The Userspace Logging Daemon (ulogd) is a flexible framework for extensive logging of packets on a firewall machine. ulogd uses the ULOG target of iptables/netfilter, the packet filtering framework of Linux 2.4 and 2.6. It supports binary plugins for adding packet interpreters and output-targets (e.g., for logging into databases, user-defined filetypes, etc.).
ulogipac is a powerful IP traffic accounting tool for Linux routers and hosts. Users can use the power of iptables rules to specify which traffic to be accounted and which not to be accounted. The size of IP packets sent through iptables ULOG is counted and buffered. After a configurable time period the daemon submits the traffic information to database servers. Traffic information can be sent to more than one server to provide redundancy.
upnp2mrtg is a simple add-on for the MRTG (Multi Router Traffic Grapher). It can be used to monitor incoming and outgoing bytes of the external interface of the FritzBox DSL router. upnp2mrtg is a command line tool to gather statistics from an upnp enabled FritzBox DSL router. It is a lightweight shell-script for use with MRTG, so no underlying external software (with the exception of netcat) or libraries are required. Using bash-networking instead of netcat is also supported.
uranos is a system that supports unattended installations of Linux and Windows. It supports kickstart, pressed, and autoyast on for Linux, and Windows 2000, XP, 2003, 2003R2, Vista, 7, 8, 2008, and 2012. It features inventory, software management, dhcp-ldap, dns-ldap, php-ssh, syslog-ng, rsyslog, switch management, LDAP browser, PXE manager, central cron management, and license management.
utcpdump is a stripped-down version of tcpdump 3.4 that was developed for Trinux but may be suitable for other low-footprint/floppy/embedded Linux/*BSD distributions. It provides only a subset of the features/protocol decodes available in the full version of tcpdump, and is primarily useful for conducting basic network troubleshooting.
uvlan is a User-space Virtual Local Area Network. In other words, uvlan peers act as nodes on a network switch. Ethernet traffic is routed between peers intelligently. This allows for multiple networks to share resources and even IP address space. Some may call it a VPN (Virtual Private Network) application, but it's much more powerful: it is peer-to-peer, is much simpler, and operates at layer 2 (ethernet). VPNs generally operate at layer-3 (IP), and layer 2 applications like gaming can't be supported with layer 3 tunneling.