permit several choices of bit rate, but the industry has converged on 2.488 gigabits per second (Gbit/s) of downstream bandwidth, and 1.244 Gbit/s of upstream bandwidth. GPON Encapsulation Method (GEM) allows very efficient packaging of user traffic with frame segmentation. By mid-2008, Verizon had installed over 800,000 lines. British Telecom, BSNL, Saudi Telecom Company, Etisalat, and AT&T were in advanced trials in Britain, India, Saudi Arabia, the UAE, and the US, respectively. GPON networks have now been deployed in numerous networks across the globe, and the trends indicate higher growth in GPON than other PON technologies. G.987 defined 10G-PON with 10 Gbit/s downstream and 2.5 Gbit/s upstream – framing is "G-PON like" and designed to coexist with GPON devices on the same network. Security Developed in 2009 by Cable Manufacturing Business to meet SIPRNet requirements of the US Air Force, secure passive optical network (SPON) integrates gigabit passive optical network (GPON) technology and protective distribution system (PDS). Changes to the NSTISSI 7003 requirements for PDS and the mandate by the US federal government for GREEN technologies allowed for the US federal government consideration of the two technologies as an alternative to active Ethernet and encryption devices. The chief information officer of the United States Department of the Army issued a directive to adopt the technology by fiscal year 2013. It is marketed to the US military by companies such as Telos Corporation. GPON used in Fiber to the x deployments may face vulnerability to Denial-of-service attack via optical signal injections, unresolved based on current commercially available technologies. IEEE In 2004, the Ethernet PON (EPON or GEPON) standard 802.3ah-2004 was ratified as part of the Ethernet in the first mile project of the IEEE 802.3. EPON is a "short haul" network using ethernet packets, fiber optic cables, and single protocol layer. EPON also uses standard 802.3 Ethernet frames with symmetric 1 gigabit per second upstream and downstream rates. EPON is applicable for data-centric networks, as well as full-service voice, data and video networks. 10 Gbit/s EPON or 10G-EPON was ratified as an amendment IEEE 802.3av to IEEE 802.3. 10G-EPON supports 10/1 Gbit/s. The downstream wavelength plan support simultaneous operation of 10 Gbit/s on one wavelength and 1 Gbit/s on a separate wavelength for the operation of IEEE 802.3av and IEEE 802.3ah on the same PON concurrently. The upstream channel can support simultaneous operation of IEEE 802.3av and 1 Gbit/s 802.3ah simultaneously