Ethernet's 64-byte minimum frame size stems from fundamental network engineering principles. In early shared-medium Ethernet (like 10BASE5), this specification prevented undetectable collisions across maximum-distance networks.

// Example frame structure showing minimum fields
typedef struct {
    uint8_t preamble[7];  // Synchronization
    uint8_t sfd;          // Start Frame Delimiter
    uint8_t dest_mac[6];  
    uint8_t src_mac[6];
    uint16_t ethertype;
    uint8_t payload[46];  // Minimum to reach 64 bytes
    uint32_t fcs;         // Frame Check Sequence
} EthernetFrame;

The 64-byte minimum derives from:

• 512-bit slot time (64 bytes × 8 bits)
• Round-trip delay calculation for 10Mbps Ethernet
• Maximum network diameter of 2500m with 4 repeaters

This ensures collision detection works properly across the entire collision domain before transmission completes.

While modern switched Ethernet doesn't face collisions, the minimum remains for:

// Modern equipment still enforces minimum size
if (frame.length < 64) {
    frame.padTo(64);  // Zero-padding implementation
    updateFCS(frame);
}

Key reasons for maintaining the standard:

1. Backward compatibility with legacy devices
2. Uniform hardware buffer allocation
3. Predictable latency calculations

Small frames create throughput inefficiency:

// Calculating channel utilization
def calculate_efficiency(frame_size):
    overhead = 20 + 8 + 12  # Preamble, IFG, headers
    return frame_size / (frame_size + overhead)

# 64-byte frame: ~64% efficiency
# 1500-byte frame: ~98% efficiency

Modern networks support jumbo frames (typically 9000 bytes), but the 64-byte minimum remains the baseline requirement for all standard Ethernet implementations.

Ethernet's 64-byte minimum frame size stems from fundamental network physics. Consider a 10Mbps Ethernet network with maximum cable length of 2,500 meters (original IEEE 802.3 spec). The round-trip propagation delay for this distance is approximately 51.2 microseconds. This creates the critical timing window for collision detection.

// Simplified collision detection timing calculation
const propagationDelay = 51.2; // μs (for 2500m)
const transmissionRate = 10; // Mbps
const minimumFrameSize = (propagationDelay * transmissionRate * 1000) / 8;
console.log(minimumFrameSize); // Output: 64 bytes

Carrier Sense Multiple Access with Collision Detection (CSMA/CD) requires that a transmitting station must still be sending when a collision report arrives. The 64-byte minimum ensures this:

• 12 bytes interframe gap
• 8 bytes preamble
• 46 bytes payload (minimum to reach 64-byte frame)
• 4 bytes FCS (checksum)

Even with modern switches eliminating collisions, the minimum remains for compatibility. Here's how network stacks handle padding:

// Python example of Ethernet frame padding
def pad_ethernet_frame(payload):
    MIN_FRAME_SIZE = 64
    frame = preamble + dst_mac + src_mac + eth_type + payload
    if len(frame) < MIN_FRAME_SIZE:
        padding = bytes([0] * (MIN_FRAME_SIZE - len(frame)))
        frame += padding
    return frame + crc32(frame)

When crafting raw packets, developers must account for this minimum:

// C example showing proper frame construction
#include 

struct ethhdr *eth = (struct ethhdr *)packet;
memcpy(eth->h_dest, dest_mac, ETH_ALEN);
memcpy(eth->h_source, src_mac, ETH_ALEN);
eth->h_proto = htons(ETH_P_IP);

// Minimum payload check
if (payload_len < 46) {
    memset(packet + sizeof(struct ethhdr) + payload_len, 
           0, 46 - payload_len);
}

The 64-byte minimum creates efficiency tradeoffs:

This explains why jumbo frames (9000 bytes) became popular for high-throughput applications.