Internet Engineering Task Force (IETF) S. Previdi, Ed.
Request for Comments: 7855 C. Filsfils, Ed.
Category: Informational Cisco Systems, Inc.
ISSN: 2070-1721 B. Decraene
S. Litkowski
Orange
M. Horneffer
Deutsche Telekom
R. Shakir
Jive Communications, Inc.
May 2016
Source Packet Routing in Networking (SPRING)
Problem Statement and Requirements
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";
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 for this document.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7855.
Previdi, et al. Informational [Page 1]RFC 7855 SPRING Problem Statement May 2016
Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Data Planes . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. SPRING Use Cases . . . . . . . . . . . . . . . . . . . . . . 4
3.1. IGP-Based MPLS Tunneling . . . . . . . . . . . . . . . . 4
3.1.1. Example of IGP-Based MPLS Tunnels . . . . . . . . . . 5
3.2. Fast Reroute (FRR) . . . . . . . . . . . . . . . . . . . 5
3.3. Traffic Engineering . . . . . . . . . . . . . . . . . . . 6
3.3.1. Examples of Traffic-Engineering Use Cases . . . . . . 7
3.4. Interoperability with Non-SPRING Nodes . . . . . . . . . 13
4. Security Considerations . . . . . . . . . . . . . . . . . . . 13
5. Manageability Considerations . . . . . . . . . . . . . . . . 15
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.1. Normative References . . . . . . . . . . . . . . . . . . 16
6.2. Informative References . . . . . . . . . . . . . . . . . 16
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 18
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
Previdi, et al. Informational [Page 2]RFC 7855 SPRING Problem Statement May 2016
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:
o Some types of network virtualization, including multi-topology
networks and the partitioning of network resources for VPNs
o Network, link, path, and node protection such as fast reroute
o Network programmability
o OAM techniques
o Simplification and reduction of network signaling components
o 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 more
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"; 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 a flag day or massive upgrade
of all network elements.
The SPRING architecture MUST allow putting the 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.
Previdi, et al. Informational [Page 3]RFC 7855 SPRING Problem Statement May 2016
The SPRING architecture objective is not to replace existing source-
routing and traffic-engineering mechanisms, but rather to 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 for this
document.
1.1. 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].
2. Data Planes
The SPRING architecture SHOULD be general in order to ease its
applicability to different data planes.
The SPRING architecture SHOULD leverage the existing MPLS data plane
without any modification and leverage the IPv6 data plane 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
[SRH].
The SPRING architecture MUST allow interoperability between SPRING-
capable and non-SPRING-capable nodes in both the MPLS and IPv6 data
planes.
3. SPRING Use Cases
3.1. IGP-Based MPLS Tunneling
The source-based routing model, applied to the MPLS data plane,
offers the ability to tunnel services like VPN ([RFC4364]), Virtual
Private LAN Service (VPLS) ([RFC4761], [RFC4762]) and Virtual Private
Wire Service (VPWS) ([RFC6624]), from an ingress Provider Edge (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 the scope of this document.
Previdi, et al. Informational [Page 4]
RFC 7855 SPRING Problem Statement May 2016
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 the
Multiprotocol Border Gateway Protocol (MPBGP) to PE1 with next-hop
address 192.0.2.2 (i.e., the local address of PE2). PE1 installs the
VPN prefix Z in the appropriate VPN Routing and Forwarding table
(VRF) and resolves the next hop onto the IGP-based MPLS tunnel to
PE2.
To cope with the reality of current deployments, the SPRING
architecture MUST allow PE-to-PE forwarding according to the IGP
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)
Fast Reroute (FRR) technologies have been deployed by network
operators in order to cope with link or node failures through
precomputation of backup paths.
Illustration of the problem statement for FRR and micro-loop
avoidance can be found in [SPRING-RESIL].
The SPRING architecture MUST address the following requirements:
o support of Fast Reroute (FRR) on any topology
o precomputation and setup of backup path without any additional
signaling (other than the regular IGP/BGP protocols)
o support of shared risk constraints
Previdi, et al. Informational [Page 5]RFC 7855 SPRING Problem Statement May 2016
o support of node and link protection
o support of micro-loop 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 addressing specific
bandwidth limitations in the network (tactical TE). In these
situations, there is a need to reduce, as much as 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 very high
scalability, in particular on midpoints.
The source-based routing model allows traffic engineering to be
implemented without the need for a signaling component.
The SPRING architecture MUST support the following traffic-
engineering requirements:
o loose or strict options
o bandwidth admission control
o distributed vs. centralized model (e.g., Path Computation Element
(PCE) [STATEFUL-PCE], Software-Defined Networking (SDN)
Controller)
o disjointness in dual-plane networks
o egress peer 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
Previdi, et al. Informational [Page 6]RFC 7855 SPRING Problem Statement May 2016
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 cases, each individual hop
in the explicit path is specified. This may result in a long list of
hops that is instantiated into a MPLS label stack (in the MPLS data
plane) or list of IPv6 addresses (in the IPv6 data plane).
It is obvious that, in the case of long, strict source-routed 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.
3.3.1. Examples of Traffic-Engineering Use Cases
Below are descriptions 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
Previdi, et al. Informational [Page 7]RFC 7855 SPRING Problem Statement May 2016
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 Autonomous System (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.
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.
Previdi, et al. Informational [Page 8]RFC 7855 SPRING Problem Statement May 2016
o The traffic is load-balanced across any ECMP path within Plane1 of
the network.
o The traffic is load-balanced across any ECMP path within Plane2 of
the network.
Most of the data traffic from A to Z would use the first option, so
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.
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
+---------+ / | AS2 |\ +------+
| |/ +------+ \| Z |
A C | |
| |\ +------+ /| AS4 |
B AS1 | \ | |/ +------+
| | +---E G
+---------+ | AS3 |
+------+\
Figure 3: Egress Peering Traffic Engineering
Let us assume, in the network depicted in Figure 3, that:
o C in AS1 learns about destination Z of AS4 via two BGP paths (AS2,
AS4) and (AS3, AS4).
o C may or may not be configured to enforce the next-hop-self
behavior before propagating the paths within AS1.
Previdi, et al. Informational [Page 9]RFC 7855 SPRING Problem Statement May 2016
o C may propagate all the paths to Z within AS1 (using BGP ADD-PATH
as specified in [ADD-PATH]).
o C may install in its Forwarding Information Base (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 of the configured behavior of the next-hop-self:
o Steer 60% of the Z-destined traffic received at A via AS2 and 40%
via AS3.
o 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
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 [SR-BGP-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 for supporting 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 Multipath
(WECMP)).
Previdi, et al. Informational [Page 10]RFC 7855 SPRING Problem Statement May 2016
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.
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 1600 Mbps
A-to-Z flow is accounted as consuming 1600 Mbps on links AB and FZ;
800 Mbps on links BC, BG, and GF; and 400 Mbps 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 Service Provider (SP), enterprise, and
data-center 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 network diagram below, which consists of a
subset of a network where already 5 ECMP paths are observed from A to
M.
Previdi, et al. Informational [Page 11]RFC 7855 SPRING Problem Statement May 2016
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, and then to compute an explicit
path for each of them and instantiate these traffic-engineered
policies in the network.
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 [STATEFUL-PCE]).
The SDN controller is responsible for controlling 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.
Previdi, et al. Informational [Page 12]RFC 7855 SPRING Problem Statement May 2016
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 optimization and the SDN use case, the
SPRING architecture MUST have the following attributes:
o Explicit routing capability with or without ECMP-awareness.
o No signaling hop-by-hop through the network.
o The policy state is only maintained at the policy head-end. No
policy state is maintained at midpoints and tail-ends.
o Automated guaranteed FRR for any topology.
o 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.
o 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 interoperate with non-SPRING nodes and in both MPLS
and IPv6 data planes 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 the traffic path by modifying the packet
header. By manipulating the traffic path, an attacker may be able to
cause outages on any part of the network.
SPRING adds some metadata 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 traverses the network, by
keeping only the next elements and forgetting the past ones.
Previdi, et al. Informational [Page 13]RFC 7855 SPRING Problem Statement May 2016
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 the 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 data plane MUST NOT expose any source-routing
information when a packet leaves the trusted domain. Special care
will be required for the existing data planes 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 a 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 midpoints, filtering
in the 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 or
instructions.
For the MPLS data plane, this is not a new requirement as the
existing MPLS architecture already allows such source routing by
stacking multiple labels. For security protection, Section 2.4 of
[RFC4381] and Section 8.2 of [RFC5920] already call 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) is filtered,
while the border router is not the originator of these label
advertisements.
As the SPRING architecture must be based on a 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.
Previdi, et al. Informational [Page 14]
RFC 7855 SPRING Problem Statement May 2016
Data-plane security considerations MUST be addressed in each document
related to the SPRING data plane (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 needed more 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 terms of privacy, SPRING does not propose change in terms of
encryption. Each data plane may or may not provide existing or
future encryption capability.
To build the source-routing information in the packet, a node in the
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 a control-layer attacker. Control-plane
security considerations MUST be addressed in each document related to
the SPRING control plane.
5. Manageability Considerations
The SPRING WG MUST define Operations, Administration, and Maintenance
(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 data planes)
or as a service path (formed by a set of service instances). The
network operator MUST be capable to monitor, control, and manage
paths (both network and service based) using OAM procedures.
OAM use cases and requirements are detailed in [OAM-USE] and
[SR-OAM].
Previdi, et al. Informational [Page 15]
RFC 7855 SPRING Problem Statement May 2016
6. References
6.1. 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>.
6.2. Informative References
[ADD-PATH] Walton, D., Retana, A., Chen, E., and J. Scudder,
"Advertisement of Multiple Paths in BGP", Work in
Progress, draft-ietf-idr-add-paths-14, April 2016.
[OAM-USE] Geib, R., Ed., Filsfils, C., Pignataro, C., Ed., and N.
Kumar, "A Scalable and Topology-Aware MPLS Dataplane
Monitoring System", Work in Progress, draft-ietf-spring-
oam-usecase-03, April 2016.
[RFC4381] Behringer, M., "Analysis of the Security of BGP/MPLS IP
Virtual Private Networks (VPNs)", RFC 4381,
DOI 10.17487/RFC4381, February 2006,
<http://www.rfc-editor.org/info/rfc4381>.
Previdi, et al. Informational [Page 16]RFC 7855 SPRING Problem Statement May 2016
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
<http://www.rfc-editor.org/info/rfc5920>.
[SPRING-RESIL]
Francois, P., Filsfils, C., Decraene, B., and R. Shakir,
"Use-cases for Resiliency in SPRING", Work in Progress,
draft-ietf-spring-resiliency-use-cases-03, April 2016.
[SR-BGP-EPE]
Filsfils, C., Ed., Previdi, S., Ed., Ginsburg, D., and D.
Afanasiev, "Segment Routing Centralized BGP Peer
Engineering", Work in Progress, draft-ietf-spring-segment-
routing-central-epe-01, March 2016.
[SR-OAM] Kumar, N., Pignataro, C., Akiya, N., Geib, R., Mirsky, G.,
and S. Litkowski, "OAM Requirements for Segment Routing
Network", Work in Progress, draft-ietf-spring-sr-oam-
requirement-01, December 2015.
[SRH] Previdi, S., Filsfils, C., Field, B., Leung, I., Linkova,
J., Kosugi, T., Vyncke, E., and D. Lebrun, "IPv6 Segment
Routing Header (SRH)", Work in Progress, draft-ietf-6man-
segment-routing-header-01, March 2016.
[STATEFUL-PCE]
Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP
Extensions for Stateful PCE", Work in Progress,
draft-ietf-pce-stateful-pce-14, March 2016.
Previdi, et al. Informational [Page 17]RFC 7855 SPRING Problem Statement May 2016
Acknowledgements
The authors would like to thank Yakov Rekhter for his contribution to
this document.
Contributors
The following individuals substantially contributed to the content of
this document:
Ruediger Geib
Deutsche Telekom
Heinrich Hertz Str. 3-7
Darmstadt 64295
Germany
Email: Ruediger.Geib@telekom.de
Robert Raszuk
Mirantis Inc.
615 National Ave.
94043 Mountain View, CA
United States
Email: robert@raszuk.net
Authors' Addresses
Stefano Previdi (editor)
Cisco Systems, Inc.
Via Del Serafico, 200
Rome 00142
Italy
Email: sprevidi@cisco.com
Clarence Filsfils (editor)
Cisco Systems, Inc.
Brussels
Belgium
Email: cfilsfil@cisco.com
Previdi, et al. Informational [Page 18]
RFC 7855 SPRING Problem Statement May 2016
Bruno Decraene
Orange
France
Email: bruno.decraene@orange.com
Stephane Litkowski
Orange
France
Email: stephane.litkowski@orange.com
Martin Horneffer
Deutsche Telekom
Muenster 48153
Germany
Email: Martin.Horneffer@telekom.de
Rob Shakir
Jive Communications, Inc.
1275 West 1600 North, Suite 100
Orem, UT 84057
United States
Email: rjs@rob.sh
Previdi, et al. Informational [Page 19]
