SLIP vs PPP: Which Serial Protocol Wins for Modern Networks?
SLIP (Serial Line Internet Protocol) is a bare-bones way to send IP packets over a serial cable; PPP (Point-to-Point Protocol) is its modern replacement that adds authentication, encryption, error-checking, and multi-protocol support.
Engineers still say “SLIP” when they mean any dial-up link because old Cisco labs and retro BBS docs used it for decades; newcomers copy the term, not realizing their cable modems and LTE sticks actually speak PPP underneath.
Key Differences
SLIP frames packets with a simple END byte, has no address or control fields, offers zero error recovery, and can’t negotiate IP addresses. PPP wraps packets in HDLC-like frames, uses LCP to set link options, NCP to assign IPs, and supports PAP/CHAP security plus multilink bonding.
Which One Should You Choose?
Choose PPP for every modern link—DSL, 4G/5G, VPN backhaul, even IoT cellular modules. Only keep SLIP if you’re reviving a 1980s UNIX workstation or debugging a microcontroller with 2 KB RAM.
Is SLIP faster because it’s simpler?
No; PPP’s framing overhead is tiny, and its error checking prevents costly retransmits, making it faster and more reliable.
Can I upgrade from SLIP to PPP on old hardware?
If the firmware or OS supports serial drivers and extra RAM for state machines, PPP libraries like pppd can replace SLIP transparently.