Re: [nat66] NPTv6 deals with "packets", not with "datagrams" - to be corrected after draft-14

[Fred Baker <[e-mail]>]

On May 3, 2011, at 11:02 AM, Rémi Després wrote:

>> I refer you to the definition of the term. A datagram is self-addressed and contains all of the information necessary to deliver it from its source to its destination.
> 
> In hosts, which perform datagram reassembly, that's correct.

You really don't understand. The distinction is between datagram networks and virtual circuit (in context, SNA and X.25) networks. A transport PDU could be carried by a virtual circuit from here to there, or it could be carried in a datagram over a connectionless network. TCP data is carried in datagrams, and UDP data is carried in datagrams. NFS routinely used fragmented UDP packets to carry its data, but when UDP was designed, that was not the intended model; anyone who has done very much UDP-with-fragmentation will tell you that it operationally doesn't work very well either if there is any kind of bottleneck in the path.

I found a formal definition of the term in RFC 1594:

Datagram
        A self-contained, independent entity of data carrying
        sufficient information to be routed from the source
        to the destination computer without reliance on earlier
        exchanges between this source and destination computer and
        the transporting network.

Is this really worth arguing about? I use the term "datagram" because the meaning is important in the context; I'm playing with the prefixes in the addresses in the datagram header. I don't use the term "packet" because it's an empty word; it can be applied at any layer (an ATM "cell" is a packet with a certain format, an IP datagram is a packet with a certain format, a LAPB or Frame Relay "frame" is a packet with a certain format, and a TCP segment is a packet with a certain format). A packet is a quantum of data moving as a single unit in the network at the layer of interest. I'm sorry it bothers you. What NPTv6 deals with is IP datagrams. You very correctly called me on using both terms in the document, and in response to your comment I corrected the usage.