Re: [6lowpan] Slight problem with format document

[Mario Mao <[e-mail]>]

To Daniel:

Thanks for you tips.

However, I believe the compression issue is not just for implementation. Thinking about the reason why we need to build IPv6 upper  lowpan node, there is high possibility of global scope cummnication. In this scenario, and considering the format defination, the class [1] and [4] could appear at the same time.

For example, one remote controll center want to access an lowpan node, they would use IPv6 global address to communicate. When the IP packet reach to 6lowpan gateway, this routing node would redeliever it to the internal lowpan node. Now, the adaptation layer of the gateway should use class [1] and [4] for destination address compression and class [1] and [3] for source address. That's also the scenario of my assumption [1].

Is it better to clarify all possible situation? 

To Gabriel:

I think the tiny literal change would work, thanks. 

Regards,

Mario

----- Original Message ----- 
From: "Daniel Park" <[e-mail]>
To: "Mario Mao" <[e-mail]>
Cc: "gabriel montenegro" <[e-mail]>; "Geoff Mulligan" <[e-mail]>; "6lowpan" <[e-mail]>
Sent: Thursday, January 18, 2007 4:05 PM
Subject: Re: [6lowpan] Slight problem with format document


> It seems a bit implementation issue. Our format document defines four classes:
> 
> [1] Prefix In-line IID In-line
> [2] Prefix In-line IID compressed
> [3] Prefix compressed IID In-line
> [4] Prefix compressed IID compressed
> 
> Most assumtion in our scenario as of today is [4]. It means IPv6
> source and destination belong to link-local scope. In your assumtion,
> perhaps, [1] and [2] are appropriate. In that sense, 6lowpan
> adoptation layer seems not meaningful. Also, 6lowpan header
> compression is only applied for 802.15.4 link due to the tiny
> bandwidth.
> 
> Daniel
> 
> On 1/18/07, Mario Mao <[e-mail]> wrote:
> >
> > I agree with gabriel, there is no interference between header compression
> > and ICMP. However, I believe two points should be noted which may cause
> > information loss.
> >
> > 1. If the processing node is lowpan gateway/router and the sent packet comes
> > from Internet but not originates by the gateway/router itself, the IID of IP
> > source address shouldn't be compressed.
> > 2. If the IP destination isn't an "on-link" node (that means the destination
> > is more than one hop away from source node), the IID of IP destination
> > address shouldn't be compressed.
> >
> > In a word, 6lowpan node could only compress the IID that derives from IEEE
> > 802.15.4 MAC address. I think that point should be emphasized in draft,
> > isn't it?
> >
> > Regards,
> >
> > Mario
> >
> >
> > ----- Original Message -----
> > From: gabriel montenegro
> > To: Geoff Mulligan ; 6lowpan
> > Sent: Thursday, January 18, 2007 3:07 PM
> > Subject: Re: [6lowpan] Slight problem with format document
> >
> >
> > Is this even necessary to be said? ICMP msgs will never be sent by
> > intermediate nodes
> > in a lowpan mesh, but only by the IPv6 end nodes as part of normal IPv6
> > processing.
> > This processing takes place after the lowpan layer delivers packets to the
> > IPv6 stack. So by the time the IPv6 stack gets the packet, it will have been
> > decompressed. This is the same for lowpan header compression or any other
> > type
> > of header compression.
> >
> > So I wonder if the text below is needed. It would be needed if the entity
> > sending
> > back ICMP messages was the lowpan layer. Yes, it would see compressed
> > headers.
> > But the entity is the IPv6 stack, which does not see those compressed
> > headers.
> >
> > Comments? Am I missing something?
> >
> > -gabriel
> >
> > ----- Original Message ----
> > From: Geoff Mulligan <[e-mail]>
> > To: 6lowpan <[e-mail]>
> > Sent: Wednesday, January 17, 2007 10:36:52 PM
> > Subject: [6lowpan] Slight problem with format document
> >
> > While reviewing the format document I realized that we didn't describe
> > handling of ICMPv6 error messages.  Since the 6lowpan headers may be
> > compressed it is necessary to uncompress the original IP and transport
> > headers before sending the ICMP error message.
> >
> > Here is my proposed text for a new section 12...
> >
> > 12. Handling ICMPv6 messages
> >
> > ICMPv6 (RFC2463) is used to report errors and carry IP layer information
> > and functions such as diagnostics.  There are two groups of ICMPv6
> > messages: error messages and informational messages. Each message
> > consists of a type field (if the high order bit is 0 it is an error
> > message), a code and checksum field.  These fields are followed by the
> > ICMPv6 message body.  For ICMPv6 error messages (Type <128) the message
> > body shall contain as much of the original (offending) IP message
> > without exceeded the minimum IPv6 MTU.
> >
> > As described in the preceding section (Header Compression), the original
> > IPv6 and Transport (TCP or UDP) headers may be compressed via HC1 and
> > HC2 encoding.  So that the destination node of an ICMPv6 error message
> > can properly process the message the source node must decompress the
> > IPv6 and transport headers before sending the ICMPv6 message.  This is
> > necessary because the original MAC addresses and the HC1 and HC2
> > encoding headers will be lost and the recipient would have no ability to
> > reconstruct the original message nor compute the proper checksum.
> >
> > The ICMPv6 message itself is carried inside and IPv6 packet and this
> > packet may be transmitted over the 6LoWPAN network utilizing header
> > compression.  ICMPv6 messages that are larger than the available payload
> > of the 6LoWPAN network will need to be fragmented. Assuming the maximum
> > frame overhead, maximum link layer security and including a 6LoWPAN Mesh
> > Header, Fragmentation Header and Dispatch Header, sending the
> > uncompressed IPv6 and transport headers should still allow for 25 octets
> > of the original packet payload.  Packets using short addresses, no
> > security, and just a 6LoWPAN Dispatch header will be able to carry 61
> > octets of the original packet.
> >
> >
> >
> >
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> >
> >
> >
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> 
> 
> -- 
> 
> 
> Daniel (Soohong Daniel Park)
> Mobile Convergence Laboratory, SAMSUNG Electronics.

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