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Due to the Protocol Issue, the R Router of E Vendor Reports a Lot of BFD Alarms When It Is Connected to Huawei Devices

Publication Date:  2013-09-30 Views:  89 Downloads:  0
Issue Description

With the development of the IP-based network reconstruction,BFD technology become more and more widely applied. BFD connections between Huawei products and products from other vendors are more and more widely used. When Huawei devices are connected with the R series router from E vendor, the router displays the following error messages:

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


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


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


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

1. Analyzing on the key error message "Unsupported Echo request tlv 15 - reply with error code", the engineer from E vendor explains that only one to ten TLVs are defined in the RFC4379 and their device cannot recognize a packet whose TLV is 15 sent from Huawei device, resulting in error messages.

The TLV is defined as follows in RFC4379:


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


However, our device is made according to the protocol RFC5884. In RFC5884, IANA defines that the TLV of the BFD in the LSP ping packet is 15. Therefore, the alarm is generated because the R series router of E vendor does not support the RFC5884 protocol.

The TLV is defined as follows in RFC5884:


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
This problem occurs because the router of a Huawei's peer vendor does not support the new RFC protocol.
Upgrade the device of the peer vendor.
In the interworking between Huawei devices and devices provided by other vendors, we must deeply understand the specifications of the protocols and avoid interconnection failures caused by certain problems of devices provided by other vendors.