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					ITU-T Compromised Solution on ATM – MPLS NETWORK INTERWORKING (Pseudo Wire Emulation)
Ghassem Koleyni Nortel Networks ghassem@nortelnetworks.com Phone : +1 613 763 4154

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ITU-T ATM-MPLS Network Interworking Provides network interworking between ATM cells and AAL5 frames with MPLS: Cell mode Encapsulations, two modes: • One ATM connection to one Interworking LSP (one-to-one mode) • n ATM connections to one Interworking LSP (n-to-one mode) Frame mode Encapsulations, two modes: • AAL5 PDU • AAL5 SDU

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0 0 1 2 3 4 5 6 7

1 8 9 0 1 2 3 4 5

2

3

6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

MPLS transport label= PSN Transport Header in PWE3 Interworking label=Pseudo Wire Header in PWE3 Common interworking indicators* ~ ATM Control Word in PWE3 ATM-MPLS interworking specific header* Payload General Encapsulation Format * Not four octets for all cases

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Cell mode encapsulation (one-to-one mode)
0 0 1 2 3 4 5 6 7 1 8 9 0 1 2 3 4 5 2 6 7 8 9 0 1 2 3 4 5 3 6 7 8 9 0 1

MPLS transport label= PSN Transport Header in PWE3 Interworking label=Pseudo Wire Header in PWE3 Length Sequence Number ATM Payload (48 octets) One ATM connection to one Interworking LSP (one-to-one mode) for a single cell (VCC)
M

V

Res

PTI

C

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0 0 1 2 3 4 5 6 7 8 9

1 0 1 2 3 4 5

2 6 7 8 9 0 1 2 3 4

3 5 6 7 8 9 0 1

MPLS transport label= PSN Transport Header in PWE3 Interworking label=Pseudo Wire Header in PWE3 Reserved VPI Length Sequence number PTI C

VCI ATM Payload (48 octets) VCI ATM Payload (48 octets)

VPI

PTI

C

n ATM connections to one Interworking LSP (n-to-one mode)

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AAL5 PDU
0 0 1 2 3 4 5 6 7 1 8 9 0 1 2 3 4 5 2 6 7 8 9 0 1 2 3 4 5 3 6 7 8 9 0 1

MPLS transport label= PSN Transport Header in PWE3 Interworking label=Pseudo Wire Header in PWE3 Length Sequence Number 16 bits VCI + Payload
M

V

Res

FR G

E C

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AAL5 SDU

0 0 1 2 3 4 5 6 7

1 8 9 0 1 2 3 4 5

2 6 7 8 9 0 1 2 3 4 5

3 6 7 8 9 0 1

MPLS transport label= PSN Transport Header in PWE3 Interworking label=Pseudo Wire Header in PWE3
Reserved

T EL C

Res

Length

Sequence number Payload

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Cell mode encapsulations are explained in ITU-T draft Recommendation Y.atmplsC AAL5 mode encapsulations are explained in ITU-T draft Recommendation Y.atmplsF

These documents can be found at: http://www.itu.int/itu-t/studygroups/com13/ip/sg13-ietf-ftp.html

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