Serval question! Thanks!! Fri, 15 April 2005 17:44 UTC

Received: from ( []) by (8.9.1a/8.9.1a) with ESMTP id NAA25818; Fri, 15 Apr 2005 13:44:04 -0400 (EDT)
Received: from ([]) by with esmtp (Exim 4.33) id 1DMV1b-0002k5-PJ; Fri, 15 Apr 2005 13:54:40 -0400
Received: from localhost.localdomain ([] by with esmtp (Exim 4.32) id 1DMUkf-0005GF-88; Fri, 15 Apr 2005 13:37:09 -0400
Received: from ([] by with esmtp (Exim 4.32) id 1DMUke-0005Fc-57 for; Fri, 15 Apr 2005 13:37:08 -0400
Received: from ( []) by (8.9.1a/8.9.1a) with ESMTP id NAA25006 for <>; Fri, 15 Apr 2005 13:37:00 -0400 (EDT)
Received: from [] ( by with esmtp (Exim 4.33) id 1DMUuf-0002H6-0C for; Fri, 15 Apr 2005 13:47:36 -0400
Received: from (unknown []) by (Postfix) with ESMTP id 8C9C20411A37; Sat, 16 Apr 2005 01:36:40 +0800 (CST)
Message-ID: <>
Date: Sat, 16 Apr 2005 01:36:44 +0800
Mime-Version: 1.0
Content-Type: multipart/related; boundary="----=_Part_560_6239160.1113586604732"
X-Mailer: Sohu Web Mail 2.0.13
X-Priority: 3
X-Sohu-Antivirus: 0
X-Spam-Score: 2.4 (++)
X-Scan-Signature: cd3fc8e909678b38737fc606dec187f0
Subject: Serval question! Thanks!!
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: "RTG Area: Bidirectional Forwarding Detection DT" <>
List-Unsubscribe: <>, <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-Spam-Score: 2.4 (++)
X-Scan-Signature: 311e798ce51dbeacf5cdfcc8e9fda21b

  1、The transmmit interval is at least 1s before the session is UP , i am not sure
  does the vlaue set to the BFD control packet! if does and at what time does the
  BFD control set the actual value to the BFD control packet , if not how to decided 
  the INIT timeout time ? Before the session is UP if received a P bit set control
  packet , it will send back a F bit set control packet , but the vlaue of MTI and MRI
  in the control packet is setted to 1s or the actual value ??
  2、In Section 4.1 it said
   "Poll (P)

      If set, the transmitting system is requesting verification of
      connectivity, or of a parameter change.  If clear, the
      transmitting system is not requesting verification."
  In Section 6.7.3 it said
   "If Demand mode is active, and either bfd.DesiredMinTxInterval is
   changed or bfd.RequiredMinRxInterval is changed, a Poll Sequence MUST
   be initiated (see section 6.7.8).

   If Demand mode is not active, bfd.SessionState is Up, and either
   bfd.DesiredMinTxInterval is changed or bfd.RequiredMinRxInterval is
   changed, all subsequent transmitted Control packets MUST be sent with
   the Poll (P) bit set until a packet is received with the Final (F)
   bit set (except for those packets sent in response to received
  In Section 6.7.13 it said
   "When it is desired to change the detect multiplier, the value of
   bfd.DetectMult can be changed to any nonzero value.  The new value
   will be transmitted with the next BFD Control packet.  See section
   6.7.8 for additional requirements."
  I am not sure whether the "parameter change" said in Section 4.1 include 
  the Detect Multiplier Change that said in Section 6.7.13 , or ONLY include 
  the timer parameters that said in Section 6.7.3.
  pls list the "parameter change" case that said in Section 4.1 !
  3、In Section 6.7.3 , it only said that when MTI increased or MRI reduced
  the actual transmission interval or detection time MUST not change until 
  a Control packet is received with the Final (F) bit set . if MTI reduced
  it will change the transmission interval immediately , but i think it will
  have problem until received a control packet from remote system if the 
  changed MTI vlaue is very low but the remote MRI is very large .
  4、a question for example :
     A    ------     B
  MTI=100ms     MTI=10ms
  MRI=20ms      MRI=30ms
  if A want to send echo packet , the actual echo transmission interval 
  will be the largest value of A's MTI and A's MRI and B's MTI and B's MRI 
  and B's MERI , is it right???   
  5、if echo function is active , i am not sure whether the echo packet is
  sent periodly in Demand mode mode and Asynchronous mode , or ONLY sent 
  periodly in Asynchronous mode and when needed in Demand mode??
  6、if echo function is active , the control packet is sent at least 1s 
  and the control packet will take the 1s value in it , is it correct??
  7、if BFD run on the multi-hop route , it will only detect whether the 
  route can reached the destination or not , it can not detect whether the
  route had changed on another route , is it correct ??
  8、BTW , in Section 6.7.8 it said
  "Note that if
   the I Hear You (H) bit is changing to zero, the session is going down
   and Demand mode will no longer be active."
   the statement is not right because the I Hear You (H) bit is removed.
Thanks for your help!!