ZMax is a file transferprotocol developed in 1990-1991 by Mike Bryeans (Micro TECH Systems) who also developed TMODEM.
Zmax is designed to replace ZMODEM. It uses 32 bit CRC's on file data blocks, the same as Zmodem, and 32 bit CRC's on its information blocks where Zmodem uses 16 bit.
In stream mode Zmax sends blocks, the size being set by the receiver, of data but doesn't require ACKs from the receiver.
Zmax should (depending on equipment, phone lines, implementation, etc.) allow about 97.5 percent efficiency at 2400 baud on a 30K file compared to Zmodem's 95 percent. Unlike Zmodem, Zmax reaches full speed on considerably smaller files. In fact, due to less overhead associated with small files, it achieves a better efficiency rating.
In Non-Stream mode (which can be set by the receiver or the sender), Zmax is a super Batch XMODEM or YMODEM depending on the block size, because it uses 32 bit CRCs instead of 16.
Unlike Zmodem which sets an upper limit of 1024 bytes on block sizes, Zmax has an upper limit of over 32K. Because of this, Zmax may be used as a mailer protocol without any modifications.
Zmax also has a lot less CPU overhead than Zmodem, so slower computers can drive highspeed modems faster. Zmax does not encode each byte of data like Zmodem does. This reduces the amount of CPU overhead and simplifies the code quite a bit. Zmax also treats all files as binary 8 bit files and will require word length to be set to 8, which is the most common setting.
The Transmission Control Protocol (TCP) is one of the main protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, the entire suite is commonly referred to as TCP/IP. TCP provides reliable, ordered, and error-checked delivery of a stream of octets (bytes) between applications running on hosts communicating via an IP network. Major internet applications such as the World Wide Web, email, remote administration, and file transfer rely on TCP, which is part of the Transport Layer of the TCP/IP suite. SSL/TLS often runs on top of TCP.
Network throughput refers to the rate of successful message delivery over a communication channel, such as Ethernet or packet radio, in a communication network.The data that these messages contain may be delivered over physical or logical links, or through network nodes. Throughput is usually measured in bits per second, and sometimes in data packets per second or data packets per time slot.
Trivial File Transfer Protocol (TFTP) is a simple lockstep File Transfer Protocol which allows a client to get a file from or put a file onto a remote host. One of its primary uses is in the early stages of nodes booting from a local area network. TFTP has been used for this application because it is very simple to implement.
bzip2 is a free and open-source file compression program that uses the Burrows–Wheeler algorithm. It only compresses single files and is not a file archiver. It was developed by Julian Seward, and maintained by Mark Wielaard and Micah Snyder.
High-Level Data Link Control (HDLC) is a bit-oriented code-transparent synchronous network layer protocol developed by the International Organization for Standardization (ISO). The standard for HDLC is ISO/IEC 13239:2002.
The Lempel–Ziv–Markov chain algorithm (LZMA) is an algorithm used to perform lossless data compression. It has been under development since either 1996 or 1998 by Igor Pavlov and was first used in the 7z format of the 7-Zip archiver. This algorithm uses a dictionary compression scheme somewhat similar to the LZ77 algorithm published by Abraham Lempel and Jacob Ziv in 1977 and features a high compression ratio and a variable compression-dictionary size, while still maintaining decompression speed similar to other commonly used compression algorithms.
ZMODEM is a file transfer protocol developed by Chuck Forsberg in 1986, in a project funded by Telenet in order to improve file transfers on their X.25 network. In addition to dramatically improved performance compared to older protocols, ZMODEM offered restartable transfers, auto-start by the sender, an expanded 32-bit CRC, and control character quoting supporting 8-bit clean transfers, allowing it to be used on networks that would not pass control characters.
XMODEM is a simple file transfer protocol developed as a quick hack by Ward Christensen for use in his 1977 MODEM.ASM terminal program. It allowed users to transmit files between their computers when both sides used MODEM. Keith Petersen made a minor update to always turn on "quiet mode", and called the result XMODEM.
YMODEM is a file transfer protocol used between microcomputers connected together using modems. It was primarily used to transfer files to and from bulletin board systems. YMODEM was developed by Chuck Forsberg as an expansion of XMODEM and was first implemented in his CP/M YAM program. Initially also known as YAM, it was formally given the name "YMODEM" in 1985 by Ward Christensen, author of the original XMODEM.
Ascii85, also called Base85, is a form of binary-to-text encoding developed by Paul E. Rutter for the btoa utility. By using five ASCII characters to represent four bytes of binary data, it is more efficient than uuencode or Base64, which use four characters to represent three bytes of data.
CRC-based framing is a kind of frame synchronization used in Asynchronous Transfer Mode (ATM) and other similar protocols.
In computer networking, jumbo frames are Ethernet frames with more than 1500 bytes of payload, the limit set by the IEEE 802.3 standard. Commonly, jumbo frames can carry up to 9000 bytes of payload, but smaller and larger variations exist and some care must be taken using the term. Many Gigabit Ethernet switches and Gigabit Ethernet network interface controllers and some Fast Ethernet switches and Fast Ethernet network interface cards can support jumbo frames.
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The Microcom Networking Protocols, almost always shortened to MNP, is a family of error-correcting protocols commonly used on early high-speed modems. Originally developed for use on Microcom's own family of modems, the protocol was later openly licensed and used by most of the modem industry, notably the "big three", Telebit, USRobotics and Hayes. MNP was later supplanted by v.42bis, which was used almost universally starting with the first v.32bis modems in the early 1990s.
Smodem refers to a bidirectional protocol for file transfer used between modems and the DOS program in which the protocol is implemented, both of which were developed by a Finnish company named Arisoft. It was mainly used in bulletin board systems because it could transfer files in both directions at the same time and allowed users to chat with each other with AriSoft's GroupChat software. Other popular bidirectional protocols such as BiModem, HS/Link and HydraCom also offered a chat option with the operator, but not with the system's other users.
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In computer networking, an Ethernet frame is a data link layer protocol data unit and uses the underlying Ethernet physical layer transport mechanisms. In other words, a data unit on an Ethernet link transports an Ethernet frame as its payload.
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The common header, which occupies the first 12 bytes. In the adjacent diagram, this header is highlighted in blue.
The data chunks, which form the remaining portion of the packet. In the diagram, the first chunk is highlighted in green and the last of N chunks (Chunk N) is highlighted in red. There are several types, including payload data and different control messages.
Janus is a file transfer protocol for use on bulletin board systems (BBSs). It has the relatively rare feature that it is fully bidirectional, allowing the protocol to upload and download files at the same time. It was written by Rick Huebner in 1987; Huebner had previously written a ZMODEM module for the Opus-CBBS system.
MEGAlink is a file transfer protocol for modem-equipped microcomputers written by Paul Meiners in 1987. Like many protocols of the era, MEGAlink is an expanded version of the seminal XMODEM. While it was a relatively simple and high-performance system, it remains relatively obscure because it was overshadowed by ZMODEM, which had been released a year earlier and saw rapid uptake.
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