Since its now available, the Phase 2 Addendum is a good document to review: https://bitsavers.org/pdf/apple/com...se_2_Protocol_Specification_Addendum_1989.pdf
Inside AppleTalk covers this, but not all together in one place.
@iigs123, does the ImageWriter appear to other Localtalk clients when the iPrint is turned off? LocalTalk has no concept of networks over the line and devices like the ImageWriter generally use non-extended DDP packets if no router is present. If I recall, one of the NBP related bugs involved the card not filling out the extended DDP header response correctly, although this shouldn't be a problem on a non-routed network.
The other bug is that it basically puts trash data in the DDP checksum field, so if TailTalk is verifying DDP checksums, it could be dropping the packets. Note that by default, Apple's network stacks on Macs do not verify DDP checksums.
Inside AppleTalk covers this, but not all together in one place.
@iigs123, does the ImageWriter appear to other Localtalk clients when the iPrint is turned off? LocalTalk has no concept of networks over the line and devices like the ImageWriter generally use non-extended DDP packets if no router is present. If I recall, one of the NBP related bugs involved the card not filling out the extended DDP header response correctly, although this shouldn't be a problem on a non-routed network.
The other bug is that it basically puts trash data in the DDP checksum field, so if TailTalk is verifying DDP checksums, it could be dropping the packets. Note that by default, Apple's network stacks on Macs do not verify DDP checksums.
