfc-editor.org/info/rfc8253>.
[RFC8283] Farrel, A., Ed., Zhao, Q., Ed., Li, Z., Zhou, C., and RFC
Publisher, "An Architecture for Use of PCE and the PCE
Communication Protocol (PCEP) in a Network with Central
Control", RFC 8283, DOI 10.17487/RFC8283, December 2017,
<https://www.rfc-editor.org/info/rfc8283>.
7.2. Informative References
[I-D.cbrt-pce-stateful-local-protection]
Barth, C. and R. Torvi, "PCEP Extensions for RSVP-TE
Local-Protection with PCE-Stateful", Work in Progress,
Internet-Draft, draft-cbrt-pce-stateful-local-protection-
01, 29 June 2018, <https://www.ietf.org/archive/id/draft-
cbrt-pce-stateful-local-protection-01.txt>.
[I-D.chen-pce-bier]
Chen, R., Zhang, Z., Chen, H., Dhanaraj, S., Qin, F., and
A. Wang, "PCEP Extensions for BIER-TE", Work in Progress,
Internet-Draft, draft-chen-pce-bier-09, 12 July 2021,
<https://www.ietf.org/archive/id/draft-chen-pce-bier-
09.txt>.
[I-D.chen-pce-pcep-extension-pce-controller-bier]
Chen, R., Xu, B., Chen, H., and A. Wang, "PCEP Procedures
and Protocol Extensions for Using PCE as a Central
Controller (PCECC) of BIER", Work in Progress, Internet-
Draft, draft-chen-pce-pcep-extension-pce-controller-bier-
03, 7 March 2022, <https://www.ietf.org/archive/id/draft-
chen-pce-pcep-extension-pce-controller-bier-03.txt>.
[I-D.dhody-pce-pcep-extension-pce-controller-srv6]
Li, Z., Peng, S., Geng, X., and M. S. Negi, "Path
Computation Element Communication Protocol (PCEP)
Extensions for Using the PCE as a Central Controller
(PCECC) for Segment Routing over IPv6 (SRv6) Segment
Identifier (SID) Allocation and Distribution.", Work in
Progress, Internet-Draft, draft-dhody-pce-pcep-extension-
pce-controller-srv6-09, 10 July 2022,
<https://www.ietf.org/archive/id/draft-dhody-pce-pcep-
extension-pce-controller-srv6-09.txt>.
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[I-D.ietf-mpls-seamless-mpls]
Leymann, N., Decraene, B., Filsfils, C., Konstantynowicz,
M., and D. Steinberg, "Seamless MPLS Architecture", Work
in Progress, Internet-Draft, draft-ietf-mpls-seamless-
mpls-07, 28 June 2014, <https://www.ietf.org/archive/id/
draft-ietf-mpls-seamless-mpls-07.txt>.
[I-D.ietf-pce-binding-label-sid]
Sivabalan, S., Filsfils, C., Tantsura, J., Previdi, S.,
and C. Li, "Carrying Binding Label/Segment Identifier
(SID) in PCE-based Networks.", Work in Progress, Internet-
Draft, draft-ietf-pce-binding-label-sid-15, 20 March 2022,
<https://www.ietf.org/archive/id/draft-ietf-pce-binding-
label-sid-15.txt>.
[I-D.ietf-pce-pcep-extension-native-ip]
Wang, A., Khasanov, B., Fang, S., Tan, R., and C. Zhu,
"PCEP Extension for Native IP Network", Work in Progress,
Internet-Draft, draft-ietf-pce-pcep-extension-native-ip-
19, 21 September 2022, <https://www.ietf.org/archive/id/
draft-ietf-pce-pcep-extension-native-ip-19.txt>.
[I-D.ietf-pce-pcep-extension-pce-controller-sr]
Li, Z., Peng, S., Negi, M. S., Zhao, Q., and C. Zhou,
"Path Computation Element Communication Protocol (PCEP)
Extensions for Using PCE as a Central Controller (PCECC)
for Segment Routing (SR) MPLS Segment Identifier (SID)
Allocation and Distribution.", Work in Progress, Internet-
Draft, draft-ietf-pce-pcep-extension-pce-controller-sr-05,
10 July 2022, <https://www.ietf.org/archive/id/draft-ietf-
pce-pcep-extension-pce-controller-sr-05.txt>.
[I-D.ietf-pce-segment-routing-ipv6]
Li, C., Negi, M. S., Sivabalan, S., Koldychev, M.,
Kaladharan, P., and Y. Zhu, "Path Computation Element
Communication Protocol (PCEP) Extensions for Segment
Routing leveraging the IPv6 dataplane", Work in Progress,
Internet-Draft, draft-ietf-pce-segment-routing-ipv6-15, 23
October 2022, <https://www.ietf.org/archive/id/draft-ietf-
pce-segment-routing-ipv6-15.txt>.
[I-D.ietf-pce-segment-routing-policy-cp]
Koldychev, M., Sivabalan, S., Barth, C., Peng, S., and H.
Bidgoli, "PCEP extension to support Segment Routing Policy
Candidate Paths", Work in Progress, Internet-Draft, draft-
ietf-pce-segment-routing-policy-cp-08, 24 October 2022,
<https://www.ietf.org/archive/id/draft-ietf-pce-segment-
routing-policy-cp-08.txt>.
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[I-D.ietf-pce-stateful-interdomain]
Dugeon, O., Meuric, J., Lee, Y., and D. Ceccarelli, "PCEP
Extension for Stateful Inter-Domain Tunnels", Work in
Progress, Internet-Draft, draft-ietf-pce-stateful-
interdomain-03, 4 March 2022,
<https://www.ietf.org/archive/id/draft-ietf-pce-stateful-
interdomain-03.txt>.
[I-D.ietf-spring-nsh-sr]
Guichard, J. and J. Tantsura, "Integration of Network
Service Header (NSH) and Segment Routing for Service
Function Chaining (SFC)", Work in Progress, Internet-
Draft, draft-ietf-spring-nsh-sr-11, 20 April 2022,
<https://www.ietf.org/archive/id/draft-ietf-spring-nsh-sr-
11.txt>.
[I-D.ietf-spring-sr-service-programming]
Clad, F., Xu, X., Filsfils, C., Bernier, D., Li, C.,
Decraene, B., Ma, S., Yadlapalli, C., Henderickx, W., and
S. Salsano, "Service Programming with Segment Routing",
Work in Progress, Internet-Draft, draft-ietf-spring-sr-
service-programming-06, 9 June 2022,
<https://www.ietf.org/archive/id/draft-ietf-spring-sr-
service-programming-06.txt>.
[I-D.ietf-teas-rfc3272bis]
Farrel, A., "Overview and Principles of Internet Traffic
Engineering", Work in Progress, Internet-Draft, draft-
ietf-teas-rfc3272bis-22, 27 October 2022,
<https://www.ietf.org/archive/id/draft-ietf-teas-
rfc3272bis-22.txt>.
[I-D.li-pce-controlled-id-space]
Li, C., Shi, H., Wang, A., Cheng, W., and C. Zhou, "Path
Computation Element Communication Protocol (PCEP)
extension to advertise the PCE Controlled Identifier
Space", Work in Progress, Internet-Draft, draft-li-pce-
controlled-id-space-14, 10 November 2022,
<https://www.ietf.org/archive/id/draft-li-pce-controlled-
id-space-14.txt>.
[MAP-REDUCE]
Lee, K., Choi, T., Ganguly, A., Wolinsky, D., Boykin, P.,
and R. Figueiredo, "Parallel Processing Framework on a P2P
System Using Map and Reduce Primitives", , May 2011,
<http://leeky.me/publications/mapreduce_p2p.pdf>.
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[MPLS-DC] Afanasiev, D. and D. Ginsburg, "MPLS in DC and inter-DC
networks: the unified forwarding mechanism for network
programmability at scale", , March 2014,
<https://www.slideshare.net/DmitryAfanasiev1/yandex-
nag201320131031>.
[RFC1195] Callon, R. and RFC Publisher, "Use of OSI IS-IS for
routing in TCP/IP and dual environments", RFC 1195,
DOI 10.17487/RFC1195, December 1990,
<https://www.rfc-editor.org/info/rfc1195>.
[RFC2328] Moy, J. and RFC Publisher, "OSPF Version 2", STD 54,
RFC 2328, DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
Swallow, G., and RFC Publisher, "RSVP-TE: Extensions to
RSVP for LSP Tunnels", RFC 3209, DOI 10.17487/RFC3209,
December 2001, <https://www.rfc-editor.org/info/rfc3209>.
[RFC3985] Bryant, S., Ed., Pate, P., Ed., and RFC Publisher, "Pseudo
Wire Emulation Edge-to-Edge (PWE3) Architecture",
RFC 3985, DOI 10.17487/RFC3985, March 2005,
<https://www.rfc-editor.org/info/rfc3985>.
[RFC4206] Kompella, K., Rekhter, Y., and RFC Publisher, "Label
Switched Paths (LSP) Hierarchy with Generalized Multi-
Protocol Label Switching (GMPLS) Traffic Engineering
(TE)", RFC 4206, DOI 10.17487/RFC4206, October 2005,
<https://www.rfc-editor.org/info/rfc4206>.
[RFC4364] Rosen, E., Rekhter, Y., and RFC Publisher, "BGP/MPLS IP
Virtual Private Networks (VPNs)", RFC 4364,
DOI 10.17487/RFC4364, February 2006,
<https://www.rfc-editor.org/info/rfc4364>.
[RFC4655] Farrel, A., Vasseur, J.-P., Ash, J., and RFC Publisher, "A
Path Computation Element (PCE)-Based Architecture",
RFC 4655, DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
[RFC5036] Andersson, L., Ed., Minei, I., Ed., Thomas, B., Ed., and
RFC Publisher, "LDP Specification", RFC 5036,
DOI 10.17487/RFC5036, October 2007,
<https://www.rfc-editor.org/info/rfc5036>.
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[RFC5150] Ayyangar, A., Kompella, K., Vasseur, JP., Farrel, A., and
RFC Publisher, "Label Switched Path Stitching with
Generalized Multiprotocol Label Switching Traffic
Engineering (GMPLS TE)", RFC 5150, DOI 10.17487/RFC5150,
February 2008, <https://www.rfc-editor.org/info/rfc5150>.
[RFC5151] Farrel, A., Ed., Ayyangar, A., Vasseur, JP., and RFC
Publisher, "Inter-Domain MPLS and GMPLS Traffic
Engineering -- Resource Reservation Protocol-Traffic
Engineering (RSVP-TE) Extensions", RFC 5151,
DOI 10.17487/RFC5151, February 2008,
<https://www.rfc-editor.org/info/rfc5151>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., Lindem, A., and RFC
Publisher, "OSPF for IPv6", RFC 5340,
DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/info/rfc5340>.
[RFC5376] Bitar, N., Zhang, R., Kumaki, K., and RFC Publisher,
"Inter-AS Requirements for the Path Computation Element
Communication Protocol (PCECP)", RFC 5376,
DOI 10.17487/RFC5376, November 2008,
<https://www.rfc-editor.org/info/rfc5376>.
[RFC5541] Le Roux, JL., Vasseur, JP., Lee, Y., and RFC Publisher,
"Encoding of Objective Functions in the Path Computation
Element Communication Protocol (PCEP)", RFC 5541,
DOI 10.17487/RFC5541, June 2009,
<https://www.rfc-editor.org/info/rfc5541>.
[RFC7025] Otani, T., Ogaki, K., Caviglia, D., Zhang, F., Margaria,
C., and RFC Publisher, "Requirements for GMPLS
Applications of PCE", RFC 7025, DOI 10.17487/RFC7025,
September 2013, <https://www.rfc-editor.org/info/rfc7025>.
[RFC7399] Farrel, A., King, D., and RFC Publisher, "Unanswered
Questions in the Path Computation Element Architecture",
RFC 7399, DOI 10.17487/RFC7399, October 2014,
<https://www.rfc-editor.org/info/rfc7399>.
[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
Uttaro, J., Drake, J., Henderickx, W., and RFC Publisher,
"BGP MPLS-Based Ethernet VPN", RFC 7432,
DOI 10.17487/RFC7432, February 2015,
<https://www.rfc-editor.org/info/rfc7432>.
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[RFC7491] King, D., Farrel, A., and RFC Publisher, "A PCE-Based
Architecture for Application-Based Network Operations",
RFC 7491, DOI 10.17487/RFC7491, March 2015,
<https://www.rfc-editor.org/info/rfc7491>.
[RFC7665] Halpern, J., Ed., Pignataro, C., Ed., and RFC Publisher,
"Service Function Chaining (SFC) Architecture", RFC 7665,
DOI 10.17487/RFC7665, October 2015,
<https://www.rfc-editor.org/info/rfc7665>.
[RFC8231] Crabbe, E., Minei, I., Medved, J., Varga, R., and RFC
Publisher, "Path Computation Element Communication
Protocol (PCEP) Extensions for Stateful PCE", RFC 8231,
DOI 10.17487/RFC8231, September 2017,
<https://www.rfc-editor.org/info/rfc8231>.
[RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Przygienda, T., Aldrin, S., and RFC Publisher, "Multicast
Using Bit Index Explicit Replication (BIER)", RFC 8279,
DOI 10.17487/RFC8279, November 2017,
<https://www.rfc-editor.org/info/rfc8279>.
[RFC8281] Crabbe, E., Minei, I., Sivabalan, S., Varga, R., and RFC
Publisher, "Path Computation Element Communication
Protocol (PCEP) Extensions for PCE-Initiated LSP Setup in
a Stateful PCE Model", RFC 8281, DOI 10.17487/RFC8281,
December 2017, <https://www.rfc-editor.org/info/rfc8281>.
[RFC8355] Filsfils, C., Ed., Previdi, S., Ed., Decraene, B., Shakir,
R., and RFC Publisher, "Resiliency Use Cases in Source
Packet Routing in Networking (SPRING) Networks", RFC 8355,
DOI 10.17487/RFC8355, March 2018,
<https://www.rfc-editor.org/info/rfc8355>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., Shakir, R., and RFC
Publisher, "Segment Routing Architecture", RFC 8402,
DOI 10.17487/RFC8402, July 2018,
<https://www.rfc-editor.org/info/rfc8402>.
[RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
Hardwick, J., and RFC Publisher, "Path Computation Element
Communication Protocol (PCEP) Extensions for Segment
Routing", RFC 8664, DOI 10.17487/RFC8664, December 2019,
<https://www.rfc-editor.org/info/rfc8664>.
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[RFC8735] Wang, A., Huang, X., Kou, C., Li, Z., Mi, P., and RFC
Publisher, "Scenarios and Simulation Results of PCE in a
Native IP Network", RFC 8735, DOI 10.17487/RFC8735,
February 2020, <https://www.rfc-editor.org/info/rfc8735>.
[RFC8751] Dhody, D., Lee, Y., Ceccarelli, D., Shin, J., King, D.,
and RFC Publisher, "Hierarchical Stateful Path Computation
Element (PCE)", RFC 8751, DOI 10.17487/RFC8751, March
2020, <https://www.rfc-editor.org/info/rfc8751>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., Voyer, D., and RFC Publisher, "IPv6
Segment Routing Header (SRH)", RFC 8754,
DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
[RFC8821] Wang, A., Khasanov, B., Zhao, Q., Chen, H., and RFC
Publisher, "PCE-Based Traffic Engineering (TE) in Native
IP Networks", RFC 8821, DOI 10.17487/RFC8821, April 2021,
<https://www.rfc-editor.org/info/rfc8821>.
[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., Li, Z., and RFC Publisher, "Segment
Routing over IPv6 (SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>.
[RFC9012] Patel, K., Van de Velde, G., Sangli, S., Scudder, J., and
RFC Publisher, "The BGP Tunnel Encapsulation Attribute",
RFC 9012, DOI 10.17487/RFC9012, April 2021,
<https://www.rfc-editor.org/info/rfc9012>.
[RFC9050] Li, Z., Peng, S., Negi, M., Zhao, Q., Zhou, C., and RFC
Publisher, "Path Computation Element Communication
Protocol (PCEP) Procedures and Extensions for Using the
PCE as a Central Controller (PCECC) of LSPs", RFC 9050,
DOI 10.17487/RFC9050, July 2021,
<https://www.rfc-editor.org/info/rfc9050>.
[RFC9087] Filsfils, C., Ed., Previdi, S., Dawra, G., Ed., Aries, E.,
Afanasiev, D., and RFC Publisher, "Segment Routing
Centralized BGP Egress Peer Engineering", RFC 9087,
DOI 10.17487/RFC9087, August 2021,
<https://www.rfc-editor.org/info/rfc9087>.
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[RFC9168] Dhody, D., Farrel, A., Li, Z., and RFC Publisher, "Path
Computation Element Communication Protocol (PCEP)
Extension for Flow Specification", RFC 9168,
DOI 10.17487/RFC9168, January 2022,
<https://www.rfc-editor.org/info/rfc9168>.
[RFC9256] Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
A., Mattes, P., and RFC Publisher, "Segment Routing Policy
Architecture", RFC 9256, DOI 10.17487/RFC9256, July 2022,
<https://www.rfc-editor.org/info/rfc9256>.
[RFC9262] Eckert, T., Ed., Menth, M., Cauchie, G., and RFC
Publisher, "Tree Engineering for Bit Index Explicit
Replication (BIER-TE)", RFC 9262, DOI 10.17487/RFC9262,
October 2022, <https://www.rfc-editor.org/info/rfc9262>.
Appendix A. Other Use Cases of PCECC
This section list some more advanced use cases of PCECC that were
discussed and could be worked on in future.
A.1. PCECC for Network Migration
One of the main advantages of PCECC solution is that it has backward
compatibility since the PCE server itself can function as a proxy
node of the MPLS network for all the new nodes which may no longer
support the signaling protocols.
As is illustrated in the following example, the current network could
migrate to a total PCECC-controlled network gradually by replacing
the legacy nodes. During the migration, the legacy nodes still need
to use the existing MPLS protocols signaling such as LDP and RSVP-TE,
and the new nodes will set up their portion of the forwarding path
through PCECC directly. With the PCECC function as the proxy of
these new nodes, MPLS signaling can populate through the network for
both: old and new nodes.
The example described in this section is based on network
configurations illustrated using the Figure 13:
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+------------------------------------------------------------------+
| PCE DOMAIN |
| +-----------------------------------------------------+ |
| | PCECC | |
| +-----------------------------------------------------+ |
| ^ ^ ^ ^ |
| | PCEP | | PCEP | |
| V V V V |
| +--------+ +--------+ +--------+ +--------+ +--------+ |
| | NODE 1 | | NODE 2 | | NODE 3 | | NODE 4 | | NODE 5 | |
| | |...| |...| |...| |...| | |
| | Legacy |if1| Legacy |if2|Legacy |if3| PCECC |if4| PCECC | |
| | Node | | Node | |Enabled | |Enabled | | Enabled| |
| +--------+ +--------+ +--------+ +--------+ +--------+ |
| |
+------------------------------------------------------------------+
Figure 13: PCECC Initiated LSP Setup In the Network Migration
In this example, there are five nodes for the TE LSP from the head
end (Node1) to the tail end (Node5). Where Node4 and Node5 are
centrally controlled and other nodes are legacy nodes.
* Node1 sends a path request message for the setup of LSP with the
destination as Node5.
* PCECC sends to Node1 a reply message for LSP setup with the path:
(Node1, if1),(Node2, if2), (Node3, if3), (Node4, if4), Node5.
* Node1, Node2, and Node3 will set up the LSP to Node5 using the
local labels as usual. Node 3 with help of PCECC could proxy the
signaling.
* Then the PCECC will program the out-segment of Node3, the in-
segment/ out-segment of Node4, and the in-segment for Node5.
A.2. PCECC for L3VPN and PWE3
As described in [RFC8283], various network services may be offered
over a network. These include protection services (including Virtual
Private Network (VPN) services (such as Layer 3 VPNs [RFC4364] or
Ethernet VPNs [RFC7432]); or Pseudowires [RFC3985]. Delivering
services over a network in an optimal way requires coordination in
the way where network resources are allocated to support the
services. A PCE-based central controller can consider the whole
network and all components of a service at once when planning how to
deliver the service. It can then use PCEP to manage the network
resources and to install the necessary associations between those
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resources.
In the case of L3VPN, VPN labels could also be assigned and
distributed through PCEP among the PE router instead of using the BGP
protocols.
Example described in this section is based on network configurations
illustrated using the Figure 14:
+-------------------------------------------+
| PCE DOMAIN |
| +-----------------------------------+ |
| | PCECC | |
| +-----------------------------------+ |
| ^ ^ ^ |
|PWE3/L3VPN | PCEP PCEP|LSP PWE3/L3VPN|PCEP |
| V V V |
+--------+ | +--------+ +--------+ +--------+ | +--------+
| CE | | | PE1 | | NODE x | | PE2 | | | CE |
| |...... | |...| |...| |.....| |
| Legacy | |if1 | PCECC |if2|PCCEC |if3| PCECC |if4 | Legacy |
| Node | | | Enabled| |Enabled | |Enabled | | | Node |
+--------+ | +--------+ +--------+ +--------+ | +--------+
| |
+-------------------------------------------+
Figure 14: PCECC for L3VPN and PWE3
In the case PWE3, instead of using the LDP signaling protocols, the
label and port pairs assigned to each pseudowire can be assigned
through PCECC among the PE routers and the corresponding forwarding
entries will be distributed into each PE routers through the extended
PCEP protocols and PCECC mechanism.
A.3. PCECC for Local Protection (RSVP-TE)
[I-D.cbrt-pce-stateful-local-protection] describes the need for the
PCE to maintain and associate the local protection paths for the
RSVP-TE LSP. Local protection requires the setup of a bypass at the
PLR. This bypass can be PCC-initiated and delegated, or PCE-
initiated. In either case, the PLR needs to maintain a PCEP session
with the PCE. The Bypass LSPs need to be mapped to the primary LSP.
This could be done locally at the PLR based on a local policy but
there is a need for a PCE to do the mapping as well to exert greater
control.
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This mapping can be done via PCECC procedures where the PCE could
instruct the PLR to the mapping and identify the primary LSP for
which bypass should be used.
A.4. Using reliable P2MP TE based multicast delivery for distributed
computations (MapReduce-Hadoop)
MapReduce model of distributed computations in computing clusters is
widely deployed. In Hadoop (https://hadoop.apache.org/) 1.0
architecture MapReduce operations on big data in the Hadoop
Distributed File System (HDFS), where NameNode has the knowledge
about resources of the cluster and where actual data (chunks) for
particular task are located (which DataNode). Each chunk of data
(64MB or more) should have 3 saved copies in different DataNodes
based on their proximity.
Proximity level currently has semi-manual allocation and based on
Rack IDs (Assumption is that closer data are better because of access
speed/smaller latency).
JobTracker node is responsible for computation tasks, scheduling
across DataNodes and also have Rack-awareness. Currently transport
protocols between NameNode/JobTracker and DataNodes are based on IP
unicast. It has simplicity as pros but has numerous drawbacks
related with its flat approach.
It is clear that we should go beyond of one DC for Hadoop cluster
creation and move towards distributed clusters. In that case we need
to handle performance and latency issues. Latency depends on speed
of light in fiber links and also latency introduced by intermediate
devices in between. The last one is closely correlated with network
device architecture and performance. Current performance of NPU
based routers should be enough for creating distribute Hadoop
clusters with predicted latency. Performance of SW based routers
(mainly as VNF) together with additional HW features such as DPDK are
promising but require additional research and testing.
Main question is how can we create simple but effective architecture
for distributed Hadoop cluster?
There is research [MAP-REDUCE] which show how usage of multicast tree
could improve speed of resource or cluster members discovery inside
the cluster as well as increase redundancy in communications between
cluster nodes.
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Is traditional IP based multicast enough for that? We doubt it
because it requires additional control plane (IGMP, PIM) and a lot of
signaling, that is not suitable for high performance computations,
that are very sensitive to latency.
P2MP TE tunnels looks much more suitable as potential solution for
creation of multicast based communications between NameNode as root
and DataNodes as leaves inside the cluster. Obviously these P2MP
tunnels should be dynamically created and turned down (no manual
intervention). Here, the PCECC comes to play with main objective to
create optimal topology of each particular request for MapReduce
computation and also create P2MP tunnels with needed parameters such
as bandwidth and delay.
This solution will require to use MPLS label based forwarding inside
the cluster. Usage of label based forwarding inside DC was proposed
by Yandex [MPLS-DC]. Technically it is already possible because MPLS
on switches is already supported by some vendors, MPLS also exists on
Linux and OVS.
A possible framework for this task is shown in Figure 15:
+--------+
| APP |
+--------+
| NBI (REST API,...)
|
PCEP +----------+ REST API
+---------+ +---| PCECC |----------+
| Client |---|---| | |
+---------+ | +----------+ |
| | | | | |
+-----|---+ |PCEP| |
+--------+ | | | | |
| | | | | |
| REST API | | | | |
| | | | | |
+-------------+ | | | | +----------+
| Job Tracker | | | | | | NameNode |
| | | | | | | |
+-------------+ | | | | +----------+
+------------------+ | +-----------+
| | | |
|---+-----P2MP TE--+-----|-----------| |
+----------+ +----------+ +----------+
| DataNode1| | DataNode2| | DataNodeN|
|TaskTraker| |TaskTraker| .... |TaskTraker|
+----------+ +----------+ +----------+
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Figure 15: Using reliable P2MP TE based multicast delivery for
distributed computations (MapReduce-Hadoop)
Communication between JobTracker, NameNode and PCECC can be done via
REST API directly or via cluster manager such as Mesos.
Phase 1: Distributed cluster resources discovery During this phase
JobTracker and NameNode should identify and find available DataNodes
according to computing request from application (APP). NameNode
should query PCECC about available DataNodes, NameNode may provide
additional constrains to PCECC such as topological proximity,
redundancy level.
PCECC should analyze the topology of distributed cluster and perform
constrain based path calculation from client towards most suitable
NameNodes. PCECC should reply to NameNode the list of most suitable
DataNodes and their resource capabilities. Topology discovery
mechanism for PCECC will be added later to that framework.
Phase 2: PCECC should create P2MP LSP from client towards those
DataNodes by means of PCEP messages following previously calculated
path.
Phase 3. NameNode should send this information to client, PCECC
informs client about optimal P2MP path towards DataNodes via PCEP
message.
Phase 4. Client sends data blocks to those DataNodes for writing via
created P2MP tunnel.
When this task will be finished, P2MP tunnel could be turned down.
Appendix B. Contributor Addresses
Following authors contributed text for this document and should be
considered as co-authors:
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Luyuan Fang
United States of America
Email: luyuanf@gmail.com
Chao Zhou
HPE
Email: chaozhou_us@yahoo.com
Boris Zhang
Amazon
Email: zhangyud@amazon.com
Artsiom Rachytski
Belarus
Email: arachyts@gmail.com
Anton Gulida
EPAM Systems, Inc.
Belarus
Email: Anton_Hulida@epam.com
Authors' Addresses
Zhenbin (Robin) Li
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing
100095
China
Email: lizhenbin@huawei.com
Dhruv Dhody
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore
Karnataka 560066
India
Email: dhruv.ietf@gmail.com
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Quintin Zhao
Etheric Networks
1009 S CLAREMONT ST
SAN MATEO, CA 94402
United States of America
Email: qzhao@ethericnetworks.com
King He
Tencent Holdings Ltd.
Shenzhen
China
Email: kinghe@tencent.com
Boris Khasanov
Yandex LLC
Ulitsa Lva Tolstogo 16
Moscow
Email: bhassanov@yahoo.com
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