/ip firewall mangle add chain=forward protocol=tcp tcp-flags=syn action=change-mss new-mss=clamp-to-pmtu passthrough=yes comment="Clamp MSS to PMTU".
2) MTU Alignment: For PPPoE connections, set interface MTU to 1492 and MRU to 1492 (max TCP MSS = 1452).
3) Routing Table: Import the ISP's BDIX BGP routing prefix list into a dedicated routing table or address list (BDIX_Subnets) and configure Policy-Based Routing (PBR) through the BDIX gateway.
BDIX Bufferless Streaming & TCP MSS Clamping Optimizer
Avoid packet fragmentation on Bangladesh National IX (BDIX) peering routes and FTP media servers. Automatically calculates MTU/MSS boundaries and generates copyable firewall rules.
/ip firewall mangle add chain=forward protocol=tcp tcp-flags=syn tcp-mss=1453-65535 action=change-mss new-mss=1452 comment="RouterPortal BDIX Clamping"
iptables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
Why BDIX Connections Stall Without TCP MSS Clamping
Ethernet frames have a standard Maximum Transmission Unit (MTU) of 1500 bytes. PPPoE adds an 8-byte encapsulation header (PPP session + protocol ID), reducing the usable IP MTU to 1492 bytes. When local BDIX servers send 1500-byte packets without Path MTU Discovery (PMTUD), intermediate routers drop the unfragmented packets, causing video buffering and stalled downloads.
BDIX Policy-Based Routing (PBR) Architecture
- Download the updated BDIX ASN prefix list (containing BTRC registered local IP blocks).
- In MikroTik, create an IP Firewall Address List named
BDIX_PREFIXES. - Add a Mangle rule: Mark routing for destination address list
BDIX_PREFIXESwith routing markto-bdix. - In
/ip route, add a static route for routing markto-bdixpointing to your ISP's dedicated BDIX gateway IP.
Bangladesh Broadband Provider BDIX Profiles
| ISP Name | Protocol & WAN Type | Default MTU / MSS | MAC Binding Policy | BDIX Peering / FTP Hub |
|---|---|---|---|---|
| Carnival Internet | PPPoE over GPON | MTU 1492 / MSS 1452 | Strict MAC Binding (Reset on Router Swap) | Carnival Movie Hub / Live TV |
| Dot Internet | PPPoE & Static Public | MTU 1492 / MSS 1452 | Port Binding + MAC Verification | Dot Net FTP / Low-Ping BDIX Peering |
| Link3 Technologies | PPPoE / 802.1Q VLAN | MTU 1492 / MSS 1452 | Strict MAC Clone Required | Link3 BDIX Hub / Live TV |
| Amber IT | PPPoE & SIP Trunking | MTU 1492 / MSS 1452 | MAC Binding with IP Phone Priority | AmberIT FTP / IP Phone Peering |
| Circle Network | PPPoE & Direct Fiber | MTU 1492 / MSS 1452 | MAC Authentication on OLT | CircleFTP (10.16.100.244) / Torrent |
| SamOnline | PPPoE over GPON | MTU 1492 / MSS 1452 | Automated MAC Locking | SamFTP / Movie Server |
| KS Network | PPPoE Broadband | MTU 1492 / MSS 1452 | Manual MAC Reset on Call | KS Media Hub / BDIX Cache |
| ICC Communication | PPPoE / Static | MTU 1492 / MSS 1452 | Centralized Radius Auth | ICC BDIX Peering / Live TV |
Our networking steps are lab-tested against standard RFC 1918 private networking protocols across Windows 11 (24H2), macOS Sequoia (15.1), iOS 18, and Android 15. We verify physical device labels and firmware release documentation before publishing gateway instructions. Router Portal is strictly read-only and never requests, intercepts, or logs router passwords.