Selective acknowledgment (SACK) is an optional feature of TCP that is necessary to effectively use all of the available bandwidth of some networks. While SACK is good for throughput, processing this type of acknowledgment has proven to be CPU intensive for the TCP sender. This weakness can be exploited by a malicious peer even under commodity network conditions. This article presents experimental measurements that characterize the extent of the problem within the Linux. . Selective acknowledgment (SACK) plays a crucial role in optimizing bandwidth usage yet introduces potential vulnerabilities affecting TCP effectiveness.. TCP Selective Acknowledgment, Network Performance, Bandwidth Efficiency. . Brittany Day
As standards wars rage on in 802.11 wireless local-area networks, the Proxim Harmony 802.11a card shows the promise of a cost-effective wireless bandwidth adequate for video and data by cranking up wireless data rates to a theoretical 54 Mbits/second and beyond, . . . . As standards wars rage on in 802.11 wireless local-area networks, the Proxim Harmony 802.11a card shows the promise of a cost-effective wireless bandwidth adequate for video and data by cranking up wireless data rates to a theoretical 54 Mbits/second and beyond, although actual throughput is lower. The device also reveals how much potential for silicon integration still lies ahead for 802.11 cards-and just how inexpensive those adapters could soon become. Proxim's 802.11a Harmony is packed in a Type II PC-card format that consists of a single pcb sandwiched between plastic and stainless-steel front and back covers. A four-layer circuit board measuring 4.8 x 11.5 cm supports an all-surface-mount component set exclusively on the topside. Approximately one-fourth of the board is devoted to the built-in diversity antenna and its ground plane. The diversity antenna elements are simple disk-shaped metal stampings that account for the bulge in the external package opposite the standard 68-pin PC-card connector. Internal electronics reflect the high level of integration already achieved in 802.11a wireless chip sets. Key to the Harmony design is the Atheros AR5000 chip set, which divides 802.11a silicon into two components: an AR5110 baseband/media-access control chip and the AR5210 so-called radio-on-a-chip. The link for this article located at eeTimes is no longer available. . Proxim's Aura 802.11g adapter provides an affordable wireless solution vital for streaming and data exchanges.. Proxim Harmony Card, Wireless Networking Card, 802.11a Standards, Cost-Effective Wireless, High-Speed Wireless. . LinuxSecurity.com Team
Freeloading commercial emailers do more than fill your mailbox with unsolicited email. They also steal server time and network bandwidth, and have even crashed mailservers. And if your mail server can be used as a relay for spam, you may find your site "blackholed", cut off from sending email to many sites, in addition to getting thousands of angry email messages from the victims of the spam. . . .. Freeloading commercial emailers do more than fill your mailbox with unsolicited email. They also steal server time and network bandwidth, and have even crashed mailservers. And if your mail server can be used as a relay for spam, you may find your site "blackholed", cut off from sending email to many sites, in addition to getting thousands of angry email messages from the victims of the spam. It used to be easy to track down spammers. And all it took to block spam were firewall or mail server rules that denied access from the spammers' domain. Spammers today use commercial tools designed to hide the source of the spam, as well as use third party sites as relays so the spam won't be blocked before it reaches its victims. SMTP (Simple Mail Transport Protocol) not only makes spam possible, but it also makes it possible to track back spam to its source. All it takes is the ability to read and understand mail headers, and knowing something about how SMTP works. By denying spammers access to relay sites, we can stamp out unsolicited commercial email (UCE). The link for this article located at Rik Farrow is no longer available. . Unwanted promotional emails can clutter your inbox and strain your server's resources. Discover ways to tackle email spam efficiently.. Email Spam Management, Spam Prevention Techniques, SMTP Security, Mailbox Protection. . LinuxSecurity.com Team
In the quest for world domination it's important not to forget your backups. And, in the world of backup software, Amanda rocks. Amanda runs from the inetd daemon and can backup multiple clients to a single backup server. It streams backup . . . . In the quest for world domination it's important not to forget your backups. And, in the world of backup software, Amanda rocks. Amanda runs from the inetd daemon and can backup multiple clients to a single backup server. It streams backup data from all of its clients to a holding disk (or directory) before writing the data to tape. This has the dual benefit of not only creating a backup if you forget to change the tape but also accelerating the entire backup process itself. With a Quantum DLT 8000 tape drive, I commonly backed up about 12GB/hour from 13 servers (and this was with no tuning whatsoever. My restores were fast as hell as well.) Amanda uses native utilities to backup the clients thus allowing you to customize whether you want to use dump or tar on a per-client basis, the amount of compression to use, and the amount of bandwidth on your network you are willing to allocate to the backup process. By using native backup utilities, amanda allows you get the benefit of not only having a backup utility which is always available on your platform but also the benefit of being able to restore your data even if Amanda is completely unavailable. One of the nice things about Amanda is that it will never screw you out of your data by using closed and proprietary formats or forcing you to dig up a licensing diskette while under stress. The link for this article located at FrankenLinux is no longer available. . Protect your important information by taking advantage of robust open-source backup solutions such as Bacula with precision.. Amanda Backup, Data Management Tools, Open Source Backup Solutions. . LinuxSecurity.com Team
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