Subject: [mpls] Questions on BFD MPLS MIB

From: Saravanan Narasimhan <[email-masked]>
Date: Sun, 3 Jun 2012 12:42:50 +0530

Hi Authors,

I have a question regarding the Section 5.2.1 of the draft
draft-vkst-bfd-mpls-mib-02.

It states that

" bfdMplsSessMapType = teIpv4(3),

 -- OID of the first accessible object (mplsTunnelName) of
 -- the mplsTunnelEntry identifying the MPLS TE tunnel (being -- monitored
using BFD) in the MPLS tunnel table.
 -- A value of zeroDotzero indicates that no association -- has been made
as yet between the BFD session and the path
 -- being monitored.
 -- In the above OID example:
 -- 100 -> Tunnel Index
 -- 1 -> Tunnel instance
 -- 3221225985 -> Ingress LSR Id 192.0.2.1
 -- 3221225987 -> Egress LSR Id 192.0.2.3

    bfdMplsSessMapPointer = mplsTunnelName.100.1.3221225985.3221225987,
    bfdSessRowStatus = createAndGo
}

Similarly BFD session would be configured on the tail-end of the tunnel.

"

Here, at the tail-end of the tunnel, "Instance" is never really known.
Tunnel can be setup with any tunnel instance (LSP ID) when it is signaled
through RSVP-TE / CR-LDP. It need not be "1" as mentioned in the above
example.

So, We should be setting the map pointer as

"bfdMplsSessMapPointer = mplsTunnelName.100.0.3221225985.3221225987". Am I
right?

Or should we take the approach as defined in PW-MPLS-STD-MIB (RFC 5602)
where OutboundTunnel is mapped to the PW through individual objects
(pwMplsOutboundTunnelIndex, pwMplsOutboundTunnelInstance,
pwMplsOutboundTunnelLclLSR and pwMplsOutboundTunnelPeerLSR with
pwMplsOutboundTunnelInstance as a READ-ONLY parameter) instead of a
RowPointer approach done here. Please clarify.

Also, Can you please clarify how this MIB can be used to monitor a tunnel
setup through 1:1 protection support (RSVP-TE signaling as in RFC 4872) (2
LSP's -> Working and Protection)?

Should we create 2 independent BFD sessions to monitor working and
protection LSP or a single BFD session to monitor both?

If we need to create 2 BFD sessions, how to map tunnel pointer to BFD
session?

Please clarify.

Thank You,
N.Saravanan

---

From: venkatesan mahalingam <[email-masked]>
Date: Mon, 4 Jun 2012 20:28:27 -0700

Hi,
Please find below the comments inline with the tag [VM].

Thanks,
Venkat.

On Sun, Jun 3, 2012 at 12:12 AM, Saravanan Narasimhan
<[email-masked]> wrote:
>  -- A value of zeroDotzero indicates that no association -- has been made as
> yet between the BFD session and the path
>  -- being monitored.

[VM] If I'm not wrong, tunnel instance 0 is reserved for configured
tunnel, we should be able to get the LSP-id through RSVP-TE or
out-of-band signalling (LSP Ping).

> RowPointer approach done here. Please clarify.

[VM] RowPointer approach should be fine.

> protection LSP or a single BFD session to monitor both?

[VM] Yes, two independent BFD sessions are required to monitor both
working and protection paths.

> If we need to create 2 BFD sessions, how to map tunnel pointer to BFD

[VM] Either you can configure tunnel pointers at the head and tail
nodes manually or use out-of-band signalling using on-demand CV.
>
> Please clarify.
>
> Thank You,
> N.Saravanan
>
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