On Fri, Mar 29, 2019 at 11:46 AM Juergen Schoenwaelder < [email protected]> wrote:
> On Fri, Mar 29, 2019 at 09:30:19AM -0700, Andy Bierman wrote: > > On Fri, Mar 29, 2019 at 9:17 AM Juergen Schoenwaelder < > > [email protected]> wrote: > > > > > On Fri, Mar 29, 2019 at 09:07:18AM -0700, Andy Bierman wrote: > > > > On Fri, Mar 29, 2019 at 4:19 AM Juergen Schoenwaelder < > > > > [email protected]> wrote: > > > > > > > > > Hi, > > > > > > > > > > this is issue is closed but I wonder whether this is correct. I > have > > > > > several questions looking at the issue on github: > > > > > > > > > > - Why is this not a YANG issue? > > > > > - Which workaround is better? > > > > > - Why is this tagged as a NETCONF issue? > > > > > > > > > > > > > > Did you mean this should be NETCONF issue? > > > > It is more of a protocol problem then a modeling problem. > > > > The goal is to use the model unaltered. > > > > > > I think it would be valuable if say the definition of ipv4-address > > > could state that a canonical binary representation is of type binary { > > > length 4; }. Doing this is only meaningful for some types but it would > > > allow to add more binary representations over time. > > > > > > > > If we want to support binary encodings, we need to allow modelers > to > > > > > define which types map to a canonical binary representation in > > > > > addition to the canonical string representation. As stated in the > > > > > issue description, hard-wiring some types in the encoding > > > > > specifications is very limited. > > > > > > > > > > In terms of backwards compatibility, this issue should IMHO be > tagged > > > > > high (adding binary encoding for some types does not cause any > > > > > backwards compatibility problem since so far we have only strings). > > > > > > > > > > > > > > Not so sure. > > > > The base64 encoding could look like a valid string. > > > > The receiver must know a binary type is being sent (XML and JSON both > > > fail > > > > here, but not CBOR). > > > > > > I am talking about CBOR, not about XML or JSON. I want to provide > > > hints to CBOR (or similar binary encodings) that values can be > > > represented in a different format. I do not expect these hints to be > > > used by XML or JSON. If you need binary encoding efficiency, use CBOR > > > instead of JSON. > > > > > > > > While I do not have a solution proposal, I think this issue is > worth > > > > > to look at and we should not close it right now. > > > > > > > > > > > > > > I have a solution proposal, but I have not implemented it yet, so it > it > > > not > > > > detailed... > > > > > > > > Both sender and receiver need to agree on the binary encoding and > how the > > > > data is tagged as binary. > > > > > > > > This expired draft should address that problem: > > > > https://tools.ietf.org/html/draft-mahesh-netconf-binary-encoding-01 > > > > > > > > For every type T that they agree on, there are standard T.b2y() and > > > T.y2b() > > > > conversion functions. > > > > There are also some extensions to define conversion templates so > vendors > > > > can add their own types. > > > > > > > > The YANG modules do not need to actually be altered. The peers will > > > > negotiate the > > > > set of types that will be sent as binary when the session starts. > > > > The receiver knows T and the SID for each object, and will accept > either > > > > the YANG or binary encoding. > > > > > > Sounds complex for me to negotiate this. I rather say once that a > > > binary encoding can ship an IPv6 address as type binary { length 16; } > > > and then CBOR will simply do the right thing. > > > > > > > > OK, but this would require new type names. > > You cannot simply change some standard type to be a union with a binary > > type. > > > > This forces all implementations of that type to support the binary > variant. > > That breaks old clients that worked with the version before the binary > > variant. > > > > The ripple effect on the models changing types would be non-trivial. > > Using this union-type approach forces every protocol to support the > binary > > encoding, > > yet base64 in a union with strings is very error-prone. > > > > I am not proposing do change the type definitions we have. My idea was > to have an optional additional definition for binary encodings. Here > is an ad-hoc example (I do not like the details of the syntax, but > perhaps this helps to understand the idea): > > typedef ipv4-address { > type string { > pattern > '(([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\.){3}' > + '([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])'; > } > description > "The ipv4-address type represents an IPv4 address in > dotted-quad notation."; > > binary-representation { > type binary { > length 4; > } > description > "The binary representation uses as 4-byte binary string > in network byte ordering."; > } > } > > The CBOR encoder (or other binary encoders) would then encode the > value as a 4 byte binary value, the XML and JSON encoder would use the > canonical string representation. If the binary-representation is not > specified, then the generic CBOR encoding rules apply. I assume that > additional binary representation definitions will only be needed for a > couple of types (and I might even be fine to restrict that to > typedefs). Anyway, details need work, but if we want to support more > efficient binary encodings, then I think we should keep the issue #46 > open. > > OK -- this is what I had in mind but off to the side, like a deviations module. If the client and server agree on the module containing the standard extension usages it will not be that complex in the protocol. ex:binary-representation ietf-inet-types:ipv4-address { ex:binary-length 4; ex:binary-pattern "b0.b1.b2.b3"; } I agree YANG 1.2 should have real statements instead of extensions. > /js > > Andy > -- > Juergen Schoenwaelder Jacobs University Bremen gGmbH > Phone: +49 421 200 3587 Campus Ring 1 | 28759 Bremen | Germany > Fax: +49 421 200 3103 <https://www.jacobs-university.de/> >
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