Internet DRAFT - draft-saad-teas-rsvpte-ip-tunnels
draft-saad-teas-rsvpte-ip-tunnels
TEAS Working Group T. Saad
Internet-Draft V.P. Beeram
Intended status: Standards Track Juniper Networks
Expires: 14 October 2022 12 April 2022
IP RSVP-TE: Extensions to RSVP for P2P IP-TE LSP Tunnels
draft-saad-teas-rsvpte-ip-tunnels-02
Abstract
This document describes the use of RSVP (Resource Reservation
Protocol), including all the necessary extensions, to establish
Point-to-Point (P2P) Traffic Engineered IP (IP-TE) Label Switched
Path (LSP) tunnel(s) for use in native IP forwarding networks.
This document proposes specific extensions to the RSVP protocol to
allow the establishment of explicitly routed IP paths using RSVP as
the signaling protocol. The result is the instantiation of an IP
Path which can be automatically routed away from network failures,
congestion, and bottlenecks.
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 14 October 2022.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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and restrictions with respect to this document. Code Components
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Overview of IP LSP Tunnels . . . . . . . . . . . . . . . . . 4
3.1. Creation and Management . . . . . . . . . . . . . . . . . 4
3.2. Path Maintenance . . . . . . . . . . . . . . . . . . . . 5
3.3. Signaling Extensions . . . . . . . . . . . . . . . . . . 5
3.3.1. RSVP Path message . . . . . . . . . . . . . . . . . . 6
3.4. RSVP Resv Label Object . . . . . . . . . . . . . . . . . 6
3.5. EAB address Handling . . . . . . . . . . . . . . . . . . 7
3.5.1. Egress Router . . . . . . . . . . . . . . . . . . . . 7
3.5.2. Ingress and Transit Router . . . . . . . . . . . . . 7
3.6. Protection . . . . . . . . . . . . . . . . . . . . . . . 8
3.7. Shared Forwarding . . . . . . . . . . . . . . . . . . . . 8
3.8. Error Conditions . . . . . . . . . . . . . . . . . . . . 9
4. Next Steps . . . . . . . . . . . . . . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 9
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
In native IP networks, each router runs a routing protocol to
determine the best next-hop(s) to a specific destination. The best
next-hop(s) are usually determined by favoring those that run along
the shortest path to the destination. When data flows across the
network, it is routed hop-by-hop and follows the selected path by
each hop towards that destination on each hop.
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It is sometimes desirable for an ingress router to be able to steer
traffic towards a destination along a pre-determined or pre-computed
path that may follow a path other than the default shortest path.
For example, some flows mayrequire to be forwarded along the least
latency path. Others, may desire to be routed with bandwidth
guarantees along the selected path, or along a path that honors
certain resource affinities or Shared Risk Link Group (SRLG)
memberships.
A solution to such use-cases entails: 1) router(s) in the network to
be able to maintain and disseminate per link state information, 2)
ingress routers or an external Path Computation Engine (PCE) to be
able to perform a stateful path computation for feasible path(s) on
top of the network topology, and 3) for ingress router(s) to be able
to steer or tunnel the traffic along the established path towards the
destination.
Mechanisms have been defined to achieve this with RSVP extensions for
Traffic Engineered Multiprotocol Label Switching (MPLS-TE) networks
as described in [RFC3209]. This document proposes extensions to the
existing mechanisms for achieving this in networks that rely on
native IP for their forwarding.
This document covers the necessary extensions for establishing Point-
to-Point (P2P) Traffic-Engineered IP (IP-TE) Label Switched Path
(LSP) Tunnels. The equivalent extensions needed for setting up
multicast IP-TE LSPs are currently out of the scope of this document.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2.1. Acronyms
The reader is assumed to be familiar with the terminology used in
[RFC2205] and [RFC3209].
IP-TE LSP (Traffic Engineered IP Label Switched Path):
The path created by programming of an IP route along the
explicitly specified or dynamically computed sequence of router
hops, allowing an IP packet to be forwarded from one hop to
another along the established path.
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IP-TE LSP Tunnel:
An IP-TE LSP which is used to tunnel traffic over the pre-
established IP path.
Traffic Engineered IP Tunnel (IP-TE Tunnel):
A set of one or more IP-TE LSP Tunnels which carries a traffic
trunk.
3. Overview of IP LSP Tunnels
IP-TE LSP tunnels are established over a native IP forwarding
network. In many cases, IP-TE LSP(s) are explicitly routed from an
ingress router. The explicit route used to establish an IP-TE LSP
may be locally computed at the ingress router, or externally computed
by an entity such as a Path Computation Element (PCE) [RFC4655].
To support the setup of IP-TE LSP tunnel(s), the egress routers
reserve one or more local IP prefixes or Egress Address Block(s)
(EABs) that are dedicated for RSVP to establish IP-TE LSP(s) tunnels.
The EAB(s) addresses at the egress router may be managed by the RSVP
protocol and are not required to be exchanged by any other routing
protocol.
It is possible in some cases, where the IP-TE LSP(s) are contained
within a single administrative domain boundary, for EAB(s) to be
allocated from the private IP address space as defined in [RFC1918]
or from the unique-local space as defined in [RFC4193] and [RFC6890].
Also useful in some applications for sets of IP-TE LSP tunnels to be
associated together to facilitate reroute operations or to spread a
traffic trunk over multiple IP-TE LSP tunnel paths. For traffic
engineering applications to IP-TE LSP tunnel(s), such sets are called
traffic engineered tunnels (TE IP tunnels).
3.1. Creation and Management
An IP-TE LSP tunnel is unidirectional in nature. To create an IP-TE
LSP tunnel, the ingress router of the IP-TE LSP tunnel creates an
RSVP Path message with a session type of LSP_TUNNEL_IPv4 or
LSP_TUNNEL_IPv6 and follows the procedures outlined in [RFC3473] to
insert a Generalized Label Request object into the Path message. The
Generalized Label Request object indicates that an IP address binding
is requested to the IP-TE LSP tunnel. The binding of an EAB address
to an IP-TE LSP tunnel happens at the egress router and is signaled
using an RSVP Resv message sent from the egress router.
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The ingress router uses a pre-computed explicit path to populate the
EXPLICIT_ROUTE object that is added the RSVP Path message. The
explicitly routed path can be administratively specified, or
automatically computed by a suitable entity based on QoS and policy
requirements, taking into consideration the prevailing network state.
In addition, RSVP-TE signaling [RFC3209] allows for the specification
of an explicit path as a sequence of strict and loose routes. Such
combination of abstract nodes, and strict and loose routes
significantly enhances the flexibility of path definitions.
The ingress MAY also add a RECORD_ROUTE object to the RSVP Path
message in order to receive information about the actual route
traversed by the IP-TE LSP tunnel. The RECORD_ROUTE object MAY also
be used by the egress router to determine whether Shared Forwarding
as described in Section 3.7 is possible amongst different IP-TE LSP
tunnel(s).
3.2. Path Maintenance
If the ingress router discovers a better path, after an IP-TE LSP
tunnel has been successfully established, it can dynamically reroute
the session by changing the EXPLICIT_ROUTE object. If problems are
encountered with the EXPLICIT_ROUTE object, either because it causes
a routing loop or because some intermediate routers do not support
it, the ingress is notified.
Make-before-break procedures can also be employed to modify the
characteristics of an IP-TE LSP tunnel. As described in [RFC3209],
the LSP ID in the Sender Template object is updated in the new RSVP
Path message that is signaled. As usual, the combination of the
LSP_TUNNEL SESSION object and the SE reservation style naturally
accommodates smooth transitions in bandwidth and routing.
For example, to trigger a bandwidth increase, a new RSVP Path Message
with a new LSP_ID can be used to attempt a larger bandwidth
reservation while the current LSP_ID continues to be refreshed to
ensure that the reservation is not lost if the larger reservation
fails.
3.3. Signaling Extensions
This section describes RSVP signaling extensions and modifications to
existing RSVP objects that are carried in RSVP Path or Resv messages
and are required to establish IP-TE LSP tunnel(s).
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3.3.1. RSVP Path message
To signal an IP-TE LSP tunnel, the Generalized Label Request object
is carried in the RSVP Path message and used to request an IP address
binding to the IP-TE LSP tunnel.
The Generalized Label Request is defined in [RFC3471] and has the
below format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Enc. Type |Switching Type | G-PID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
To request an IPv4 or IPv6 binding to an IP-TE LSP tunnel, the
Generalized Label object carries the following specifics:
1. the LSP encoding type is set to Packet (1) [RFC3471].
2. the LSP switching type is set to "IPv4-TE" (TBD1), or IPv6-TE
(TBD2)
3. the Generalized Payload Identifier (G-PID) MAY be set to All
(0) or in some cases to the specific payload type if known,
e.g. Ethernet (33) [RFC3471].
3.4. RSVP Resv Label Object
The egress is responsible to bind an IP EAB address to an IP-TE LSP
tunnel.
Once the egress router receives the RSVP Path message with the
Generalized Label Request object containing the parameters described
in Section 3.3.1, the egress router determines and binds an EAB
address to the newly established IP-TE LSP tunnel. Note, subject to
a local policy and additional path check(s), the egress MAY assign an
already in used EAB address to the newly established IP-TE LSP
tunnel.
The RSVP Resv message that is created by the egress router uses the
Generalized Label defined in [RFC3471] to carry the EAB address that
is bound to newly established IP-TE LSP tunnel.
The RSVP Generalized Label object has the following format:
LABEL class = 16, C_Type = 2
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The information carried in a Generalized Label is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Label (Variable Length):
Carries label information. The interpretation of this field
depends the parameters signaled in the Generalized Label
Request.
3.5. EAB address Handling
The RSVP Resv message that is created by the egress router is
forwarded upstream along the signaling path towards the ingress
router. Each router starting from the egress will perform the
following steps when binding the EAB address to the IP-TE LSP tunnel.
3.5.1. Egress Router
The egress router manages the EAB addresses for the use of
establishing IP LSP tunnel(s).
The egress router MAY assign unique EAB address to newly established
IP-TE LSP tunnel(s) and MAY free an existing EAB address upon
destroying a previously established IP-TE LSP tunnel. Note that an
egress router MAY hold on to an EAB when the IP-TE LSP is being
destroyed if it determines other IP-TE LSP(s) are sharing it.
Once an EAB address is allocated and bound to a new IP-TE LSP tunnel,
the egress router programs the address in its forwarding table as
local address - hence, resulting in decapsulation of the outer IP
header on any packet arriving over the IP-TE LSP tunnel and hence
yielding the original IP datagram that was tunneled over the IP LSP
tunnel,
3.5.2. Ingress and Transit Router
A transit or an ingress router extracts the EAB address that the
egress router binds to the IP-TE LSP tunnel from the Generalized
Label object contained in the RSVP Resv message that is propagated
upstream as described in Section 3.4. The transit or ingress router
uses the EAB address to program an IP route in the Routing
Information Base (RIB) and uses the previously signaled
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EXPLICIT_ROUTE object to derive the next-hop information associated
with the EAB route at that hop.
An advantage of using RSVP to establish IP-TE LSP tunnels is that it
enables the allocation of resources along the path. For example,
bandwidth can be allocated to each IP-TE LSP tunnel using standard
RSVP reservations as described in [RFC3209].
3.6. Protection
Fast Reroute (FRR) procedures that are defined in [RFC4090] describe
the mechanisms for router along the LSP path to act as a Point of
Local Repair (PLR) and reroute traffic and signaling of a protected
RSVP-TE LSP onto a pre-established bypass tunnel in the event of a
protected TE link or node failure.
Similar mechanisms can be employed for protecting IP-TE LSP tunnel(s)
in IP network(s). An ingress or transit router acting as potential
PLR can pre-establish bypass tunnel(s) that protect the primary IP-TE
LSP tunnel against the protected link or downstream node failure.
Upon failure of the protected link, the traffic arriving over the
protected IP-TE LSP on the PLR is automatically tunneled over the
pre-established bypass IP-TE LSP tunnel and packets are forwarded
towards the Merge Point (MP) router. At the MP router, the incoming
IP packets are decapsulated exposing the original IP header of the
protected IP-TE LSP tunnel. The packets are forwarded downstream of
the MP router along the
3.7. Shared Forwarding
One capability of the IP data plane is its ability to reuse the IP
forwarding entry when setting up IP-TE LSP(s) from multiple sources
and that share a common destination. This capability MAY be
preserved provided certain requirements are met. We refer to this
capability as "Shared Forwarding". Shared Forwarding is a local
policy local to egress router responsible for binding an EAB address
to the signaled IP-TE LSP tunnel.
The Shared Forwarding function allows the reduction of forwarding
entries on any transit router RIB. The Shared forwarding paths are
identical in function to independently routed Multi-point to Point
(MP2P) paths that share part of their path(s) from the intersecting
router and towards the egress router.
If the egress router policy allows for Shared Forwarding, and upon
signaling a new IP-TE LSP tunnel, the egress inspects the recorded
path (extracted from the RECORD_ROUTE object). If the egress router
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determines that the newly signaled IP-TE LSP path intersects and
merges with other IP-TE LSP from the intersection point to the
egress, and if Shared Forwarding is enabled, it MUST assign the same
EAB address bound to the existing IP-TE LSP tunnel.
Note, forwarding memory savings from Shared Forwarding can be quite
dramatic in some topologies where a high degree of meshing is
required.
3.8. Error Conditions
This section will be updated in future revisions of this document.
4. Next Steps
The authors of this document are following up with the DetNet Working
Group on ways to leverage this solution to signal and establish a TE
IP path for a DetNet IP flow. The DetNet IP data plane uses
"6-tuple" based flow identification as described in
[I-D.ietf-detnet-ip].
A new revision of this document will be posted to describe the
extensions required to signal the necessary flow identification so it
can be programmed on all hops of the IP Path.
5. IANA Considerations
This section will be updated in future revisions of this document.
6. Security Considerations
This section will be updated in future revisions of this document.
7. Acknowledgement
The authors would like to thank Igor Bryskin for providing valuable
feedback to this document.
8. Contributors
Raveendra Torvi
Juniper Networks
Email: rtorvi@juniper.net
9. References
9.1. Normative References
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[I-D.ietf-detnet-ip]
Varga, B., Farkas, J., Berger, L., Fedyk, D., and S.
Bryant, "Deterministic Networking (DetNet) Data Plane:
IP", Work in Progress, Internet-Draft, draft-ietf-detnet-
ip-07, 3 July 2020, <https://www.ietf.org/archive/id/
draft-ietf-detnet-ip-07.txt>.
[RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.
J., and E. Lear, "Address Allocation for Private
Internets", BCP 5, RFC 1918, DOI 10.17487/RFC1918,
February 1996, <https://www.rfc-editor.org/info/rfc1918>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
September 1997, <https://www.rfc-editor.org/info/rfc2205>.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>.
[RFC3471] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description",
RFC 3471, DOI 10.17487/RFC3471, January 2003,
<https://www.rfc-editor.org/info/rfc3471>.
[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
DOI 10.17487/RFC3473, January 2003,
<https://www.rfc-editor.org/info/rfc3473>.
[RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
DOI 10.17487/RFC4090, May 2005,
<https://www.rfc-editor.org/info/rfc4090>.
[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,
<https://www.rfc-editor.org/info/rfc4193>.
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[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
9.2. Informative References
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
[RFC6890] Cotton, M., Vegoda, L., Bonica, R., Ed., and B. Haberman,
"Special-Purpose IP Address Registries", BCP 153,
RFC 6890, DOI 10.17487/RFC6890, April 2013,
<https://www.rfc-editor.org/info/rfc6890>.
Authors' Addresses
Tarek Saad
Juniper Networks
Email: tsaad@juniper.net
Vishnu Pavan Beeram
Juniper Networks
Email: vbeeram@juniper.net
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