Internet Working Group D. Fedyk(ed.)
Internet Draft Nortel
Date Created: May 23, 2008 Y Rekhter(ed.)
Expiration Date: November 23, 2008 Juniper Networks
Intended Status: Standards Track D. Papadimitriou
Alcatel-Lucent
R. Rabbat
Google
L. Berger
LabN
Layer 1 VPN Basic Mode
draft-ietf-l1vpn-basic-mode-05.txt
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Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This document describes the Basic Mode of Layer 1 VPNs (L1VPN BM).
L1VPN Basic mode is a port-based VPN. In L1VPN Basic Mode (BM), the
basic unit of service is a Label Switched Path (LSP) between a pair
of customer ports within a given VPN port-topology. This document
defines the operational model using either provisioning or a VPN
auto-discovery mechanism, and the signaling extensions for the L1VPN
BM.
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Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
This document expects that the reader is familiar with the
terminology defined and used in [RFC3945], [RFC3471], [RFC3473],
[RFC3477], [RFC4201], [RFC4202], [RFC4204], [RFC4208] and referenced
therein.
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Table of Contents
1. Introduction...............................................4
2. Layer 1 VPN Service........................................5
3. Addressing, Ports, Links and Control Channels..............7
3.1 Service Provider Realm....................................7
3.2 Layer 1 Ports and Index...................................8
3.3 Port and Index Mapping....................................8
4. Port Based L1VPN Basic Mode...............................10
4.1 L1VPN Port Information Tables............................11
4.1.1. Local Auto-Discovery Information......................12
4.1.2. PE Remote Auto-Discovery Information..................12
4.2 CE to CE LSP Establishment...............................14
4.3 Signaling................................................14
4.3.1 Signaling Procedures...................................15
4.3.1.1 Shuffling Sessions...................................16
4.3.1.2 Stitched or Nested Sessions..........................17
4.3.1.3 Other Signaling......................................17
4.4 Recovery Procedures......................................18
5. Security Considerations...................................19
6. IANA Considerations.......................................20
7. Intellectual Property Considerations......................20
8. References................................................21
8.1 Normative References.....................................21
8.2 Informative References...................................21
9. Acknowledgments...........................................23
10. Authors' Addresses.......................................23
11. Disclaimer of Validity...................................23
12. Copyright Statement......................................24
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1. Introduction
This document describes the basic mode of Layer 1 VPNs (L1VPN BM)
that is outlined in [RFC4847]. The applicability of Layer 1 VPNS is
covered in [L1VPN-APPLIC]. In this document, we consider a layer 1
service provider network that consists of devices that support GMPLS
(e.g., Lambda Switch Capable devices, Optical Cross Connects,
SONET/SDH Cross Connects, etc.). We partition these devices into P
(provider) and PE (provider edge) devices. In the context of this
document we will refer to the former devices as just "P", and to the
latter devices as just "PE". The Ps are connected only to the
devices within the provider's network. The PEs are connected to the
other devices within the network (either Ps or PEs), as well as to
the devices outside of the service provider network. We'll refer to
such other devices as Customer Edge (CE) devices. An example of a CE
would be a GMPLS-enabled device that is either a router, an SDH
cross-connect, or an Ethernet switch.
[RFC4208] defines signaling from the CE to the PE. In the [RFC4208],
the term Core Node (CN) corresponds to P and PE Nodes, edge Core
Node corresponds to PE, and Edge Node (EN) corresponds to CE.
Figure 1 illustrates the components in an L1VPN network.
+---+ +---+
| P |....| P |
+---+ +---+
/ \
+-----+ +-----+ +--+
+--+ | PE | | |----| |
|CE|----| | | | |CE|
+--+\ +-----+ | |----| |
\ | | PE | +--+
\ +-----+ | |
\| PE | | | +--+
| | | |----|CE|
+-----+ +-----+ +--+
\ /
+---+ +---+
| P |....| P |
+---+ +---+
Figure 1: Generalized Layer 1 VPN Reference Model
This document specifies how the L1VPN Basic Mode (BM) service can be
realized using off-line provisioning or VPN auto-discovery,
Generalized Multi-Protocol Label Switching (GMPLS) Signaling
[RFC3471], [RFC3473], Routing [RFC4202], and LMP [RFC4204]
mechanisms.
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L1VPN auto-discovery has similar requirements [RFC4847] to L3VPN
auto-discovery. As with L3VPNs, there are protocol choices to be
made with auto-discovery. Section 4.1.1 deals with the information
that needs to be discovered.
GMPLS routing and signaling are used without extensions within the
service provider network to establish and maintain Lambda Switch
Capable (LSC) or SONET/SDH (TDM) connections between service
provider nodes. This follows the model in [RFC4208].
In L1VPN Basic Mode (BM), the use of LMP facilitates the population
of the service provider port information tables. Indeed, LMP MAY be
used as an option to automate local CE-PE link discovery. LMP also
MAY augment routing in extended mode as well as failure handling
capabilities.
Consideration of inter-AS and inter-provider L1VPNs requires further
analysis beyond the scope of this document.
2. Layer 1 VPN Service
Layer 1 VPN (L1VPN) services on the interfaces of customer and
service provider ports MAY be any of the Layer 1 interfaces
supported by GMPLS. Since the mechanisms specified in this document
use GMPLS as the signaling mechanism, and since GMPLS applies to
both SONET/SDH (TDM) and Lambda Switch Capable (LSC) interfaces, it
follows that L1VPN services include (but are not restricted) to
Lambda Switch Capable or TDM-based equipment. Note that this
document describes Basic Mode L1VPNs and as such requires that:
(1) GMPLS RSVP-TE is used for signaling both within the service
provider (between PEs), as well as between the customer and the
service provider (between CE and PE);
(2) GMPLS Routing on the CE-PE link is outside the scope of the
basic mode of operation of L1VPN see [RFC4847].
A CE is connected to a PE via one or more links. In the context of
this document a link is a GMPLS Traffic Engineering (TE) link
construct, as defined in [RFC4202]. In the context of this document,
a TE link is a logical construct that is a member of a VPN hence
introducing the notion of membership to a set of CEs forming the
VPN. Interfaces at the end of each link are limited to type LSC or
TDM that are supported by GMPLS. More specifically a <CE, PE> link
MUST be of the type <X, LSC> or <Y, TDM> where X = PSC, L2SC or TDM
and Y = PSC or L2SC. In case the LSP is not terminated by the CE, X
MAY also = LSC and Y = TDM. One of the applications of a L1VPN
connection is to provide a "virtual private lambda" or similar. In
this case, the CE is truly the end point in GMPLS terms and its
switching capability on the TE link is not relevant (although its
GPID MUST be signaled and identical at both CEs i.e. head-end and
tail-end CE). )
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Likewise, PEs could be any Layer 1 devices that are supported by
GMPLS (e.g., optical cross connects, SDH cross-connects), while CEs
MAY be devices at layers 1, 2 and 3 such as an SDH cross-connect, an
Ethernet switch, and a router respectively).
Each TE link MAY consist of one or more channels or sub-channels
(e.g., wavelength or wavelength and timeslot respectively). For the
purpose of this discussion all the channels within a given link MUST
have similar shared characteristics (e.g., switching capability,
encoding, type, etc.), and MAY be selected independently from the
CE's point of view. Channels on different links of a CE need not
have the same characteristics.
There MAY be more than one TE link between a given CE-PE pair. A CE
MAY be connected to more than one PE (with at least one port per
PE). And, conversely, a PE MAY have more than one CE from different
VPNs connected to it.
If a CE is connected to a PE via multiple TE links and all the links
belong to the same VPN, these links (referred to as component links)
MAY be treated as a single TE link using the link bundling
constructs [RFC4201].
In order to satisfy the requirements of the L1VPN Basic Mode it is
REQUIRED that for a given CE-PE pair at least one of the links
between them has at least one data bearing channel, and at least one
control bearing channel, or there is IP reachability between the CE
and the PE that could be used to exchange control information.
A point-to-point link has two end-points - one on the CE and one on
the PE. This document refers to the former as "CE port", and to the
latter as "PE port". From the above it follows that a CE is
connected to a PE via one or more ports, where each port MAY consist
of one or more channels or sub-channels (e.g., wavelength or
wavelength and timeslot respectively), and all the channels within a
given port have shared similar characteristics and can be
interchanged from the CE's point of view. Similar to the definition
of a TE link, in the context of this document, ports are logical
constructs that are used to represent a grouping of physical
resources that are used to connect a CE to a PE on a per L1VPN
basis.
At any point in time, a given port on a PE is associated with at
most one L1VPN, or to be more precise with at most one Port
Information Table maintained by the PE (although different ports on
a given PE could be associated with different L1VPNs, or to be more
precise with different Port Information Tables). The association of
a port with a VPN MAY be defined by provisioning the relationship on
the service provider devices. In other words the context of a VPN
membership in Basic mode is enforced through service provider
control.
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It is REQUIRED that the interface between the CE and PE used for the
purpose of signaling be capable of initiating/processing GMPLS
protocol messages [RFC3473] and follow the procedures described in
[RFC4208].
An important goal of L1VPN service is the ability to support what is
known as "single-ended provisioning", where the addition of a new
port to a given L1VPN involves configuration changes only on the PE
that has this port. The extension of this model to the CE is
outside the scope of the L1VPN BM.
Another important goal in the L1VPN service is the ability to
establish/terminate an LSP between a pair of (existing) ports within
an L1VPN from the CE devices without involving configuration changes
in any of the service provider's devices. In other words, the VPN
topology is under the CE device control (provided that the
underlying PE-PE connectivity be provided and allowed by the
network).
The mechanisms outlined in this document aim to achieve these above
goals. Specifically, as part of the L1VPN service offering, these
mechanisms (1) enable the service provider to restrict the set of
ports to which a given port could be connected, (2) enable a CE to
establish the actual LSP to a subset of ports. Finally, the
mechanisms allow arbitrary L1VPN topologies to be supported ranging
from hub-and-spoke to full mesh point-to-point connections. Only
point-to-point links are supported.
The exchange of CE routing or topology information to the service
provider is out of scope for L1VPN BM mode.
3. Addressing, Ports, Links and Control Channels
GMPLS-established conventions for addressing and link numbering are
discussed in [RFC3945]. This section builds on those definitions
for the L1VPN case where we now have customer and service provider
addresses in a Layer 1 context.
3.1 Service Provider Realm
It is REQUIRED that a service provider, or a group of service
providers that collectively offer L1VPN service, have a single
addressing realm that spans all PE devices involved in providing the
L1VPN service. This is necessary to enable GMPLS mechanisms for path
establishment and maintenance. We will refer to this realm as the
service provider addressing realm. It is further REQUIRED that each
L1VPN customer have its own addressing realm with complete freedom
to use private or public addresses. We will refer to such realms as
the customer addressing realms. Customer addressing realms MAY
overlap addresses (i.e. non unique address) with each other, and MAY
also overlap addresses with the service provider realm.
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3.2 Layer 1 Ports and Index
Within a given L1VPN, each port on a CE that connects the CE to a PE
has an identifier that is unique within that L1VPN (but need not be
unique across several L1VPNs). One way to construct such an
identifier is to assign each port an address that is unique within a
given L1VPN, and use this address as a port identifier. Another way
to construct such an identifier is to assign each port on a CE an
index that is unique within that CE, assign each CE an address that
is unique within a given L1VPN, and then use a tuple <port index, CE
address> as a port identifier. Note that both the port and the CE
address MAY be an address in several formats. This includes, but is
not limited to IPv4, and IPv6. This identifier is part of the
Customer addressing Realm and is used by the CE device to identify
the CE port and the CE remote port for signaling. CEs do not know
or understand the service provider Realm addresses.
Within a service provider network, each port on a PE that connects
that PE to a CE has an identifier that is unique within that
network. One way to construct such an identifier is to assign each
port on a PE an index that is unique within that PE, assign each PE
an IP address that is unique within the service provider addressing
realm, and then use a tuple <port index, PE IPv4 address> or <port
index, PE IPv6 address> as a port identifier within the service
provider network. Another way to construct such an identifier is to
assign an IPv4 or IPv6 address that is unique within the service
provider addressing realm to each such port. Either way, this IPv4
or IPv6 address is internal to the service provider network and is
used for GMPLS signaling within the service provider network.
As a result, each link connecting the CE to the PE is associated
with a CE port that has a unique identifier within a given L1VPN,
and with a PE port that has a unique identifier within the service
provider network. We'll refer to the former as the customer Port
Identifier (CPI), and to the latter as the Provider Port Identifier
(PPI).
3.3 Port and Index Mapping
This document requires that each PE port that has a PPI also has an
identifier that is unique within the L1VPN customer addressing realm
of the L1VPN associated with that port. One way to construct such
an identifier is to assign each port an address that is unique
within a given L1VPN customer addressing realm, and use this address
as a port identifier. Another way to construct such an identifier is
to assign each port an index that is unique within a given PE,
assign each PE an IP address that is unique within a given L1VPN
customer addressing realm (but need not be unique within the service
provider network), and then use a tuple <port index, PE IP address>
that acts as a port identifier. We'll refer to such port identifier
as the VPN-PPI. See Figure 2.
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For L1VPNs it is a requirement that service provider operations are
independent of the VPN customer's addressing realm and the service
provider addressing realm is hidden from the customer. To achieve
this we have created two identifiers at the PE, one customer facing
and the other service provider facing. The PE IP address used for
the VPN-PPI is independent of the PE IP address used for the PPI (as
the two are taken from different address realms, the former from the
customer's addressing realm and the latter from a VPN service
Provider's addressing realm). If for a given port on a PE, the PPI
and the VPN-PPI port identifiers are unnumbered, then they both
could use exactly the same port index. This is a mere convenience
since the PPI and VPN_PPI can be in any combination of valid
formats.
(Customer realm)
+----+ +----+
| |<Port Index> <Port Index> | |
| |CPI VPN-PPI | |
---| CE |-----------------------------| PE |---
| | <Port Index> | |
| | PPI | |
+----+ +----+
(Provider realm)
Figure 2: Customer/Provider Port/Index Mapping
Note, as stated earlier, that IP addresses used for the CPIs, PPIs
and VPN-PPIs could be either IPv4, or IPv6 format addresses.
For a given link connecting a CE to a PE:
- If the CPI is an IPv4 address, then the VPN-PPI MUST be an IPv4
address as well since VPN-PPI are created from the customer address
space. If the CPI is a <port index, CPI IPv4 address>, then the
VPN-PPI MUST be a <port index, PE IPv4 address> for the same reason.
- If the CPI is an IPv6 address, then the VPN-PPI MUST be an IPv6
address as well since VPN-PPI are created from the customer address
space. If the CPI is a <port index, CPI IPv6 address>, then the
VPN-PPI MUST be a <port index, PE IPv6 address> for the same reason.
Note: for a given port on PE, whether the VPN-PPI of that port is an
IP address or a <port index, PE IP address> is independent of the
format of the PPI of that port.
This document assumes that assignment of the PPIs is controlled
solely by the service provider (without any coordination with the
L1VPN customers), while assignment of addresses used by the CPIs and
VPN-PPIs is controlled solely by the administrators of L1VPN. This
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provides maximum flexibility. The L1VPN administrator is the entity
that controls the L1VPN service specifics for the L1VPN customers.
This function may be owned by the service provider but may also be
performed by a third party who has agreements with the service
provider. And, of course, each L1VPN customer could assign such
addresses on its own, without any coordination with other L1VPNs.
This document also requires IP connectivity between the CE and the
PE as specified earlier, which is used for the control channel
between CE and PE. This connectivity could be either a single IP
hop, which could be realized by either a dedicated link or by an L2
VPN, or an IP private network, such as L3VPN. The only requirement
on this connectivity is an unambiguous way to correlate a particular
CE-PE control channel with a particular L1VPN. When such a channel
is realized by a dedicated link, such a link should be associated
with a particular L1VPN. When such channel is realized by an L2VPN,
a distinct L2VPN should be associated with an L1VPN. When such
channel is realized by an L3VPN, a distinct L3VPN should be
associated with an L1VPN.
We'll refer to the CE's address of this channel as the CE Control
Channel Address (CE-CC-Addr), and to the PE's address of this
channel as the PE Control Channel Address (PE-CC-Addr). Both CE-CC-
Addr and PE-CC-Addr are REQUIRED to be unique within the L1VPN they
belong to, but are not REQUIRED to be unique across multiple L1VPNs.
Control channel addresses are not shared amongst multiple VPNs.
Assignment of CE-CC-Addr and PE-CC-Addr is controlled by the
administrators of the L1VPN.
Multiple ports on a CE could share the same control channel only as
long as all these ports belong to the same L1VPN. Likewise, multiple
ports on a PE could share the same control channel only as long as
all these ports belong to the same L1VPN.
4. Port Based L1VPN Basic Mode
An L1VPN is a port-based VPN service where a pair of CEs could be
connected through the service provider network via a GMPLS-based LSP
within a given VPN port topology. It is precisely this LSP that
forms the basic unit of the L1VPN service that the service provider
network offers. If a port by which a CE is connected to a PE
consists of multiple channels (e.g., multiple wavelengths), the CE
could establish LSPs to multiple other CEs in the same VPN over this
single port.
In the L1VPN, the service provider does not initiate the creation of
an LSP between a pair of CE ports. The LSP establishment is
initiated by the CE. However, the SP, by using the
mechanisms/toolkit outlined in this document, restricts the set of
other CE ports, which may be the remote endpoints of LSPs that have
the given port as the local endpoint. Subject to these restrictions,
the CE-to-CE connectivity is under the control of the CEs
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themselves. In other words, the SP allows a L1VPN to have a certain
set of topologies (expressed as a port-to-port connectivity matrix.
CE-initiated signaling is used to choose a particular topology from
that set.
For each L1VPN that has at least one port on a given PE, the PE
maintains a Port Information Table (PIT) associated with that L1VPN.
This tables contains a list of <CPI, PPI> tuples for all the ports
within its L1VPN. In addition, for local PE ports of a given L1VPN
the tuples also include the VPN-PPIs of these ports.
PE PE
+---------+ +--------------+
+--------+ | +------+| | +----------+ | +--------+
| VPN-A | | |VPN-A || | | VPN-A | | | VPN-A |
| CE1 |--| |PIT || Route | | PIT | |-| CE2 |
+--------+ | | ||<----------->| | | | +--------+
| +------+|Dissemination| +----------+ |
| | | |
+--------+ | +------+| | +----------+ | +--------+
| VPN-B | | |VPN-B || -------- | | VPN-B | | | VPN-B |
| CE1 |--| |PIT ||-( GMPLS )-| | PIT | |-| CE2 |
+--------+ | | || (Backbone ) | | | | +--------+
| +------+| --------- | +----------+ |
| | | |
+--------+ | +-----+ | | +----------+ | +--------+
| VPN-C | | |VPN-C| | | | VPN-C | | | VPN-C |
| CE1 |--| |PIT | | | | PIT | |-| CE2 |
+--------+ | | | | | | | | +--------+
| +-----+ | | +----------+ |
+---------+ +--------------+
Figure 3 Basic Mode L1VPN Service
4.1 L1VPN Port Information Tables
Figure 3 illustrates three VPNs, VPN-A, VPN-B, and VPN-C with their
associated PITs. A PIT consists of local information as well as
remote information. It follows that PIT on a given PE is populated
from two information sources:
1. The information related to the CEs' ports attached to the ports
local to that PE.
2. The information about the CEs connected to the remote PEs
A PIT MAY be populated via provisioning or by auto-discovery
procedures. When provisioning is used the entire table MAY be
populated by provisioning commands either at a console or by a
management system which may have some automation capability.
As the network grows some form of automation is desirable.
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For local information between a CE and a PE, a PE MAY leverage LMP
to populate the <CPI, VPN-PPI> link information. This local
information also needs to be propagated to other PEs that share the
same VPN. The mechanisms for this are out of scope for this document
but the information needed to be exchanged is described in section
4.1.1.
The PIT is by nature VPN-specific. A PE is REQUIRED to maintain a
PIT for each L1VPN for which it has member CEs locally attached. A
PE is does not need to maintain PITs for other L1VPNs. However, the
full set of PITs with all L1VPN entries for multiple VPNs MAY also
be available to all PEs.
The remote information in the context of a VPN identifier (i.e., the
remote CEs of this VPN) MAY also be sent to the local CE belonging
to the same VPN. Exchange of this information is outside the scope
of this document.
4.1.1. Local Auto-Discovery Information
The information that needs to be discovered on a PE local port is
the local CPI and the VPN-PPI.
This information MAY be configured or if LMP is used between the CE
and PE, LMP MAY be used to exchange this information.
Once a CPI has been discovered, the corresponding VPN-PPI maps in a
local context to a VPN Identifier and a corresponding PPI.
One way to enforce a provider controlled VPN context is to pre-
provision VPN-PPI's with a VPN identifier. Other policy mechanisms
to achieve this are outside the scope of this document. In this
manner, a relationship of a CPI to a VPN and PPI port can be
established when the port is provisioned as belonging to the VPN.
4.1.2. PE Remote Auto-Discovery Information
This section provides the information that is carried by any auto-
discovery mechanism, and is used to dynamically populate a PIT. The
information provides a single <CPI, PPI> mapping. Each auto-
discovery mechanism will define the method(s) by which multiple
<CPI, PPI> mappings are communicated, as well as invalidated.
This information should be consistent regardless of the mechanism
used to distribute the information [L1VPN-BGP-AD], [L1VPN-OSPF-AD].
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The format of encoding a single <PPI, CPI> tuple is:
+---------------------------------------+
| PPI Length (1 octet) |
+---------------------------------------+
| PPI (variable) |
+---------------------------------------+
| CPI AFI (2 octets) |
+---------------------------------------+
| CPI (length) |
+---------------------------------------+
| CPI (variable) |
+---------------------------------------+
Figure 4: Auto-Discovery Information
The use and meaning of these fields are as follows:
PPI Length:
A one octet field whose value indicates the length of the PPI
field.
PPI field:
A variable length field that contains the value of the PPI
(either an address or <port index, address> tuple. Note, PPI is
always encoded consistently within a provider domain so the
format of the PPI field is implicit within a given provider
network.
CPI AFI field:
A two octets field whose value indicates address family of the
CPI. This value is assigned in [L1VPN-BGP-AD].
CPI Length:
A one octet field whose value indicates the length of the CPI
field.
CPI (variable):
A variable length field that contains the CPI value (either an
address or <port index, address> tuple.
<PPI, CPI> tuples MUST also be associated with one or more globally
unique identifiers associated with a particular VPN. A globally
unique identifier can encode a VPN-ID, a route target, or any other
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globally unique identifier. The globally unique identifiers are
under control of network providers. Uniqueness within a service
provider administrative domain is sufficient for basic mode
operation. In the case of multiple provider networks which is beyond
the scope of this document, the globally unique identifier need only
be unique and consistent between the those providers. In this
document we specify a generic encoding format for the globally
unique identifier common to all the auto-discovery mechanisms.
However, each auto-discovery mechanism will define the specific
method(s) by which the encoding is distributed and the association
with a <PPI, CPI> tuple is made. The encoding of the globally
unique identifier associated with the VPN is:
+------------------------------------------------+
| L1vpn Globally unique identifier (8 octets) |
+------------------------------------------------+
Figure 5: Auto-Discovery Globally unique identifier Format
4.2 CE to CE LSP Establishment
In order to establish an LSP, a CE needs to identify all other CEs
in the CE's L1VPN it wants to connect to. A CE may already have
obtained this information through provisioning or through some other
schemes (such schemes are outside the scope of this document).
Ports associated with a given CE-PE link, in addition to their CPI
and PPI MAY also have other information associated with them that
describes characteristics and constraints of the channels within
these ports, such as encoding supported by the channels, bandwidth
of a channel, total unreserved bandwidth within the port, etc. This
information could be further augmented with the information about
certain capabilities of the service provider network (e.g., support
regeneration section overhead (RSOH) Data Communications Channel
(DCC) transparency, arbitrary concatenation, etc.). This information
is used to ensure that ports at each end of an LSP have compatible
characteristics, and that there are sufficient unallocated resources
to establish an LSP between these ports.
It may happen that for a given pair of ports within an L1VPN, each
of the CEs connected to these ports would concurrently try to
establish an LSP to the other CE. If having a pair of LSPs between a
pair of ports is viewed as undesirable, the way to resolve this is
to require the CE with the lower value of the CPI to terminate the
LSP originated by the CE. This option could be controlled by
configuration on the CE devices.
4.3 Signaling
In L1VPN BM a CE needs to be configured with the CPIs of other
ports. Once a CE is configured with the CPIs of the other ports
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within the same L1VPN, which we'll refer to as "target ports", the
CE uses a (subset of) GMPLS signaling, to request the provider
network to establish an LSP to a target port.
For inter-CE connectivity, the request originated by the CE contains
the CPI of the port on the CE that CE wants to use for the LSP, and
the CPI of the target port. When the PE attached to the CE that
originated the request receives the request, the PE identifies the
appropriate PIT, and then uses the information in that PIT to find
out the PPI associated with the CPI of the target port carried in
the request. The PPI should be sufficient for the PE to establish an
LSP. Ultimately the request reaches the CE associated with the
target CPI (note that the request still carries the CPI of the CE
that originated the request). If the CE associated with the target
CPI accepts the request, the LSP is established.
Note that a CE need not establish an LSP to every target port that
CE knows about - it is a local CE matter to select a subset of
target ports to which the CE will try to establish LSPs.
The procedures for establishing an individual connection between two
corresponding CEs is the same as the procedure specified for GMPLS
overlay [RFC4208].
4.3.1 Signaling Procedures
When an ingress CE sends an RSVP Path message to an ingress PE, the
source IP address in the IP packet that carries the message is set
to the appropriate CE-CC-Addr, and the destination IP address in the
packet is set to the appropriate PE-CC-Addr. When the ingress PE
sends back to the ingress CE the corresponding Resv message, the
source IP address in the IP packet that carries the message is set
to the PE-CC-Addr, and the destination IP address is set to the CE-
CC-Addr.
Likewise, when an egress PE sends an RSVP Path message to an egress
CE, the source IP address in the IP packet that carries the message
is set to the appropriate PE-CC-Addr, and the destination IP address
in the packet is set to the appropriate CE-CC-Addr. When the egress
CE sends back to the egress PE the corresponding Resv message, the
source IP address in the IP packet that carries the message is set
to the CE-CC-Addr, and the destination IP address is set to the PE-
CC-Addr.
In addition to being used for IP addresses in the IP packet that
carries RSVP messages between CE and PE, CE-CC-Addr and PE-CC-Addr
are also used in the Next/Previous Hop Address field of the IF_ID
RSVP_Hop Object that is carried between CEs and PEs.
In the case where a link between CE and PE is a numbered non-bundled
link, the CPI and VPN-PPI of that link are used for the Type 1 or 2
TLVs of the IF_ID RSVP Hop Object that is carried between the CE and
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PE. In the case where a link between CE and PE is an unnumbered non-
bundled link, the CPI and VPN-PPI of that link are used for the IP
Address field of the Type 3 TLV. In the case where a link between CE
and PE is a bundled link, the CPI and VPN-PPI of that link are used
for the IP Address field of the Type 3 TLVs.
Additional processing related to unnumbered links is described in
the "Processing the IF_ID RSVP_Hop Object"/"Processing the IF_ID
TLV", and "Unnumbered Forwarding Adjacencies" sections of RFC 3477
[RFC3477].
When an ingress CE originates a Path message to establish an LSP
from a particular port on that CE to a particular target port, the
CE uses the CPI of its port in the Sender Template object. If the
CPI of the target port is an IP address, then the CE uses it in the
Session object. And if the CPI of the target port is a <port index,
IP address> tuple, then the CE uses the IP address part of the tuple
in the Session object, and the whole tuple as the Unnumbered
Interface ID subobject in the ERO.
There are two options for RSVP-TE sessions. One option is to have a
single RSVP-TE session end to end where the addresses of the
customer and the provider are swapped at the PE, termed shuffling.
The other option is when stitching or hierarchy is used to create
two LSP sessions, one between the provider PE(s) and another end to
end session between the CEs.
4.3.1.1 Shuffling Sessions
Shuffling sessions are used when the desire is to have a single LSP
originating at the CE and terminating at the far end CE. The
customer addresses are shuffled to provider addresses at the ingress
PE, and back to customer addresses at the egress PE by using the
mapping provided by the PIT.
When the Path message arrives at the ingress PE, the PE selects the
PIT associated with the L1VPN, and then uses this PIT to map CPIs
carried in the Session and the Sender Template objects to the
appropriate PPIs. Once the mapping is done, the ingress PE replaces
CPIs with these PPIs. As a result, the Session and the Sender
Template objects that are carried in the GMPLS signaling within the
service provider network carry PPIs, and not CPIs.
At the egress PE, the reverse mapping operation is performed. The PE
extracts the ingress/egress PPI values carried in the Sender
Template and Session objects (respectively). The egress PE
identifies the appropriate PIT to find the appropriate CPI
associated with the PPI of the egress CE. Once the mapping is
retrieved, the egress PE replaces the ingress/egress PPI values with
the corresponding CPI values. As a result, the Session and the
Sender Template objects included in the GMPLS RSVP-TE Path message
sent from the egress PE to the egress CE carry CPIs, and not PPIs.
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Here also, for the GMPLS RSVP-TE Path messages sent from the egress
PE to CE, the source IP address (of the IP packet carrying this
message) is set to the appropriate PE-CC-Addr, and the destination
IP address (of the IP packet carrying this message) is set to the
appropriate CE-CC-Addr.
At this point the CE's view is a single LSP point to point between
the two CEs with a virtual link between the PE nodes. CE-PE(-)PE-
CE. The L1VPN PE nodes have a view of the PE-PE LSP segment in all
its detail. The PEs MAY filter the RSVP-TE signaling removing
information about the provider topology and replacing it with a view
of a virtual link.
This translation of addresses and session ids is termed shuffling
and driven by the L1VPN Port information tables (see section 4).
This MUST be performed for all RSVP-TE Messages at the PE edges. In
this case there is one CE to CE session.
4.3.1.2 Stitched or Nested Sessions
Stitching or Nesting options are dependent on the LSP switching
types. If the CE to CE and PE to PE LSPs are identical in switching
type and capacity the LSP MAY be stitched together and the
procedures in [RFC5150] apply. If the CE to CE LSPs and the PE to PE
LSPs are of not the same switching type or of different but
compatible capacity the LSPs MAY be Nested and the procedures for
[RFC4206] apply. The Stitched and Nested LSP signaling are
analogous procedures and can be discussed together.
When the Path Message arrives at the ingress PE, the PE selects the
PIT associated with the L1VPN, and then uses this PIT to map CPIs
carried in the Session and the Sender Template objects to the
appropriate PPIs. Once the mapping is done, a new PE to PE session
is established with the parameters compatible with the CE session.
Upon successful establishment of the PE to PE session, the CE
signaling request is sent to the egress PE.
At the ingress PE, when stitching and nesting are used a PE to PE
session is established. This could be achieved by several means:
- Associating an already established PE-PE FA-LSP or LSP to the
destination that meets the requested parameters.
- Establishing a compliant PE-PE LSP segment.
At this point the CE's view is a single LSP point to point between
the two CEs with a virtual node between the PE nodes. CE-PE(-)PE-
CE. The L1VPN PE nodes have a view of the PE-PE LSP segment in all
its detail. The PEs do not have to filter the RSVP-TE signaling
removing information about the provider topology because the PE-PE
signaling is not visible to the CE nodes.
4.3.1.3 Other Signaling
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An ingress PE may receive and potentially reject a Path message that
contains an Explicit Route Object and so cause the switched
connection setup to fail. However, the ingress PE may accept EROs,
which include a sequence of {<ingress PE (strict), egress CE CPI
(loose)>}.
- Path message without ERO: when an ingress PE receives a Path
message from an ingress CE that contains no ERO, it MUST calculate a
route to the destination for the PE-to-PE LSP and include that route
in an ERO, before forwarding the Path message. One exception would
be if the egress core node were also adjacent to this core node.
- Path message with ERO: when an ingress PE receives a Path message
from an ingress CE that contains an ERO (of the form detailed
above), the former computes a path to reach the egress PE. It then
inserts this path as part of the ERO before forwarding the Path
message.
In the case of Shuffling the overlay rules for Notification and RRO
Processing are identical to the UNI or Overlay Model[RFC4208] which
state that Edge PE MAY remove/edit Provider Notification and RRO
objects when passing the messages to the CEs.
4.4 Recovery Procedures
Signaling:
A CE requests a network protected (from PE-to-PE) LSP by using
[RFC4873] technique. Dynamic identification of merge nodes is
supported via the LSP Segment Recovery Flags carried in the
Protection object (see Section 6.2 of [RFC4873]).
Notification:
A Notify Request object MAY be inserted in Path or Resv messages to
indicate the address of a CE that should be notified of an LSP
failure. Notifications MAY be requested in both the upstream and
downstream directions:
o) Upstream notification is indicated via the inclusion of a Notify
Request object in the corresponding Path message.
o) Downstream notification is indicated via the inclusion of a
Notify Request object in the corresponding Resv message.
A PE receiving a message containing a Notify Request object SHOULD
store the Notify Node Address in the corresponding RSVP state block.
The PE SHOULD also include a Notify Request object in the outgoing
Path or Resv message. The outgoing Notify Node Address MAY be
updated based on local policy. This means that a PE upon reception
of this object from the CE MAY update its value.
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If the ingress CE includes a Notify Request object into the Path
message, the ingress PE MAY replace the received 'Notify Node
Address' by its own selected 'Notify Node Address', and in
particular the local TE Router_ID. The Notify Request object MAY be
carried in Path or Resv messages (Section 7 of [RFC3473]). The
format of the Notify Request object is defined in [RFC3473].
In GMPLS, Notify Node Addresses may be IPv4 or IPv6 [RFC3473].
Inclusion of a Notify Request object is used to request the
generation of notifications upon failure occurrence but does not
guarantee that a Notify message will be generated.
5. Security Considerations
Security for L1VPNs is covered in [RFC4847] and [L1VPN-APPLIC]. In
this document we discuss the security aspects with respect to the
control plane.
The association of a particular port with a particular L1VPN (or to
be more precise with a particular PIT) is a configuration operation,
generally done manually by the service provider as part of the
service provisioning process. Thus, it cannot be altered via
signaling between CE and PE. This means that the signaling cannot be
used to deliver L1VPN traffic to the wrong customer. The operator
should apply appropriate security mechanisms to the management and
configuration process, and should consider data plane verification
techniques to protect against accidental misconfiguration. The
customer may also apply end-to-end (i.e., CE to CE) data plane
connectivity tests over the L1VPN connection to detect
misconnection. Data plane connectivity testing can be performed
using the Link Management Protocol (LMP) [RFC4204].
Note that it is also possible to populate the local part of a PIT
using autodiscovery through LMP. LMP may be secured as described in
[RFC4204]. Signaling between CE and PE is assumed to be over a
private link (for example, in-band or in-fiber) or a private
network. Use of a private link makes the CE-PE connection secure at
the same level as the data link described in the previous
paragraphs. The use of a private network assumes that entities
outside the network cannot spoof or modify control plane
communications between CE and PE. Furthermore, all entities in the
private network are assumed to be trusted. Thus, no security
mechanisms are required by the protocol exchanges described in this
document.
However, an operator that is concerned about the security of their
private control plane network may use the authentication and
integrity functions available in RSVP-TE [RFC3473] or utilize IPsec
[RFC4301], [RFC4302], [RFC4835], [RFC4306], and [RFC2411] for the
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point-to-point signaling between PE and CE. See [MPLS-SEC] for a
full discussion of the security options available for the GMPLS
control plane.
Note further that a private network (e.g., Layer 2 VPN, or Layer 3
VPN) might be used to provide control plane connectivity between a
PE and more than one CE. In this scenario, it is RECOMMENDED that
each L1 VPN customer would have its own such private network. Then
the security mechanisms provided by the private network SHOULD be
used to ensure security of the control plane communication between a
customer and a service provider.
6. IANA Considerations
This document makes no requests for IANA action.
7. Intellectual Property Considerations
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed
to pertain to the implementation or use of the technology described
in this document or the extent to which any license under such
rights might or might not be available; nor does it represent that
it has made any independent effort to identify any such rights.
Information on the procedures with respect to rights in RFC
documents can be found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use
of such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository
at http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at ietf-
ipr@ietf.org.
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8. References
8.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3471] Berger, L. (editor), "Generalized MPLS -Signaling
Functional Description", January 2003, RFC3471.
[RFC3473] Berger, L. (editor), "Generalized MPLS Signaling - RSVP-TE
Extensions", RFC3473, January 2003.
[RFC3477] Kompella, K. and Y. Rekhter, "Signalling Unnumbered
Links in Resource ReSerVation Protocol - Traffic
Engineering (RSVP-TE)", RFC 3477, January 2003.
[RFC4202] Kompella, K., Rekhter, Y., "Routing Extensions in Support
of Generalized Multi-Protocol Label Switching (GMPLS)",
RFC 4202, October 2005.
[RFC4204] J. Lang (editor), "Link Management Protocol (LMP)," RFC
4204, October 2005.
[RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
Hierarchy with Generalized Multi-Protocol Label Switching
(GMPLS)Traffic Engineering (TE)", RFC 4206, October 2005.
[RFC4208] Swallow, G., et al., "Generalized Multiprotocol Label
Switching (GMPLS) User-Network Interface (UNI): Resource
ReserVation Protocol-Traffic Engineering (RSVP-TE) Support
for the Overlay Model", RFC 4208, October 2005.
[RFC4873] Berger, L., Bryskin, I., Papadimitriou, D. Farrel, A.,
"GMPLS Based Segment Recovery", RFC 4873, May 2007.
[RFC5150] A. Ayyangar, K. Kompella, J.P. Vasseur, A. Farrel, "Label
Switched Path Stitching with Generalized MPLS Traffic
Engineering", RFC 5150, February 2008.
8.2 Informative References
[RFC3945] E. Mannie (editor), "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture" RFC3945, October 2004.
[RFC4201] Kompella, K., Rekhter, Y., Berger, L., "Link Bundling in
MPLS Traffic Engineering (TE)", RFC 4201, October 2005.
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[RFC4847] Takeda, T., Editor "Framework and Requirements for Layer 1
Virtual Private Networks", RFC 4847, April 2007.
[RFC2411] R. Thayer, N. Doraswamy, R. Glenn, "IP Security Document
Roadmap," November 1998.
[RFC4301] S. Kent, K. Seo, "Security Architecture for the Internet
Protocol," December 2005.
[RFC4302] S. Kent, "IP Authentication Header," December 2005.
[RFC4306] C. Kaufman, "Internet Key Exchange (IKEv2) Protocol",
December 2005.
[RFC4835] V. Manral, "Cryptographic Algorithm Implementation
Requirements for Encapsulating Security Payload (ESP) and
Authentication Header (AH)", April 2007.
[L1VPN-BGP-AD] Ould-Brahim, H., Fedyk, D., Rekhter, Y., "BGP-based
Auto-Discovery for L1VPNs", work in progress.
[L1VPN-OSPF-AD] Bryskin, I., Berger, Lou "OSPF Based L1VPN Auto-
Discovery", work in progress.
[L1VPN-APPLIC] Takeda, T (editor), "Applicability Statement for
Layer 1 Virtual Private Networks (L1VPNs) Basic Mode",
draft-ietf-l1vpn-applicability-basic-mode, work in
progress.
[MPLS-SEC] Fang, L., " Security Framework for MPLS and GMPLS
Networks", draft-ietf-mpls-mpls-and-gmpls-security-
framework, work in progress.
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9. Acknowledgments
The authors would like to thank Adrian Farrel, Hamid Ould-Brahim,
and Tomonori Takeda for their valuable comments.
Sandy Murphy, Charlie Kaufman, Pasi Eronen, Russ Housley, Tim
Polk, and Ron Bonica provided input during the IESG review process.
10. Authors' Addresses
Don Fedyk
Nortel Networks
600 Technology Park
Billerica, Massachusetts
01821 U.S.A
Phone: +1 (978) 288 3041
Email: dwfedyk@nortel.com
Yakov Rekhter
Juniper Networks
1194 N. Mathilda Avenue
Sunnyvale, CA 94089
Email: yakov@juniper.net
Dimitri Papadimitriou
Alcatel-Lucent
Fr. Wellesplein 1,
B-2018 Antwerpen, Belgium
Phone: +32 3 240-8491
Email: Dimitri.Papadimitriou@alcatel-lucent.be
Richard Rabbat
Google, Inc
1600 Amphitheatre Pkwy
Mountain View, CA 95054
Email: rabbat@alum.mit.edu
Lou Berger
LabN Consulting, LLC
Phone: +1 301-468-9228
EMail: lberger@labn.net
11. Disclaimer of Validity
"This document and the information contained herein are provided on
an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE
Fedyk & Rekhter. [Page 23]
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IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL
WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY
WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY
RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE.
12. Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
Fedyk & Rekhter. [Page 24]
