Internet Leased Line là gì? Kênh thuê riêng là gì? – VNPT Online

Internet Leased Line

Internet Leased Line, also known as a dedicated channel, is a direct connection between network nodes using a privately rented data transmission channel. Typically, a data transmission channel provides users with options for seamless connectivity using different protocols on the leased line, such as PPP, HDLC, LAPB, and more. The physical form of a leased line can be a direct copper cable connection between two points or a combination of different copper cables and transmission networks.

When a leased line passes through multiple networks, communication regulations with the transmission network will be determined by the service provider. Therefore, the necessary CSU/DSU terminal equipment to connect the leased line will depend on the service provider. Some main connection standards used are HDSL, G703, and more.

When using a leased line, users need to have sufficient communication on the routing devices to provide a WAN connection for each leased line connection at each node. This means that at a node point with a leased line connection to 10 different points, there must be 10 WAN interfaces to serve the leased line connections. This is a limitation in terms of initial equipment investment, lack of flexibility in expansion, and complex management, especially when it comes to high-cost leased lines for long-distance connections.

The protocols commonly used with Internet leased lines are HDLC, PPP, and LAPB. HDLC is a protocol used with Cisco routers, meaning that HDLC can only be used when both ends of the leased line connection are Cisco routers. PPP is an international standard protocol compatible with routers from different manufacturers. When establishing a leased line connection between a Cisco device and a third-party device, it is necessary to use this connection protocol. PPP is a layer 2 protocol that allows multiple different network protocols to run on it, making it widely used. LAPB is a layer 2 communication protocol similar to the X.25 network protocol, with complete transmission control procedures, development, error correction, and fault detection. However, LAPB is less commonly used.

Some Related Information

  • When using Frame-Relay, only one Serial port on the Router is required.
  • HDLC does not require both ends to be Cisco devices; as long as they are devices from the same manufacturer and support HDLC, it is sufficient.
  • If the distance between branches is not too far (less than 5 km), LAN extension devices can be used (for example, Planet G.SHDSL modem), which eliminates the need for Router and NTU investment costs.
  • In terms of installation configuration, it follows the pattern: Router <—> CSU/DSU <—-WAN—-> CSU/DSU <—-> Router. The connecting cable is just a regular RJ45 cable.
  • Configuration of the devices is as mentioned by Five; it simply involves configuring the two Serial ports on the Router.

Leased lines have two types of connections:

  • Leased line point-to-point: used to connect two sites.
  • Leased line local-loop: used to serve internet connectivity and public services (ISPs will provide a range of public IPs from 8 to 16). Depending on usage requirements, customers can choose the appropriate connection type.

Devices Used

  • Router: You can use routers from Juniper, Cisco, but it is advisable to use Cisco routers as they have a larger user base and more learning resources available. It is recommended to use the ISR 1800 modular series or higher.
  • Serial interface: You can use the WIC 1T, WIC 2T, or NM-4T cards. It is recommended to use the WIC 2T to ensure redundancy.

Connection Cables

  • V.35 (DB 60 – 60 pin) if using the WIC 1T card.
  • Smart serial V.35 (DB 26 – 26 pin) if using the WIC 2T card.

Network Termination Unit (NTU)

  • BRAS using TDM technology: Use Adtran NTU.
  • BRAS using ATM technology: Use Verilink NTU.
  • It is best to let the ISP provide the NTU to synchronize with the currently used devices.
  • FPT has currently deployed fiber optic leased lines that can be converted to RJ45 standards. In this case, there is no need for an NTU, serial interface, or cable (however, this type of connection is only available in limited areas).

Device Configuration

  • If using a fiber optic leased line, you only need to configure the Fast Ethernet port, without having to think about using the serial interface.
  • Leased lines point-to-point and local-loop have slightly different configurations.
  • NTU configuration is straightforward, only requiring a few synchronization parameters.

***If you have three branches, usually you will lease two leased lines to connect the two subsidiary branches to the headquarters.

  • ADSL is a shared connection (you only have a separate line from your house to the nearest DSLAM), so its security level is not high. Besides, ADSL is an asymmetric connection (download speed > upload speed), and the more users there are, the slower the speed becomes.
  • Leased Line connections between branches are private dedicated channels. Only you can transmit and receive data on them, so they are more secure (ISPs are responsible for ensuring a smooth connection, and if there is a disconnection due to a transmission line error, they must fix it as soon as possible, not postpone until tomorrow as with ADSL). The download speed is the same as the upload speed, and this speed is usually much lower than the committed speed of ADSL (of course, if you have the budget, you can lease a high-speed Leased Line, but the cost will increase significantly). Typically, the speed is about 256Kbps for domestic Leased Line connections (between branches within the same province/city) and 512Kbps for interprovincial Leased Line connections. Of course, with Leased Line backbone connections, you can calculate and select the most optimal speed. Typically, only organizations such as banks/securities companies require high security, so they need to use Leased Lines. Regarding the equipment, it is true that, in general, one WAN interface is required for one Leased Line. However, you can use Frame-Relay with sub-interfaces (point-to-multipoint), or with the G703 interface, you can use a channel bank/multiplexer, which also helps save WAN interfaces.***

Advantages of Leased Line Services

  1. Stability: Customers are provided with an Internet connection through a leased line that does not have to share bandwidth with other subscribers, unlike regular ADSL or FTTH services.
  2. Continuous Connectivity: With the PPP connection protocol, leased line services ensure continuous 24/7 connectivity through dedicated fiber optic cables.
  3. Flexibility: Leased line services can be upgraded or downgraded based on customer usage needs within 5 minutes, without requiring device changes or cable system reconstruction.
  4. Cost-Effective Investment: Leased line service packages provide customers with free 8 static IP addresses for building Mail Servers, Web Servers, VPNs, VoIP, and more.
  5. Professional Customer Support: Maximum deployment time is 5 days from contract signing, providing customers an Ethernet interface (FE) for easy connection to servers and internal LAN systems. Commitment to 24/7*365 support, with technical teams on-site within 30 minutes, and problem resolution (if any) within 2 hours.

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