IP Pseudowire

1
IP Pseudowire

• Florin Balus
• August, 2004

2
Requirements - Existing topology FR/ATM VPNs
Large Branch
Frame Relay Access Network
HQ
ATM Network
Frame Relay Access Network
ATM Network - backbone for FR Access
Networks FRF.8 used for Service Interworking to
ATM connected sites
3
Requirements - Introducing Ethernet, PWs
Large Branch
PE
PE
IP/MPLS Core
Ethernet 10/100/1000
HQ
Ethernet 10/100/1000
PWs to be used for transport between un-like ACs
4
IP Pseudo-wire Deployment Scenarios
HQ
Eth Aggregation
MPLS
Office A
FR/ATM Network
IWF
IWF

• CE1

PW (IP)
(QinQ, PW AC)
PE
PE
HQ
MPLS
FR Access
ATM Network
Office A
IWF
IWF

• CE1

PW (IP)
PE
PE
5
Definition and Scope

• IP PW Encapsulation IP payload encapsulated in
  a 2 (MPLS) labels stack a Control Word/PID for
  OAM non-IP frames (IS-IS)
• Assumes 2 unlike ACsIP customer payload - e.g.
  IP/ATM as in RFC 2684 Routed mode
• Define the elements required to support IP
  Pseudo-wire in PWE3 WG
• To be used initially for Service IW, Routed
  Mode/IP Encapsulation

6
Ensure Consistent PW OAM
AC X OAM
AC Y OAM
HQ
MPLS PW (IP)
Office A
IWF
IWF

• CE1

LDP Status TLV VCCV Ping, BFD
PE
PE
VC Label
Tunnel Label
Control Word
Local Header
OAM Payload VCCV Ping, BFD
4 Bytes
PPP DLL Protocol Number reserved 0 0 0 1

• IP PW support for consistent PW OAM VCCV ping,
  BFD
• Same scheme to be used for IS-IS frames
• PPP DLL Protocol Nb 0023 for OSI, NLPID 83
  for IS-IS

7
Addressing ECMP Loadsharing

• IP PW Packets need to follow the same path with
  PW OAM ones
• OAM Packets directed based on Labels and I/f
• Disambiguate the PW packets from an IP flow by
  using a CW
• CWs 0000 instead of IPv4

VC Label
Tunnel Label
Control Word
Local Header
OAM Payload VCCV Ping, BFD
4 Bytes (OAM) PID
PPP DLL Protocol Number reserved 0 0 0 1
VC Label
Control Word
Tunnel Label
Local Header
Native Service (IP) Payload
4 Bytes CW
Sequence Length FRG Flags 0 0 0 0
MUST use CW to avoid that OAM and PW IP payload
take different path
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IP PW Control Word

• Follows the guidelines and the bit format
  described in draft-martini-l2circuit-encap-mpls-07
  .txt
• 0 1 2
  3
• 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0
  1 2 3 4 5 6 7 8 9 0 1
• ---------------------
  -----------
• Rsvd BFD0RSV RSVD
  Sequence
• ---------------------
  -----------
• Customer
  IP PDU
• 
  "
  
• 
  "
  
• 
  "
  
• ---------------------
  -----------

Fragmentation and Padding via the IP Header Pass
the L2 Discard Priority using D flag, Signal (FR)
congestion using B flag Flags could be ignored at
reception for older PEs / if using EXP bits etc
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Summary why define an IP PW encapsulation?

• Ensures ltconsistentgt L2 (PW) OAM
• Ensures consistent forwarding of OAM data
  packets
• Forwarding of non-IP (IS-IS) frames
• Translation of mechanisms between the unlike ACs

• Optimized IP PW encapsulation, interoperability
  between vendors
• Routed Mode ATM/FR-IP PW-ETH, FR-IP PW-ATM