The MPLS WG Archive

["Arumugamr" <arumugamr@future.futsoft.com>]

Hi,

I am not sure, whether this is the right forum to ask the question, but
since the RR feature is very much needed for the MPLS-RSVPTE I am posting
this question.

1. RFC 2961 states two methods of refresh overhead reductions namely the
Bundle and SRefresh mechanism. If an implementation supports RR, then it has
to support the both extensions.  SRefresh has an advantage over Bundling in
terms conserving bandwidth and processing overhead.  Is there any specific
scenario, wherein the Bundle message is advantageous over SRefresh message.

2. RFC 3209 section 5 Hello extn states that the Hello message can be
included in the Bundle message. The usage of hello is for rapid node failure
detection, wherein the Bundle message is for reducing the refresh overhead.
Eventhough thousands of refreshes are sent to the neighbour there will be
only one hello message sent to the neighbour.  Also the delay in hello being
sent can result in the other node to assume the peer has reset.   Is there
any specific reason behind the hello messages being bundled.

3.  In RFC 2961 section 4.5 states that

"If a Path
   or Resv message contains the same Message_Identifier value that was
   used in the most recently received message for the same session and,
   for Path messages, SENDER_TEMPLATE then the receiver SHOULD treat the
   message as a state refresh.  "

With respect to the above statement, I have the following questions.

   a)  In Accordance to RFC 3209, assume Refreshes with MsgIds (SRefresh
probably) are going between Ingress/Egress and its immediate neighbour. Also
the refresh messages carry RRO's.  When  RRO too large for MTU error message
is received, the Ingress(In case of PATH msg)/Egress(In case of Resv
message) should have to stop sending RRO's. Now the question being the
Refresh message without RRO will be send with the same MsgId, which was used
for the previous session (or) will be a new one.
         Since an implementation on receiving a message with the same MsgId,
Session and SenderTemplate, if it treats it as the refresh and fails to
updates the RRO removal indication, the node that generated the error will
still retransmit the error msg. Which MsgId should be transmitted Old/New.

  b)  Also in the RRO's flags may toggle because of some local failure
detection & recovery process. In these cases the MsgId Should be a Newly
generated/Old one being retransmitted..


I welcome your comments

Thanks and Regards
Arumugam R

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