why I was concerned about IP header cksum
Craig Partridge <craig@aland.bbn.com> Mon, 16 October 1995 20:21 UTC
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Subject: why I was concerned about IP header cksum
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From: Craig Partridge <craig@aland.bbn.com>
Date: Mon, 16 Oct 1995 12:53:25 -0700
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Hi folks: When I posted notes about a month ago about IP header checksum issues, I got some queries about what I was building. The press release that explains what I'm up to went out last week and is appended. Regarding the IP header checksum, I can now explain a bit more about what the issue is. We are using off the shelf components (the boards are custom designed, but none of the chips or processors are). And the core of the forwarding process is a workstation-class processor (e.g., Pentium, Alpha, PowerPC) that examines each header, modifies it and decides where to send the packet affiliated with the header (along with the updated header). The instruction budget, as you might imagine, is tight. We're doing several million datagrams per second per processor, so the total instruction budget (for an "average" datagram including device driver) is in the neighborhood of 50 to 100 instructions. That's feasible. (As a check, I took VJ's fastest IP forwarding code plus our proposed device driver interface and hand compiled it for an older model Alpha, yielding 60 instructions in 46 clock cycles -- the Alpha was memory bound rather than software bound -- I couldn't load and store the header plus SNMP variables any faster). For some RISC processors, summing 10 16-bit words is painful (even if you use larger word sizes) due to the lack of a carry bit, so the instruction count can easily get to 10 or 15 instructions (which added to 50 instructions total, is a real performance killer...) Craig ************************ FOR IMMEDIATE RELEASE: Press Contacts: Donna Lane Paul Davis BBN For BBN (617) 873-2559 (617) 494-9500 Internet: dlane@bbn.com pdavis@fitzcomm.com BBN Wins Contract to Develop Multigigabit Router Two-Year Pact will Result in Development of High Speed IP Router 25 Times Faster than Current Commercial Products CAMBRIDGE, Mass., October 10, 1995. BBN (NYSE:BBN) today announced that it has been awarded a contract by the Department of Defense's Advanced Research Projects Agency (ARPA) to develop an ultra high-speed Internet Protocol (IP) router that will enable breakthrough levels of traffic to be routed among wide-area and local-area (LAN) networks. Under terms of the contract, BBN Systems and Technologies will deliver a prototype multigigabit router in late 1997. The base contract is valued at $4.8 million, with options totaling $2.1 million. BBN Systems and Technologies was the developer of the ARPANET, the forerunner to today's global Internet. Routers are communications devices that are critical components of IP networks, such as the Internet. Routers interconnect multiple networks and work by forwarding information from one network to another, dynamically determining the best path to any destination. Scheduled for delivery in 1997, the BBN multigigabit router is intended to provide router performance for IP data that far exceeds current transmission levels. "Without a doubt, the demand for higher Internet speeds and capacities is readily predictable," said Dr. Vinton Cerf, senior vice president for data architecture, MCI Data Services Division. "This research effort is a natural next step in the evolution of the Internet and, if successful, will provide a much-needed capability for future growth of this exciting new telecommunications infrastructure." Dr. Cerf is the co-inventor of the Internet's Transmission Control Protocol/Internet Protocol (TCP/IP). "The work we plan to do under this contract will enable ARPA to continue to use IP networks and routers to connect to more expansive, complex networks in the future," said David Campbell, president of BBN Systems and Technologies. "The router points the way toward extremely fast backbone and hub routers, which will be capable of forwarding large amounts of data with extremely low delay. It also enhances our ability to experiment with and operationally use multigigabit networks. "In addition, the router will have significant relevance to government agencies, especially for military applications. The multigigabit router's ability to transmit large, high-resolution digital images quickly will enable US military analysts to access minutes-old data for more efficient and accurate decision-making," Campbell said. The contract calls for BBN to develop a prototype of the router that supports two 622 megabits-per-second Asynchronous Transfer Mode (ATM) interfaces, with an option to build 2.4 gigabit-per-second interfaces to work on the same prototype. "The technology developed for this prototype can provide the basis for a more powerful router that supports dozens of interfaces," said Dr. Craig Partridge, BBN's technical leader for the multigigabit router project. "The multigigabit router, with an aggregate data transfer rate of 50 gigabits per second, will be 25 times faster than currently available commercial routers, and will be able to handle the combined traffic of nearly 500 FDDI rings." An FDDI ring is a 100 megabit-per-second LAN. A router of this performance level is capable of interfacing with new gigabit-per-second and faster networking technologies, such as ATM, High-Performance Parallel Interface (HIPPI) and Fibre Channel. BBN Systems and Technologies is a pioneer of many of today's leading-edge technologies, including the global Internet. The company conducts research and development in computer, communications and information sciences, and develops advanced technology products, systems and application software that help people work and learn together. Headquartered in Cambridge, Mass., BBN (Bolt Beranek and Newman Inc., NYSE:BBN) is a leading provider of internetworking technologies, data analysis software and collaborative systems and services for commercial customers, government agencies and educational institutions. The company posted revenue of $215 million for its fiscal year ended June 30, 1995. Further information about BBN products and customers may be obtained through BBN's Internet Web site at http://www.bbn.com. # # # - -------- Joan L. Irons Corporate Communications BBN Corporation 150 CambridgePark Drive Cambridge, MA 02140 (617) 873-3514 Voice (617) 873-6899 Fax JIrons@bbn.com Internet
- why I was concerned about IP header cksum Craig Partridge