TD-LTE Router In-Depth Comparison: AirMaster 3100V vs GreenPacket DT-350

Evaluating indoor TD-LTE desktop modems for Band 42 (3500 MHz) deployments requires comparing RF sensitivity, throughput stability under weak signal conditions, and hardware VoIP capabilities. Here is an empirical comparison between the AirMaster 3100V and the GreenPacket DT-350.

Tested Models: AirMaster 3100V (Firmware V2.0.0B31) • GreenPacket DT-350 (Unlocked Band 42 SIMs)

Key Findings and Benchmark Summary

Feature	AirMaster 3100V	GreenPacket DT-350
VoIP Hardware	No FXS RJ-11 port	Built-in SIP client & RJ-11 port
Wi-Fi Performance	802.11n 300Mbps	802.11n 300Mbps
Weak Signal Stability	Superior antenna gain (RSRP stability)	Moderate gain; benefits from external SMA antennas
Firmware Flexibility	Clean web management	Requires unlocking for full VoIP/APN menus

Recommendation: If telephone VoIP handset integration is required, the GreenPacket DT-350 is the clear choice. For raw RF reception in fringe coverage areas, the AirMaster 3100V delivers more consistent speeds.

How to Perform Path MTU Discovery on Linux and macOS (Ping and Tracepath)

Mismatched Maximum Transmission Unit (MTU) sizes across VPNs, tunnels (WireGuard, IPsec, PPPoE), and intermediate network links frequently cause silent TCP connection hangs and packet fragmentation issues. Testing your path's effective MTU using the "Don't Fragment" (DF) bit pinpoints the exact link threshold.

Formula: Total MTU = ICMP Payload Size + 28 bytes (20 bytes IP header + 8 bytes ICMP header).

1. Path MTU Discovery on Linux

Use ping with -M do (enforce Don't Fragment) or tracepath:

# Ping with 1472 bytes payload (1472 + 28 = 1500 MTU)
ping -M do -s 1472 8.8.8.8

# If it reports "Frag needed and DF set", step down until packets pass:
ping -M do -s 1392 8.8.8.8 # (1392 + 28 = 1420 MTU, standard for WireGuard)

# Automatic MTU trace across intermediate hops:
tracepath 8.8.8.8

2. Path MTU Discovery on macOS

# On macOS, use -D to set DF bit:
ping -D -s 1472 8.8.8.8