ethernet over sonet vcat lcas gfp

Short introduction

Ethernet over SDHVirtual Concatenation

LCASGFP

New SDH basics

Ethernet over SDH (VC, GFP, LCAS) page 2

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Ethernet through MAN/WANEthernet through MAN/WAN

- 10M/100M/1GbE- 10 GbE LAN PHY- 10 GbE WAN PHY

- 1GbE- 10 GbE LAN PHY- 10 GbE WAN PHY

- 10 GbE WAN PHY SDH

Dark Fiber

DWDM

Something is going on in OTN

Something is going on in SDH

In case there is a dark fibre or an optical channel in a DWDM system available the most practical way to transmit Ethernet is by using the LAN interface. LAN interfaces are offering a 4% bigger capacity instead of WAN interfaces. The disadvantage is: LAN does not offer the same possibilities in monitoring the quality of the signal as the WAN does. But in the LAN we can use the full monitoring functionality of SDH. DWDM-technology (without OTH) has similar functionalities, but it has to be ensured that the transponder in front of the DWDM-multiplexer can handle signals without SDH structure.

Info to 10GbE: 10GbE WAN PHY is able to use the SDH-functionality regarding Line and Path-Monitoring. 10GbE LAN PHY offers 4 % more capacity. However 10 GbE offers within the description of the MDIO for LAN PHY a register, which contains information regarding the BER of the RX-links. The register will be set if the PCS has identified a BER |>10E-4.

MDIO: Management Date Input/Output InterfacePCS: Physical Coding SublayerOTN: Optical Transport NetworkOTH: Optical Transport Hierarchy


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Ethernet - SDHEthernet - SDH

Access Backboneconversion

Ethernet SDH

GFP

GFP

L2 S

witc

hVL

AN

Stor

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For

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rnet

Inte

rfac

es

Virt

ual

Con

cate

natio

n

LCA

S

SDH

MU

X/D

MU

X

Ethe

rnet

Inte

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GFP

Virt

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This picture shows which additional features are necessary in order to get Ethernet packets and Ethernet specific switching mechanism (Transparent Switching, VLAN) over a SDH network.

Ethernet Interfaces: Access interface for „Native“ Ethernet-Client signals.Store & Forward: The received asynchronous Ethernet-Packets are buffered before further processing.L2 Switching: This function is necessary, if additional switching on Ethernet-address-layer within the SDH-network (or over the whole SDH network) is necessary. VLAN: This functionality is necessary, if the Ethernet (layer 2) carried over the SDH network, is further organized in logical separated Ethernets.GFP: Adapt the asynchronous received Ethernet packets to the fixed bit rate of a SDH

channel. Virtual Concatenation: This function allows to connect single VCn to a virtual bigger SDH channel.LCAS: Activate and deactivate single VCn within a VCG. Protocol running in between two

SDH multiplexer to adjust the capacity (VCn) according the requested bandwidth of the Ethernet Client signal.

VLAN: Virtual Local Area Network GFP: Generic Framing ProcedureVC: Virtual Container VCG: Virtual Container GroupLCAS: Link Capacity Adjustment Scheme

SDH goes future

Virtual ConcatenationLink Capacity Adjustment Scheme


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SDH - Virtual ConcatenatingSDH - Virtual Concatenating

Where to go with 10 MBit Ethernet?Why not

5 x VC-12?VC Type VC Bandwidth VC PayloadVC-11 1664 kbit/s 1600 kbit/sVC-12 2240 kbit/s 2176 kbit/sVC-2 6848 kbit/s 6784 kbit/sVC-3 48 960 kbit/s 48 384 kbit/sVC-4 150 336 kbit/s 149 760 kbit/s

VC-4-4c 601 344 kbit/s 599 040 kbit/sVC-4-16c 2 405 376 kbit/s 2 396 160 kbit/sVC-4-64c 9 621 504 kbit/s 9 584 640 kbit/s

VC-4-256c 38 486 016 kbit/s 38 338 560 kbit/s

sensible?10 Mbit/s

VC-12 2240 kbit/s 2176 kbit/s

VC-xc: Virtuell ContainerVC-12-5c: Contiguous concatenation of 5 VC-12 container


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AU-4 pointer

MSOH

RSOH

VC-4-4c

J1

C2G1F2H4F3K3N1

C-4-4c

4 x 9 bytes 4 x 261 bytes

4 x 261 bytes

ATM-cell

B3

Fixe

d st

uffin

g by

tes

The first pointer indicates the beginning of the container areaThe payload is now connected together

STM-4, VC-4 Contiguous ConcatenationSTM-4, VC-4 Contiguous Concatenation


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AU-4 pointer

MSOH

RSOH

VC-4-4v

C2

H4F3K3N1

C-4-4v

4 x 9 bytes 4 x 261 bytes

4 x 261 bytes

ATM-cellAll VC-4 are carried individual through the networkto their destination. There the payload will be connectedTogether, controlled by H4 byte. All VC-4 pointers are active.

C2

F3K3N1

H4

C2

H4F3K3N1

C2

H4F3K3N1

F2 F2 F2 F2

J1 J1 J1 J1B3 B3 B3 B3

G1 G1 G1 G1

STM-4, VC-4 Virtual ConcatenationSTM-4, VC-4 Virtual Concatenation


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SDH - Virtual ConcatenatingSDH - Virtual Concatenating

C-12-5cC-12-12cC-12-46c

C-3-2cC-3-4cC-3-8cC-4-6cC-4-7c

SDH

92%98%

100%100%100%100%89%95%

C-4-64c 100%

EthernetATM

ESCON

Fibre Channel

Fast Ethernet

Gigabit Ethernet

data

10 Mbit/s25 Mbit/s

200 Mbit/s400 Mbit/s800 Mbit/s

100 Mbit/s

1 Gbit/s10 Gb Ethernet 10 Gbit/s

efficiency

VC-xc: Virtuell ContainerVC-12-5c: Contiguous concatenation von 5 VC 12 Containern


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Next step LCASNext step LCAS

capacity:5 x VC-12

1. Define VC-Xc group (VCG) over network management.

networkmanagement

LCAS

2. Activate the single VC-Xv over LCAS; this allows risingcapacity hitless

clientsignal

DMU DMU

VC-12 (1-1-9)VC-12 (1-1-8)VC-12 (1-1-5)VC-12 (1-1-2)VC-12 (1-1-1)

LCASVC-12-5c

Virtual Concatenation allows a more flexible scalable of the transport capacity on SDH- or OTH-links. However, as long as such links have to be establish per hand, the concept is not usable for the demands of a new multimedia network. An additional demand is to switch the scaleable links within a dynamic process. However switching the links should be only visible for the customer in an increase of the bandwidth and as well it should not generate bit errors. LCAS describes the mechanism of hitless switching SDH-channels as well as OTH-paths. The NM has the task to control the generation of VCG and as well the switching of the VCG by utilizing LCAS. NM can be realized as a kind of central controlled management (Overlay Model) or can be based on GMPLS (Peer Model).

LCAS: Link Capacity Adjustment Scheme (G.7042)VC: Virtual ContainerVCG: Virtual Concatenation GroupSDH: Synchronous Digital HierarchyOTH: Optical Transport HierarchyGMPLS: Generalized Multiprotocol Label SwitchingNM: Network Management


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LCAS in SDHLCAS in SDH

LCAS information will be curried within:

H4-byte of the Higher Order Path Overheadused for Virtual Concatination of VC-n-Xv (n = 3, 4)

VirtuallyConcat.VC-m-XvVC-n-Xv

So

VirtuallyConcat.VC-m-XvVC-n-Xv

Skdirection of data signal

LCAS info

LCAS info

K4-byte of the Lower Order Path Overheadused for Virtual Concatenation of VC-m-Xv (m = 11,12, 2)

LCAS enables to activate and deactivate single VCn within a VCG. Therefore both ends of a SDH-path have to exchange control information. In SDH Higher Order Path the H4-byte and in SDH Low Order Path K4 byte is used for this information exchange.LCAS works unidirectional.Within bi-directional connections two separate LCAS functions (in each direction one) are necessary.

So: SourceSk: Sink


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LCAS example Higher Order LCAS example Higher Order

VirtuallyConcat.

VC-n-Xv

So

VirtuallyConcat.

VC-n-Xv

Sk

LCAS InfoH4

H4

H4

H4

LCAS Info

LCAS Info

LCAS Info

J1J1B3B3C2C2G1G1F2F2H4H4F3F3K3K3N1N1

H4

LCAS information will be transmitted within their VCG in parallel. Each H4 byte covers the general and specific information.

So: SourceSk: SinkVCG: Virtual Channel Group


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Differential DelayDifferential Delay

1

1

VC-n-2v

Differential delay time

n

n

n

n

VC-n-2v

tDifferential Delay

If the routing of the signal through the network for each VCn is the same, every container arrives at the same time at it‘s destination. But what will happen if the routing is different? Caused by different lengths, a delay between the different VCn of one VCG will arise (Differential Delay). It is necessary to rebuilt the signal at the sink as it was sent at the source. Therefore an additional indication has to be added to the signal to allows the sink to detect which VCn belong to the same VCG and compensate the Differential Delay.


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Higher Order Path H4: MFI1/MFI2Higher Order Path H4: MFI1/MFI2

MFI2 (8)0

1

2The complete

multiframe has 4096 steps.Target for delay

compensation of 512ms

012

4095

255

01

15

MFI1 (4)

01

150

The MFI1 and MFI2 together define a two-dimensional multiframe-structure. After a complete loop of the MFI1 (4 bit = 16 steps) the value of MFI2 will be incremented by one. MFI2 consists of one byte (256 steps). 16 multiplied by 256 = 4096 steps. Each frame has a periodical time of 125ms. 4096 x 125us = 512 ms. Based on the multiframe- structure a Differential Delay up to 512ms in between the VCn can be detected.

MFI: MultiFrame Indicator


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Differential Delay CompensationDifferential Delay Compensation

1

1

VC-m-2v

1

buffer

differential delay timen

n1

2

1

2

3

2 1

1

2

2

4 3

1

13 2

2

2

3

5 4 VC-m-2v

The MFI values allows the sink to identify which VCn belong to the same VCG. Additionally the values can be taken to identify and compensate the Differential Delay.Therefore VCn with low Differential Delay will be buffered until the corresponding VCn with longer Differential Delay will arrive at the sink. The example shows a two time longer Differential Delay of the blue line against the red line (2 x 125µs).


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VC-n-Xv H4 coding (1)VC-n-Xv H4 coding (1)

MSTMST

RS-AckReservedReservedReserved

SQ MSBs (bits 1-4)SQ LSBs (bits 5-8)

MFI2 MSBs (bits 1-4)MFI2 MSBs (bits 5-8)

CTRLGID

ReservedReserved

CRC-8CRC-8

bit1 bit2 bit3 bit41 0 0 01 0 0 11 0 1 01 0 1 11 1 0 01 1 0 11 1 1 01 1 1 10 0 0 00 0 0 10 0 1 00 0 1 10 1 0 00 1 0 10 1 1 00 1 1 1

bit5 bit6 bit7 bit8

H4 byteMFI1

MSTMST

RS-Ack


MFI2 MSBs (bits 1-4)MFI2 LSBs (bits 5-8)

GID

Down-stream

Upstream

1 0 0 01 0 0 11 0 1 01 0 1 11 1 0 01 1 0 11 1 1 01 1 1 10 0 0 00 0 0 10 0 1 00 0 1 10 1 0 00 1 0 10 1 1 00 1 1 1

CTRL

MFI1/2: Every member of a VCG have the same MFI values. SQ: Each VCn has according to his position within the VCG a fixed Sequence Indicater.MST: Indicates the status of each VCn within a VC-n-Xv. For each VCn one bit is used.GID: Every VCn of a VCG gets within the same MFI frame the same GID-value. This allows the sink to identify that every received VCn has been transmitted from the same source. RSA (RS-Ack): Will be used to indicate from sink to source each changeing (increase or decrease) of the sequence.CRTL: Covers the commands for activating or deactivating of VCn

VCG = VC-n-Xv Member = VC-n MFI: MultiFrame Indicator CTRL: LCAS Control WordsGID: Group Identifier CRC8: LCAS Cyclic Redundancy CheckMST: LCAS Member Status Field LCAS: Link Capacity Adjustment SchemeRSA (RS-Ack): Re-Sequence Acknow. SQ: Sequence IndicatorRES: Reserved for future international standardizationSo: Source Sk: Sink


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VC-n-Xv H4 coding (2)VC-n-Xv H4 coding (2)

MFI2 frame number member number0 1 2 30, 32, 64, 96, 128, 160, 192, 2244 5 6 7

member statusmultiframe

8 9 10 111, 33, 65, 97, 129, 161, 193, 22512 13 14 15

240 241 242 24330, 62, 94, 126, 158, 190, 222, 254244 245 246 247248 249 250 25131, 63, 95, 127, 159, 191, 223, 255252 253 254 256

0 1 2 34

n MST bit activated

MST: Indicates the status of each VCn within a VC-n-Xv. For each VCn one bit is used.It is possible to concatenate up to 256 VCn within one VCG. Per MFI2 multiframe the status of 8VCn will be transmitted (from sink to source).

MST: LCAS Member Status Field


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VC-m-Xv K4 coding (1)VC-m-Xv K4 coding (1)

V5V5J2J2N2N2K4K4K4

MSTbit1 bit2 bit3 bit4

R R x xbit5 bit6 bit7 bit8

APS

Lower Order Virtual Conc. Extended Signal Label1 32 321

1

4

Different to the H4-byte (Higher Order Path) which can be fully used for LCAS, for Lower Order Path not the complete byte is available .There are 4 bytes which are transmitted in a multiframe structure of which the K4 byte is the fourth.V5 is used for Parity checkJ2 is used for Path traceN2 is used for TCM (Tandem Connection Monitoring)K4 is used half for Automatic Protection Switching (APS)The only possibility is to use the other half of K4 Of that other half only bit 7 and bit 8 are defined for LCAS. This means, an additionalmultiframe is necessary to handle all the needs of LCAS (multiframe within multiframe).Lower order Virtual Concatenated and Extended Signal Label are now generating the necessary 32 bit multiframe. A complete Lower Order Virtual Concatenated Multiframe takes some time to be completely transmitted:

125µs (SDH –frame) x 4 (V5,J2,N2,K4- multiframe) = 500µs500µs x 32 bit-multiframe = 16ms

16ms for transmission.The same is valid for the Extended Signal Label Multiframe


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MFAS0111 0000 110

Reserved

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32K4 byte; bit 8 shown as 32 bit multiframe

Extended SignalLabel

0

Lower Order Extended Signal Label Multiframe

First, before we have access to the LCAS important Lower Order Virtual Concatenated Multiframe the receiver has to synchronize on the Extended Signal Label Multiframe which contains the Multi Frame Alignment Signal (MFAS).


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FrameCount

MFI

SequenceIndicator

SQCTRL

GID

RSA

MemberStatusMST

CRC-3

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32K4 byte; bit 7 shown as 32 bit multiframe

Res.

VirtuallyConcat.VC-m-Xv

So

VirtuallyConcat.VC-m-Xv

Sk

LCAS info

LCAS info

Lower Order Virtual Concatinated Multiframe

How can the same 512ms for detecting the maximum Differential Delay on VC-12 be realized?

125µs (SDH-frame) x 4 (V5,J2,N2,K4- multiframe) = 500µs500µs x 32 bit-multiframe = 16ms32 steps (MFI)32 (MFI) x 16ms = 512ms

MFI: Every member of a VCG have the same MFI values. SQ: Each VCn has according his position within the VCG a fixed Sequence Indicator.MST: indicates the status of each VCn within a VC-n-Xv. For each VCn one bit is used.GID: Every VCn of a VCG gets within the same MFI frame the same GID-value. This allows the sink to identify that every received VCn has been transmitted from the same source. RSA (RS-Ack): Will be used to indicate from sink to source each changing (increase or decrease) of the sequence.CRTL: covers the commands for activating or deactivating of VCn.

VCG = VC-n-Xv Member = VC-mMFI: MultiFrame Indicator CTRL: LCAS Control WordsGID: Group Identifier CRC3: LCAS Cyclic Redundancy CheckMST: LCAS Member Status Field LCAS: Link Capacity Adjustment SchemeRSA (RS-Ack): Re-Sequence Acknow. SQ: Sequence IndicatorRES: Reserved for future international standardizationSo: Source Sk: Sink


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Member NumberFrame Number0 1 2 3 4 5 6 70, 8, 16, 248 9 10 11 12 13 14 151, 9, 17, 25

16 17 18 19 20 21 22 232, 10, 18, 2624 25 26 27 28 29 30 313, 11, 19, 2732 33 34 35 36 37 38 394, 12, 20, 2840 41 42 43 44 45 46 475, 13, 21, 2948 49 50 51 52 53 54 556, 14, 22, 3056 57 58 59 60 61 62 NA7, 15, 23, 31

memberstatus

multiframe

0 1 2 3 4

MST: Indicates the status of each VC-m within a VC-m-Xv. For each VCm one bit is used.It is possible to concatenate up to 63 VCm within one VCG. Per MFI multiframe the status of 8 VCm will be transmitted (from sink to source).

MST: LCAS Member Status Field


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LCAS Protocol ArchitectureLCAS Protocol Architecture

VirtuallyConcat.VCn-Xv

VirtuallyConcat.VCn-Xv

transmission from left to right

MFI: Multiframe IndicatorSQ: Sequence IndicatorGID: Group Identification

vorward direction

MST: Member StatusRS-Ack: Re-Sequence Acknowledge

backward direction

protocol andparameter:

CTRL: Control

So SkVCG Members VCG

The picture shows the elements of a complete LCAS connection. Each LCAS connection is always unidirectional. To establish a bi-directional virtual link a LCAS process in both directions is necessary. A VCG consists of minimum one up to X (X: VC-3/4 256; VC-12 63)VCs. Each VC is a member of the VCG. LCAS is responsible for hitless switching of each member.

VCG: Virtual Concatenation GroupSo: SourceSk: Sink


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CRTL CommandCRTL Command

ReservedReservedReserved


MFI2 MSBs (bits 1-4)MFI2 MSBs (bits 5-8)

CTRLGID

CTRL

comm.value commentWeist darauf hin, , das dieses Ende eine feste

Bandbreite verwendet (non-LCAS mode)ADD0001 Ein Mitglied (OPUk) einer VCG hinzugefügen

NORM0010 Normale Übertragung (Aktiver Zustand) EOS0011 Wie NORM, nur letztes Mitglied der VCG IDLE0101 Kein VCG Mitglied oder soll deaktiviert werden DNU1111 Do Not Use (the payload) Sk meldet FAIL Status

FIXED0000

ADD0001 Add a new member (VCn) to VCGNORM0010 Normal transmission (active state) EOS0011 Same as NORM, only the last member of VCG IDLE0101 No VCG member or has to be deactivatedDNU1111 Do Not Use (the payload) Sk reports FAIL Status

Indicates that a fixed bandwidth is used(non-LCAS mode)

FIXED0000

CTRL commands are responsible first to add or release VCs to a VCG and second to activate or deactivate its payload. How much VCs belongs to a VCG is already predefined due to the Network Management. LCAS is only the „operator“ who adds or releases VCs to VCG. Nothing happens without the NM who has to allow e.g adding a VC. This is a fundamental aspect. You can imagine what will happen if LCAS adds a new VC to VCG and activates its payload but the NM has not established the link though the network itself.

Signalling in between the NM and the network element can be done either by RSVP-TE or CR-LDP.

NM: Network ManagementEOS: End of SequenceDNU: Do not useRSVP-TE: Resource Reservation Protocol - Traffic EngineeringCR-LDP: Constrained Based -Label Distribution Protocol


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Member to VCG

Add and Release MemberAdd and Release Member

Payload of a member to VCG-Payload

Payload of a member from VCG-PayloadMember from VCG

Release of a member temporary from VCGRelease Payload of a member temporary from VCG-Payload

Member SQ = 1Member SQ = 2Member SQ = 3

Add

Release:

Trouble mode:

Member SQ = 4Member SQ = n

LCAS LCAS

All togheter six LCAS proceedings are possible. These are listed above.

Adding a member to a VCG means ,his channel (VC) relates to the VCG.Till now the payload is not activated. This will happen in an additional step.

This is different for the release of VCs.First the member will be released from the VCG. In the second step the payload will be deactivated. The order to add or release a VC member and its corresponding payload will be always controlled by a Network Management Process. LCAS is only responsible for hitless switching. Has an error occurred and therefore the VC member has to be released, this can be done by LCAS but only temporarily.After fixing the error the member will be added again to the VCG by LCAS.

SQ: Sequence IndicatorVCG: Virtual Concatenation Group


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Add a new MemberAdd a new Member

SQ = 2 EOS MST = Okay

SQ = 1 NORM MST = OkaySQ = 2 EOS MST = OkaySQ = 3 ADD MST = Okay

SQ = 1 NORM MST = OkaySQ = 2 NORM MST = OkaySQ = 3 EOS MST = Okay

Phase 1:VCG with two membersand active Payload

Phase 2:Add of a new memberto VCGPayload is not active atThat time

Phase 3:Activation of the Payload

So SkSQ = 1 NORM MST = Okay

Phase 1: The VCG consists of two members. The CTRL-values NORM and EOS with their corresponding Okay (MST) indicates an error free and active operation. Phase 2: An additional member has to be added to the existing two members of the VCG. LCAS set as CTRL command „ADD“ within the VC who has to be added to the VCG. This will be done as long as in the backward direction the corresponding „Okay“ (MST) will be received. Now the Channel (VC) is part of the VCG. Remember, the payload of this channel is still inactive. 3. Phase: With the changing status from „ADD“ to „NORM“ or „EOS“ the source is now signalling the activation of the payload itself. Due to the fact that SQ=3 is now the last member of the VCG, SQ=2 changes it‘s value from „EOS“ to „NORM“ and SQ=3 is starting to transmit payload with „EOS“.

Frame = n CTRL = ADD (Payload without data)Frame = n+1 CTRL = EOS (Payload without data)Frame = n+2 CTRL = EOS (Payload with data)


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Relaese of a MemberRelaese of a Member

SQ = 1 NORM MST = OkaySQ = 2 EOS MST = OkaySQ = 3 IDLE MST = FAIL

SQ = 1 NORM MST = OkaySQ = 2 NORM MST = OkaySQ = 3 EOS MST = Okay

Phase 1:VCG with 3 Membersand active Payload

Phase 2:Release of a Member From the VCGVC n = 0Payload is still active

Phase 3:VC n = 1Payload is now inactive

SQ = 1 NORM MST = OkaySQ = 2 EOS MST = Okay

IDLE MST = FAIL

So Sk

Phase 1: The VCG consists of three members. The CTRL-values NORM and EOS with their corresponding Okay (MST) indicates an error free and active operation. Phase 2: Now the member wit SQ=3 should be released. LCAS will indicated this by changing the value from „EOS“ to „IDLE“. This will be acknowledged from the sink by exchanging „Okay“ with „FAIL“ in the corresponding MST. Now, this channel (VC) is now longer a member of the VCG. The payload within the VC who has sent the first time „IDLE“ is still active. With the next following frame the payload is already inactive. Phase 3: Only SQ=1 and SQ=2 are now active members of the VCG

Frame = n CTRL = NORM or EOS (Payload with data)Frame = n+1 CTRL = IDLE (Payload without data)Frame = n+2 CTRL = IDLE (Payload without data)


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1. VC-122. VC-123. VC-124. VC-12

t1 2 3 4

8

246

Mbit

t1 2 3 4

LCAS VariationLCAS Variation

Stor

e &

Forw

ard

GFP

10 Mbit/sEthernet

LCAS LCAS

SDH

MU

X

SDH

MU

X

STM-4

ControlControl

SDH-VC-CapacityEthernet

The left diagram shows the load of a 10MB Ethernet interface. The right diagram shows additionally the capacity of SDH containers. Timestamp 1: The Ethernet load has achieved a value which causes the switching an additional VC-12. In between realising the need of an additional VC-12 and the final switching it takes a certain time. At timestamp 1, the increasing bandwidth is almost flat so that the second VC-12 is right in time available. The complete Ethernet signal can be transmitted without any restrictions. At timestamp 2, the increasing bandwidth is more steep. The third VC-12 is available too late. Therefore a restriction in the Ethernet traffic occurs. This restriction does not mean losing data in every case. The function „Store & Forward“ has addressable memory to buffer Ethernet packets. As soon as the third VC-12 is available, the buffered Ethernet frames will be transmitted with the higher capacity.

GFP - Generic Framing Procedure


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GFP

Classify of GFPClassify of GFP

Ethernet IP/PPP Other Bearer Services

GFP Client Specific Aspects

GFP Common Aspects

SONET/SDH Path OTN ODUk Path

Asynchrone Packages

Synchronous Path

Adaptation

GFP describes the technology, mapping different sizes of packets in to a serial transmitted container (SDH/OTH). Frame diversion will be done like it is at ATM by realising the cell-header. Due to the fact that packets can have different sizes the GFP-header covers an additional length indication for its encapsulated packet. The receiver knows now where to find the next following GFP-header within the serial stream. Are there no user packets to transmit, idle frames (4 byte) will be added to the signal by GFP.

IP: Internet ProtocolPPP: Point.to-Point ProtocolGFP: Generich Framing ProcedureOTN: Optical Transport NetworkODU: Optical Channel Data Unit


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GFP MappingGFP Mapping

ID Ethernet Frame IDLEs Eth Frame IDLEs E Frame1 GbE

GFP-F GFP GFP

Transparent Payload GFPTransparent Payload GFPP

GFP GFP GFPFP

GFP-T

GFP defines two different Mapping modes:Transparent GFP: Das Client Signal will be transparent mapped into a (GFP-T) GFP-Frame with constant size.Frame-Mapped GFP: Die Client Packages will be mapped 1:1 into(GFP-F) a GFP-Frame.

E FrameEth FrameEthernet Frame

Frame by Frame

Block by Block

GFP defines two different types of mapping client signals into a transport channel.

Frame-Mapped GFP: Each packet of a packet oriented client signal will be directly mapped into a GFP-frame. Therefore GFP-frames have different sizes.

Transparent GFP: Independent of the packet structure, the client signal will be mapped transparent in to a transport channel. Attention: Within the picture, the relation in between transparent payload and GFP-header is not displayed in scale.You could think that the clock rate of the transparent GFP-frame in not enough for a transparent transmission of all client signal data. This is not the case.


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GFP-F Mapper

Constant Transport Rate

Frame Mapped GFPFrame Mapped GFP

Variable Traffic

GFP adapt it Clients Variable Traffic towards the ConstantTransport RateAdvantage: Interface Rate Client Signal >> or << as Transport RateNecessary: Store & Forward FunctionDisadvantage: Generates Delay

IDLEConstant Interface Rate

At Frame-Mapped GFP the interface rate of the client signal can be bigger or smaller in size as the transport rate of the transmission channel. With the help of the Store & Forward function, the bit rates of the client signal and the transport channel will be decoupled. Disadvantage: With the Store & Forward function an additional delay of the user data will be generated.


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Ethernet per GFP into SDHEthernet per GFP into SDH

SOH

Transport capacity

PayloadPOH GFP GFP GFP

GFP

GFPGFPGFPGFPGFPGFPGFP

GFP Ethernet Frame

Ethernet Frame

Ethernet Frame

Ethernet FrameGFP Ethernet Frame

The picture shows the way how GFP-IP packets (client signal) will be mapped in to the payload area of a STM-1 frame. In case of missing packets from the IP-layer, GFP fills the gaps automatically with GFP-IDLE-frames. A GFP-IDLE-frame consists only of 4 header-bytes.

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GFP: Generic Framing Procedure


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Constant data streamwith variable traffic Constant Transport Rate

GFP-T Mapper

Transparent GFPTransparent GFP

GFP is mapping the complete Client Signal transparentinto the Transport SignalAdvantage: Very low delayNecessary: Transport Rate >= Client Signal Rate

Mapper

e.g.: 1 GbE e.g.: VC-4-7c

Due to the fact that in Transparent GFP the complete data stream of the client signal (data and control characters) will be mapped in to a transport channel, it is necessary that the rate of the transport channel corresponds or even better is above the bitrate of the client signal. The GFP Mapper itself has a buffer inside.Client signals for Transparent GFP: 1GbE, Fiber Channel, ESCON and FICON

1GbE: 1 Gigabit EthernetESCON: Enterprise Systems ConnectionFICON: Fiber ConnectionVC-4-7c: A transport channel within SDH consisting of 7 concatinaled VC-4


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ID Ethernet Frame IDLEs Eth Frame IDLEs E Frame

Transparent GFP for 1GbETransparent GFP for 1GbE

1. Decoding: 1 GbE GFPData Codes Data Bytes (8 Bit)Control Codes Control Character (4 Bit)

2. 64B/65B Block Code

3. Superblock: 8 x Block Code + CRC

L1

Octets512

Block Code 8L

8B/10B Codewords

L8

CRC16

Block Code 1L Block Code 2L

8 8 8 8 8 8 88C1 D2 D3 D4 D5 D6 D7 D8

1. Decoding: Ethernet is 8B/10B coded. GFP decodes from the 10bit data codes the original data bytes. The 10 bit control code will be transformed into a 4 bit control character. With the 4 bits possible 16 coding modes are enough because GbE only has the need of 12 special GbE control codes. 2. 64B/65B Block Code: The data bytes and control characters will be added together to a block of 8 bytes. The 4 bit control characters will be added together with 4 additional bits to one byte. The additional 4 bits are used to allocate the position of the control characters. Within the block code all control characters (C1) will be placed independently of its former position at the beginning of the block. To each block code a Leading Flag (L) will be added. It identifies if the block code consists of one or more control characters. 3. Superblock: To get from the consisting 65 bit block codes an octet-structure, 8 block codes will be added together to one Superblock. The L-Flags of all 8 block codes will be transmitted behind the last block code byte as one byte. For error detection an additional 2 byte CRC-checksum will be added to the signal.

CRC: Cyclic Redundancy Check 8B/10B: 8 bits (1 byte) will be after recoding 10 bits (codeword)


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Transparent GFP for 1GbE (2)Transparent GFP for 1GbE (2)

Octets512

L CRC8 16

Superblock 1 Superblock 2 Superblock N

GFP8x8

GFP Frame with constant sizeN x ((65 x 8) + 16) + (8 x 8)

N = minimum 95 (for 1 GbE)

Octets

ITU-T G.7041 recommends that a minimum of 95 Superblocks should be added together to one GFP-frame. This allows a good adaptation in between client signal and transport signal rate.


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GFP-T Mapper

Transparent GFP Rate adaptationTransparent GFP Rate adaptation

Buffer Decoding/Coding

TransparentGFP-Frames

65B-Pad

8B/10B1 GbE signal

Client Signal Rate = 100 Transport Channel Rate = 100+

GFP-T Mapper has to support a possible clock offset of the Client Signal from +/- 100 till +/- 200 ppm.

Due to the fact that in Transparent GFP the complete data stream of the client signal (data and control characters) will be mapped into a transport channel, it is necessary that the rate of the transport channel correspond or even better is above the bit rate of the client signal. This moves the GFP-entrance-buffer continuously into a underflow-mode. Is at the exit of the mapper currently a transparent GFP-frame in work, the mapper adds a 65B-pad.


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GFP frame: 4 - 65599 bytes

Paketseperation: Header Error Control method (GFP) Paketseperation: Header Error Control method (GFP)

1 2 0 - 65535 bytes

1010111000101101100101011010010110010010001111101010101110001011011001010110100

Example GFP: packet based, payload = variable size 0 - 65535 bytes

HEC

HECHEC

Frame border

analyse packet length

„comparator“

GFP describes the technology mapping different sizes of packets into a serial transmission container (SDH/OTH). Frame diversion will be done like it is at ATM by realising the cell-header. Due to the fact that packets can have different sizes the GFP-header covers an additional length indication for its encapsulated packet. The receiver knows now where to find the next following GFP-header within the serial stream. Are there no user packets to transmit, idle frames (4 byte) will be added to the signal by GFP. GFP-synchronizing knows three different modes: HUNT, PRESYNCH and SYNCH. Within the HUNT-mode the receiver is searching for a valid header. Once he finds a valid header he changes his mode in to PRESYNCH-status. In case he has found then afterwards in DELTA+1 also a valid header he will change again his mode into SYNCH-status. With the help of the HEC-algoritm GFP is able to correct one bit error within the GFP-header. Are there more than one bit errors detected within the GFP-header, GFP changes iststate to HUNT.

GFP: Generic Framing ProcedureHEC: Header Error Control modePoS: Packet over Sonet


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GFP Frame FormatGFP Frame Format

Payload Area

Core Header

1234

1 8bits

65535

bytes

PLIPLI

cHECcHEC

Payload Header 4 - 64

Payload FCS(optional)

4

Payload 0 - 65531

A GFP-frame consists of a core-header an a payload-area. The core-header itself consists of 4 bytes. PLI: The first two bytes indicates the length of the full GFP-frame. The minimum length of a single GFP-frame is 4 bytes. The PLI-values 0-3 are reserved for GFP-control-frames. At the moment only the control-frame with the PLI-value = 0 is defined. An IDLE-frame is always 4 bytes long. cHEC: The bytes 3 and 4 carry the value of HEC over the first two PLI-bytes.

The payload-area itself is divided into three parts. The Payload Header is used for transmitting data link management procedures corresponding to the higher layer client signals. The Payload contains the client signal (data gram).Payload FCS: (optional) A FCS (inclusive Payload Header) can be calculated and added to the signal.

PLI: PDU Length Indicator (PDU: Protocol Data Unit)cHEC: Core HEC (HEC: Header Error Check)FCS: Frame Check Sequence


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PLIPLI

cHECcHEC

Payload

Payload Header

Payload FCS(optional)

Payload Header

Type

GFP Payload HeaderGFP Payload Header

Typ 2tHEC 2

Extension 0 - 60

eHEC 2

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16PTI PFI EXI UPI

Extension HeadersAlready defined

Null Extention HeaderLinear Frame Ring Frame

type

Possible Extension Headers forcorresponding Data Link Headers

Virtual Link IdentifiersSource/Destination AddressPort NumbersService ClassesExtended HEC

The GFP-Payload Header describes the content of the following data within the Payload area.

Type: Indicate the content and format of the Payload PTI: Payload Type Identifier (Coding like table below.)PFI: Payload FCS Indicator ( indicate if a FCS is added to the Payload).EXI: Extension Header Identifier UPI: User Payload Identifier (Under further study)tHEC: Header Error Check value Extension: For further description and support of the Data Link HeaderseHEC: Header Error Check value for the Extension

PTI = 000 Client DataPTI = 100 Client ManagementRest Reserved


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TyptHEC

Extension

eHEC

Extension

Extension Header Point-to-PointExtension Header Point-to-Point

TypeTypetHECtHEC

Null Extention Linear Frame

ExtentionSpar

TypeTypetHECtHECCID

eHEC

ExtentionSpar

TypeTypetHECtHEC

DP SP

eHECITU-T ANSI

one Client Signal perTransport Path (SDH-Channel)

more Client Signals perTransport Path (SDH-Channel)

Null Extension Header is used at point-to-point connections were a transport channel (SDH channel) is dedicated to a client signal. Extension Header of the Linear Frame is used at point-to-point connections were more than one client signals will be transmitted through one transport channel. The packets of the different client signals will be multiplexed, based on frame-by-frame. Are there no packets to transmit, GFP-IDLE-Frames will be implemented.

ITU-T G.7041 specifies the use of a CID to separate the different client signals. The corresponding ANSI-specification describes the use of DP and SP.

CID: Channel IdentifierDP: Destination Port Field SP: Source Port FieldSpar: Spare FieldeHEC: Header Error Check value for Extension


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Point-to-point Extension Header for a linear framePoint-to-point Extension Header for a linear frame

ExtentionSpar

TypeTypetHECtHEC

DP SP

eHEC

Frame Mux

IDLE Frames

Frame Demux

IDLE Termination

byte-streamfrom GFP ClientSpecific Process

SP 1

SP 16

byte-streamtowards GFP ClientSpezific Process

DP 1

DP 16

Example according ANSI standardisation

With the help of the Extension Header for point-to-point connections, GFP is able to multiplex up to 16 different logical connections (ports). The packets from the different ports will be multiplexed, based on frame-by-frame. Are there no packets to transmit, GFP-IDLE-Frames will be implemented.

DP: Destination Port FieldSP: Source Port FieldSpar: Spare FieldeHEC: Header Error Check value for Extension-field


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Frame Mapping EthernetFrame Mapping Ethernet

SFDDestination Address

Source AddressLength/Type

MAC Client DataPadding

Ethernet MAC framePLI

cHECTypetHEC

GFP Extension Hdr

GFP

Payload

GFP frame

Preamble

Ethernet FCS

At GFP-Ethernet Mapping the complete Ethernet MAC-packet, except of the Preamble and SFD, will be mapped in to the GFP-Payload. Preamble and SFD is used within Ethernet for packet distinguishing and clock-synchronisation of the receiver.GFP covers this job

SFD: Start of Frame Delimiter


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SwitchSwitchGFP Frames

GFP perceive and report ErrorsGFP perceive and report Errors

Ingress Client Process

GFP Client-specificSource Adaptation Process

GFP Common Process(Transmitter)

Transport NetworkSONET/ OTH

Egress Client Process

GFP Client-specificSource Adapt. ProcessGFP Common Process

(Receiver)Transport Network

SONET/ OTH

X

X

X

X

X Detected Error Error message

TSF

SSF

CSF

The GFP Process is able to handle and generate alarms from the different layers and to forward this to the GFP Client Process. Are there problems (Loss of Client Signal, Loss of Client Synchronisation) with the client signal at the GFP transmitter side, this can be reported to the receiver side (Far End Client Signal Fail Indication). CSF can be transmitted in intervals of 1 seconds.

CSF: Client Signal FailSSF: Server Signal FailTSF: Trail Signal Fail

ethernet over sonet vcat lcas gfp

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