802.1Qay PBB-TE Protection Switching Overview - ITU

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802.1Qay PBB-TE Protection Switching Overview - ITU Powered By Docstoc
					               Joint ITU-T/IEEE Workshop
           on The Future of Ethernet Transport
                          (Geneva, 28 May 2010)

802.1Qay PBB-TE Protection Switching

                       Panagiotis Saltsidis

 Geneva, 28 May 2010
                   What is PBB-TE?
                              Provisioned Control


Custome                                                    BEB    Custome
   r        BEB
Network                                                            Network


    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
                                                              S6                 B-VLAN1

        S1                       I-SID1                                              S4
       S2                                                                              S5
                     BEB                                                               S6

                                                         I-SID2                        S7

             S1                                                            BEB
     S5                    BEB

     S6                                   I-SID3
          S7                                                       TESI
    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


                                  B-VID1    I-SID2



                      S9           S-VID1

Geneva, 28 May 2010                                     4
           IEEE802.1Qay –

Enables construction of point-to-point and point-
to-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 B-
VIDs under provisioned control.
Supports the operation of Continuity Check,
Loopback, and Linktrace protocols on point-to-
point 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 point-
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 B-
VID entries on the Customer Backbone Ports associated with the TESI
                  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.

The protected entity is different.
    G.8031 protection applies to point-to-point VLAN based Ethernet Subnetwork
    IEEE802.1Qay protection applies to a point-to-point TESI in a traffic engineered

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          Protection   Working   Protection   Coordinated
sharing as the TE service             Group        TESI      TESI         PGs
instances that are assigned to a      PG_A         TESI_1    TESI_2       {PG_A, PG_C}
TE protection group can be re-
used in a number of TE protection     PG_B         TESI_3    TESI_4
groups enabling a list of I-SIDs to   PG_C         TESI_2    TESI_1       {PG_A, PG_C}
be distributed among a set of
interdependent TE protection
A set of interdependent TE
protection groups forms a                    Backbone Service    Protection
coordinated protection group.                Instance            Group
Protection switching requests to             I-SID_1             PG_A
interdependent TE protection
groups must be coordinated for               I-SID_2             No PG
an operator to manage the TESIs
in a coherent manner and to                  I-SID_3             PG_C
avoid potentially competing                  I-SID_4             PG_B
requests for each TESI.
                                             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

                   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
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

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