MPLS over L2TPv3 Encapsulation

1
MPLS over L2TPv3 Encapsulation

• IETF 61

2
L2TPv3 Multiservice Tunneling
Frame Relay
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Version Version Version Version IHL IHL IHL IHL TOS TOS TOS TOS TOS TOS TOS TOS Total length Total length Total length Total length Total length Total length Total length Total length Total length Total length Total length Total length Total length Total length Total length Total length
Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Flags Flags Flags Fragment offset Fragment offset Fragment offset Fragment offset Fragment offset Fragment offset Fragment offset Fragment offset Fragment offset Fragment offset Fragment offset Fragment offset Fragment offset
TTL TTL TTL TTL TTL TTL TTL TTL Protocol 0x73 (L2TP) Protocol 0x73 (L2TP) Protocol 0x73 (L2TP) Protocol 0x73 (L2TP) Protocol 0x73 (L2TP) Protocol 0x73 (L2TP) Protocol 0x73 (L2TP) Protocol 0x73 (L2TP) Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum
Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router)
Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router)
PPP
HDLC
Session ID (32 bits)
Ethernet (VPWS or VPLS)
Cookie (32 or 64 bits, Optional)
Payload
ATM (Cell or Packet)
TDM

• L2TPv3 Encapsulation defined in RFC 3931
  (draft-ietf-l2tpext-l2tp-base-14.txt)
• MPLS over L2TPv3 encapsulation defined in
  draft-townsley-l2tpv3-mpls-02.txt

MPLS
3
L2TPv3 Encapsulation
Session ID (32 bits)
Cookie (32 or 64 bits, Optional)

• Session ID and Cookie (if present) may be
  signaled, or manually configured.
• Session ID is used during decapsulation to
  identify service or session context for L2TPv3.
• Before processing the L2TPv3 payload, the Cookie
  returned via the Session ID context lookup and
  the Cookie in the received packet header are
  compared to ensure they match.

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MPLS over L2TPv3
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
Version Version Version Version IHL IHL IHL IHL TOS TOS TOS TOS TOS TOS TOS TOS Total length Total length Total length Total length Total length Total length Total length Total length Total length Total length Total length Total length Total length Total length Total length Total length
Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Flags Flags Flags Fragment offset Fragment offset Fragment offset Fragment offset Fragment offset Fragment offset Fragment offset Fragment offset Fragment offset Fragment offset Fragment offset Fragment offset Fragment offset
TTL TTL TTL TTL TTL TTL TTL TTL Protocol 0x73 (L2TP) Protocol 0x73 (L2TP) Protocol 0x73 (L2TP) Protocol 0x73 (L2TP) Protocol 0x73 (L2TP) Protocol 0x73 (L2TP) Protocol 0x73 (L2TP) Protocol 0x73 (L2TP) Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum Header checksum
Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router) Source IP address (Local address on PE router)
Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router) Destination IP address (Local address on PE router)
Tunnel IP
Session ID (32 bits)
L2TPv3
Cookie (32 or 64 bits, Optional)
Label Exp S TTL
MPLS PDU
MPLS Stack PDU
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Alignment with other MPLS tunneling methods

• Draft-ietf-mpls-in-gre-or-ip-08.txt defines
• MPLS over IP
• MPLS over GRE with full header
• MPLS over GRE with simplified header
• MPLS over IP with IPsec transport mode
• MPLS over GRE with IPsec transport mode
• There are a number of common issues when
  encapsulating MPLS over IP, GRE or L2TPv3 which
  should continue to be defined in a single
  location.

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MPLS over L2TPv3 Specification

• Any specification defining the MPLS over L2TPv3
  encapsulation should include an applicability
  section similar to that for MPLS over IP vs. MPLS
  over GRE vs. MPLS over IPsec. For example,
• Two routers may already be adjacent over an
  L2TPv3 tunnel for other services outside of
  MPLS-based services
• Implementation considerations may dictate the use
  of MPLS over L2TPv3. For example, a hardware
  device might be better equipped to handle L2TPv3,
  utilize the L2TPv3 Session ID to aid in
  distributed processing of different services,
  etc.
• L2TPv3 Cookie allows a decapsulating PE to
  perform a context lookup validation based on the
  L2TPv3 session or service

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Next Steps?

• Add L2TPv3 to the list of methods for tunneling
  MPLS traffic
• Create a short and concise (5 pages or less!)
  MPLS over L2TPv3 WG draft with an appropriate
  applicability statement and reference to
  draft-ietf-mpls-in-gre-or-ip-08.txt for common IP
  encapsulation issues
• draft-townsley-l2tpv3-mpls-02.txt could be a
  start.

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End.