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Versions: 00 01 02 03 04 05 06 RFC 6060
Internet Draft Don Fedyk, Nortel
Category: Standards Track Himanshu Shah, Ciena
Expiration Date: January 14, 2009 Nabil Bitar, Verizon
Attila Takacs, Ericsson
July 14, 2008
GMPLS control of Ethernet PBB-TE
draft-ietf-ccamp-gmpls-ethernet-pbb-te-01.txt
Status of this Memo
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Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This specification is complementary to the GMPLS controlled Ethernet
architecture document [ARCH] and describes the technology specific
aspects of GMPLS control for Provider Backbone Bridging Traffic
Engineering (PBB-TE) [IEEE 802.1Qay]. The necessary GMPLS extensions
and mechanisms are described to establish Ethernet PBB-TE point to
point (P2P) and point to multipoint (P2MP) connections. This document
supports, but does not modify, the standard IEEE data plane.
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Table of Contents
1 Introduction .............................................. 3
1.1 Co-authors ................................................ 3
2 Terminology ............................................... 4
2.1 PBB-TE Terminology ........................................ 5
3 Creation and Maintenance of PBB-TE Service Instances ...... 6
3.1 Ethernet Service .......................................... 7
3.2 Addresses, Interfaces, and Labels ......................... 7
4 Specific Procedures ....................................... 10
4.1 P2P connections ........................................... 10
4.1.1 Shared Forwarding ......................................... 11
4.1.2 P2P connections with shared forwarding .................... 12
4.1.3 Dynamic P2P symmetry with shared forwarding ............... 13
4.1.4 Planned P2P symmetry ...................................... 13
4.1.5 P2P Path Maintenance ...................................... 13
4.2 P2MP Signaling ............................................ 14
4.3 P2MP ESP-MAC DA Connections ............................... 14
4.3.1 Setup procedures .......................................... 14
4.3.2 Maintenance Procedures .................................... 14
4.4 Ethernet Label ............................................ 15
4.5 OAM MEP ID and MA ID synchronization ...................... 16
4.6 Protection Paths .......................................... 16
5 Error conditions .......................................... 17
5.1 Invalid ESP-VID value for PBB-TE MSTI range ............... 17
5.2 Invalid MAC Address ....................................... 17
5.3 Invalid ERO for UPSTREAM_LABEL Object ..................... 17
5.4 Invalid ERO for LABEL_SET Object .......................... 18
5.5 Switch is not ESP P2MP capable ............................ 18
5.6 Invalid ESP-VID in UPSTREAM_LABEL object .................. 18
6 Deployment Scenarios ...................................... 18
7 Security Considerations ................................... 18
8 IANA Considerations ....................................... 18
9 References ................................................ 19
9.1 Normative References ...................................... 19
9.2 Informative References .................................... 19
10 Acknowledgments ........................................... 21
11 Author's Address .......................................... 21
A. Rational and mechanism for PBB_TE Ethernet Forwarding ..... 22
A.1. Overview of configuration of VID/DMAC tuples .............. 25
A.2 Overview of configuration of VID port membership .......... 28
A.3 OAM Aspects ............................................... 28
A.4 QOS Aspects ............................................... 29
A.5 Resiliency Aspects ........................................ 29
A.5.1 E2E Path protection ....................................... 29
12 Full Copyright Statement .................................. 30
13 Intellectual Property ..................................... 30
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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].
1. Introduction
IEEE 802.1 is specifying Traffic Engineered Ethernet paths in the
Provider Backbone Bridged network (PBB-TE) [IEEE 802.1Qay] based on
managed objects that can be separated from the Spanning Tree Control
Plane and statically configured or managed by another control plane.
These paths have minor changes to Ethernet data plane specified in
the IEEE. IEEE 802 termed these paths "PBB-TE service instances".
Generalized MPLS (GMPLS) [RFC3945] is a family of control plane
protocols designed to operate in connection oriented and traffic
engineering transport networks. GMPLS is applicable to a range of
network technologies including Layer 2 Switching capable networks
(L2SC). The purpose of this document is to specify extensions for a
GMPLS based control plane to manage PBB-TE service instances. This
draft is aligned with the GMPLS Ethernet Label Switching Architecture
and Framework [ARCH].
It should be noted that due to the changes in the separation of the
Spanning Tree Control plane and PBB-TE forwarding, the behavior of
PBB-TE for the specified VLAN range is a new behavior. (It does not
default to conventional Ethernet forwarding with learning at any
time). Note, currently PBB-TE is under specification in the
Interworking Task Group of the IEEE 802.1 Working Group (WG), the
actual draft has version 3.5. Appendix A summarizes the rational for
this data plane technology until the IEEE specification is released
for Working Group Ballot in the IEEE 802.1 WG.
1.1. Co-authors
This document is the result the a large team of authors and
contributors. The following is a list of the co-authors:
Don Fedyk (Nortel)
David Allan (Nortel)
Himanshu Shah (Ciena)
Nabil Bitar (Verizon)
Attila Takacs (Ericsson)
Diego Caviglia (Ericsson)
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Alan McGuire (BT)
Nurit Sprecher (Nokia Siemens Networks)
Lou Berger (LabN)
2. Terminology
In addition to well understood GMPLS terms, this memo uses
terminology from IEEE 802.1 and introduces a few new terms:
- BEB Backbone Edge Bridge
- B-MAC Backbone MAC
- B-VID Backbone VLAN ID
- B-VLAN Backbone VLAN
- CBP Customer Backbone Port
- CCM Continuity Check Message
- COS Class of Service
- CLI Command Line Interface
- CIP Customer Instance Port
- C-MAC Customer MAC
- C-VID Customer VLAN ID
- C-VLAN Customer VLAN
- DMAC Destination MAC Address
- ESP Ethernet Switched Path
- Eth-LSP Ethernet Label Switched Path
- I-SID Ethernet Service Instance Identifier
- LBM Loopback Message
- LBR Loopback Reply
- LLDP Link Layer Discovery Protocol
- LMM Loss Measurement Message
- LMR Loss Measurement Reply
- MAC Media Access Control
- MMAC Multicast MAC
- MSTID Multiple Spanning Tree Identifier
- MP2MP Multipoint to multipoint
- PBB Provider Backbone Bridges
- PBB-TE Provider Backbone Bridges Traffic Engineering
- PIP Provider Instance Port
- PCP Priority Code Points
- PNP Provider Network Port
- P2P Point to Point
- P2MP Point to Multipoint
- QOS Quality of Service
- ESP-MAC SA Source MAC Address
- S-VID Service VLAN ID
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- SVL Shared VLAN Learning
- TE-MSTID Traffic Engineering MSTID
- VID VLAN ID
- VLAN Virtual LAN
2.1. PBB-TE Terminology
The PBB-TE specification has defined some additional terminology to
clarify the PBB-TE functions. We repeat these here in expanded
context to translate from IEEE to GMPLS terminology.
- Ethernet Switched Path (ESP):
A provisioned traffic engineered unidirectional connectivity path
between two or more Customer Backbone Ports (CBPs) which extends
over a Provider Backbone Bridge Network (PBBN). The path is
identified by the 3-tuple <ESP-MAC DA, ESP-MAC SA, ESP-VID> where
the ESP-VID value is allocated to the PBB-TE Multiple Spanning
Tree Identifier (MSTID). (A set of VIDs for PBB-TE is allocated
to the new TE-MSTID.) An ESP is analogous to a GMPLS LSP.
- Point-to-Point PBB-TE service instance:
An instance of the MAC service provided by two unidirectional co-
routed ESPs forming a bidirectional service. A GMPLS
bidirectional path is analogous to a P2P PBB-TE Service instance.
- Point-to-Multipoint PBB-TE service instance:
An instance of the MAC service provided by a set of ESPs which
comprises one point-to-multipoint ESP plus n unidirectional
point-to-point ESPs. The n P2P ESPs are co-routed but in the
opposite direction from the root-to-leaf sub-ESPs comprising the
P2MP ESP. Note that due to traditional Ethernet data plane
design this definition is different to the way P2MP connections
are generally defined. That is, while P2MP connections are
generally root-to-leaves unidirectional trees, P2MP PBB-TE
services can be regarded as bidirectional trees.
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3. Creation and Maintenance of PBB-TE Service Instances
PBB-TE is an Ethernet connection oriented technology, being specified
in the IEEE, which can be controlled by configuration of static
filtering entries (see Appendix A for some details on the rational
for the data plane). PBB-TE ESPs are created switch by switch by
simple configuration of Ethernet logical ports and assignment of PBB-
TE labels or by a control plane. This document describes GMPLS as a
valid control plane for Eth-LSPs that are based on PBB-TE ESPs. A
Point-to-Point PBB-TE service instance is a form of Ethernet LSP
(Eth-LSP) which is more broadly defined in [ARCH]. This memo
describes GMPLS as a mechanism to automate set-up teardown,
protection and recovery of PBB-TE ESPs and specifies the specific
TLVs for control of PBB-TE service instances.
When configuring a PBB-TE ESP with GMPLS, the ESP-MAC DA and ESP-VID
are carried in a generalized label object and are assigned hop by hop
but are invariant within a domain. This invariance is similar to
GMPLS operation in transparent optical networks. As is typical with
other technologies controlled by GMPLS, the data plane receiver must
accept, and usually assigns, labels from its available label pool.
This, together with the label invariance requirement mentioned above,
result in each PBB-TE label being a domain wide unique label, with a
unique ESP-VID + ESP-MAC DA, for each direction.
The following illustrates the identifiers for Labels and ESPs.
GMPLS Upstream Label <ESP:MAC1(DA), VID1> (60 bits)
GMPLS Downstream Label <ESP:MAC2(DA), VID2> (60 bits)
Upstream PBB-TE ESP 3-tuple <ESP:MAC1, MAC2, VID1> (108 bits)
Downstream PBB-TE ESP 3-tuple <ESP:MAC2, MAC1, VID2> (108 bits)
Table 1 Labels and ESPs
The MAC is domain wide unique in the network. PBB-TE defines the
tuple of <ESP-MAC DA, ESP-MAC SA, ESP-VID> as a unique connection
identifier in the data plane but the forwarding operation only uses
the ESP-MAC DA (DMAC) and the ESP-VID in each direction. Note that
the MAC addresses for PBB-TE are part of the Backbone Component
Relay (B-Component) and are associated with Provider addresses
corresponding to the Customer Backbone ports (CBP) of the Backbone
Component (B-Component) as described in section 3.2.
The ESP-VID (VID) typically comes from a small number of VIDs
dedicated to PBB-TE MSTID. The ESP-VID (VID) can be reused across
ESPs. There is no requirement the ESP-VID for two ESPs that form a
PBB-TE Service instance be the same.
Several attributes may be associated with an Eth-LSP. These are
reviewed in Section 3 of [ARCH]. Several other aspects of GMPLS
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covered by [ARCH] also apply equally to PBB-TE. This includes the
GMPLS routing and addressing model, link management, path
computation and selection, and multiple domains.
3.1. Ethernet Service
Ethernet Switched Paths that are setup either by configuration or
signaling can be used to provide an Ethernet service to customers of
the Ethernet network. The Metro Ethernet Forum has defined some
services in [MEF.6] (e.g., Ethernet Private Line), and these are also
aligned with ITU-T G.8011-x Recommendations. Of particular interest
are the bandwidth profile parameters in [MEF.10] and whose associated
bandwidth profile algorithm are based on [RFC4115] [RFC3270].
Consideration should be given to supporting these in any signaling
extensions for Ethernet LSPs. This will be addressed in a future
version of this specification.
3.2. Addresses, Interfaces, and Labels
This specification uses an addressing scheme and a label space for
the ingress/egress connection; the hierarchical TE Router
ID/Interface ID and the Ethernet ESP-VID/ESP-MAC DA tuple or ESP-
VID/Multicast MAC as a label space. This draft is intended to be
consistent with GMPLS addressing and Routing [ARCH].
PBB-TE is defined for a PBB Network. As with PBB services, PBB-TE is
typically implemented in the Service and Backbone components of an
IB-Backbone Edge Bridge (BEB). This is illustrated in Figure 1. The
Ethernet service is attached to a Customer Instance Port (CIP) of the
Backbone Service Instance (I-component) Relay. The CIP is connected
via the I-Component Relay to a Virtual instance port (VIP) which is
identified with a configured service instance (I-SID) and attached to
a Provider Instance Port (PIP). The PIP is configured to be attached
to a customer Backbone port (CBP). (A point to point service instance
is illustrated. A point to multipoint service could allow more than
one CBP to be attached to a single PIP.) The CBP has a B-MAC that
defines the MAC for the PBB-TE Service Instance. That source B-MAC
address is the PIP MAC address which in the case of backbone service
instances that are supported by TE service instances is configured to
take the same value as the CBP B-MAC of the internally connected CBP
on the B-component. As a result, the backbone MAC addresses of
frames associated with traffic engineered services, the ESP-MACs, are
always equal to the CBP B-MAC. The I-Component PIP adds the ESP-MAC
DA and the ESP-MAC SA. The B-Component CBP adds the ESP-VID. GMPLS
is being defined here to connect CBP MACs to signal the PBB-TE
service Instance before the association of ESP-MAC DA and ESP-MAC SA
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is defined.
The diagram also shows the addition of a TE Router ID to the PBB
switch and the TE Link identifier to enable GMPLS. TE Links are not
associated with CBPs. TE Links are associated with PNPs. TE links are
associated with bridge identifiers of backbone edge bridges (BEB) and
backbone core bridges (BCB). CBPs are also associated with these
bridge ids. For GMPLS the bridge IDs are expressed as IP addresses
as TE- Router IDs. [RFC4990]
Backbone Edge Bridge (BEB)
+------------------------------------------------------+
| <TE - Router ID > |
| |
| I-Component Relay B-Component Relay |
| +-----------------------+ +---------------------+ |
| | +---+ | | B-VID | |
| | |VIP| | | +---+ +---+ | | <TE Link>
| | +---+ | +---|CBP| |PNP|------
| | | | | +---+ +---+ | |
| | +---+ +---+ | | | | |
------|CIP| |PIP|----+ | | |
| | +---+ +---+ | | | |
| +-----------------------+ +---------------------+ |
| |
| PBB Edge Bridge |
+------------------------------------------------------+
^--------Configured--------------^
^-GMPLS or Configured-^
Figure 2 Ethernet/GMPLS Addressing & Label Space
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TE Router ID TE Router ID
| (TE Link) |
V | V N=named port
+----+ | +-----+ <port index>
| | | label=ESP:VID/MAC DA | | <MAC>
| PB | V label=ESP:VID/MMAC | | <string>
-----N N----------------------------N PBB N----------
| | |(MAC)| \
| | / | Customer
+----+ /+-----+ Facing
BCB ESP:MAC BEB Ports
Figure 3 Ethernet/GMPLS Addressing & Label Space
For a GMPLS based system, the TE Router ID/logical port is the
logical signaling identifier for the control plane via which Ethernet
layer label bindings are solicited. In order to create a P2P path an
association must be made between the ingress and egress switch. The
actual label distributed via signaling and instantiated in the switch
forwarding tables identifies the upstream and downstream egress ESP-
VID/ESP-MAC DA of the PBB-TE ESP (see Figure 3).
GMPLS uses identifiers in the form of 32 bit numbers which are in the
IP address notation which may or may not be IP addresses. The
provider MAC port addresses are exchanged by the LLDP [IEEE 802.1AB]
and by LMP [RFC4204] if supported. However these identifiers are
merely for link control and legacy Ethernet support and have local
link scope. Actual label assignment is performed by the ingress and
egress switches using CBP MAC addresses.
A particular PNP would have:
- A VID/MAC
- An IP address, which is typically the TE router ID, plus a 32 bit
interface Identifier also call an unnumbered link.
- One (or more) Mnemonic String Identifiers
This multiple naming convention leaves the issue of resolving the set
given one of the port identifiers. On a particular switch, mapping is
relatively straightforward. Per [ARCH], standard GMPLS mechanisms
are used for signaling resolution. In so doing, the problem of
setting up a path is reduced to figuring out what switch supports an
egress CBP MAC address and then finding the corresponding egress IP
address and performing all signaling and routing with respect to the
egress.
There are several options to achieve this:
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- Provisioning - Auto discovery protocols that carry MAC address
- Augmenting Routing TE with MAC Addresses
- Name Servers with identifier/address registration
The specific procedures will be clarified in a subsequent version
of this document.
4. Specific Procedures
4.1. P2P connections
The PBB-TE Service Instance is defined by the ESP 3-tuples for each
of the unidirectional ESPs. From a GMPLS control plane point of view
an Ethernet LSP is also identified as any other LSP using the 5-
tuple [Ip_Source_Sddr, Ip_Dest_Addr, LSP_Id, Tunnel_ID,
Extended_Tunnel_ID]. The ESP-VID and ESP-MAC DA tuple identifies the
forwarding multiplex at transit switches and a simple degenerate form
of the multiplex is a single P2P connection.
This results in unique labels end to end. The data streams MAY merge,
the forwarding entries MAY be shared but the headers are still unique
allowing the connection to be de-multiplexed downstream. Note that
in addition to the ESP 3-tuples the I-SID in the I-TAG also provides
for unambiguous identification of frames belonging to a certain
service. This adds further protection against misconfiguration and
misconnectivity errors, by allowing simple detection and immediate
squelching of unintended traffic.
On the initiating and terminating switches, a function administers
the ESP-VIDs associated with the ESP-MAC SA and ESP-MAC DA
respectively. PBB-TE is designed to be bidirectional and
symmetrically routed just like Ethernet. Therefore in PBB-TE, the
packet ESP-MAC SA and ESP- MAC DA pair is same in the forwarding path
and the associated reverse path except they are flipped in the
reverse direction.
To initiate a bidirectional ESP-VID/ESP-MAC DA P2P or P2MP path, the
initiator of the PATH message uses procedures outlined in [RFC3473]
possibly augmented with [RFC4875], it:
1) Sets the LSP encoding type to Ethernet.
2) Sets the LSP switching type to 802_1 PBB-TE [IANA to define].
3) Sets the GPID to service type [IANA to define].
4) Sets the UPSTREAM_LABEL to the ESP-VID/ESP-MAC SA tuple where the
ESP-VID is administered from the configured ESP-VID/ESP-MAC DA range.
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5) Optionally sets the LABEL_SET or SUGGESTED_LABEL if it chooses to
influence the choice of ESP-VID/ESP-MAC DA.
6) Optionally look at Call / Connection ID for Carrying I-SID.
Intermediate and egress switch processing is not modified by this
document, i.e., is per [RFC3473] and, in the case of P2MP, as
extended in [RFC4875]. Note, as previously stated intermediate
bridges supporting the 802_1 switching type may not modify LABEL
values.
The ESP-VID/ESP-MAC SA tuple contained in the UPSTREAM_LABEL is used
to create a static forwarding entry in the Filtering Database of
bridges at each hop for the upstream direction. This behavior is
inferred from the switching type which is 802_1 [IANA to define].
The port derived from the RSVP_HOP object and the ESP-VID and ESP-
MAC DA included in the label constitute the static entry.
At the destination, a ESP-VID is allocated in the local MAC range for
the ESP-MAC DA and the ESP-VID/ESP-MAC DA tuple is passed in a LABEL
object in the RESV message. As with the PATH message, intermediate
switch processing is per [RFC3473] and [RFC4875], and the LABEL
object is passed on unchanged, upstream. The ESP-VID/ESP-MAC DA
tuple contained in the LABEL Object is installed in the forwarding
table as a static forwarding entry at each hop. This creates a
bidirectional path as the PATH and RESV messages follow the same
path.
4.1.1. Shared Forwarding
One capability of a connectionless Ethernet data plane is to reuse
destination forwarding entries for packets from any source within a
VLAN to a destination. When setting up P2P PBB-TE connections for
multiple sources sharing a common destination this capability MAY be
preserved provided certain requirements are met. We refer to this
capability as Shared Forwarding. Shared forwarding is invoked based
on policy when conditions are met. It is a local decision by label
allocation at each end. Shared forwarding has no impact on the actual
paths setup, but it allows the reduction of forwarding entries.
Shared forwarding paths are identical to independently routed paths
with the exception that they share the same labels and same path from
the merge point.
To achieve shared forwarding, a Path computation engine [PATHCOMP]
should ensure the ERO is consistent with an existing path for the
shared segments. If a path satisfies the consistency check, the
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upstream end of the signaling may chose to share an existing ESP-
VID/ESP-MAC DA for the upstream traffic with an existing Eth-LSP.
The criteria for shared forwarding is the Eth-LSPs must share the
same destination port and the paths of the Eth-LSP share one or more
hops consecutively. Once the paths converge they must remain
converged. If no existing path has this behavior when a new path is
being created, the new path will be created without sharing either by
using another ESP-VID or another ESP-MAC DA or both.
In other words, shared forwarding is possible when paths share
segments either from the source or the destination. There is no
requirement that the paths share reservations or other attributes.
For the source, the UPSTREAM_LABEL is chosen to be the same as an
existing path that shares the ERO for some number of hops. Similarly
for the destination, shared forwarding is possible when an existing
path that shares segments with the new paths ERO, viewed from the
destination switch. The downstream label in this case is chosen to
be the same as the existing path. In this manner shared forwarding is
a function that is controlled primarily by policy and in combination
with the local label allocation at the end points of the path.
4.1.2. P2P connections with shared forwarding
The ESP-VID/ESP-MAC DA MAY be considered to be a shared forwarding
identifier or label for a multiplex consisting of some number of P2P
connections distinctly identified by the MAC ESP-VID/ESP-MAC DA/ESP-
MAC SA tuple. In some ways this is analogous to an LDP label merge
but in the shared forwarding case only the forwarding entry is
reused. Resources can continue to be allocated per LSP.
VLAN tagged Ethernet packets include priority marking. Priority bits
MAY be used to indicate class of Service (COS) and drop priority.
Thus, traffic from multiple COSs could be multiplexed on the same
Eth-LSP (i.e., similar to E-LSPs) and queuing and drop decisions are
made based on the p-bits. This means that the queue selection can be
done based on a per flow (i.e., Eth-LSP + priority) basis and is
decoupled from the actual steering of the packet at any given switch.
A switch terminating an Eth-LSP will frequently have more than one
suitable candidate path and it may choose to share a forwarding entry
(common ESP-VID/ESP-MAC DA, unique ESP-MAC SA). It is a local
decision of how this is performed but the best choice is a path that
maximizes the shared forwarding.
The concept of bandwidth management still applies equally well with
shared forwarding. As an example consider a PBB-TE edge switch that
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terminates an Ethernet LSP with the following attributes: bandwidth
B1, ESP-MAC DA D, ESP-MAC SA S1, ESP-VID V. A request to establish an
additional Ethernet LSP with attributes (bandwidth B2, ESP-MAC DA D,
ESP-MAC SA S2, ESP-VID V) can be accepted provided there is
sufficient link capacity remaining.
4.1.3. Dynamic P2P symmetry with shared forwarding
Similar to how a destination switch MAY select a ESP-VID/ESP-MAC DA
from the set of existing shared forwarding multiplexes rooted at the
destination switch, the originating switch MAY also do so for the
reverse path. Once the initial ERO has been computed and the set of
existing Ethernet LSPs that include the target ESP-MAC DA have been
pruned, the originating switch may select the optimal (by whatever
criteria) existing shared forwarding multiplex for the new
destination to merge with and offer its own ESP-VID/ESP-MAC DA tuple
for itself as a destination.
4.1.4. Planned P2P symmetry
Normally the originating switch will not have knowledge of the set of
shared forwarding paths rooted on the destination switch.
Use of a Path Computation Server [PATHCOMP] or other planning style
of tool with more complete knowledge of the network configuration may
wish to impose pre-selection of shared forwarding multiplexes to use
for both directions. In this scenario the originating switch uses
the LABEL_SET and UPSTREAM_LABEL objects to indicate complete
selection of the shared forwarding multiplexes at both ends. This may
also result in the establishment of a new ESP-VID/ESP-MAC DA path as
the LABEL_SET object may legitimately refer to a path that does not
yet exist.
4.1.5. P2P Path Maintenance
Make before break procedures can be employed to modify the
characteristics of a P2P Ethernet LSP. As described in [RFC3209], the
LSP ID in the sender template is updated as the new path is signaled.
The procedures (including those for shared forwarding) are identical
to those employed in establishing a new LSP, with the extended tunnel
ID in the signaling exchange ensuring that double booking of the
associated resources does not occur.
Where individual paths in a protection group are modified, signaling
procedures may be combined with Protection Switching (PS)
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coordination to administratively force PS switching operations such
that modifications are only ever performed on the protection path.
4.2. P2MP Signaling
Note specifics for P2MP paths are being defined. This section will be
updated to align with the PBB-TE specification [IEEE 802.1Qay].
To initiate a P2MP VID/Multicast MAC (MMAC) path the initiator of the
PATH message uses procedures outlined in [RFC3473] and [RFC4875]. A
P2MP tree consists of a VID tree forward direction (from root to
leaves) and a set of P2P paths running on identical paths from Tree
leaves to root in the reverse direction. The result is a composite
path with a ESP- MMAC DA label with a single ESP-MMAC DA in the
forward direction and a symmetric set of unidirectional ESP-VID/ESP-
MAC DA labels in the reverse direction:
1-4) Same points as P2P paths previously specified.
5) Sets the downstream label as the ESP-MMAC DA.
4.3. P2MP ESP-MAC DA Connections
4.3.1. Setup procedures
The group ESP-MMAC DA is administered from a central pool of
multicast addresses and the VLAN selected from the PBB-TE VID range.
The P2MP tree is constructed via incremental addition of leaves to
the tree in signaling exchanges where the root is the originating
switch (as per (RFC4875). The multicast VID/ESP-MMAC DA is encoded in
the LABEL_SET (as a member of one) object using the Ethernet label
encoding.
Where a return path is required the unicast MAC corresponding to the
originating interface and a VID selected from the configured VID/ESP-
MAC DA range is encoded as an Ethernet label in the UPSTREAM_LABEL
object.
4.3.2. Maintenance Procedures
Maintenance and modification to a P2MP tree can be achieved by a
number of means. The preferred technique is to modify existing VLAN
configuration vs. assignment of a new label and completely
constructing a new tree.
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Make before break on a live tree reusing existing label assignments
requires a 1:1 or 1+1 construct. The protection switch state of the
traffic is forced on the working tree and locked (PS not allowed)
while the backup tree is modified. Explicit path tear of leaves to be
modified is required to ensure no loops are left behind as artifacts
of tree modification. Once modifications are complete, a forced
switch to the backup tree occurs and the original tree may be
similarly modified. This also suggests that 1+1 or 1:1 resilience can
be achieved for P2MP trees for any single failure (switch on any
failure and use restoration techniques to repair the failed tree).
4.4. Ethernet Label
The Ethernet label is a new generalized label with a suggested format
of:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| ESP VID | ESP MAC (highest 2 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ESP MAC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This format can be used to carry P2P and P2MP labels. For P2P labels
the fields specify ESP <VID, MAC DA>. The semantics for a P2MP label
using a MMAC DA is that that the label is passed unchanged. This
label is also a domain wide label. This has similarity to the way in
which a wavelength label is handled at an intermediate switch that
cannot perform wavelength conversion, and is described in [RFC3473].
Label Allocation for Domain wide labels is similar to other label
switching technologies with the exception that the labels are owned
by the switch where the path is terminated. In Ethernet, unique MAC
based labels can be created using one of two methods. One option is
to allocate the ESP-MAC DAs from globally unique addresses assigned
to the either the switch manufacturer. The other option is to use
ESP-MAC DAs out of the local admin space and ensure these labels are
unique within the domain. Labels only have significance within the
domain.
In the case of local label allocation there is no need to use
globally assigned OUIs. However when using this configuration, some
way of ensuring label consistency should be provided to make sure
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that labels were unique. When using GMPLS signaling it is assumed a
unique pool of labels would be owned or assigned to each switch. The
ESP-MAC DA addresses are domain wide unique and so is the combination
of ESP <VID, MAC DA>. It is intended that the ESP <VID, MAC DA> be
only used by one destination. However, should an error occur and a
somehow a duplicate label be assigned to one or more destination
switches GMPLS signaling procedures would allow the first assignment
of the label and prevent any duplicate label from colliding. If a
collision occurs an alarm would be generated. In fact some of these
procedures have been defined in GMPLS control of photonic networks
where a lambda may exist as a form of domain wide label.
4.5. OAM MEP ID and MA ID synchronization
This section is aligned with [IEEE 802.1Qay]. At present Ethernet OAM
is signaled in Ethernet protocol data units. Extensions to GMPLS
[OAM-EXT] are proposed to automatically setup OAM for Ethernet LSPs.
The Maintenance association point IDs (MEP IDs) and maintenance
association IDs for the switched path endpoints can be synchronized
using the ETH-MCC (maintenance communication channel) transaction set
once the switched path has been established.
MEPs are located at the endpoints of the Ethernet LSP. Typical
configuration associated with a MEP is Maintenance Domain Name, Short
Maintenance Association Name, and MD Level, MEP ID, and CCM
transmission rate (when ETH-CC functionality is desired). As part of
the synchronization, it is verified that the Maintenance Domain Name,
Short Maintenance Association Name, MD Level, and CCM transmission
rate are the same. It is also determined that MEP IDs are unique for
each MEP.
Besides the unicast CCM functionality, the PBB-TE MEPs can also offer
the LBM/LBR and LMM/LMR functionalities for on-demand connectivity
verification and loss measurement purposes.
4.6. Protection Paths
The IEEE is currently defining protection procedures for PBB-TE [IEEE
802.1Qay]. This section will be updated when these procedures are
documented.
When protection is used for path recovery it is required to associate
the working and protection paths into a protection group. This is
achieved as defined in [RFC4872] and [RFC4873] using the ASSOCIATION
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and PROTECTION objects. Protection may be used for P2P VID/ESP-MAC
DA, P2MP VID/ESP-MMAC DA and P2MP VID configured modes of operation.
The 'P' bit in the protection object indicates the role (working or
protection) of the LSP currently being signaled.
If the initiating switch wishes to use G.8031 [G-8031] data plane
protection switching coordination (vs. control plane notifications),
it sets the N bit to 1 in the protection object. This must be
consistently applied for all paths associated as a protection group.
If the terminating switch does not support G.8031, the error
"Admission Control Failure/Unsupported Notification Type" is used.
5. Error conditions
The following errors have been identified as being unique to these
procedures and in addition to those already defined. This will be
addressed in a proper IANA considerations section in a future version
of the document:
5.1. Invalid ESP-VID value for PBB-TE MSTI range
The originator of the error is not configured to use the ESP-VID
value in conjunction with GMPLS signaling of <ESP: VID, MAC DA >
tuples. This may be originated by any switch along the path.
5.2. Invalid MAC Address
The MAC address is out of a reserved range that cannot be used by the
switch which is processing the address. While almost all MAC
addresses are valid there are a small number of IEEE reserved MAC
addresses.
5.3. Invalid ERO for UPSTREAM_LABEL Object
The ERO offered has discontinuities with the identified ESP-
VID/ESP-MAC DA path in the UPSTREAM_LABEL object.
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5.4. Invalid ERO for LABEL_SET Object
The ERO offered has discontinuities with the identified ESP-VID/ESP-
MAC DA path in the LABEL_SET object.
5.5. Switch is not ESP P2MP capable
This error may arise only in P2MP Tree allocation.
5.6. Invalid ESP-VID in UPSTREAM_LABEL object
The ESP-VID in the UPSTREAM_LABEL object for the "asymmetrical ESP-
VID" P2MP tree did not correspond to the ESP-VID used in previous
transactions.
6. Deployment Scenarios
Deployment scenarios are covered in [ARCH]. This section will detail
more specific PBB-TE deployment scenarios in a later revision of this
document.
7. Security Considerations
The architecture assumes that the GMPLS controlled Ethernet subnet
consists of trusted devices and that the UNI ports or in this case
BEB Ethernet UNI Ports to the domain are untrusted. Care is required
to ensure untrusted access to the trusted domain does not occur.
Where GMPLS is applied to the control of VLAN only, the commonly
known techniques for mitigation of Ethernet DOS attacks may be
required on UNI ports.
8. IANA Considerations
New values are required for signaling and error codes as indicated.
This section will be completed in a later version.
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9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[ARCH] Fedyk, D. Berger, L., Andersson L., "GMPLS Ethernet Label
Switching Architecture and Framework", work in progress.
[RFC3473] Berger, L. et.al., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) Extensions", IETF RFC 3473, January 2003.
[RFC3945] Mannie, E. et.al., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", IETF RFC 3945, October 2004.
9.2. Informative References
[IEEE 802.1Qay] "IEEE standard for Provider Backbone Bridges Traffic
Engineering", work in progress.
[RFC4115] Aboul-Magd, O. et.al. "A Differentiated Service Two-Rate,
Three-Color Marker with Efficient Handling of in-Profile Traffic",
IETF RFC 4115, July 2005
[G-8031] ITU-T Recommendation G.8031 (2006), Ethernet Protection
Switching.
[IEEE 802.1AB] "IEEE Standard for Local and Metropolitan Area
Networks, Station and Media Access Control Connectivity
Discovery".
[IEEE 802.1ag] "IEEE Standard for Connectivity Fault
Management", (2007).
[IEEE 802.1ah] "IEEE Standard for Local and Metropolitan Area
Networks - Virtual Bridged Local Area Networks
- Amendment 6: Provider Backbone Bridges", (2008)
[RFC4204] Lang. J. Editor, "Link Management Protocol (LMP)" RFC4204,
October 2005
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[MEF.6] The Metro Ethernet Forum MEF 6 (2004), "Ethernet Services
Definitions - Phase I".
[MEF.10] The Metro Ethernet Forum MEF 10 (2004), "Ethernet Services
Attributes Phase 1".
[RFC3270] Le Faucheur, F. et.al., "Multi-Protocol Label Switching
(MPLS) Support of Differentiated Services" IETF RFC 3270, May
2002.
[RFC4875] Aggarwal, R. Ed., "Extensions to RSVP-TE for Point to
Multipoint TE LSPs", IETF RFC 4875, May 2007
[PATHCOMP] Farrel, A. et.al., "Path Computation Element (PCE)
Architecture", work in progress.
[RFC3985] Bryant, S., Pate, P. et al., "Pseudo Wire Emulation Edge-
to Edge (PWE3) Architecture", IETF RFC 3985, March 2005.
[RFC4872] Lang et.al., "RSVP-TE Extensions in support of End-to-End
Generalized Multi-Protocol Label Switching (GMPLS)-based Recovery
", RFC 4872, May 2007.
[RFC4873] Berger, L. et.al.,"MPLS Segment Recovery", RFC 4873, May
2007.
[RFC3209] Awduche et.al., "RSVP-TE: Extensions to RSVP for LSP
Tunnels, IETF RFC 3209, December 2001.
[Y.1731] ITU-T Draft Recommendation Y.1731(ethoam), " OAM Functions
and Mechanisms for Ethernet based Networks ", (2006).
[RFC4990] Shimoto, K., Papneja, R., Rabbat, R., "Use of Addresses in
Generalized Multi-Protocol Label Switching (GMPLS) Networks",
IETF RFC4990, September 2007.
[OAM-EXT] Takacs, A., Gero, B., "GMPLS RSVP-TE Extensions to Control
Ethernet OAM", work in progress.
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10. Acknowledgments
The authors would like to thank Dinesh Mohan, Nigel Bragg, Stephen
Shew, Dave Martin and Sandra Ballarte for their contributions to this
document.
11. Author's Address
Don Fedyk
Nortel Networks
600 Technology Park Drive
Billerica, MA, 01821
Email: dwfedyk@nortel.com
David Allan
Nortel Networks
3500 Carling Ave.
Ottawa, Ontario, CANADA
Email: dallan@nortel.com
Himanshu Shah
Ciena
35 Nagog Park,
Acton, MA 01720
Email: hshah@ciena.com
Nabil Bitar
Verizon,
40 Sylvan Rd.,
Waltham, MA 02451
Email: nabil.n.bitar@verizon.com
Attila Takacs
Ericsson
1. Laborc u.
Budapest, HUNGARY 1037
Email: attila.takacs@ericsson.com
Diego Caviglia
Ericsson
Via Negrone 1/A
Genoa, Italy 16153
Email: diego.caviglia@ericsson.com
Fedyk, et. al. Standards Track [Page 21]
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Alan McGuire
BT Group PLC
OP6 Polaris House,
Adastral Park, Martlesham Heath,
Ipswich, Suffolk, IP5 3RE, UK
Email: alan.mcguire@bt.com
Nurit Sprecher
Nokia Siemens Networks,
GmbH & Co. KG
COO RTP IE Fixed
3 Hanagar St. Neve Ne'eman B,
45241 Hod Hasharon, Israel
Email: nurit.sprecher@nsn.com
Lou Berger
LabN Consulting, L.L.C.
Phone: +1-301-468-9228
Email: lberger@labn.net
A. Rational and mechanism for PBB_TE Ethernet Forwarding
This appendix describes work currently being undertaken in the 802.1
PBB-TE [IEEE 802.1Qay] project. This information is for reference
only and will be removed when 802.1Qay becomes mature. This text
captures some of the original rational for changing Ethernet
forwarding. The PBB-TE [IEEE 802.1Qay] document simply documents the
PBB-TE data plane.
Ethernet as specified today is a complete system consisting of a data
plane and a number of control plane functions. Spanning tree, data
plane flooding and MAC learning combine to populate forwarding tables
and produce resilient any-to-any behavior in a bridged network.
Ethernet consists of a very simple and reliable data plane that has
been optimized and mass produced. By simply disabling some Ethernet
control plane functionality, it is possible to employ alternative
control planes and obtain different forwarding behaviors.
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Customer Provider Provider
Bridge/ Bridge Backbone
Bridge
C-MAC/C-VID------------------802.1Q -------------------C-MAC-CVID
S-VID-----------802.1ad------------S-VID
B-MAC---802.1ah---B-MAC
B-VID---802.1ah---B-VID
Figure A.1 802.1 MAC/VLAN Hierarchy
Recent works in IETF Pseudo Wire Emulation [RFC3985] and IEEE 802 are
defining a separation of Ethernet functions permitting an increasing
degree of provider control. The result is that the Ethernet service
to the customer appears the same, yet the provider components and
behaviors have become decoupled from the customer presentation and
the provider has gained control of all VID/B-MAC endpoints.
One example of this is the 802.1ah work in hierarchical bridging
whereby customer Ethernet frames are fully encapsulated into a
provider Ethernet frame, isolating the customer VID/C-MAC space from
the provider VID/B-MAC space. In this case, the forwarding behavior
of the of the Backbone MAC in the provider's network is as per
802.1Q.
The Ethernet data plane provides protocol multiplexing via the
Ethertype field which allows encapsulation of different protocols
supporting various applications. More recently, the Carrier Ethernet
effort has created provider and customer separation that enables
another level of multiplexing. This in effect creates provider MAC
endpoints in the Ethernet sub-network controlled by the provider. In
this appendix we concentrate on the provider solutions and therefore
subsequent references to VLAN, VID and MAC refer to those under
provider control, be it in the backbone layer of 802.1ah. The
Customer Ethernet service is the same native Ethernet service with
functions such as bridging, learning and spanning trees all
functioning over the provider infrastructure.
Bridging offers a simple solution for any-to-any connectivity within
a VLAN partition via the Spanning tree, flooding and MAC learning.
Spanning tree provides some unnecessary capabilities for P2P services
and since the Spanning tree must interconnect all MACs with the same
VLAN IDs (VIDs) it consumes a scarce resource (VIDs). In this
document we present that it is easier to modify Ethernet to scale
engineered P2P services and this is the approach we take with PBB-TE.
(The number of usable VLANs IDs in conventional Ethernet bridging is
constrained to 4094, therefore the use of VLAN only configuration for
all forwarding could be limited for some applications where large
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number of P2P connections are required.) This is because in
Ethernet, each Spanning tree is associated with one or more VLAN IDs.
Also Port membership in a VLAN is configured which controls the
connectivity of all MAC interfaces participating in the VLAN.
The roots for PBB-TE capability exist in the Ethernet management
plane. The management of Ethernet switches provides for static
configuration of Ethernet forwarding. The Ethernet Control plane
allows for forwarding entries that are statically provisioned or
configured. In this document we are expanding the meaning of
"configured" from an Ethernet Control plane sense to mean either
provisioned, or controlled by GMPLS. The connectivity aspects of
Ethernet forwarding is based upon VLANs and MAC addresses. In other
words the VLAN + DMAC are an Ethernet Label that can be looked up at
each switch to determine the egress link (or links in the case of
link aggregation).
This is a finer granularity than traditional VLAN networks since each
P2P connection is independent. By provisioning MAC addresses
independently of Spanning tree in a domain, both the VLAN and the
VLAN/DMAC configured forwarding can be exploited. This greatly
extends the scalability of what can be achieved in a pure Ethernet
bridged sub network.
The global/domain wide uniqueness and semantics of MAC addresses as
interface names or multicast group addresses has been preserved. (In
Ethernet overlap of MAC addresses across VLANs is allowed. However
for PBB-TE MAC addresses should be unique for all VLANs assigned to
PBB-TE. With PBB-TE it is an operational choice if the operator uses
PBT-TE labels out of the global MAC address space or the local admin
space.) We then redefine the semantics associated with administration
and uses of VLAN values for the case of explicit forwarding such as
with statically configured Ethernet.
The PBB_TE is Ethernet Forwarding where configured VID + DMAC provide
a forwarding table that is consistent with existing PBB and Ethernet
switching. At the same time it provides domain wide labels that can
be controlled by a common GMPLS control plane. This makes GMPLS
control and resource management procedures ideal to create paths. The
outcome is that the GMPLS control plane can be utilized to set up the
following atomic modes of connectivity:
1) P2P connectivity and MP2P multiplexed connectivity based
on configuration of unicast MAC addresses in conjunction
with a VID from a set of pre-configured VIDs.
2) P2MP connectivity based on configuration of multicast MAC
address in conjunction with a VID from a set of pre-
configured VIDs. This corresponds to (Source, Group) or
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(S,G) multicast.
3) P2MP connectivity based on configuration of VID port
membership. This corresponds to (S,*) or (*,*) multicast
(where * represents the extent of the VLAN Tree).
4) MP2MP connectivity based on configuration of VID port
membership (P2MP trees in which leaves are permitted to
communicate). Although, we caution that this approach
poses resilience issues (discussed in section 5) and hence
is not recommended.
The modes above are not completely distinct. Some modes involve
combinations of P2P connections in one direction and MP connectivity
in the other direction. Also, more than one mode may be combined in
a single GMPLS transaction. One example is the incremental addition
of a leaf to a P2MP tree with a corresponding MP2P return path
(analogous to a root initiated join).
In order to realize the above connectivity modes, a partition of the
VLAN IDs from traditional Ethernet needs to be established. The
partition allows for a pool of Ethernet labels for manual
configuration and/or for GMPLS control plane usage. The VID partition
actually consists of a "configured VID/DMAC range" and "configured
VID range" since in some instances the label is a VID/ DMAC and
sometimes the label is a VID/Multicast DMAC.
A.1. Overview of configuration of VID/DMAC tuples
Statically configured MAC and VID entries are a complete 60 bit
lookup. The basic operation of an Ethernet switch is filtering on VID
and forwarding on DMAC. The resulting operation is the same as
performing a full 60 bit lookup (VID (12) + DMAC(48)) for P2P
operations, only requiring uniqueness of the full 60 bits for
forwarding to resolve correctly. This is an Ethernet domain wide
label.
Complete route freedom is available for each domain wide label (60
bit VLAN/DMAC tuple) and the ability to define multiple connectivity
instances or paths per DMAC for each of the VIDs in the "configured
VID/DMAC range".
The semantics of MAC addresses are preserved, and simply broaden the
potential interpretations of VLAN ID from spanning tree identifier to
topology instance identifier. Therefore, operation of both standard
bridging and configured unicast/multicast operation is available side
by side. The VID space is partitioned and a range of VIDs is
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allocated(say 'n' VIDs) as only significant when combined with a
configured DMAC address (the aforementioned "configured VID/DMAC
range" of VIDs). A VID in that range is considered as an individual
connectivity instance identifier for a configured P2P path
terminating at the associated DMAC address. Or in the case of P2MP, a
P2MP multicast tree corresponding to the destination multicast group
address. Note that this is destination based forwarding consistent
with how Ethernet works today. The only thing changed is the
mechanism of populating the forwarding tables.
Ethernet MAC addresses are typically globally unique since the 48
bits consists of 24 bit Organizational Unique Identifier and a 24 bit
serial number. There is also a bit set aside for Multicast and for
local addresses out of the OUI field. We define domain wide as within
a single organization, or more strictly within a single network
within an organization. For provider MAC addresses that will only be
used in a domain wide sense we can define MAC addresses out of a
either the local space or the global space since they both have the
domain wide unique property. When used in the context of GMPLS, it is
useful to think of a domain wide pool of labels where switches are
assigned a set of MAC addresses. These labels are assigned traffic
that terminates on the respective switches.
It is also worth noting that unique identification of source in the
form of the ESP-MAC SA is carried e2e in the MAC header. So although
we have a 60 bit domain wide unique label, it may be shared by
multiple sources and the full connection identifier for an individual
P2P instance is 108 bits (ESP-MAC SA, VID and DMAC). The ESP-MAC SA
is not referenced in forwarding operations but it would allow
additional context for tracing or other operations at the end of the
path.
For multicast group addresses, the VID/DMAC concatenated label can be
distributed by the source but label assignment (as it encodes global
multicast group information) requires coordination within the GMPLS
controlled domain.
As mentioned earlier, this technique results in a single unique and
invariant identifier, in our case a VID/DMAC label associated with
the path termination or the multicast group. There can be up to 4094
labels to any one MAC address. However, practically, from an
Ethernet network wide aspect; there would be only a handful of VLANs
allocated for PBB-TE. In addition, all 48 bits are not completely
available for the MAC addresses. One way to maximize the space is to
use the locally administered space. This is a large number for
P2P applications and even larger when shared or multiplexed
forwarding is leveraged. In practice, most network scaling
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requirements may be met via allocation of only a small portion of the
VID space, to the configured VID/DMAC range. The result is minimal
impact on the number of remaining bridging VLANs that can be
concurrently supported.
In order to use this unique 60 bit label, we disable the normal
mechanisms by which Ethernet populates the forwarding table for the
allocated range of VIDs. When a path is setup, for a specific label
across a contiguous sequence of Ethernet switches, a unidirectional
connection is the functional building block for an Ethernet Label
Switched path (Eth-LSP).
In P2P mode a bidirectional path is composed of two unidirectional
paths that are created with a single RSVP-TE session. The technique
does not require the VID to be common in both directions. However,
keeping in line with regular Ethernet these paths are symmetrical
such that a single bidirectional connection is composed of two
unidirectional paths that have common routing (i.e. traverse the same
switches and links) in the network and hence share the same fate.
In P2MP mode a bidirectional path is composed of a unidirectional
multicast tree and a number of P2P paths from the leaves of the tree
to the root. Similarly these paths may have bandwidth and must have
common routing as in the P2P case.
There are a few modifications required to standard Ethernet to make
this approach robust:
1. In Standard Ethernet, discrepancies in forwarding table
configuration in the path of a connection will normally result in
packets being flooded as "unknown". For configured operation (e.g.
PBB-TE), unknown addresses are indicative of a fault or configuration
error and the flooding of these is undesirable in meshed topologies.
Therefore flooding of "unknown" unicast/multicast MAC addresses must
be disabled for the "configured VID/DMAC range".
2. MAC learning is not required, and although it will not interfere
with management/control population of the forwarding tables, since
static entries are not overridden, it appears prudent to explicitly
disable MAC learning for the configured VID/DMAC and VID range.
3. Spanning tree is disabled for the allocated VID/DMAC and VID range
and port blocking must be disabled to achieve complete configured
route freedom. As noted earlier, it is a control plane requirement to
ensure configured paths are loop free.
All three modifications described above are within the scope of
acceptable configuration options defined in IEEE 802.1Q
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specification.
A.2 Overview of configuration of VID port membership
Procedures almost identical to that for configuration of P2P VID/DMAC
tuples can also be used for the incremental configuration of P2MP VID
trees. For the replication of forwarding in this case the label is
common for the multipoint destinations. The MAC field is set to
multicast address and is common to the multicast community. The VID
is a distinguisher common to the multicast community. The signaling
procedures are per that for [RFC4875].
Since VID translation is relatively new and is not a ubiquitously
deployed capability, we consider a VID to be a domain global value.
Therefore, the VID value to be used by the originating switch may be
assigned by management and nominally is required to be invariant
across the network. The ability to indicate permissibility of
translation will be addressed in a future version of the document.
A procedure known as "asymmetrical VID" may be employed to constrain
connectivity (root to leaves, and leaves to root only) when switches
also support shared VLAN learning (or SVL). This would be consistent
with the root as a point of failure.
A.3 OAM Aspects
Robustness is enhanced with the addition of data plane OAM to provide
both fault and performance management.
For the configured VID/DMAC unicast mode of behavior, the hardware
performs unicast packet forwarding of known MAC addresses exactly as
Ethernet currently operates. The OAM currently defined, [802.1ag and
Y.1731] can also be reused minor modification of the protocols.
An additional benefit of domain wide path identifiers, for data plane
forwarding, is the tight coupling of the 60 bit unique connection ID
(VID/DMAC) and the associated OAM packets. It is a simple matter to
determine a broken path or misdirected packet since the unique
connection ID cannot be altered on the Eth-LSP. This is in fact one
of the most powerful and unique aspects of the domain wide label for
any type of rapid diagnosis of the data plane faults. It is also
independent of the control plane so it works equally well for
provisioned or GMPLS controlled paths.
Bidirectional transactions (e.g. ETH-LB) and reverse direction
Fedyk, et. al. Standards Track [Page 28]
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transactions MAY have a different VID for each direction. PBB-TE is
specifying this aspect of CFM.
For configured multicast VID/DMAC mode, the current versions of
802.1ag and Y.1731] make no representation as to how PDUs which are
not using unicast addresses or which use OAM reserved multicast
addresses are handled. Therefore this specification makes no
representation as to whether such trees can be instrumented.
When configured VID mode of operation is used PBB-TE can be forced to
use the same VID in both directions, emulating the current Ethernet
data plane and the OAM functions as defined in the current versions
of 802.1ag and Y.1731 can be used with no restriction.
A.4 QOS Aspects
Ethernet VLAN tags include priority tagging in the form of the PCP
priority bits. When combined with configuration of the paths via
management or control plane, priority tagging produces the Ethernet
equivalent of an MPLS-TE E-LSPs [RFC3270]. Priority tagged Ethernet
PDUs self-identify the required queuing discipline independent of the
configured connectivity.
It should be noted that the consequence of this is that there is a
common COS model across the different modes of configured operation
specified in this document.
The actual QOS objects required for signaling will be in a future
version of this memo.
A.5 Resiliency Aspects
A.5.1 E2E Path protection
One plus One(1+1) protection is a primary LSP with a disjoint
dedicated back up LSP. One for one (1:1) protection is a primary LSP
with a disjoint backup LSP that may share resources with other LSPs.
One plus One and One for One Automatic Protection Switching
strategies are supported. Such schemes offer:
1) Engineered disjoint protection paths that can protect both
directions of traffic.
2) Fast switchover due to tunable OAM mechanisms.
3) Revertive path capability when primary paths are restored.
4) Option for redialing paths under failure.
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Specific procedures for establishment of protection paths and
associating paths into "protection groups" are TBD.
Note that E2E path protection is able to respond to failures with a
number of configurable intervals. The loss of CCM OAM frames in the
data plane can trigger paths to switch. In the case of CCM OAM
frames, the detection time is typically 3.5 times the CCM interval
plus the propagation delay from the fault.
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Fedyk, et. al. Standards Track [Page 30]
Internet-Draft draft-ietf-ccamp-gmpls-ethernet-pbb-te-01.txtJuly 14, 2008
at http://www.ietf.org/ipr.
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Fedyk, et. al. Standards Track [Page 31]
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