Re: (virtual) hum on CARD open issues

Hi Vijay,

please find another comment below.

marco

Vijay Devarapalli wrote:

>Singh Ajoy-ASINGH1 wrote:
>  
>
>>>1. Issue #2: R-flag for CARD Request rate limiting. What to do about potential Dos issues? WG consensus is to Keep the R-flag approach. Meeting consensus is to add clarifying text to section 4.2 (4.3?)
>>>      
>>>
>>this is wrong, IMHO. rate limiting is a well known mechanism.
>>introducing a new flag is not a bright idea.
>>
>>ajoy-> Why it is a bad idea?  Well, I am neutral in this
>>issue but I am not convinced why using R bit is worse than
>>your proposed solution.
>>    
>>
>
>simple. rate-limiting is implemented in a wide variety of
>protocols (infact for any message that creates state at
>the receiving node). nothing new here. you dont need a new
>mechanism for this.
>
>  
>
>>>3. Issue #33: Inter-AR CARD protocol transport from UDP to ICMP. The editor recommends the use of ICMP to make it consistent with the mobile interface. Potential downsides: ICMP has potential security implications. ICMP message types on binding is also very implementation specific. Also, securing ICMP would require that all ICMP packets be secured. Meeting consensus is to keep UDP.
>>>      
>>>
>>2 and 3 dont go togetheer. defining CARD messages as ICMP
>>options lets you piggyback these options on FMIPv6 messages.
>>I am not sure how you can achieve piggybacking if the MN-AR
>>signaling becomes UDP. ICMP was the right choice between
>>the MN and the AR.
>>
>>AJOY-> Well I did not attend IETF meeting, but I guess this means ICMP for
>>MN-AR and UDP for AR-AR interface. Others' please correct me.
>>    
>>
>
>oops... I misunderstood. I thought the concensus at the 
>meeting was to use UDP for both.
>
>  
>
>>BTW, why are you in favor of
>>using ICMP for AR-AR interface?
>>    
>>
>
>otherwise you need seperate code for processing an ICMP
>CARD Request (from the MN) and UDP CARD Request (from 
>the PAR). also, if it is an ICMP message, I can piggyback
>CARD messages on HI/HACK messages of FMIPv6.
>  
>
I see the point and that's why we addressed this issue during the meeting.
According to some feedback (also before the meeting), not everybody sees
a problem with changing transport characteristics between MN-AR
and inter-AR interfaces.
Also not sure if piggybacking of CARD messages with HI/HACK
makes sense, since inter-AR CARD is in most cases required before
FastMIPv6 HI/HACK is performed. And HI/HACK is performed only with
the selected target AR. Of course, current AR could use this sequence
to update its own and target AR's CAR table entries, but I guess this
would make the "one time inter-AR CARD piggybacking, another time
stand-alone inter-AR CARD"-thing much more complicated.
What do you think?




>
>  
>
>>unbelievable. the CARD protocol is already complicated (IMO).
>>the emphasis should be on reducing the complexity. just use
>>a value of infinity for the lifetime field to indicate a
>>static capability. any other value for the lifetime indicates
>>dynamic capability. I think for the CARD protocol, emphasis
>>should be on making it a simpler protocol than saving 4 bytes
>>over the air. :)
>>
>>if you are concerned about an overhead of 4 bytes, make the
>>lifetime field 2 bytes. a 2 byte lifetime field gives you
>>65536 seconds which should be enough. do you need a 4 byte
>>lifetime field?
>>
>>AJOY-> I disagree here. Saving even 2 bytes per capability is
>>huge saving for bandwidth constraint network. I am not sure
>>processing one flag will make CARD protocol any more complicated.
>>Btw, in cellular standard I have seen even more complicated
>>procedure for saving 4 bits per frame. Please note that
>>the CARD protocol is being proposed as an experimental
>>protocol so we will have opportunity to make such
>>changes in future if required.
>>    
>>
>
>but in the current form not many people are going to use 
>it. it might remain forever as an experimental, untouched,
>ignored, just another RFC.... that is something we should 
>avoid. I want a protocol that I can use. :)
>
>Vijay
>
>_______________________________________________
>Seamoby mailing list
>[email protected]
>https://www1.ietf.org/mailman/listinfo/seamoby
>  
>