Networking · Cluster
Link Layer
Ethernet, framing, and local delivery.
- 01 Ethernet Frame Layout and the 64-Byte Minimum The field-by-field layout of an Ethernet II frame, why the payload floor is 46 bytes, and how a receiver distinguishes padding from real data.
- 02 MAC Address Structure and How a NIC Filters Group Traffic The bit layout of a 48-bit MAC address, why the I/G and U/L bits sit in the first transmitted byte, and the receive-filter modes a NIC applies before any driver code runs.
- 03 The Frame Check Sequence: CRC-32 and the Errors It Misses How the four-byte Ethernet trailer is computed, why CRC-32 catches every burst up to 32 bits, and which corruption patterns pass it undetected.
- 04 MAC Learning and How a Bridge Builds Its Forwarding Table A transparent bridge learns source addresses, forwards unknown destinations out every port, and ages entries out; the failure modes of each step.
- 05 Spanning Tree Port States and the Cost of a Blocked Link BPDU exchange elects a root, each bridge picks a least-cost port, and the resulting states determine which ports forward; convergence delays are the price.
- 06 ARP and the Neighbour Cache Lifecycle How an IPv4 address becomes a MAC address, why the cache entry has states rather than an expiry, and what happens to queued packets during resolution.
- 07 802.1Q Tagging and the Four-Byte Insertion Where the VLAN tag sits in a frame, what PCP and DEI carry, how untagged and priority-tagged frames are told apart, and what a trunk port must do.
- 08 Link MTU, Jumbo Frames, and Where the Path Breaks Why 1500 bytes became the standard payload, what changes when both ends agree on more, and how MTU mismatches appear as silent large-packet loss.
- 09 Link Aggregation and the Hash That Chooses a Member How LACP bundles links, why the distributor hashes rather than round-robins, and the ordering guarantee that constrains every possible choice.
- 10 Inside the NIC Receive Path: Descriptors, Rings, and NAPI A frame arriving at a network interface moves through a DMA ring, a descriptor, an interrupt, and a poll loop; where each step can drop it.