should packet.data really be length-prefixed?

[michielbdejong]

https://github.com/interledger/rfcs/blob/master/asn1/InterledgerPacket.asn#L43 says that the InterledgerPacket's data field should be "a length-prefixed header", and that seems to be what https://github.com/interledgerjs/ilp-packet/blob/master/index.ts#L22 does.

But when I read the ASN.1 without reading that comment, my interpretation is that PACKET.type is an ASN.1 OpenType of the PACKET CLASS, and although I couldn't really find a good reference on asn.1, from what I've read, I would expect PACKET.&Type ({PacketSet}{@type}) to just be replaceable with e.g. InterledgerProtocolPayment if typeId is 1?

cc @justmoon

see also interledgerjs/btp-packet#10

[justmoon]

OER does indeed add a length prefix in this situation. I don't have the reference handy, but we generated plenty of examples using OSS Nokalva's ASN.1 implementation and at one point I did look up the relevant section in the X.696 specification and open types in OER are length-prefixed.

[michielbdejong]

Thanks! Looked it up, and adding the length prefix is indeed correct for an ASN.1 Open Type. See
https://www.itu.int/rec/T-REC-X.696-201408-S/en section 30: