mail waits

BBS mail made the path visible. you could see who handled a message and when.

store and forward

before always-on, mail moved when the modem dialed. your message sat in an outbound spool, patient, until 2am rates kicked in and the node upstream picked up. delivery was measured in hops and hours, and nobody thought that was broken. it was legible. you could read the whole path.

seer-line is that model, revived in C, with modern crypto stapled where the trust used to be implied:

/* every hop signs the envelope it forwards.
   the path is the provenance. */
int sl_hop_sign(sl_envelope *env, const sl_key *node_key) {
    sl_hash_update(&env->path_hash, node_key->fingerprint, 20);
    return sl_sign(env, node_key);
}

why bother

because a transport that assumes the network is sometimes there survives conditions that break the always-on stack: bad links, hostile middleboxes, plain distance. offline-first was not a feature in 1993. it was the physics.

the spool keeps a record until the next hop takes the packet.

next: notes on the routing table format. it is a text file.