[WEBINAR] Bulletproof: How Today's Business Leaders Stay on Top


Definition - What does XMODEM mean?

XMODEM is a popular file transfer protocol developed by Ward Christensen in 1977. It sends data blocks associated with checksums and waits for the acknowledgment of a block receipt. Xmodem is implemented in both hardware and software.

XMODEM was simple to implement, but it lacked efficiency. As a result, modified versions of XMODEM were created to address some of the issues with the protocol. Eventually, XMODEM was replaced by YMODEM and then ZMODEM.

Techopedia explains XMODEM

XMODEM is a half-duplex communication protocol that has an effective error detection strategy. It breaks the original data into a series of packets, which are sent to the receiver together with additional information that permits the receiver to determine whether packets were properly received.

Files are marked complete with an end-of-file character that is sent after the last block. This character is not in the packet, but is sent as a single byte. Because file length is not passed as part of the protocol, the last packets are padded with known characters, which can be dropped.

Files are transferred one packet at a time. On the receiving side, the packet checksum is calculated and compared to the one received at the end of the packet. When the receiver sends an acknowledgment message to the sender, the next set of packets is sent. If there is a problem with the checksum, the receiver sends a message requesting retransmission. Upon receiving the negative acknowledgment, the sender resends the packet and retries the transmission continuously for about 10 times before aborting the transfer.

Share this:

Connect with us

Email Newsletter

Join thousands of others with our weekly newsletter

The 4th Era of IT Infrastructure: Superconverged Systems
The 4th Era of IT Infrastructure: Superconverged Systems:
Learn the benefits and limitations of the 3 generations of IT infrastructure – siloed, converged and hyperconverged – and discover how the 4th...
Approaches and Benefits of Network Virtualization
Approaches and Benefits of Network Virtualization:
Businesses today aspire to achieve a software-defined datacenter (SDDC) to enhance business agility and reduce operational complexity. However, the...
Free E-Book: Public Cloud Guide
Free E-Book: Public Cloud Guide:
This white paper is for leaders of Operations, Engineering, or Infrastructure teams who are creating or executing an IT roadmap.
Free Tool: Virtual Health Monitor
Free Tool: Virtual Health Monitor:
Virtual Health Monitor is a free virtualization monitoring and reporting tool for VMware, Hyper-V, RHEV, and XenServer environments.
Free 30 Day Trial – Turbonomic
Free 30 Day Trial – Turbonomic:
Turbonomic delivers an autonomic platform where virtual and cloud environments self-manage in real-time to assure application performance.