How to enforce BFD to be sent over different paths between two systems?

[Linda Dunbar <ldunbar at huawei.com>]

Dave,

 

I have some questions on “draft-ietf-bfd-base-09.txt”. Hope you can help.

 

1. Section 3: 3^rd line of the first paragraph states “A pair of systems transmit BFD packets periodically over each path between the two systems”.

 

Question: when there are multiple paths between two systems, do you mean to have multiple BFD sessions between those two systems, with each session covering individual path? How to enforce each path being traversed?

 

2. The Echo function is pretty much like “Ping”. Each system can initiate a “Ping” to another system. Is “periodic Ping” an accurate description of the “Echo function”?

 

 

3. Section 4.1 under the “Control Plane Independent” sub-section:

The first paragraph states “if clear, the transmitting system’s BFD implementation share fate with its control plane”.

Question: When the transmitting system is running multiple routing protocols, more than one signaling schemes for different services, is it necessary to indicate which routing protocol and which signaling protocol?    Actually, BFD is to test connectivity which can be up when the corresponding control plane is done. What is the reason to have BFD share fate with its transmitting system’s control plane?

 

4. The BFD’s Control Packet Format described in Section 4.1 has a bit field for Demand mode. Why not having a bit field for the other two modes (Async and Echo)?

 

5. Is the Discriminator field of the BFD’ Control Packet Format same as unique identifier for particular BFD session from one system? Why not call it Identifier? Is it negotiated between the two systems?

 

6. Section 6.18.17 Concatenated Paths

In transport network, Concatenated paths mean to combine (or bundle) multiple paths to form a bigger path which has higher bandwidth. Therefore, failure on one of the paths concatenated together will not cause connectivity problem for the two systems exchanging BFD. This failure will only cause the bandwidth of the concatenated path to be smaller. Do you mean that when one of the paths within a concatenated path fail, the BFD should indicate this partial failure of the concatenated path?

 

7. Editorial: Section 2 Design: 6^th line of the first paragraph: “making it useful in concert with”? Is it a typo?

 

Thank you very much for helping me.

 

Best Regards, Linda Dunbar

Advanced Technology Dept, Wireline Networks,

Huawei Technologies, Inc.