Internet DRAFT - draft-ietf-spring-problem-statement
draft-ietf-spring-problem-statement
Network Working Group S. Previdi, Ed.
Internet-Draft C. Filsfils, Ed.
Intended status: Informational Cisco Systems, Inc.
Expires: October 8, 2016 B. Decraene
S. Litkowski
Orange
M. Horneffer
Deutsche Telekom
R. Shakir
Jive Communications
April 6, 2016
SPRING Problem Statement and Requirements
draft-ietf-spring-problem-statement-08
Abstract
The ability for a node to specify a forwarding path, other than the
normal shortest path, that a particular packet will traverse,
benefits a number of network functions. Source-based routing
mechanisms have previously been specified for network protocols, but
have not seen widespread adoption. In this context, the term
'source' means 'the point at which the explicit route is imposed' and
therefore it is not limited to the originator of the packet (i.e.:
the node imposing the explicit route may be the ingress node of an
operator's network).
This document outlines various use cases, with their requirements,
that need to be taken into account by the Source Packet Routing in
Networking (SPRING) architecture for unicast traffic. Multicast use-
cases and requirements are out of scope of this document.
Requirements Language
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 RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 8, 2016.
Copyright Notice
Copyright (c) 2016 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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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Dataplanes . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. SPRING Use Cases . . . . . . . . . . . . . . . . . . . . . . 4
3.1. IGP-based MPLS Tunneling . . . . . . . . . . . . . . . . 4
3.1.1. Example of IGP-based MPLS Tunnels . . . . . . . . . . 4
3.2. Fast Reroute (FRR) . . . . . . . . . . . . . . . . . . . 5
3.3. Traffic Engineering . . . . . . . . . . . . . . . . . . . 5
3.3.1. Examples of Traffic Engineering Use Cases . . . . . . 7
3.4. Interoperability with non-SPRING nodes . . . . . . . . . 13
4. Security Considerations . . . . . . . . . . . . . . . . . . . 13
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
6. Manageability Considerations . . . . . . . . . . . . . . . . 15
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 15
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
9.1. Normative References . . . . . . . . . . . . . . . . . . 16
9.2. Informative References . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction
The ability for a node to specify a unicast forwarding path, other
than the normal shortest path, that a particular packet will
traverse, benefits a number of network functions, for example:
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Some types of network virtualization, including multi-topology
networks and the partitioning of network resources for VPNs
Network, link, path and node protection such as fast re-route
Network programmability
OAM techniques
Simplification and reduction of network signaling components
Load balancing and traffic engineering
Source-based routing mechanisms have previously been specified for
network protocols, but have not seen widespread adoption other than
in MPLS traffic engineering.
These network functions may require greater flexibility and per
packet source imposed routing than can be achieved through the use of
the previously defined methods. In the context of this document, the
term 'source' means 'the point at which the explicit route is
imposed' and therefore it is not limited to the originator of the
packet (i.e.: the node imposing the explicit route may be the ingress
node of an operator's network). Throughout this document we refer to
this definition of 'source'.
In this context, Source Packet Routing in Networking (SPRING)
architecture is being defined in order to address the use cases and
requirements described in this document.
The SPRING architecture MUST allow incremental and selective
deployment without any requirement of flag day or massive upgrade of
all network elements.
The SPRING architecture MUST allow to put policy state in the packet
header and not in the intermediate nodes along the path. Hence, the
policy is instantiated in the packet header and does not requires any
policy state in midpoints and tail-ends.
The SPRING architecture objective is not to replace existing source
routing and traffic engineering mechanisms but rather complement them
and address use cases where removal of signaling and path state in
the core is a requirement.
Multicast use-cases and requirements are out of scope of this
document.
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2. Dataplanes
The SPRING architecture SHOULD be general in order to ease its
applicability to different dataplanes.
The SPRING architecture SHOULD leverage the existing MPLS dataplane
without any modification and leverage IPv6 dataplane with a new IPv6
Routing Header Type (IPv6 Routing Header is defined in [RFC2460]) and
a proposal for a new type of routing header is made by
[I-D.ietf-6man-segment-routing-header].
The SPRING architecture MUST allow interoperability between SPRING
capable and non-capable nodes and this in both MPLS and IPv6
dataplanes.
3. SPRING Use Cases
3.1. IGP-based MPLS Tunneling
The source-based routing model, applied to the MPLS dataplane, offers
the ability to tunnel services like VPN ([RFC4364]), VPLS ([RFC4761],
[RFC4762]) and VPWS ([RFC6624]), from an ingress PE to an egress PE,
with or without the expression of an explicit path and without
requiring forwarding plane or control plane state in intermediate
nodes. Point-to-multipoint and multipoint-to-multipoint tunnels are
outside of the scope of this document.
3.1.1. Example of IGP-based MPLS Tunnels
This section illustrates an example use-case.
P1---P2
/ \
A---CE1---PE1 PE2---CE2---Z
\ /
P3---P4
Figure 1: IGP-based MPLS Tunneling
In Figure 1 above, the four nodes A, CE1, CE2 and Z are part of the
same VPN. CE2 advertises to PE2 a route to Z. PE2 binds a local
label LZ to that route and propagates the route and its label via
MPBGP to PE1 with nhop 192.0.2.2 (i.e.: the local address of PE2).
PE1 installs the VPN prefix Z in the appropriate VRF and resolves the
next-hop onto the IGP-based MPLS tunnel to PE2.
In order to cope with the reality of current deployments, the SPRING
architecture MUST allow PE to PE forwarding according to the IGP
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shortest path without the addition of any other signaling protocol.
The packet each PE forwards across the network will contain the
necessary information derived from the topology database in order to
deliver the packet to the remote PE.
3.2. Fast Reroute (FRR)
FRR (Fast Reroute) technologies have been deployed by network
operators in order to cope with link or node failures through pre-
computation of backup paths.
Illustration of the problem statement for FRR and microloop avoidance
are to be found in [I-D.ietf-spring-resiliency-use-cases].
The SPRING architecture MUST address the following requirements:
o support of Fast Reroute (FRR) on any topology
o pre-computation and setup of backup path without any additional
signaling (other than the regular IGP/BGP protocols)
o support of shared risk constraints
o support of node and link protection
o support of microloop avoidance
3.3. Traffic Engineering
Traffic Engineering (TE) is the term used to refer to techniques that
enable operators to control how specific traffic flows are treated
within their networks. Different contexts and modes have been
defined (single vs. multiple domains, with or without bandwidth
admission control, centralized vs. distributed path computation,
etc).
Some deployments have a limited use of TE such as addressing specific
application or customer requirements or address specific bandwidth
limitation in the network (tactical TE). In this situation, there is
need to reduce as much of possible the cost (such as the number of
signaling protocols and the number of nodes requiring specific
configurations/features. Some other deployments have a very high
scale use of TE, such as fine tuning flows at the application level.
In this situation, there is a need for a very high scalability, in
particular on mid-points.
The source-based routing model allows traffic engineering to be
implemented without the need of a signaling component.
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The SPRING architecture MUST support the following traffic
engineering requirements:
o loose or strict options
o bandwidth admission control
o distributed vs. centralized model (PCE
[I-D.ietf-pce-stateful-pce], SDN Controller)
o disjointness in dual-plane networks
o egress peering traffic engineering
o load-balancing among non-parallel links (i.e.: links connected to
different adjacent neighbors).
o Limiting (scalable, preferably zero) per-service state and
signaling on midpoint and tail-end routers.
o ECMP-awareness
o node resiliency property (i.e.: the traffic-engineering policy is
not anchored to a specific core node whose failure could impact
the service.
In most cases, Traffic Engineering makes use of the "loose" route
option where most of the explicit paths can be expressed through a
small number of hops. However, there are use cases where the
"strict" option may be used and, in such case, each individual hop in
the explicit path is specified. This may incur into a long list of
hops that is instantiated into a MPLS label stack (in the MPLS
dataplane) or list of IPv6 addresses (in the IPv6 dataplane).
It is obvious that in case of long strict source routing paths, the
deployment is possible if the head-end of the explicit path supports
the instantiation of long explicit paths.
Alternatively, a controller could decompose the end-to-end path into
a set of sub-paths such as each of these sub-paths is supported by
its respective head-end and advertised with a single identifier.
Hence, the concatenation (or stitching) of the sub-paths identifiers
gives a compression scheme allowing an end-to-end path to be
expressed in a smaller number of hops.
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3.3.1. Examples of Traffic Engineering Use Cases
Here follows the description of two sets of use cases:
o Traffic Engineering without Admission Control
o Traffic Engineering with Admission Control
3.3.1.1. Traffic Engineering without Bandwidth Admission Control
In this section, we describe Traffic Engineering use-cases without
bandwidth admission control.
3.3.1.1.1. Disjointness in dual-plane networks
Many networks are built according to the dual-plane design, as
illustrated in Figure 2:
Each aggregation region k is connected to the core by
two C routers C1k and C2k where k refers to the region.
C1k is part of plane 1 and aggregation region k
C2k is part of plane 2 and aggregation region k
C1k has a link to C2j iff k = j.
The core nodes of a given region are directly connected.
Inter-region links only connect core nodes of the same plane.
{C1k has a link to C1j} iff {C2k has a link to C2j}.
The distribution of these links depends on the topological
properties of the core of the AS. The design rule presented
above specifies that these links appear in both core planes.
We assume a common design rule found in such deployments: the inter-
plane link costs (Cik-Cjk where i != j) are set such that the route
to an edge destination from a given plane stays within the plane
unless the plane is partitioned.
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Edge Router A
/ \
/ \
/ \ Agg Region A
/ \
/ \
C1A----------C2A
| \ | \
| \ | \
| C1B----------C2B
Plane1 | | | | Plane2
| | | |
C1C--|-----C2C |
\ | \ |
\ | \ |
C1Z----------C2Z
\ /
\ / Agg Region Z
\ /
\ /
Edge Router Z
Figure 2: Dual-Plane Network and Disjointness
In this scenario, the operator requires the ability to deploy
different strategies. For example, Edge Router A should be able to
use the three following options:
o the traffic is load-balanced across any ECMP path through the
network
o the traffic is load-balanced across any ECMP path within the
Plane1 of the network
o the traffic is load-balanced across any ECMP path within the
Plane2 of the network
Most of the data traffic from A to Z would use the first option, such
as to exploit the capacity efficiently. The operator would use the
two other choices for specific premium traffic that has requested
disjoint transport.
The SPRING architecture MUST support this use case with the following
requirements:
o Zero per-service state and signaling on midpoint and tail-end
routers.
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o ECMP-awareness.
o Node resiliency property: the traffic-engineering policy is not
anchored to a specific core node whose failure could impact the
service.
3.3.1.1.2. Egress Peering Traffic Engineering
+------+
| |
+---D F
+---------+ / | AS 2 |\ +------+
| |/ +------+ \| Z |
A C | |
| |\ +------+ /| AS 4 |
B AS1 | \ | |/ +------+
| | +---E G
+---------+ | AS 3 |
+------+\
Figure 3: Egress peering traffic engineering
Let us assume, in the network depicted in Figure 3, that:
C in AS1 learns about destination Z of AS 4 via two BGP paths
(AS2, AS4) and (AS3, AS4).
C may or may not be configured so to enforce next-hop-self
behavior before propagating the paths within AS1.
C may propagate all the paths to Z within AS1 (BGP add-paths,
[I-D.ietf-idr-add-paths]).
C may install in its FIB only the route via AS2, or only the route
via AS3, or both.
In that context, the SPRING architecture MUST allow the operator of
AS1 to apply a traffic-engineering policy such as the following one,
regardless the configured behavior of next-hop-self:
Steer 60% of the Z-destined traffic received at A via AS2 and 40%
via AS3.
Steer 80% of the Z-destined traffic received at B via AS2 and 20%
via AS3.
The SPRING architecture MUST allow an ingress node (i.e., an explicit
route source node) to select the exit point of a packet as any
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combination of an egress node, an egress interface, a peering
neighbor, and a peering AS.
The use cases and requirements for Egress Peer Engineering are
described in [I-D.ietf-spring-segment-routing-central-epe].
3.3.1.1.3. Load-balancing among non-parallel links
The SPRING architecture MUST allow a given node to load share traffic
across multiple non parallel links (i.e.: links connected to
different adjacent routers) even if these lead to different
neighbors. This may be useful to support traffic engineering
policies.
+---C---D---+
| |
PE1---A---B-----F-----E---PE2
Figure 4: Multiple (non-parallel) Adjacencies
In the above example, the operator requires PE1 to load-balance its
PE2-destined traffic between the ABCDE and ABFE equal-cost paths in a
controlled way where the operator MUST be allowed to distribute
traffic unevenly between paths (Weighted Equal Cost Multiplath,
WECMP).
3.3.1.2. Traffic Engineering with Bandwidth Admission Control
The implementation of bandwidth admission control within a network
(and its possible routing consequence which consists in routing along
explicit paths where the bandwidth is available) requires a capacity
planning process.
The spreading of load among ECMP paths is a key attribute of the
capacity planning processes applied to packet-based networks.
3.3.1.2.1. Capacity Planning Process
Capacity Planning anticipates the routing of the traffic matrix onto
the network topology, for a set of expected traffic and topology
variations. The heart of the process consists in simulating the
placement of the traffic along ECMP-aware shortest-paths and
accounting for the resulting bandwidth usage.
The bandwidth accounting of a demand along its shortest-path is a
basic capability of any planning tool or PCE server.
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For example, in the network topology described below, and assuming a
default IGP metric of 1 and IGP metric of 2 for link GF, a 1600Mbps
A-to-Z flow is accounted as consuming 1600Mbps on links AB and FZ,
800Mbps on links BC, BG and GF, and 400Mbps on links CD, DF, CE and
EF.
C-----D
/ \ \
A---B +--E--F--Z
\ /
G------+
Figure 5: Capacity Planning an ECMP-based demand
ECMP is extremely frequent in SP, Enterprise and DC architectures and
it is not rare to see as much as 128 different ECMP paths between a
source and a destination within a single network domain. It is a key
efficiency objective to spread the traffic among as many ECMP paths
as possible.
This is illustrated in the below network diagram which consists of a
subset of a network where already 5 ECMP paths are observed from A to
M.
C
/ \
B-D-L--
/ \ / \
A E \
\ M
\ G /
\ / \ /
F K
\ /
I
Figure 6: ECMP Topology Example
When the capacity planning process detects that a traffic growth
scenario and topology variation would lead to congestion, a capacity
increase is triggered and if it cannot be deployed in due time, a
traffic engineering solution is activated within the network.
A basic traffic engineering objective consists of finding the
smallest set of demands that need to be routed off their shortest
path to eliminate the congestion, then to compute an explicit path
for each of them and instantiating these traffic-engineered policies
in the network.
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The SPRING architecture MUST offer a simple support for ECMP-based
shortest path placement as well as for explicit path policy without
incurring additional signaling in the domain. This includes:
o the ability to steer a packet across a set of ECMP paths
o the ability to diverge from a set of ECMP shortest paths to one or
more paths not in the set of shortest paths
3.3.1.2.2. SDN Use Case
The SDN use-case lies in the SDN controller, (e.g.: Stateful PCE as
described in [I-D.ietf-pce-stateful-pce].
The SDN controller is responsible to control the evolution of the
traffic matrix and topology. It accepts or denies the addition of
new traffic into the network. It decides how to route the accepted
traffic. It monitors the topology and upon topological change,
determines the minimum traffic that should be rerouted on an
alternate path to alleviate a bandwidth congestion issue.
The algorithms supporting this behavior are a local matter of the SDN
controller and are outside the scope of this document.
The means of collecting traffic and topology information are the same
as what would be used with other SDN-based traffic-engineering
solutions.
The means of instantiating policy information at a traffic-
engineering head-end are the same as what would be used with other
SDN-based traffic-engineering solutions.
In the context of Centralized-Based Optimization and the SDN use-
case, here are the functionalities that the SPRING architecture MUST
deliver:
Explicit routing capability with or without ECMP-awareness.
No signaling hop-by-hop through the network.
Policy state is only maintained at the policy head-end. No policy
state is maintained at mid-points and tail-ends.
Automated guaranteed FRR for any topology.
The policy state is in the packet header and not in the
intermediate nodes along the path. The policy is absent from
midpoints and tail-ends.
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Highly responsive to change: the SDN Controller only needs to
apply a policy change at the head-end. No delay is introduced due
to programming the midpoints and tail-end along the path.
3.4. Interoperability with non-SPRING nodes
SPRING nodes MUST inter-operate with non-SPRING nodes and in both
MPLS and IPv6 dataplanes in order to allow a gradual deployment of
SPRING on existing MPLS and IPv6 networks.
4. Security Considerations
SPRING reuses the concept of source routing by encoding the path in
the packet. As with other similar source routing architecture, an
attacker may manipulate traffic path by modifying the packet header.
By manipulating traffic path, an attacker may be able to cause
outages on any part of the network.
SPRING adds some meta-data on the packet, with the list of forwarding
path elements that the packet must traverse. Depending on the data
plane, this list may shrink as the packet traverse the network, by
only keeping the next elements and forgetting the past ones.
SPRING architecture MUST provide clear trust domain boundaries, so
that source routing information is only usable within the trusted
domain and never exposed to the outside world.
From a network protection standpoint, there is an assumed trust model
such that any node imposing an explicit route on a packet is assumed
to be allowed to do so. This is a significant change compared to
plain IP offering shortest path routing but not fundamentally
different compared to existing techniques providing explicit routing
capability. It is expected that, by default, the explicit routing
information is not leaked through the boundaries of the administered
domain.
Therefore, the dataplane MUST NOT expose any source routing
information when a packet leaves the trusted domain. Special care
will be required for the existing dataplanes like MPLS, especially
for the inter-provider scenario where a third-party provider may push
MPLS labels corresponding to a SPRING header anywhere in the stack.
The architecture document MUST analyze the exact security
considerations of such scenario.
Filtering routing information is typically performed in the control
plane, but an additional filtering in the forwarding plane is also
required. In SPRING, as there is no control plane (related to source
routed paths) between the source and the mid points, filtering in the
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control plane is not possible (or not required, depending on the
point of view). Filtering MUST be performed on the forwarding plane
on the boundaries and MAY require looking at multiple labels/
instruction.
For the MPLS data plane, this not a new requirement as the existing
MPLS architecture already allow such source routing by stacking
multiple labels. And for security protection, RFC4381 section 2.4
and RFC 5920 section 8.2 already calls for the filtering of MPLS
packets on trust boundaries.
If all MPLS labels are filtered at domain boundaries, then SPRING
does not introduce any change. If only a subset of labels are
filtered, then SPRING introduces a change since the border router is
expected to determine which information (e.g.: labels) are filtered
while the border router is not the originator of these label
advertisements.
As the SPRING architecture must be based on clear trust domain,
mechanisms allowing the authentication and validation of the source
routing information must be evaluated by the SPRING architecture in
order to prevent any form of attack or unwanted source routing
information manipulation.
Dataplane security considerations MUST be addressed in each SPRING
dataplane related document (i.e.: MPLS and IPv6).
The IPv6 data plane proposes the use of a cryptographic signature of
the source routed path which would ease this configuration. This is
indeed more needed for the IPv6 data plane which is end to end in
nature, compared to the MPLS data plane which is typically restricted
to a controlled and trusted zone.
In the forwarding plane, data plane extension documents MUST address
the security implications of the required change.
In term of privacy, SPRING does not propose change in term of
encryption. Each dataplane, may or may not provide existing or
future encryption capability.
In order to build the source routing information in the packet, a
node in SPRING architecture will require learning information from a
control layer. As this control layer will be in charge of
programming forwarding instructions, an attacker taking over this
component may also manipulate the traffic path. Any control protocol
used in the SPRING architecture SHOULD provide security mechanisms or
design to protect against such control layer attacker. Control plane
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security considerations MUST be addressed in each SPRING control
plane related document.
5. IANA Considerations
This document does not request any IANA allocations.
6. Manageability Considerations
The SPRING WG MUST define Operations and Management (OAM) procedures
applicable to SPRING enabled networks.
In SPRING networks, the path the packet takes is encoded in the
header. SPRING architecture MUST include the necessary OAM
mechanisms in order for the network operator to validate the
effectiveness of a path as well as to check and monitor its liveness
and performance. Moreover, in SPRING architecture, a path may be
defined in the forwarding layer (in both MPLS and IPv6 dataplanes) or
as a service path (formed by a set of service instances). The
network operator MUST be capable to monitor, control and manage paths
(network and service based) using OAM procedures.
OAM use cases and requirements are detailed in
[I-D.ietf-spring-oam-usecase] and
[I-D.ietf-spring-sr-oam-requirement].
7. Contributors
The following individuals substantially contributed to the content of
this documents:
Ruediger Geib
Deutsche Telekom
Heinrich Hertz Str. 3-7
Darmstadt 64295
DE
Email: Ruediger.Geib@telekom.de
Robert Raszuk
Mirantis Inc.
615 National Ave.
94043 Mt View, CA
US
Email: robert@raszuk.net
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8. Acknowledgements
The authors would like to thank Yakov Rekhter for his contribution to
this document.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <http://www.rfc-editor.org/info/rfc4364>.
[RFC4761] Kompella, K., Ed. and Y. Rekhter, Ed., "Virtual Private
LAN Service (VPLS) Using BGP for Auto-Discovery and
Signaling", RFC 4761, DOI 10.17487/RFC4761, January 2007,
<http://www.rfc-editor.org/info/rfc4761>.
[RFC4762] Lasserre, M., Ed. and V. Kompella, Ed., "Virtual Private
LAN Service (VPLS) Using Label Distribution Protocol (LDP)
Signaling", RFC 4762, DOI 10.17487/RFC4762, January 2007,
<http://www.rfc-editor.org/info/rfc4762>.
[RFC6624] Kompella, K., Kothari, B., and R. Cherukuri, "Layer 2
Virtual Private Networks Using BGP for Auto-Discovery and
Signaling", RFC 6624, DOI 10.17487/RFC6624, May 2012,
<http://www.rfc-editor.org/info/rfc6624>.
9.2. Informative References
[I-D.ietf-6man-segment-routing-header]
Previdi, S., Filsfils, C., Field, B., Leung, I., Linkova,
J., Kosugi, T., Vyncke, E., and D. Lebrun, "IPv6 Segment
Routing Header (SRH)", draft-ietf-6man-segment-routing-
header-01 (work in progress), March 2016.
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Internet-Draft SPRING Problem Statement April 2016
[I-D.ietf-idr-add-paths]
Walton, D., Retana, A., Chen, E., and J. Scudder,
"Advertisement of Multiple Paths in BGP", draft-ietf-idr-
add-paths-13 (work in progress), December 2015.
[I-D.ietf-pce-stateful-pce]
Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP
Extensions for Stateful PCE", draft-ietf-pce-stateful-
pce-14 (work in progress), March 2016.
[I-D.ietf-spring-oam-usecase]
Geib, R., Filsfils, C., Pignataro, C., and N. Kumar, "Use
Case for a Scalable and Topology-Aware Segment Routing
MPLS Data Plane Monitoring System", draft-ietf-spring-oam-
usecase-01 (work in progress), October 2015.
[I-D.ietf-spring-resiliency-use-cases]
Francois, P., Filsfils, C., Decraene, B., and R. Shakir,
"Use-cases for Resiliency in SPRING", draft-ietf-spring-
resiliency-use-cases-03 (work in progress), April 2016.
[I-D.ietf-spring-segment-routing-central-epe]
Filsfils, C., Previdi, S., Ginsburg, D., and D. Afanasiev,
"Segment Routing Centralized BGP Peer Engineering", draft-
ietf-spring-segment-routing-central-epe-01 (work in
progress), March 2016.
[I-D.ietf-spring-sr-oam-requirement]
Kumar, N., Pignataro, C., Akiya, N., Geib, R., Mirsky, G.,
and S. Litkowski, "OAM Requirements for Segment Routing
Network", draft-ietf-spring-sr-oam-requirement-01 (work in
progress), December 2015.
Authors' Addresses
Stefano Previdi (editor)
Cisco Systems, Inc.
Via Del Serafico, 200
Rome 00142
Italy
Email: sprevidi@cisco.com
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Clarence Filsfils (editor)
Cisco Systems, Inc.
Brussels
BE
Email: cfilsfil@cisco.com
Bruno Decraene
Orange
FR
Email: bruno.decraene@orange.com
Stephane Litkowski
Orange
FR
Email: stephane.litkowski@orange.com
Martin Horneffer
Deutsche Telekom
Hammer Str. 216-226
Muenster 48153
DE
Email: Martin.Horneffer@telekom.de
Rob Shakir
Jive Communications, Inc.
1275 West 1600 North, Suite 100
Orem, UT 84057
Email: rjs@rob.sh
Previdi, et al. Expires October 8, 2016 [Page 18]
