1. Loop Protection in EVPN Networks draft-snr-bess-evpn-loop-protect-00
Jorge Rabadan (Nokia)
Senthil Sathappan (Nokia)
Kiran Nagaraj (Nokia)
Julio Bueno (Telefonica)
Jose Manuel Crespo (Telefonica)
IETF99, July 2017
Prague

2. Local vs Global loops in EVPN Broadcast Domains
draft-snr-bess-evpn-loop-protect addresses global loops
A local Loop
A non-expected situation in which BUM frames are received on the same PE and BD from where they were sent.
Either within the same AC or different ACs.
Resolution is implementation specific and independent of the other PEs
Host-1
PE1
MAC-VRF
broadcast
CE6
AC6
PE2
PE3
EVPN
CE2
AC2
Local
LOOP!
MAC-VRF
MAC-VRF
Global
LOOP!
Local
LOOP!
AC4
AC3
AC5
CE5
Backdoor link
A Global Loop
Across multiple PEs in the same BD
Usually caused by accidental backdoors between CEs or ACs connected to the same BD.
Addressed by this draft.
CE3
CE4

3. Global Loop Protection Proposal
For EVPN networks
It completes the RFC7432 MAC Duplication mechanism with an optional Loop Protection procedure for Global Loops.
RFC7432-compatible.
It does not modify/add any control plane piece of information.
Upon detecting a loop, it carries out the following Loop Protection actions:
The PE SHOULD discard looping flows while allowing other non-looping flows.
The PE MAY bring down the ACs involved in the loop, as opposed to only discarding the flows involved.

4. Add M2 to duplicate-MAC list
Loop Protection Solution for EVPN Broadcast Domains M2
MAC-VRF
PE2
PE3
Backdoor link
EVPN
AC2
AC3
AC4
broadcast
MAC (M2, SEQ x)
MAC (M2, SEQ y)
PE3 stops advertising M2 and logs a duplicate event
RFC7432 1 2
PE3 initializes a retry-timer “R”
This document
PE3 triggers Loop Protection and “black-holes” M2 3
t=0
x=0
M2/SEQ
y=0
t=0
A Black-Hole MAC M2 means:
It is installed in the BT as Black-Hole (not associated to any AC).
For any ingress frame on PE3:
If MAC SA=M2  frame MUST be discarded
If MAC DA=M2  frame SHOULD be discarded
Optionally, for any ingress frame on a PE3 AC
If MAC SA=M2  AC MAY be brought oper down.
A Black-Hole M2 is flushed if:
R expires
Manual flush
PE2 withdraws M2 or sends M2 with sticky bit.
M2/SEQ+1
y=1
x=1
withdraw
x=2
M2/SEQ+2
withdraw
y=2
M2/SEQ+3
y=3
x=3
withdraw …
x=N-1
M2/SEQ+N-1
withdraw
y=N-1
y=N (t<M)
Add M2 to duplicate-MAC list
Actions

5. Observations and conclusions
Why is this draft Informational
It is compatible with RFC7432 procedures and does not modify EVPN routes
Can be deployed in an EVPN BD where not all the PEs support Loop Protection
Why do we think it is important
Accidental (or not) backdoor paths happen
Global Loops are a big concern in Operators and Service Providers
What do we ask the WG
Feedback / Comments

6. Thank you