Network Working Group Don Fedyk, David Allan, Nortel
Internet Draft Himanshu Shah, Ciena
Category: Standards Track Nabil Bitar, Verizon
Attila Takacs, Diego Caviglia, Ericsson
Alan McGuire, BT
Nurit Sprecher, Nokia Siemens Networks
Lou Berger, LabN
November 19, 2007
GMPLS control of Ethernet PBB-TE
draft-fedyk-gmpls-ethernet-pbb-te-02.txt
Status of this Memo
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This Internet-Draft will expire in May 2008.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This memo is complementary to [ARCH] and describes how a GMPLS
control plane may be applied to the Provider Backbone Bridges Traffic
Engineering (PBB-TE) [IEEE 802.1Qay] amendment to 802.1Q and how
GMPLS can be used to configure VLAN-aware Ethernet switches in order
to establish Ethernet point to point (P2P) and P2MP MAC switched
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paths and P2P/P2MP VID based trees. This document supports, but does
not modify, the standard IEEE data.
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].
Document History
This document has under gone name changes to follow the
standardization of Provider Backbone Bridges and the Traffic
engineering capability.
draft-fedyk-gmpls-ethernet-ivl-00.txt.
This was the original draft.
draft-fedyk-gmpls-ethernet-pbt-00.txt
draft-fedyk-gmpls-ethernet-pbt-01.txt
This draft was renamed to reflect the Provider Backbone Transport
(PBT) nomenclature. Several co-authors joined the draft.
draft-fedyk-gmpls-ethernet-pbb-te-00.txt
The standardization of PBT is called Provider Backbone Bridges
Traffic Engineering (PBB-TE). The draft was aligned the PBB-TE
Technology.
draft-fedyk-gmpls-ethernet-pbb-te-01.txt
This is the second revision of the PBB-TE draft with editing to
clarify the document and the addition of co-authors.
draft-fedyk-gmpls-ethernet-pbb-te-02.txt
This is a third revision with the general aspects of Ethernet being
move to the architecture and framework [ARCH] and the specifics for
PBB-TE becoming more clear.
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Table of Contents
1. Introduction..................................................4
2. Terminology...................................................4
2.1 PBB-TE Terminology..........................................5
3. GMPLS creation and maintenance of PBB-TE Service Instances....5
3.1 Ethernet Service............................................6
3.2 Addresses, Interfaces, and Labels...........................7
4. Specific Procedures...........................................9
4.1 P2P connections.............................................9
4.1.1 Shared Forwarding........................................ 10
4.1.2 P2P connections with shared forwarding................... 11
4.1.3 Dynamic P2P symmetry with shared forwarding.............. 12
4.1.4 Planned P2P symmetry..................................... 12
4.1.5 P2P Path Maintenance..................................... 12
4.2 P2MP Signaling............................................ 13
4.3 P2MP VID/ESP-MAC DA Connections........................... 13
4.3.1 Setup procedures......................................... 13
4.3.2 Maintenance Procedures................................... 13
4.4 Ethernet Label............................................ 14
4.5 OAM MEP ID and MA ID synchronization...................... 15
4.6 Protection Paths.......................................... 15
5. Error conditions............................................ 16
5.1 Invalid ESP-VID value for PBB-TE MSTI range............... 16
5.2 Invalid MAC Address....................................... 16
5.3 Invalid ERO for UPSTREAM_LABEL Object..................... 16
5.4 Invalid ERO for LABEL_SET Object ......................... 16
5.5 Switch is not ESP P2MP capable............................ 16
5.6 Invalid ESP-VID in UPSTREAM_LABEL object ................. 16
6. Deployment Scenarios........................................ 16
7. Security Considerations .................................... 16
8. IANA Considerations......................................... 17
9. References.................................................. 17
9.1 Normative References...................................... 17
9.2 Informative References.................................... 17
10. Author's Address.......................................... 18
11. Intellectual Property Statement........................... 19
12. Disclaimer of Validity.................................... 20
13. Copyright Statement....................................... 20
14. Acknowledgments........................................... 20
Appendix A..................................................... 21
Rational and mechanism for PBB_TE Ethernet Forwarding.......... 21
A 1. Overview of configuration of VID/DMAC tuples............. 23
A 2. Overview of configuration of VID port membership......... 26
A 3. OAM Aspects ............................................. 26
A 4. QOS Aspects ............................................. 27
A 5. Resiliency Aspects ...................................... 27
A 5.1. E2E Path protection.................................... 27
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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 a 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".
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 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 the 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). Appendix A summarized the rational for this data plane
technology until the IEEE specification is more mature.
2. Terminology
In addition to well understood GMPLS terms, this memo uses
terminology from IEEE 802.1 and introduces a few new terms:
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
MSTI Multiple Spanning Tree Instance
MP2MP Multipoint to multipoint
PBB Provider Backbone Bridges
PBB-TE Provider Backbone Bridges Traffic Engineering
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PIP Provider Instance Port
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
SVL Shared VLAN Learning
VID VLAN ID
VLAN Virtual LAN
2.1 PBB-TE Terminology
The PBB-TE specification has defiend some additional termminology 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 Instance (MSTI)(A set of VIDs for
PBB-TE is allocated as a set of MSTIs). An ESP is analogous to an
GMPLS LSP.
- PBB-TE Region: A set of PBB switches and PB switches by a set of
Service-VLANs allocated to provisioned Ethernet Switched Paths
(ESPs).
- PBB-TE service instance: A Point-to-Point or a Point-to-Multipoint
PBB-TE service instance.
- PBB-TE Trunk: A Point-to-Point PBB-TE service instance.
- 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
multipoint ESP plus n unidirectional point-to-point ESPs, routed
along the leaves of the multicast ESP. A P2MP GMPLS bidirectional
tree is analogous to a P2MP PBB-TE service instance.
3. GMPLS 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
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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 Backbone Customer ports as described in section
3.2. The ESP-VID (VID) typically comes from a small number of VIDs
dedicated to PBB-TE MSTI. The ESP-VID (VID) can be reused across
ESPs. There is no requirement the ESP-VID for two ESPs that for 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
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
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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 IB-Bridge. 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 interfaced 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 BMAC that defines
the MAC for the PBB-TE Service Instance. The B-Component relay adds
the ESP Header the ESP-MAC DA, ESP-MAC SA and the ESP-VID. GMPLS is
being defined here to connect CPB MACs to signal the PBB-TE service
Instance before the association of ESP-MAC DA and ESP-MAC SA 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 CPBs. TE Links are associated with PNPs. TE links are
associated with node identifiers of backbone edge bridges (BEB) and
backbone core bridges (BCB). CBPs are also associated with these node
ids. For GMPLS the node IDs are expressed as IP addresses as TE-
Router IDs. [ADDRESS]
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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
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 node. 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 4).
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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 nodes using CPB 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 node, 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:
- 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 MAY also be 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.
On the initiating and terminating nodes, 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-
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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.
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 node 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 nodes
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 node 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
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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
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 node.
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
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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
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 node, 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 node.
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)
coordination to administratively force PS switching operations such
that modifications are only ever performed on the protection path.
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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 or MMAC tree in the
forward direction (from root to leaves) and a set of P2P paths
running on identical paths from Tree to root in the reverse
direction. The result is a composite path with Multicast VID/ESP-
MMAC DA labels with a single ESP-MMAC DA in the forward direction
and a symmetric unidirectional ESP-VID/ESP-MAC DA label in the
reverse direction:
1-4) Same points as P2P paths previously specified.
5) Sets the downstream label as the Multicast VID/ESP-MMAC DA.
6) VID translation may optionally be permitted on a local basis
between two switches by a downstream switch replying with a
Multicast VID/ESP-MMAC DA other than the LABEL_SET. The upstream
switch then sets a VID translation on the port associated with the
label to allow VID translation. This flexibility allows the tree to
be constructed with out having to worry about colliding with another
tree using the same VID. (Inclusion of this point is TBD by [IEEE
802.1Qay])
4.3 P2MP VID/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 MSTI range.
The P2MP tree is constructed via incremental addition of leaves to
the tree in signaling exchange where the root is the originating
switch (as per (RFC4875). The multicast VID/ESP-MAC 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 P2MP label o
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]. The option to allow just a Multicast VID to be signaled
without a MAC (A zero MAC) is for cases where a single VID is
desired to be signaled for P2MP trees in cases where a multicast MAC
is not desired.
These domain wide labels are allocated to switches that control the
assignment of labels. There are two options for Ethernet MAC based
domain wide unique labels. One option is to allocate the ESP-MAC DAs
from globally unique addresses assigned to the either the switch
manufacturer or the owner. The other option is to use ESP-MAC DAs
out of the local admin space and ensue these labels are unique
within the domain. This local ESP-MAC DA space does not have to be
globally unique because the labels are only valid within a single
provider domain.
In the case of local label allocation there is less administrative
overhead to allocate labels. However when using configuration, a
tool would have to perform a consistency check to make sure that
labels were unique. When using GMPLS signaling it is assumed a
unique pool of labels would be assigned to each switch. The ESP-MAC
DA addresses are domain wide unique and so is the combination of ESP
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<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 it Ethernet
OAM is signaled in Ethernet packet data units.
The Maintenance end 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 MA 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, MA 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 and PROTECTION objects. Protection may be used for P2P
VID/ESP-MAC DA, P2MP VID/ESP-MAC 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.
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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 any switch along the path.
5.2 Invalid MAC Address
The MAC address is out of a reserved range that cannot be used by
then node which is processing the address. While almost all MAC
addresses are valid there are a small number of 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.
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 VID 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
This technique of GMPLS controlled Ethernet switching is applicable
to all deployment scenarios considered by the design team [CCAMP-
ETHERNET].
7. Security Considerations
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The architecture assumes that the GMPLS controlled Ethernet subnet
consists of trusted devices and that the 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.
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.
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 Draft Recommendation G.8031, 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 Draft Standard for Connectivity Fault
Management", work in progress.
[IEEE 802.1ah] "IEEE standard for Provider Backbone Bridges", work in
progress.
[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 ", work in progress.
[ADDRESS] Shimoto, K., Papneja, R., Rabbat, R., "Use of Addresses in
Generalized Multi-Protocol Label Switching (GMPLS) Networks",
work in progress.
[CCAMP-ETHERNET] Papadimitriou, D. et.al, "A Framework for
Generalized MPLS (GMPLS) Ethernet", internet draft, draft-
papadimitriou-ccamp-gmpls-ethernet-framework-00.txt, June 2005
10. 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
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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
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
11. Intellectual Property Statement
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
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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.
12. 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
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.
13. Copyright Statement
Copyright (C) The IETF Trust (2007).
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.
14. Acknowledgments
The authors would like to thank Dinesh Mohan, Nigel Bragg, Stephen
Shew and Sandra Ballarte for their contributions to this document.
Fedyk et al. Expires May 2008 [Page 20]
Appendix A
Rational and mechanism for PBB_TE Ethernet Forwarding
This appendix describes work currently being undertaken in the 801.1
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.
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 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/DMAC
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/DMAC space from
the provider VID/DMAC 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 ether
type field which allows encapsulation of different protocols
supporting various applications. More recently, the Carrier Ethernet
effort has created provider and customer separation that enables
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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 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 you get with statically configured Ethernet.
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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
(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
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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 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
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
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P2P applications and even larger when shared or multiplexed
forwarding is leveraged. In practice, most network scaling
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, discontinuities 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 IEEE802.1Q
specification.
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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 as 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 without modification of the protocols.
However currently if the VID for PBB-TE is different in each
direction some modification of the OAM may be required.
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
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
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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
802.1p 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.
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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