Joint ITU-T/IEEE Workshop
on The Future of Ethernet Transport
(Geneva, 28 May 2010)
802.1Qay PBB-TE Protection Switching
Overview
Panagiotis Saltsidis
Ericsson
Geneva, 28 May 2010
What is PBB-TE?
Provisioned Control
BCB
BCB
Custome
r
Network
BEB
BEB
BCB
Custome
r
Network
BCB
Provider Backbone Bridges – Traffic Engineering is the latest
development in a series of ongoing efforts to enable support for
advanced connectivity service offerings by a network of Bridges.
It corresponds to a set of functions that enable support for full
traffic engineering of paths in a bridged network.
PBB-TE disables the MSTP control plane for a subset of VLANs,
using instead either the management plane or another (possibly
external) control plane to populate filtering database table entries
of related bridges
Services in a Bridged
Network
S4
S5
S6
B-VLAN1
BEB
I-SID1
S1
S2
S3
S4
S5
S6
BEB
S9
BEB
S-VLAN1
I-SID2
S7
S1
S2
S3
BEB
S8
S4
S5
S6
BEB
I-SID3
S7
S8
TESI
S9
The main design principle is based on a building blocks model where the added
functionality is mainly confined at the external interfaces associated with a specific
service demand.
The same network is able to offer PBB-TE services (Traffic Engineered Service
Instances – TESIs), Provider Backbone Bridged services (B-VLANs) and Provider
Bridged services (S-VLANs).
Geneva, 28 May 2010
3
UNI
S1
S2
S3
I-SID1
B-VID1
I-SID2
S4
S5
S6
UNI
I-SID3
S7
TESI
S8
S9
Geneva, 28 May 2010
S-VID1
4
IEEE802.1Qay –
Summary
Enables construction of point-to-point and pointto-multipoint traffic engineered paths (TESIs) by
splitting of the VID space between distributed
spanning tree protocols and provisioned control.
Supports discard of frames with unknown
destination addresses and disables learning for BVIDs under provisioned control.
Supports the operation of Continuity Check,
Loopback, and Linktrace protocols on point-topoint and point-to-multipoint TESIs.
Supports 1:1 protection switching capable of load
sharing for point-to-point TESIs.
Provides required extension to SNMP
management by SMIv2 MIB modules
TESI Definitions
Ethernet Switched Path (ESP): A provisioned traffic
engineered unidirectional connectivity path among two or
more Customer Backbone Ports (CBPs) that extends over a
PBBN. An Ethernet Switched Path is point-to-point or pointto-multipoint.
point-to-point TE service instance: A TE service
instance supported by two point-to-point ESPs where the
ESPs’ endpoints have the same Customer Backbone Port
(CBP) MAC addresses.
point-to-multipoint TE service instance: A TE service
instance supported by a set of ESPs that comprises one
point-to-multipoint ESP from the root to n leaves plus a
point-to-point ESP from each of the leaves to the root.
802.1Qay - Protection
PBB-TE provides end-to-end linear protection for point-to-point TESIs,
where a dedicated protection point-to-point TESI is established for one
particular working point-to-point TESI, and the traffic is automatically
switched from the working TESI to the protection TESI when a failure
occurs on the working entity.
Failure is detected by the operation of the Continuity Check protocol
Switching is achieved by changing the Backbone Service Instance table BVID entries on the Customer Backbone Ports associated with the TESI
MEPs.
IEEE802.1Qay –
PS State Machines
The local protection commands and protection behavior specified by IEEE802.Qay
follow the architectural model used in ITU-T Recommendation G.8031.
The priorities associated with the various requests in IEEE802.1Qay are in general
alignment with the corresponding priorities in ITU-T G.8031 and the corresponding
state machine operation in IEEE802.Qay is in alignment to the state transition tables
in G.8031. The only differences in the state machine operation are related to the
inclusion of the MStoWorking request which is referred by protection switching
documents in ITU-T (e.g., G870) but has been dropped by G.8031 and that the
precedence of p.SF and FS are inverted since G.8031 relies on an APS protocol to be
running on the protection path.
G.8031/IEEE802.1Qay
differences
The protected entity is different.
G.8031 protection applies to point-to-point VLAN based Ethernet Subnetwork
Connections.
IEEE802.1Qay protection applies to a point-to-point TESI in a traffic engineered
region.
The protection scope is different.
G.8031 supports linear 1+1 and linear 1:1 protection switching architectures.
IEEE802.1Qay is required to support 1:1 path protection capable of load sharing.
G.8031 specifies an in-band Automatic Protection Switching (APS)
protocol, whereas signaling in IEEE802.1Qay is provided by CCM flags.
There are a few specific differences regarding the externally observable
protection switching behavior. In particular, in IEEE802.1Qay:
The Hold-off function is applied to all SF indications,
A Manual Switch request is supported to switch traffic to the working entity,
A Force Switch has precedence over an SF-P,
The receiver combines traffic from both the working and protected entities,
An SF results from any of the following defects: xconCCMdefect, errorCCMdefect,
someRMEPCCMdefect, someRDIdefect.
TE Protection Groups
and load sharing
The protection switching
mechanism is capable of load
sharing as the TE service
instances that are assigned to a
TE protection group can be reused in a number of TE protection
groups enabling a list of I-SIDs to
be distributed among a set of
interdependent TE protection
groups.
A set of interdependent TE
protection groups forms a
coordinated protection group.
Protection switching requests to
interdependent TE protection
groups must be coordinated for
an operator to manage the TESIs
in a coherent manner and to
avoid potentially competing
requests for each TESI.
Protection
Group
Working
TESI
Protection
TESI
Coordinated
PGs
PG_A
TESI_1
TESI_2
{PG_A, PG_C}
PG_B
TESI_3
TESI_4
PG_C
TESI_2
TESI_1
{PG_A, PG_C}
Backbone Service
Instance
Protection
Group
I-SID_1
PG_A
I-SID_2
No PG
I-SID_3
PG_C
I-SID_4
PG_B
I-SID_5
PG_B
Traffic Field
in the CCM flags
TESI MEPs make use of the Traffic Field in the
CCM Flags Field in order to identify traffic
misalignments on point-to-point TESIs
RDI
Traffic Field
CCM Interval
The bit is set whenever the BSI instance table
associated to the TESI MEP has an I-SID entry for
the monitored TESI
Mismatch Defects
Mismatch Defects are detected whenever
Differences in the Traffic fields of transmitted
and received CCMs
simultaneous settings of the RDI and Traffic
fields
are reported for a specified period of time
802.1Qay –
PS operation summary
IEEE802.1Qay follows the architectural model
used in ITU-T Recommendation G.8031 and the
state machine operation is similar to the state
transition tables in G.8031.
The main differences are due to the different
requirements associated with PBB-TE
TESIs are provided in a network domain that is under
the overall control of an external agent with high levels
of management/control requirements
The PBB-TE PS operation is capable of load sharing