Ben Mack-Crane

Apr 10, 2023 1

bp-sajassi-cfm-0711-v01.pdf Flow-Level CFM:

◦ CFM functions performed on the user flows.

Network-Level CFM:◦ CFM functions performed on a test “VLAN” that covers the

network. Test flows are chosen to exercise all ECMPs for the Test VLAN.

Service-Level CFM:◦ CFM functions performed on a service VLAN. Test flows are

chosen to exercise all ECMPs for that VLAN. It can be considered as a special case of Network Level CFM.

Apr 10, 2023 2

bp-sajassi-cfm-0711-v01.pdf Test Flow Discovery Path Trace Path Verification Fault Monitoring Fault Isolation

Apr 10, 2023 3

Test Flow Discovery◦ Computed set of (SA, DA, Flow Hash) for Network or Service

Path Trace◦ Link Trace

Path Verification◦ Loopback

Fault monitoring◦ CCM, infer Flow Hash from RDI

Fault Isolation◦ Loopback◦ DDCFM

Apr 10, 2023 4

LTM sent to individual DA with specific Flow Hash Each hop sends back LTR (if LTM TTL is not 0) Forwards LTM to ECMP selected hop (if LTM TTL is >1) LTR frames identify path for DA+Flow Hash

Apr 10, 2023 5

LTM to individual address w/ flow

hash LTR may take any path

LBMs sent to individual DA with Flow Hash to select path LBM MIP TLV contains MIP address MIP responds with LBR LBR may take different path from LBM

◦ Could add Flow Hash TLV to LBM to attempt to make LBR symmetric…◦ But there is no guarantee that LBR is symmetric if network is misbehaving!

Apr 10, 2023 6

LBM to Individual DA,

MIP address in TLV LBR to LBM SA

CCMs sent from B-VLAN endpoint (CBP) use a source specific tree* Each endpoint expects to receive CCMs from all other endpoints Detects unreachable endpoint Does not test all paths

Apr 10, 2023 7

CCM to Group Address

Cs-ss-ss-00-00-FF

*Or a shared tree using group address 80-1E-83-00-00-FF

CCMs sent from a CBP MEP within a TESI mux (specific to VID, SA, DA) using a specific Flow Hash

Multiple paths can be tested using a list of Flow Hash values, each sent at least three consecutive times

Detects broken path (but not rerouted path)

Apr 10, 2023 8

CCM to Individual Address*

Flow Hash A

Flow Hash B

Flow Hash C

*Option to use flow-specificgroup address?

MEP location in baggy pant leg◦ “Support for Flow Filtering” shim with 6.11 (or

6.9)◦ MEP/MIP locations unchanged◦ Use TESI mux (6.19) for path test MEPs

PNP only supports ECMP MIPs◦ Partial paths ECMP VLAN are not interesting

Apr 10, 2023 9

Apr 10, 2023 10

Placing Flow Filtering shim with CBP shim:-Keeps all tag processing together

CFM :-MEP generates CCM frames with group address for default I-SID.

Apr 10, 2023 11

Placing Flow Filtering shim with CBP shim:-Keeps all tag processing together

CFM :-MEP generates CCM frames with individual address-Flow Hash value(s) selected to test desired path(s)

Apr 10, 2023 12

Placing Flow Filtering shim with VLAN tag shim:-Keeps all tag processing together-Could have used one tag to carry all info

Only MIPs supported on PNP for ECMP VLANs-ECMP makes MEPs less useful here

Path verification◦ Determine expected path via computation or LTM◦ Use Loopback to verify each hop in path

Fault isolation◦ Use Loopback to find “broken” hop◦ DDCFM supports special diagnostics, i.e.

reflecting specific frames or injecting test frames

Apr 10, 2023 13