MPLS-TP Shared Mesh Protection
draft-cheung-mpls-tp-mesh-protection-05
IETF 83 – Paris, March 2012
Taesik Cheung and Jeong-dong Ryoo (ETRI)
Yaacov Weingarten and Nurit Sprecher (NSN)
Daniel King (Old Dog)
Main Points of Solution
• Utilizes the existing linear protection as is
– No modification needed in the state transition tables
– Only the additional coordination actions for SMP are
defined in this draft
• One LSP for each protection path
– Each LSP has end-to-end OAM/PSC channel
• Parallel coordination of protection segments
– Use SPMEs for direct communication
– Minimize coordination processing time
• Immediate traffic switchover
– Rapid failover as fast as linear protection
Changes from 04
• Block function at the SEN was added.
– To reduce possible congestion during pre-emption
– SEN blocks protection LSP to be pre-empted and sends
Lockout of Protection (LoP) request.
– When an end node of the protection LSP completes the
LoP operation, it will send an acknowledge to SEN.
– SEN unblocks protection LSP when it receives the LoP Ack.
• SMP protocol message format was defined.
– Initial definition
• The mechanism was described more in detail.
• Editorial changes
SMP protocol message format
(4b)
(4b)
(4b)
Version
1
Mode
0 – Bidirectional
1 – Unidirectional
Type
1–
2–
3–
4–
5–
(2b)
PS Event
LoP Request
LoP Ack
RA Notification
RA Ack
(10b)
(8b)
ST
(Sub-type)
0 – Switch to working
(for PS Event) or
Clear LoP
(for LoP Request)
1 – Switch to protection
(for PS Event) or
Assert LoP
(for LoP Request)
ID
0x01~0xFE – ID value
Next steps
• Currently, there are multiple drafts regarding SMP.
• We will continue the discussion with the authors of
the other drafts to explore a possibility to develop a
single solution optimized for MPLS-TP networks.
• We kindly ask the WG experts to review our
document and provide us feedback.
Backup slides
Protocol Messages
•
•
•
•
Blue: Linear protection protocol messages
Red: PS Event (EN  SEN)
Orange (solid / dotted): RA Notification / Ack (SEN  SSN)
Green (solid / dotted): LoP Request / Ack (SEN/SSN  EN)
A
[Acronyms]
PS: Protection Switching
RA: Resource Allocation
LoP: Lockout of Protection
EN: End Node
SEN: Shard End Node
SSN: Shared Start Node
SF (AB)
W2
X
B
P2
P
Q
R
P1
C
W1
S
T
P3
D
E
W3
U
P4
F
[ Priority: P1>P2>P3>P4 ]
G
W4
H
Backup slides
Principle of Operation
• End node detecting failure initiates protection
– Starts linear protection and sends PS Event to SEN
• SEN coordinates use of shared resource
–
–
–
–
Sends RA Notification to SSN (and waits for RA Ack from SSN)
Blocks the equal or lower priority protection LSP
Sends LoP Request to the end node of the protection LSP
Unblocks the protection LSP when it receives LoP Ack
• SSN coordinates use of shared resource
– Sends RA Ack to SEN
– Same procedures with SEN (step 2-4)
Backup slides
Example 1 (SF at high priority LSP)
• Procedures
–
–
–
–
–
A detects SF, sends PS Event to P and starts linear protection.
P blocks P2, sends LoP Request to C and RA Notification to Q.
Q blocks P2 and sends LoP Request to D (and replies RA Ack to P).
C and D perform LoP and send LoP Ack to P and Q.
P and Q unblock P2.
A
B
A
X
1. SF (AB)
B
W1
W1
P1
P1
P
Priority
P1 > P2
Q
P2
P
P2
W2
C
Q
W2
D
C
D
Lockout
[ Normal ]
Lockout
[ Protection ]
Backup slides
Example 2 (SF at low priority LSP)
• Procedures
– C detects SF, sends PS Event to P and starts linear protection.
– P does nothing.
A
B
A
B
W1
W1
P1
P1
P
Q
P
Q
P2
P2
W2
W2
C
D
[ Normal ]
C
X
1. SF (CD)
[ Protection ]
D
Backup slides
Example 3 (Pre-emption)
• Procedures (continued from Example 2)
–
–
–
–
–
A detects SF, sends PS Event to P and starts linear protection.
P blocks P2, sends LoP Request to C and RA Notification to Q.
Q blocks P2, sends LoP Request to D (and replies RA Ack to P).
C and D perform LoP and send LoP Ack to P and Q. (return to failed W2)
P and Q unblock P2.
A
B
A
X
W1
P1
P1
Priority
P1 > P2
Q
P2
P
1. SF (CD)
[ P2 occupies P-Q ]
D
Q
P2
W2
X
B
W1
P
C
2. SF (AB)
C
Lockout
X
X
W2
1. SF (CD)
[ P2 pre-empted ]
D
Lockout
Backup slides
Example 4 (Equal priority)
• Procedures (First come, first served)
–
–
–
–
–
–
A detects SF, sends PS Event to P and starts linear protection.
P sends RA Notification to Q and waits for reply.
Q blocks P2, sends LoP Request to D and replies RA Ack to P.
P blocks P2 and sends LoP Request to C.
C and D perform LoP and send LoP Ack to P and Q.
P and Q unblock P2.
A
B
A
X
1. SF (AB)
B
W1
W1
P1
P1
P
Priority
P1 = P2
Q
P2
P
P2
W2
C
Q
W2
D
C
D
Lockout
[ Normal ]
Lockout
[ Protection ]
Backup slides
Example 5 (Race condition)
• Procedures (Equal priority resolved by Protection path ID)
–
–
–
–
–
–
B and C detect SF, send PS Event to Q and P and start linear protection.
Q and P send RA Notification to each other and wait for reply.
P blocks P2, sends LoP Request to C and replies RA Ack to Q.
Q blocks P2 and sends LO Request to D.
C and D perform LoP and send LO Ack to P and Q. (return to failed W2)
P and Q unblock P2.
A
B
1. SF (AB) X
A
W1
W1
P1
P
P1
Priority
P1 = P2
(ID1 > ID2)
Q
P2
P
D
C
Lockout
[ Normal ]
Q
P2
W2
C
B
X
X
W2
1. SF (CD)
[ Protection: P2 rejected ]
D
Lockout