Docstoc

Next Generation SDH GFP and LCAS

Document Sample
Next Generation SDH GFP and LCAS Powered By Docstoc
					Viola project : LCAS tests
     A contribution to the second
     international Viola workshop
   Bonn, March 22nd and 23rd 2006

 Author :
 Paul Wagner   Deutsche Telekom, T-Com
               Headquarters Darmstadt
Viola LCAS tests : Preamble
Preamble …

The Viola network aims to investigate next generation networking – not only
„classical“ IP-Networks with increased bandwidth.

Therefore Ethernet-over-SDH (“New-SDH”) is implemented as one of the transport
technologies. One of the building blocks that are employed to modernize classical
SDH into a next generation technology is LCAS. LCAS (Link Capacity Adjustment
Scheme) complements Virtual Concatenation (VCat) and GFP (Generic Framing
Protocol) that allow New-SDH equipment to transport very efficiently Ethernet-
Frames which in turn is the layer 2 protocol used in Viola.

SDH technology is very mature but LCAS and its implementations are relatively
recent – that’s why it makes sense to investigate further its potential to help
convergence of SDH and Ethernet.
Viola LCAS tests : facts and fiction
   LCAS enables hitless bandwidth adjustment – TRUE
        The NMS may add or remove SDH-VCs to an LCAS group and thereby augmenting or
          reducing the bandwidth without interrupting service.

   LCAS automatically adds bandwidth if a path is congested – FALSE
        There is strictly no interaction between the data layer and the LCAS-protocol. LCAS reacts
          only to NMS commands and to transport layer failures.

   LCAS allows survivability (sometimes incorrectly called protection) – TRUE
        A service will not go down if one or more members fail provided that there is at least one
          working member left (in general this requires path diversity).

   LCAS is usable even in “old” SDH networks – Partly TRUE
        Only the network edge needs to support EoS functions not the core but LCAS cannot be
          added to old edge devices via software update only.

   LCAS is only slow protocol, so it should be doable in Software only – FALSE
          do to its numerous multiframes and state-machines it is impossible to realize a correctly
          working LCAS in software only -> this explains the above mentioned point.
Viola LCAS tests : outline questions ...


                                        ? ?   ?
   What is LCAS ?
                                         ? ? ? ?
       How does it work ?


           … and how should we test it ?


               Does it really work ?
Viola LCAS tests : How does LCAS work ? (1)
How does LCAS work ?               (explanations limited to LCAS applied to High Order (VC4) Virtual Concatenation, Low Order differs slightly)

... diagrams   will show the multi frame, the protocol paths and the state machines !
   Protocol is contained in the H4-Byte of the Path Overhead of the SDH Container (=member)
              Same Overhead is used for Virtual Concatenation ! (short : VCat, cf. ITU-T G.707, handles the
               differential delay compensation between members, up to ½ multiframe = 256 msecs)
              Multiframe composed of 256 times 16 Bytes carried in 1 Byte every 125 microseconds
               -> complete multiframe takes 512 msecs to be transmitted !
               Fortunately for LCAS purposes all needed information is repeated every 32x16x125µs = 64 ms
              Theoretically up to 256 members possible, in real life (Viola) 1 to 7 x VC4
              Each member contains a Multiframe -> multiple parallel protocol paths = redundancy
               (up to 7+7 paths for a single GigE in Viola)!
   Protocol works quasi-unidirectionally :
     each transmission direction has its own protocol entity (a couple of Source and Sink So/Sk) :
     It is up to the external NMS to cater for symmetrical bandwidth service if required.
              The backward communication channel needed by the protocol (for MST and RS-Ack)
               is provided by the multiframes in the opposite direction VCs – which are independent !
              Each VC (=LCAS member) has its own State-Machines (So+Sk) that means a
               maximum of 28 State-Machines for a single GigE-Service !
                   Viola LCAS tests : composition of multi frame
                                                                                        SOH
                                                                                       SOH
       Structure of a SDH signal at 2.5                                 16            SOH
                                                                                     SOH
                                                                                    SOH
                                                                                   SOH
          Gbit/s = STM16 (~OC48)                                                 SOH AU-PTR POH
                                                                                  SOH
                                                                                SOH AU-PTR POH  POH                            Payload
                                                                                                                               Payload
                                                                               SOH AU-PTR POH
                                                                              SOH AU-PTR POH
                                                                                  AU-PTR
                                                                                               POH
                                                                                                                              Payload
                                                                                                                              Payload
                                                                             SOH
                                                                            SOH  AU-PTR
                                                                           SOH AU-PTR POH
                                                                          SOH AU-PTR SOH
                                                                         SOH AU-PTR SOH
                                                                                           POH                               Payload
                                                                                                                             Payload
                                                                                                                            Payload
                                                                                                                            Payload
                                                                              AU-PTR SOH POH
                                                                             AU-PTR SOH
                                                                            AU-PTR SOH POH
                                                                           AU-PTR SOH   POH                                Payload
                                                                                                                           Payload
                                                                                                                          Payload
                                                                                                                          Payload
                                                                          AU-PTR SOH POH
                                                                        AU-PTR SOHO
                                                                               SOH
                                                                                     P
                                                                         AU-PTR SOH POH
                                                                                     POH
                                                                                    POH                                  Payload
                                                                                                                         Payload
                                                                                                                        Payload
                                                                                                                        Payload
                                                                              SOH
                                                                             SOH
                                                                            SOH H
                                                                           SOH
                                                                          SOH
                                                                         SOH


                                                   H4 byte                                                                   H4-multi frame
                   Bit 1     Bit 2   Bit 3      Bit 4   Bit 5   Bit 6    Bit 7   Bit 8   MFI1 MFI2
                                                        1st multiframe indicator MFI1                          in all VC-members path overhead (SDH-POH)
                           SQ MSB (bit 1-4)               1        1      1       0      14
                                                                                              n-1
                            SQ LSB (bit 5-8)              1        1      1       1      15
                           MFI2 MSB (bit 1-4)             0        0      0       0      0                   MST : Member Status Bits repeats every 32 MFI2
                           MFI2 MSB (bit 5-8)             0        0      0       1      1
                                CTRL                      0        0      1       0      2
2ms = 125ms x 16




                             GID ("000x")                 0        0      1       1      3
                                                                                                                                                         Me mbe r   n u mbe r
                           Reserved ("0000")              0        1      0       0      4                                       MFI2
                           Reserved ("0000")              0        1      0       1      5                                                              Bit0 Bit1   Bit2 Bit3
                                CRC-8                     0        1      1       0      6                                                               0    1       2    3
                                                                                                                   0, 32, 64, 96, 128, 160, 192, 224
                                CRC-8                     0        1      1       1      7                                                               4    5       6    7
                                                                                               n                                                         8    9      10 11
                                 MST                      1        0      0       0      8                          1, 33, 65 97, 129, 161, 193, 225
                                 MST                      1        0      0       1      9                                                              12 13        14 15
                           RS-Ack ("000x")                1        0      1       0      10                                       …                     …     …      …     …
                           Reserved ("0000")              1        1      0       0      11                                                             248 249     250 251
                                                                                                                  31, 63, 95, 127, 159, 191, 223, 255
                           Reserved ("0000")              1        1      0       1      12                                                             252 253     254 255
                           Reserved ("0000")              1        1      1       0      13
                           SQ MSB (bit 1-4)               1        1      1       1      14
                            SQ LSB (bit 5-8)              1        1      1       1      15
                           MFI2 MSB (bit 1-4)             0        0      0       0      0
                           MFI2 MSB (bit 5-8)             0        0      0       1      1    n+1      MFI1+2 values must be synchronized between all LCAS-group
                           Reserved ("0000")              0        0      1       0      2           members -> this is the synchronization of the Virtual concatenation :
                                                                                                     One must compensate any difference of transmission delay before
                                                                                                      you can reassemble one concatenated payload out of the virtual
                                                                                                                                 containers.
              Viola LCAS tests : graphical view – single member

Ethernet-over-SDH-                                                                                    Ethernet-over-SDH-
  Service-Group                                                                                         Service-Group


                                                                   Sink                    Source

                                                                                          •MFI_z
                                                                                          •SQ_p
                                                                                          •CTRL_p
                                                               •MST_a(n)                  •GID_z
                                                               •RS-Ack_a                  •CRC_y

                                                                           1 SDH-VC in
                                                                                both
                                                                  Source     directions      Sink
                                                               •MFI_a
                                                               •SQ_n
 Gigabit Ethernet PHY-




                                                                                                                                                 Gigabit Ethernet PHY-
                                                               •CTRL_n                    •MST_z(p)
   Layer IEEE 802.3




                                                                                                                                                   Layer IEEE 802.3
                                                               •GID_a                     •RS-Ack_z
                         Ethernet to GFP-F




                                                                                                                             Ethernet to GFP-F
                                                               •CRC_x
                                             N x VC4 Virtual




                                                                                                           N x VC4 Virtual
                                             Concatenation




                                                                                                           Concatenation
                           Encapsulation




                                                                                                                               Encapsulation
              Viola LCAS tests : graphical view – multiple members

Ethernet-over-SDH-                                                           Sink
                                                                                                                             Ethernet-over-SDH-
                                                                                                                           Source
  Service-Group                                                             Sink
                                                                          Sink
                                                                                                                               Service-Group
                                                                                                                          Source
                                                                                                                        •MFI_z
                                                                                                                        Source
        A                                                               Sink
                                                                                                                      •MFI_z
                                                                                                                        •SQ_p
                                                                                                                      Source         B
                                                                                                                     •MFI_z
                                                                                                                      •SQ_p
                                                                       Sink                                             •CTRL_p
                                                                                                                     Source
                                                                                                                    •MFI_z
                                                                                                                     •SQ_p
                                                                                                                      •CTRL_p
                                                                     Sink
                                                                      •MST_a(n)                                         •GID_z
                                                                                                                    Source
                                                                                                                  •MFI_z
                                                                                                                    •SQ_p
                                                                    Sink                                             •CTRL_p
                                                                                                                   Source
                                                                                                                     •GID_z
                                                                                                                 •MFI_z
                                                                    •MST_a(n)
                                                                      •RS-Ack_a                                       •CRC_y
                                                                                                                  •SQ_p
                                                                                                                   •CTRL_p
                                                                   •MST_a(n)                                        •GID_z
                                                                                                                •MFI_z
                                                                                                                     •CRC_y
                                                                                                                 •SQ_p
                                                                    •RS-Ack_a                                     •CTRL_p
                                                                                                                   •GID_z
                                                                  •MST_a(n)
                                                                   •RS-Ack_a                                        •CRC_y
                                                                                                                •SQ_p
                                                                                                                 •CTRL_p
                                                                 •MST_a(n)                                        •GID_z
                                                                                                                   •CRC_y
                                                                  •RS-Ack_a               7 SDH-VCs             •CTRL_p
                                                                                                                 •GID_z
                                                                •MST_a(n)
                                                                 •RS-Ack_a                                        •CRC_y
                                                               •MST_a(n)   Source           in both             •GID_z
                                                                                                                 •CRC_y Sink
                                                                •RS-Ack_a Source           directions           •CRC_y Sink
                                                               •RS-Ack_a
                                                                      •MFI_a
                                                                        Source
                                                                    •MFI_a
                                                                      •SQ_n
                                                                       Source
                                                                                                                          Sink
                                                                   •MFI_a
                                                                    •SQ_n                                               Sink
                                                                                                                       •MST_z(p)
                                                                      •CTRL_n
                                                                     Source
                                                                  •MFI_a                                               Sink
                                                                   •SQ_n
                                                                    •CTRL_n
                                                                    Source                                           •MST_z(p)
                                                                                                                       •RS-Ack_z
                                                                      •GID_a
                                                                 •MFI_a
                                                                  •SQ_n                                              Sink
                                                                   •CTRL_n
                                                                   Source
                                                                    •GID_a                                          •MST_z(p)
                                                                                                                     •RS-Ack_z
                                                                •MFI_a
                                                                 •SQ_n•CRC_x                                        Sink
                                                                                                                   •MST_z(p)
                                                                  •CTRL_n
                                                                   •GID_a
                                                               •MFI_a                                               •RS-Ack_z
                                                                    •CRC_x
                                                                •SQ_n
                                                                 •CTRL_n                                          •MST_z(p)
                                                                  •GID_a
                                                                   •CRC_x
                                                               •SQ_n                                               •RS-Ack_z
                                                                •CTRL_n                                          •MST_z(p)
                                                                                                                  •RS-Ack_z
 Gigabit Ethernet PHY-




                                                                                                                                                                          Gigabit Ethernet PHY-
                                                                 •GID_a
                                                                  •CRC_x                                        •MST_z(p)
                                                               •CTRL_n                                           •RS-Ack_z
   Layer IEEE 802.3




                                                                                                                                                                            Layer IEEE 802.3
                                                                •GID_a
                                                                 •CRC_x
                                                               •GID_a                                           •RS-Ack_z
                                                                •CRC_x
                         Ethernet to GFP-F




                                                                                                                                                      Ethernet to GFP-F
                                                               •CRC_x
                                             N x VC4 Virtual




                                                                                                                                    N x VC4 Virtual
                                             Concatenation




                                                                                                                                    Concatenation
                           Encapsulation




                                                                                                                                                        Encapsulation
                                                                   1 Single „LCAS-GigE-Service“ = 28 state machines
                                                                   linked by 28 communication paths carried within 14
                                                                                     multi frames
Viola LCAS tests : How does LCAS work ? (2)
How does LCAS work (2) ?


   LCAS contains provisions to be compatible with non-LCAS EoS endpoints.
   LCAS contains options that are not required for basic function :
          Hold-Off and Wait-To-Restore timers in accordance with ITU-T (G.808.1 Generic
           Protection Switching…) to alleviate the effects of short transient fault conditions or
           nested protection.
          GID-Bit (Group ID) is a pseudo-random binary sequence (PRBS15) which allows to
           identify the members originating of the same Source-Group.


          The above options should prove useful in larger SDH networks.


 An   LCAS-Implementation may decide to use explicit or implicit Add and Remove actions : one
     EoS-device will bring in service immediately any configured group-size while another will
     wait for explicit Add-commands after configuration of the LCAS group.


          We find exactly this behavioral difference between the 2 device types in Viola !
Viola LCAS tests : things to test
Only 2 out of 3 SDH equipment types in the Viola network support LCAS :
 Alcatel MCC1678
 Adva FSP1500 Release 3.1
 Siemens HiT7070 does not support LCAS (12/05)


Things to test :
 Get LCAS running : Configuring a working GigE-transmission :
      Two Nodes of the same type back-to-back -> traffic over GigE


   LCAS functions back to back : Add/Remove, survivablility to failures, tolerance to misconfiguration
        Alcatel MCC1678 with Alcatel MCC1678
        Adva FSP1500 with Adva FSP1500


Testing   against a reference test set :
          Alcatel MCC1678 with Acterna ONT50 / Anritsu MP1590B
          Adva FSP1500 with Acterna ONT50 / Anritsu MP1590B

   Interoperability between different types of equipment
         Alcatel MCC1678 with Adva FSP1500 -> traffic over GigE
Viola LCAS tests : test setup (1)
Back to back and interoperability (NEs of same / different type) :


                            GigE-Testset       Alcatel                Alcatel   GigE-Testset
                                              1678MCC                1678MCC
   Back to back with
identical device type (is
  also the case in the
     Viola network)
                                                ADVA                  ADVA
                            GigE-Testset                                        GigE-Testset
                                               FSP1500               FSP1500


 This combination was
  not considered as                            Siemens                Alcatel
LCAS wasn’t supported       GigE-Testset                                        GigE-Testset
                                               hiT7070               1678MCC
        (12/05)



                                                ADVA                  Alcatel
                            GigE-Testset                                        GigE-Testset
                                               FSP1500               1678MCC



 This combination was
  not considered as                             ADVA                 Siemens
                            GigE-Testset                                        GigE-Testset
LCAS wasn’t supported                          FSP1500               hiT7070
        (12/05)
Viola LCAS tests : test setup (2)
Single Device-Under-Test (DUT) against reference test set :


            STM-16              DUT :                            ADVA FSP1500R3.1
                               Alcatel
                              1678MCC
                                                     STM-16


                                     GEth
                                     (1000baseSX)

              EoS-Testset


                                                                               GEth
            STM-16              DUT :                                          (1000baseSX)
                                ADVA
                             FSP1500 R3.1
                                                       Anritsu
                                                       MP1590B                   or
                                                                                 Acterna ONT50




              EoS-Testset
Viola LCAS tests : tolerance to misconfiguration




Tolerance to (configuration) errors : Two ADVA NEs are connected – and traffic is correctly
transmitted – even if the number of members is configured differently and initial sequence numbering
is totally different. -> This behaviour is true also for the Alcatel NEs.
Viola LCAS tests : Adding Members to a Group
Back-to-back test ADVA with ADVA : Re-enabling
6 VC4s of the group of 7 (Modify-action via NMS
         on one side only, implicit add).

  Result : this implementation of LCAS adds all
members in parallel in less than 2 secs. The ADVA
 NEs try to work symmetrically : backward and
 forward bandwidth graphs nearly overlap (pink
                  and blue lines).



                                                     Back-to-back Alcatel with Alcatel : Activation of all 7
                                                    configured members of our LCAS group (explicit add
                                                         via an NMS action onto one endpoint only)

                                                         Result : this time LCAS adds each member
                                                     sequentially one every 3-4 secs which sums up to
                                                     some 20 secs. Also in this case the NEs keep both
                                                      directions symmectrical (cf. pink and blue lines).




                                                    Conclusion : With both vendors we can loss-lessly
                                                     add and remove members to increase/reduce the
                                                                  service‘s bandwidth.
Viola LCAS tests : Survivability to faults of members

  Back2back Alcatel with Alcatel : 7 VC4-Members,
       failure of 2 members (consecutively)

  Results: LCAS deactivates the failed members and
  the remaining group resumes working with reduced
   bandwidth. The events provoke traffic loss – this is
normal. The originating failure events and the resulting
traffic interruption are symmetrical. (We cannot infer a
  precise measurement of the interruption time of the
graph. Tests with the reference test indicate values of
                    less than 1 second)


Reestablishing the same 2 members at some 45
                seconds distance :
LCAS automatically reactivates the members and
 the available bandwidth augments as expected.
This process is again lossless (and symmetrical).



                  The results of
          ADVA with ADVA are equivalent.

                    Conclusion :
  Both systems will provide survivability to failures
          which do not affect all members.
Viola LCAS tests : Results overview
   Get LCAS running : Configuring a working GigE-transmission : OK.
(Transmission performance is not affected)


   Two Nodes of the same type back-to-back :
           Alcatel MCC1678 with Alcatel MCC1678 -> traffic OK.
           Adva FSP1500 with Adva FSP1500 -> traffic OK.
           Lossless Add and Remove members OK, Survivability is OK, tolerance to
            misconfiguration OK.


   Testing against a reference test set :
           Alcatel MCC1678 with Acterna ONT50 / Anritsu MP1590B
           Adva FSP1500 with Acterna ONT50 / Anritsu MP1590B
            -> protocol can be shown to work OK – but no further conformance testing desired.


   Interoperability between different types of equipment
           Alcatel MCC1678 with Adva FSP1500 -> traffic OK, Survivability OK, some cases of
            malfunction in special situations should be clarified later.
Viola LCAS tests : Conclusion
   What is LCAS ?
    A very useful extension to the preceding version of EoS (Ethernet over SDH with VCat).
    Makes EoS much more robust to network problems, easier to setup and diagnose
    problems.

        How does it work ?
         As you may deduce from my slides the inner function of LCAS is a quite complex
         arrangement of wheels and pipes, nuts and bolts ... but Usability from the network
         perspective is very simple !


             … and how should we test it ?
              A full protocol conformance test is far to long and complex for Viola’s
              purpose; so it was most important to get the protocol and its important
              features up and running with the Vendors NMSs.


                  Does it really work ?
                   Yes, it does ! And it is a major advancement for next generation
                   transmission networks.
The end … la fin … Ende …


      Thank you for your attention !




      ====== T===Com
                  Paul Wagner
                  Testcenter Networks


                  T-Com Headquarters
                  Ida-Rhodes Str. 3, 64295 Darmstadt
                  Phone +49 6151 83-5141
                  E-mail Paul.Wagner@t-com.net
Viola LCAS tests : appendix : state machines




Source States                                           Sink States
IDLE: Not provisioned member                            IDLE: Not provisioned member
ADD: In process of being added to the VCG               OK: Provisioned and active member
NORM: Active and provisioned member, good path          FAIL: Provisioned member but its path has failed
DNU (Do Not Use): Provisioned but its path has failed
REMOVE: In process of being removed of the VCG
Viola LCAS tests : State machine monitoring in NMS
          LCAS State Monitoring ADVA

              Group has 7 members
               Number 4 is failed


 LCAS State Monitoring Alcatel

Group has 7 members, of which 4
           are failed
Viola LCAS tests : appendix : timing diagrams
 timing diagrams to be found in
                                     Note 1               LCAS                          mem4                    mem5                    mem6(EOS)
ITU-T Recommendation G.7042                   NMS           So                               Sk                     Sk                              Sk
                                               Decrease cmnd
                                     Note 2

                                     Note 3
                                                                           CTRL=IDLE                CTRL=IDLE              CTRL=EOS
                                                                           SQ>3                     SQ>3                   SQ=3
example of a LCAS timing diagram :   Note 4

      removing 2 members             Note 5                       MST=FAIL

                                                                  MST=FAIL
                                     Note 6
                                                                  RS-Ack inverted

                                     Note 7    Decrease cmnd




                                     Note 1                                          memn-1(EOS)             mema(new)                  mema +1(new)
                                                          LCAS
                                              NMS           So                               Sk                     Sk                              Sk
                                               Add Cmnd
                                     Note 2

                                     Note 3                                                                                         CTRL=ADD
                                                                                              CTRL=ADD                               connectivity
                                                                                                                                     check
                                     Note 4                           MST=OK

                                     Note 5
                                                                                 CTRL=NORM                                          CTRL=EOS

                                     Note 6                    RS-Ack inverted
example of a LCAS timing diagram :                                                                                   connectivity
        an Add procedure                                                                                             check
                                     Note 7                           MST=OK

                                     Note 8
                                                                                                         CTRL=EOS                   CTRL=NORM

                                     Note 9                    RS-Ack inverted

				
DOCUMENT INFO