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An R Device from E Supplier Generates Massive BFD Alarms Because of the Difference in Protocol Implementation when the R

Publication Date:  2013-01-08 Views:  49 Downloads:  0
Issue Description

As carriers improve IP networks, the BFD technology is being widely used. A Huawei device unavoidably sets up BFD sessions with other non-Huawei devices. When a Huawei device is connected to an R device from E supplier, the R device continuously generates the following alarms.

Feb 21 15:06:53.231: [0000]: %RSVP-7-PING: [rsvp_lsp_ping_handler] received a mpls ping for endpoint 10.0.1.15, tunnel_id 108 extended tunnel_id 10.0.1.4, sender 10.0.11.26 lsp_id 1

Feb 21 15:06:53.231: [0000]: %RSVP-7-PING: [rsvp_lsp_ping_handler] in interface 10.0.12.17 in nbr 10.0.1.15

Feb 21 15:06:53.232: [0000]: %RSVP-7-PING: [rsvp_lsp_ping_handler] RSVP returns code 3 in interface 10.0.12.17 in nbr 10.0.1.15 out interface 0.0.0.0 out nbr 0.0.0.0 out_mtu 0

Feb 21 15:06:53.232: %LM-3-ERR: Unsupported Echo request tlv 15 - reply with error code

Handling Process

1.         The on-site Huawei technical support personnel consults E supplier's technical support personnel on the key information in the alarm "Unsupported Echo request tlv 15 - reply with error code". E supplier's technical support personnel explain that R devices support TLVs defined in RFC 4379. RFC 4379 defines TLVs with the Type field ranging from 1 to 10 only. When the R device receives LSP ping messages carrying a BFD discriminator TLV with the type field 15 from the Huawei device, the R device fails to identify the TLV in the LSP ping messages and generates an alarm as a result.

RFC 4379 defines TLVs as follows:

7.2. TLVs

TLVs and sub-TLVs defined in this document are the following:

   Type  Sub-Type  Value Field

   ----  --------  -----------

   1      Target FEC Stack

       1   LDP IPv4 prefix

       2   LDP IPv6 prefix

       3   RSVP IPv4 LSP

       4   RSVP IPv6 LSP

       5   Not Assigned

       6   VPN IPv4 prefix

       7   VPN IPv6 prefix

       8   L2 VPN endpoint

       9   "FEC 128" Pseudowire (Deprecated)

      10   "FEC 128" Pseudowire

      11   "FEC 129" Pseudowire

      12   BGP labeled IPv4 prefix

      13   BGP labeled IPv6 prefix

      14   Generic IPv4 prefix

      15   Generic IPv6 prefix

      16   Nil FEC

   2      Downstream Mapping

   3      Pad

   4      Not Assigned

   5      Vendor Enterprise Number

   6      Not Assigned

   7      Interface and Label Stack

   8      Not Assigned

   9      Errored TLVs

     Any value  The TLV not understood

   10      Reply TOS Byte

Then the on-site Huawei technical support personnel collect information about the Huawei device from a Huawei BFD professional. The Huawei device supports RFC 5884 in which the IANA defines that the Type field value in a BFD discriminator TLV carried in LSP ping messages is 15. The alarm is generated because the R device from E supplier does not support RFC 5884.

RFC 5884 defines BFD discriminator TLV in LSP ping messages as follows.

6.1. BFD Discriminator TLV in LSP Ping

 LSP Ping Echo request and Echo reply messages carry a BFD

 discriminator TLV for the purpose of session establishment as

 described above. IANA has assigned a type value of 15 to this TLV.

 This TLV has a length of 4. The value contains the 4-byte local

 discriminator that the LSR, sending the LSP Ping message, associates

 with the BFD session.

 If the BFD session is not in UP state, the periodic LSP Ping Echo

 request messages MUST include the BFD Discriminator TLV.

Root Cause

The cause for the problem lies in that the R device from E supplier does not support RFC 5884 that is the latest release. To resolve the problem, the software version running on the R device must be upgraded.

Solution

upgrade the E device.

Suggestions
Before setting up a BFD session between a Huawei device and a non-Huawei device, familiarize yourself with the implementation of standard protocols to prevent a failure in BFD session establishment as a result of the differences in implementation.

END