zCOM Protocol Stacks

The zCOM library is there to provide a composable stack of protocols, down from osi layer 1 (e.g. ethernet frames, IEEE_802.11) up to osi layer 7 (DNS, DHCP, Tiny TP, …).

The library is designed in a way that you can stack each protocol onto a compatible protocol, for example serving Tiny TP over UDP instead of IrLMP or use PPP over a serial line.

Goals

• Provide a general purpose implementation of a lot of link protocols
• Protocol implementations should be configurable so they are suitable for both high end machines (desktop, server) and embedded devices
  • This means that a protocol might require comptime configuration to restrict the number of allowed connections (for example, allow only up to 3 TCP connections to save RAM)
• Allow the use of any physical layer
• Provide APIs that allows the use of async, but doesn’t enforce it
• Make the APIs be usable for byte-by-byte inputs and don’t require any specified packet size. Feeding a recording of 1 MB of data should work the same way as feeding a single byte.

Project Status

The whole project is just in planning phase, no concrete implementation done yet.

Supported Protocols

Each protocol with a tick is at least in a somewhat usable state

Layer 1

• Ethernet
• IEEE802.11 (WLAN)

Layer 2

• ARP
• PPP
• IrLAP

Layer 3

• IPv4
• IPv6
• ICMP
• IGMP
• IrLMP
• ESP-NOW

Layer 4

• TCP
• UDP
• Tiny TP

Layer 7

• DHCP
• DNS
• mDNS
• NTP
• PTP

Documents / Blogs / Further Reading

• https://www.saminiir.com/lets-code-tcp-ip-stack-1-ethernet-arp/

Dictionary

Message

A message is a sequence of octets a user wants to transmit/receive. Messages are application specific and don’t contain any protocol headers.

Examples:

• A chat message formatted in JSON

Buffer

A buffer is a sequence of octets that are stored for temporary/implementation reasons.

Packet

A packet is a delimited sequence of octets with known (but maybe dynamic) length. Packets have a protocol defined format and usually contain protocol headers.

Examples:

• UDP sockets transmit/receive packets called datagrams.
• IEEE 802.11 transmits/receives packets called frames.

Stream

A stream is a unlimited sequence of octets without a well defined length.

Examples:

• TCP sockets transmit/receive streams.
• Serial ports transmit/receive streams.