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Cisco Bug: CSCvt25458 - MPLS TE is not coming UP when bandwidth configured on Juniper head end

Last Modified

Sep 10, 2020

Products (1)

  • Cisco ASR 900 Series Aggregation Services Routers

Known Affected Releases

16.9.5

Description (partial)

Symptom:
Topology is attached.

1. Next scheme was created:
 
Juniper MX is head-end here, NCS540 is tail-end here.
 
МХ-->XR9010-->ASR903-->XR9001-->NCS540
 
ASR903 always sends RSVP RESV with Peak Rate 0 to XR9010.
No RSVP message is received on Juniper, so tunnel is DOWN from head end side.

Packet capture was made on ASR903, and we see that it receives RSPV message with INF, however sends it with 0 value.

* As per XR BU analysis:

The ASR9010 drops the RESV from the ASR903 because the peak rate (0) is less than the rate.
In the path messages the peak rate is IEEE_INFINITY.

We have a check in XR rsvp code to see if peak rate is less than rate, mark object as invalid.

2. Next scheme was created: МХ-->ASR903-->XR9001-->NCS540.

In such situation tunnel comes UP, in such scheme RSVP RESV is received on MX.
However, peak rate is still 0 in the message sent from ASR903 to XR 9010.

 
3. If we exclude ASR903 from the topology and build scheme like this:
 
МХ-->XR9010-->XR9001-->NCS540
 
TE tunnel also comes UP.


So, looks like ASR903 is always changing Peak Rate from INFINITY to 0, which is not expected thing for me.

When Peak Rate is not less than the rate, XR is not dropping the packet (this is what is happening with no bandwidth configured, when tunnel comes UP).
When Peak Rate is less than the rate, XR is dropping the packet (this is what is happening with bandwidth configured, when tunnel is DOWN).

This is what RFC says:

In this TSpec, the parameters [r] and [b] are set to reflect the
   sender's view of its generated traffic. The peak rate parameter [p]
   may be set to the sender's peak traffic generation rate (if known and
   controlled), the physical interface line rate (if known), or positive
   infinity (if no better value is available).  Positive infinity is
   represented as an IEEE single-precision floating-point number with an
   exponent of all ones (255) and a sign and mantissa of all zeros.  The
   format of IEEE floating-point numbers is further summarized in [RFC
   1832].

Conditions:
Scheme like this:

Juniper MX is head-end here, NCS540 is tail-end here.
 
МХ-->XR9010-->ASR903-->XR9001-->NCS540
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