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Re: [RRG] What do we have consensus on?
On 5/28/08 3:57 AM, Tony Li allegedly wrote:
|Tony suggested 3 branches:
|
|- Transport: this falls with #1 in the above
|- Map-n-encap: this is #2 in the above
|- Translation: I did not get exactly what this one is, if it is
| not the GSE rewrite.
|
|there was a debate between Tony and Brian at the time about whether
|SHIM6 is translation. I dont think I fully understood Tony's argument
|on why SHIM6 is a translation; may be Tony could try one more
|time here.
The way that I look at it, Shim6 establishes a set of 'identifiers' that the
transport protocols will use and then plays some games to determine the set
of 'locators' for network layer operations. Since it is doing wholesale
swapping of the locators for the identifiers, I'd claim that it's mostly a
translation approach.
I think that it's clear that it's not actually changing transport. Further,
it's pretty clear that while it is piggybacking some information, it really
isn't going to the full-scale extent of a real encapsulation.
On 5/28/08 7:37 PM, Christian Vogt allegedly wrote:
More specifically, in my view, the fundamental difference between
encapsulation and translation is where you store the information
needed to perform a packet transformation. With classic tunneling,
this information is included in packets. With classic translation,
the information takes the form of state at the entity performing
packet transformation. The information carried in packets is then
reduced to a "state lookup key", which enables the receiver to find
the state it needs for the packet transformation. In classic
translation, the state lookup key is a translated port number.
The primary intent in encapsulation is to preserve the original packet
during an exchange between two intermediate hops. The simple case is
classic "layer networking", like IP over ATM or Ethernet. A packet is
encapsulated in total, and the "link" between encapsulation and
decapsulation is seen as one IP hop. In the case of IP-aware
encapsulation, the TTL of the header may be deprecated. So in that case
there is no transformation whatever, by intent.
What you describe above one might call reversible translation. But we
need to differentiate between that and translations where there is no
expectation of ever going back, e.g. IPv6->IPv4 or NAT, and just saying
"classic translation" versus "reversible translation" gets awkward.
1-to-1 translation differs from both encapsulation and classic
translation since it requires neither state nor in-packet information.
Due to its statelessness, it does not suffer from aforementioned
rerouting limitations, even if it is performed inside the network.
What is 1-to-1 translation?
Scott
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