1 T1X1.5/2002-046

Applications and Overview ofGeneric Framing Procedure (GFP)

Mike Scholten (AMCC)

e-mail: mscholten@amcc.com

New ITU-T standard, G.7041 describes a Generic Framing Procedure (GFP) which may be used for efficiently mapping client signals into and transporting them over SONET/SDH or G.709 links. This presentation provides an overview of network applications which have driven the development of the GFP standard within T1X1.5 and ITU-T SG15. Applications are related to some of the features included in G.7041.

This contribution is intended only to provide introductory background to G.7041 and does not make any proposals not already reflected in the standard. Previewing this contribution may help in understanding motivation behind and application of the capabilities included in G.7041.

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What is GFP?

• Emerging new standard for Data Encapsulation• Accept any client, encapsulate in simple frame, transport over network• Uses length/HEC frame delineation of variable length packets• Allows multiple data streams to be transported over single path

– Packet aggregation for router applications

– Common encapsulation of different client data types (e.g. Ethernet, HDLC)

• Transparent Mapping supports LAN/SAN extension over WAN• Extension headers support various network topologies

– Null Extension Header for channelized Point-to-Point network

– Linear Extension Header for Port Aggregation over Point-to-Point network

– Ring Header for Resilient Packet Ring applications (removed to Living List)

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Basic GFP Frame Structure

Core Header

FCS (optional)

PayloadArea

Length MSB

Length LSB

cHEC MSB

Payload

Payload Header

FCS[31:24]

FCS[23:16]

FCS[15:8]

FCS[7:0]

Payload Type MSB

Payload Type LSB

tHEC MSB

tHEC LSB

OptionalExtensionHeader

cHEC LSB

eHEC MSB

eHEC LSB

Ext Hdr Byte 1

Ext Hdr Byte 2

Ext Hdr Byte n

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Application: Packet Routing through Big Fat Pipes

PacketSwitch

N x GbE

SONETSDH

Mapper

SONETSDH

Mapper

SPI-4

SPI-3 Router-basedWAN

OC-48STM-16

OC-192STM-64

• Packet Switch encodes/decodes 8B/10B and routes packets to appropriate SPI-n• SONET/SDH Mapper encapsulates packets using PPP over GFP and maps them into

concatenated payload (STS-48c/VC-4-16c or STS-192c/VC-4-64c)– Alternative to POS using PPP or EoS/LAPS using PPP

– Avoids indeterminate bandwidth expansion due to HDLC transparency processing

• All packet switching in WAN handled by Layer 2 routing• Single traffic type aggregated in edge switch & routers into big-fat-pipes going to desired hop

in routing table• Control info from 8B/10B encoding not preserved• Relies on PPP for Link Configuration

Edge Switch

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GFP Frame: PPP Packet Routing via GFP

Core Header

PayloadArea

Length MSB

Length LSB

cHEC MSB

PPPPacket

Payload

Payload Header

Payload Type MSB

Payload Type LSB

tHEC MSB

tHEC LSB

cHEC LSB

FCS (optional)FCS[31:24]

FCS[23:16]

FCS[15:8]

FCS[7:0]

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Application: Port Aggregation over Digital Wrapper

PacketSwitch

N x GbE

OTNMapper

OTNMapper

SPI-4

SPI-3 DWDMWAN

OTU-1

OTU-2

Packet Switch encodes/decodes 8B/10B and routes packets to appropriate SPI-nOTN Mapper encapsulates packets using GFP with extension header and aggregates them into OPU-n payload.Single or multiple traffic types may be aggregated in edge switch onto single wavelengthControl info from 8B/10B encoding not preserved

Edge Switch

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GFP Frame: Packet Aggregation over OTU-n

Core Header

PayloadArea

Length MSB

Length LSB

cHEC MSB

PacketPayload

Payload Header

Payload Type MSB

Payload Type LSB

tHEC MSB

tHEC LSB

LinearExtensionHeader

cHEC LSB Channel ID

Spare

eHEC MSB

eHEC LSB

FCS (optional)FCS[31:24]

FCS[23:16]

FCS[15:8]

FCS[7:0]

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Application: Resilient Packet Rings

GbEMAC

OC-mSTM-n

PacketRing

HDLCProc.

SONETSDH

MapperFramer

• Multiplex packet streams into single STS-Nc / VC-4-Xc• Each packet encapsulated into GFP Frame• Payload Type ID in payload header supports multi-service applications• Allows spatial reuse (packet statistical muxing, rather than TDM at each node)• GFP Extension headers support RPR

• Ring Node addressing• Class of Service packet prioritization

• 802.17 RPR WG developed alternative to GFP extension Ring Header:• RPR MAC generates/processes non-GFP ring header which is presented to GFP as part of payload

NetworkProcess.

&Switch

SPI-nSPI-n

8B/10BClient

PacketStream

Ring Node RingNode

RingNode

RingNode

Packet Add/Drop

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GFP Frame: RPR Using GFP Ring Header

Core Header

PayloadArea

Length MSB

Length LSB

cHEC MSB

PacketPayload

Payload Header

Payload Type MSB

Payload Type LSB

tHEC MSB

tHEC LSB

DestPort SrcPort

Spare

Spare DE CoS

TTL

Dest MAC[47:40]

Dest MAC[39:32]

Dest MAC[31:24]

Dest MAC[23:16]

Dest MAC[15:8]

Dest MAC[7:0]

Src MAC[47:40]

Src MAC[39:32]

Src MAC[31:24]

Src MAC[23:16]

Src MAC[15:8]

Src MAC[7:0]

eHEC MSB

eHEC LSB

RingExtensionHeader

cHEC LSB

FCS (optional)

FCS[31:24]

FCS[23:16]

FCS[15:8]

FCS[7:0]

NOTE: GFP Ring Header removed to Living List; 802.17 RPR proposes to include ring header as part of GFP payload).

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Application: Extending LAN / SAN over WAN

GbEFC

8B/10BClients

STS-mSTM-n

8B/10BClient

STS-mSTM-n

SONET / SDHNetwork

GbEFC

GbEFC

GbEFC

LAN /SAN

8B/10BClient GbE

FC

SONETSDH

MapperFramer

SONETSDH

MapperFramer

SONETSDH

MapperFramer

• Want to preserve individual 8B/10B block-coded channels, but…...Cannot fit two 1.25 Gb/s GbE channels into a single OC-48 / STM-16

• Transport of single 1.25 Gb/s stream over OC-48 / STM-16 is excessively wasteful.• Need to preserve control info (e.g. link configuration) for LAN extension, so…

…Cannot just send data packets.• Cannot just interleave two streams into single path and still expect SONET/SDH to

deliver to different destinations.

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SAN Transport through Right-Sized Pipes using VC/GFP

N xFibre Chan,

GbE,FICON,ESCON SONET

SDHMapperwith VC

SONET/SDHSwitched

WAN

OC-48/STM-16 orOC-192/STM-64

• Transparent Encapsulation / Decapsulation preserves Control Info• Virtually-concatenated paths sized to fit individual client signals• Client signals preserved intact through the network• Signals routed by switching VC paths (STS-1/VC-3 or STS-3c/VC-4 switching)• Mix of protocols may be carried, each in its own VC path• Virtual Concatenation (VC) essential to compete against SAN over dark fiber

SAN - WAN PHY

8B/10BCodec

8B/10BCodec

TransparentEncapsulate

/ Extract

TransparentEncapsulate

/ Extract

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Solution: VC + Transparent GFP

• Use Virtual Concatenation (VC) to partition SONET/SDH link into “right-sized” pipes• “Right-sized” is smallest number of STS-3c/VC-4 or STS-1/VC-3 needed for client• Compress 8B/10B client without losing control information• Encapsulate compressed client signal into standard adaptation mechanism (GFP)• T1X1.5/2000-046 (Jul-2000) established target VC-path sizes for various clients:

– Gigabit Ethernet• 1000 Mb/s; 1250 Mb/s 8B/10B block-coded fit into STS-3c-7v or VC-4-7v• 2 STS-3c/VC-4 available after 2 GbE signals VC-mapped into OC-48/STM-16

– Fibre Channel and FICON• 850 Mb/s; 1062.5 Mb/s 8B/10B block-coded fit into STS-3c-6v or VC-4-6v• 4 STS-3c/VC-4 available after 2 Fibre Channel signals VC-mapped into OC-48/STM-16

– ESCON• 160 Mb/s; 200 Mb/s 8B/10B block-coded fit into STS-1-4v or VC-3-4v• 12 ESCON signals can be VC-mapped into OC-48/STM-16

Client Signal / Line Rate VC-Path Size

Gigabit Ethernet (GbE) / 1250 Mb/s STS-3c-7v / VC-4-7vFibre Channel / 1062.5 Mb/s STS-3c-6v / VC-4-6vFICON / 1062.5 Mb/s STS-3c-6v / VC-4-6vESCON / 200 Mb/s STS-1-4v / VC-3-4v

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Solution: VC + Transparent GFP (cont.)

• T1X1.5/2001-04R1 (Jan-2001) established 64B/65B compression scheme:– Map 8-bit data directly into 64-bit block with pre-pended SyncBit = 0

– Map 12 control characters into 3-bit location + 4-bit control code

Input Data SyncBit 64-bit Field

All Data 0 D1 D2 D3 D4 D5 D6 D7 D8

7 Data + 1 Control 1 0,aaa,C1 D1 D2 D3 D4 D5 D6 D7

6 Data + 2 Control 1 1,aaa,C1 0,bbb,C2 D1 D2 D3 D4 D5 D6

5 Data + 3 Control 1 1,aaa,C1 1,bbb,C2 0,ccc,C3 D1 D2 D3 D4 D5

4 Data + 4 Control 1 1,aaa,C1 1,bbb,C2 1,ccc,C3 0,ddd,C4 D1 D2 D3 D4

3 Data + 5 Control 1 1,aaa,C1 1,bbb,C2 1,ccc,C3 1,ddd,C4 0,eee,C5 D1 D2 D3

2 Data + 6 Control 1 1,aaa,C1 1,bbb,C2 1,ccc,C3 1,ddd,C4 1,eee,C5 0,fff,C6 D1 D2

1 Data + 7 Control 1 1,aaa,C1 1,bbb,C2 1,ccc,C3 1,ddd,C4 1,eee,C5 1,fff,C6 0,ggg,C7 D1

All Control 1 1,aaa,C1 1,bbb,C2 1,ccc,C3 1,ddd,C4 1,eee,C5 1,fff,C6 1,ggg,C7 0,hhh,C8

aaa = 3-bit representation of the 1st control code’s original positionbbb = 3-bit representation of the 2nd control code’s original position…hhh = 3-bit representation of the 8th control code’s original position

Ci = 4-bit representation of the ith control codeDi = 8-bit representation of the ith data value in order of transmission

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Transparent GFP Mapping (cont.)

• 12 8B/10B “Special Characters” remapped to 4-bit codes as shown• 10B Violations mapped as “10B_ERR” (RD errs, unrecognized 10B codes)• Rate adapt by inserting “65B_PAD” code

NAME Byte Value 10B Codeword (RD-)abcdei fghj

10B Codeword (RD+)abcdei fghj

64B/65B4-bit Mapping

/K28.0/ 1C 001111 0100 110000 1011 0000

/K28.1/ 3C 001111 1001 110000 0110 0001

/K28.2/ 5C 001111 0101 110000 1010 0010

/K28.3/ 7C 001111 0011 110000 1100 0011

/K28.4/ 9C 001111 0010 110000 1101 0100

/K28.5/ BC 001111 1010 110000 0101 0101

/K28.6/ DC 001111 0110 110000 1001 0110

/K28.7/ FC 001111 1000 110000 0111 0111

/K23.7/ F7 111010 1000 000101 0111 1000

/K27.7/ FB 110110 1000 001001 0111 1001

/K29.7/ FD 101110 1000 010001 0111 1010

/K30.7/ FE 011110 1000 100001 0111 1011

10B_ERR N/A Unrecognized RD- Unrecognized RD+ 1100

65B_PAD N/A N/A N/A 1101

Spare N/A N/A N/A 1110

Spare N/A N/A N/A 1111

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GFP Encapsulation of N x [536,520] Superblocks

Encapsulate N x [536,520] superblocks into standard GFP Frames• Relocate leading “sync bits” of 8 x 65B blocks to end of 8 x 64-bit blocks• Compute & append CRC-16 after 8 x 65B blocks to create [536,520] superblock• [536,520] superblock maintains byte alignment• Choose N to fit available bandwidth of selected virtually-concatenated path• Scramble Payload Area using self-synchronous x43+1 scrambler

4. Pre-pend with GFP core & payload headers.

Leading Bit8 byte block

8 x 65B blocks = 520 bits

1. Group 8 x 65B blocks

2. Rearrange Leading Bits at end

3. Generate & append CRC-16 checkbitsto form [536,520] superblock.

Payload Header (4 bytes)

Core Header (4 bytes)

N x [536,520] SuperblocksOptional FCS (4 bytes)

6. Form GFP frames with N x [536,520]superblocks.

5. Scramble payload header & payloadwith x43+1. (Core header not scrambled.)

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Handling 8B/10B Disparity

ClientSource

Transp.GFP

MapperFramer

Transp.GFP

De-map

ClientSink

8B/10B ClientSTS-mSTM-n

8B/10BClient

STS-mSTM-n

SONET / SDHNetwork•1.25Gb/s GbE,

•1.0625Gb/s FCor FICON,

•200Mb/s ESCON

Client Ingress Client Transport Client Egress

Ingress Code Violations Detected:• Invalid Codewords• Running Disparity Errors• Map 10B_ERR into GFP Frame.

Egress Codeword Generation:• Generate correct disparity.• Prevent disparity error propagation across

data packets.• Handle received 10B_ERR.

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Signal Fail Handling in Transparent Mapping

ClientSource

Transp.GFP

MapperFramer

Transp.GFP

De-map

ClientSink

8B/10B ClientSTS-mSTM-n

8B/10BClient

STS-mSTM-n

SONET / SDHNetwork•1.25Gb/s GbE,

•1.0625Gb/s FCor FICON,

•200Mb/s ESCON

Client Ingress Client Transport Client Egress

Signal Fail Conditions on Ingress:• Protocol-specific Client Signal Failures

• Loss of Signal GFP_CSF• Loss of Synchronization GFP_CSF

Signal Fail Handling on Egress:• Locally detected Signal Fail

• Section / RS defects (LOS, OOF/LOF, RS-TIM) 10B_ERRs• Line / MS defects (AIS-L) 10B_ERRs• Path defects (LOP-P, PLM, UNEQ, MS-TIM) 10B_ERRs• VC-Path defects (dLOM, dSQM, dLOA) 10B_ERRs• GFP Frame Sync Loss 10B_ERRs

• Received Signal Fail conditions• GFP_CSF 10B_ERRs

• Handling of non-failure errors• Errored 8 x 65B Superblock 8 x 8 10B_ERR chars• Non-decodable 65B Block 8 x 10B_ERR chars

Definitions:GFP_CSF = GFP Client Mgt Frame with Client Signal Fail Indication10B_ERRs = stream of consecutive 10B_ERR codewords

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Clocking Options for Egress Client Signals

ClientSource

Transp.GFP

MapperFramer

Transp.GFP

De-map

ClientSink

8B/10B ClientSTS-mSTM-n

8B/10BClient

STS-mSTM-n

SONET / SDHNetwork•1.25Gb/s GbE,

•1.0625Gb/s FCor FICON,

•200Mb/s ESCON

Client Ingress Client Transport Client Egress

Egress Clock Options:• Recover Client clock from transported

GFP-mapped client signal; or• Rate adapt extracted client to locally derived

client reference clock.

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Frame-Mapped GFP vs. Transparent GFP

Frame-Mapped GFP Transparent-Mapped GFP

Variable Length GFP Frames Fixed Length GFP Frames

1-to-1 mapping of Data Packets to GFPFrames

N-to-1 mapping of client “characters” to GFPFrames

Point-to-Point, Packet Aggregation, orResilient Packet Ring Network Topology

Primarily Point-to-Point Topology using VirtualConcatenation

Requires “MAC” to terminate client signal andpass only data packets.

Only 8B/10B PHY layer terminated; “MAC”not required to terminate higher layer protocol.

Data only passed in 8B format. Data and control compressed using 64B/65Bre-coding.

Channel-associated control possible usingGFP Control Frames.

Channel-associated control possible usingGFP Control Frames.

Unclear if client LOS, Loss-of-Sync, or codeviolations should be communicated to far-end.

Transparent mapping defines mechanisms forcommunicating LOS, Loss-of-Sync, codeviolations to far end.

Doesn’t define client egress action due toSONET/SDH signal failure.

Defines client egress action due toSONET/SDH signal failure.

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GFP Overview Summary• Various GFP Applications have been described and illustrated

– Packet routing

– Port aggregation over SONET/SDH or OTN using Linear Extension Headers

– Resilient Packet Ring applications using Ring Extension Headers

– Transparent Transport of 8B/10B clients

• Basic GFP Frame Structure has been described and shown– Length/cHEC frame delineation, similar to ATM cell delineation.

– Payload Headers ID encapsulated payload & encapsulation options• Presence or absence of optional FCS• Presence and type or absence of extension header• Payload type allows for mixing data types in a single SONET/SDH or OTN path

– Extension headers support various network topologies• Null Extension Header for channelized Point-to-Point network• Linear Extension Header for Port Aggregation over Point-to-Point network• Ring Header for Resilient Packet Ring applications

• LAN/SAN extension over WAN using Transparent Mapping described and shown– 64B/65B re-coding preserves data & control for “transparent” transport

– [536,520] superblocks provide error detection / correction over relatively small blocks

– Supports efficient transport of full-rate 8B/10B clients over smallest paths

• Foundation laid for more easily understanding ITU-T G.7041 GFP Standard