Space-based local area network

Paper ID# 901709.PDF

SPACE-BASED LOCAL AREA NETWORK Ronald Scrofano, Paul R. Anderson, Jorge P. Seidel, Joshua D. Train, Grace H. Wang, Lyle R. Abramowitz, Joseph A. Bannister The Aerospace Corporation El Segundo, CA and Chantilly, VA

Maj. David Borgeson U.S. Air Force Space and Missile Systems Center Developmental Planning Directorate El Segundo, CA

ABSTRACT With the phenomenal success and productivity of terrestrial networks, there is interest in using similar technology in space. For instance, there currently are projects aimed at deploying Internet routers in space. In this paper, we discuss the general concept ofconnecting a cluster ofsatellites with a local area network. We discuss the advantages and challenges of such a network, as well as possible missions. We also describe a specific implementation that would connect a cluster ofgeosynchronous satellites with a network based on the IEEE standard 802.16 protocol. We also describe our testbed and the terrestrial experiments that we are performing to validate our approach.

INTRODUCTION With the phenomenal success of terrestrial networks, there is interest in using similar technology in space. For instance, Internet Routing in Space (IRIS) is a commercial project to put an Internet router in space [1]. We are studying another such concept: Space-based Local Area Network (SbLAN). The goal of SbLAN is to leverage proven, standardized networking protocols to enable new satellite missions. The concept is to interconnect a local cluster of satellites to form a local area network (LAN). In the LAN, one satellite provides basic wide-band communication services and a link to an associated ground network for the other satellites in the cluster. Such an approach brings the following benefits: (1) decoupling of development schedules or requirement changes of spacecraft mission payloads from the development and launch of the necessary communication infrastructure, (2) use of modem net-centric communication technology in satellite systems, and (3) establishment of a standard space communication protocol that can be shared among a wide variety of spacecraft. In the next section, we further describe the SbLAN concept, first in general terms and then as a specific 978-1-4244-5239-2/09/$26.00 ©2009 IEEE

implementation. We then describe some of the benefits and challenges of implementing such a system. Next, we describe some possible missions that would benefit from the SbLAN system. We then discuss some specific network features of an initial implementation, followed by a description of experiments that we are performing in order to better characterize and understand the performance of such a network in a satellite-cluster environment.

CONCEPT In general, the SbLAN concept could be used in a wide variety of orbits and configurations. General SbLAN Concept

The SbLAN concept is illustrated in Figure 1. All satellites in the system are in the same type of Earth orbit, such as the geosynchronous orbit or the low Earth orbit, with the satellites all flying as a cluster or group. The system consists of a hub satellite and several mission satellites. The hub satellite hosts a communications payload that provides a network link between ground stations on Earth and the mission satellites; in principle, all communications to and from the mission satellites go through the hub satellite. This would include both telemetry and command communications, as well as communication services for the mission satellites. This hub satellite payload may be the only payload carried by the hub satellite, or it may be a secondary payload carried on a larger satellite. Mission satellites are smaller satellites that will typically be located 50 to 100 km from the hub satellite. There may be 1 to perhaps 10 or 12 mission satellites associated with one hub satellite. Although a network that connects nodes separated by distances of 50 to 100 km is often considered a widearea network, we describe this as a local area network because (1) the nodes are all on the same subnet and (2) the network would connect mission satellites and a hub satellite that are all flying in the same formation or cluster.

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Fig. 1.

protocol [2] (commercialized as "WiMAX"), selecting an appropriate physical layer (single-carrier modulation) for use in space. As described later, IEEE standard 802.16 has several features that make it applicable to SbLAN. The inter-satellite links will operate in either the 22.55 to 23.55 GHz Inter-Satellite Service (ISS) band, or the 59.0 to 71.0 GHz ISS band. The network is sized to provide an aggregate 100 Mbps downlink throughput from all of the mission satellites to the ground, and a maximum throughput of 20 Mbps on the inter-satellite links.

SbLAN concept

A key part of the SbLAN concept is the use of open standards for communication and networking between the hub and mission satellites. A lightweight network router is located on the hub satellite to provide network connectivity between the host and mission satellites. The hub will use a standard wireless protocol for communication with the mission satellites. Communication resources can then be dynamically allocated among the mission satellites, as managed by the hub. These are the primary advantages of the SbLAN concept-highly flexible and standardized communications with mission satellites. The mission satellites are able to enter and leave the cluster at will. Residency in a cluster is assumed to be weeks to years in duration. The size of the mission satellites can cover a wide range, from cubesats to minisatellites. These satellites fly in volumes of space ahead of and/or behind the hub satellite so that they maintain the same orbital period as the hub satellite. In general, it is also possible to place multiple hub satellites in space, each forming a wireless "hot spot" to serve mission satellites in its vicinity. Such a concept is particularly well-suited for hub satellites spaced strategically in geosynchronous orbit. A Specific ShLAN Implementation

We are developing an implementation of the SbLAN concept that is designed to fly in geosynchronous orbit. The hub satellite is planned to be a large commercial communication satellite that hosts an SbLAN communications payload, as well as other unrelated commercial payloads. The associated mission satellites could, for example, collect and report information on space weather or provide a telemetry and command communication service for lowEarth-orbiting government satellites. It is planned that the mission satellites be launched independently of the commercial communication satellite that hosts the SbLAN hub. The SbLAN network will use the IEEE standard 802.16

BENEFITS In general, the SbLAN concept has many benefits for government customers. The most important of these follow. Net-Centric Communications for Space Applications

As noted above, communication networks have played a huge role in improving the performance, usability and flexibility of electronic communications in terrestrial applications. SbLAN is designed to bring the practical functionality of a terrestrial local area network into space. Decoupling ofMission Payloads and Communications Payloads

Because mission satellites do not need to communicate directly with Earth, they require a less sophisticated, lower power communications payload. The mission satellites are thus smaller, less expensive, and more easily replaced. Decoupling of Mission Payloads From Each Other

Placing many mission payloads on a single large spacecraft bus has an advantage in efficiency. That is, for large spacecraft, relatively less bus mass is required to serve a given mission payload. However, if many different mission payloads are being installed on one large spacecraft, then all of these mission payloads must be compatible with each other, and they all must be ready for installation and launch at the same time. In the SbLAN concept, the build schedule, launch schedule, and design lifetimes of these mission payloads become independent of each other. Such independence is also a goal of the DARPA System F6 program (see Related Work and [3]). Incompatibilities between payloads becomes rare or non-existent. The mission payloads become decoupled from each other, and can be essentially anything that is needed, provided that these payloads do not interact negatively with the other mission payloads in the cluster.

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Paper ID# 901709.PDF Standardization

Standardization of a space network provides several benefits. A major advantage of using a widely accepted, nonproprietary standard protocol is that any satellite conforming to the nonproprietary standard is able to join the network. Hence, the government is not locked in to a particular vendor, nor is it locked in to a particular hardware component. Any components conforming to the standard can be used in a satellite. Because of this standardization, we envision the creation of a "kit" that provides basic mission satellite functionality. The kit will contain an antenna, a communications front end, and components necessary for satellite control. The kit will also provide a standard interface and a development package. The availability of an SbLAN kit will reduce the amount of development required to make a mission satellite. Adapting terrestrial standards in particular is also beneficial. These are standards that are in common use and that have proven capabilities. For instance, terrestrial standards have useful features for quality of service (QoS) guarantees and for security. Additionally, these standards have commercial support that can be leveraged to create products suitable for space. Ride-Sharing

A small mission satellite has the potential to share a ride on a launch vehicle with a larger satellite and hence enjoy more frequent launch opportunities. In particular, mission satellites will be able to take advantage of the faster pace of launches from the commercial world.

CHALLENGES While there are many benefits to the SbLAN concept, it is not without its challenges. Some of the more significant ones follow. Adaptation of Terrestrial Standards

Terrestrial standards have been optimized for existing terrestrial applications. For example, many wireless network standards utilize Orthogonal Frequency-Division Multiplexing (OFDM), which is a poor fit for space applications. Thus, it may be necessary to modify the chosen standard or to adopt a version that is not in wide-spread use terrestrially. Network Security

Information assurance is always important, but it becomes even more so when sensitive or classified mission data travels through a commercial hub satellite. Thus, it

will be important to employ classic techniques like encryption, firewalls, and packet filtering. Additionally, the possibility of unauthorized satellites joining the network must be guarded against. There must therefore be a mechanism in place for authentication of satellites joining the LAN. Constellation Control

The hub satellite and the mission satellites will be flying in close proximity to one another. This raises a number of issues associated with the safe day-to-day operation of the constellation itself. Relative ranging accuracy between the hub and mission satellites, and between mission satellites, must be sufficiently accurate to predict and maintain adequate orbital separation between all elements of the satellite cluster. In the case of a commercially-operated hub satellite and government-operated mission satellites, different ranging systems may be in use and this can introduce relative range uncertainties between them. Also, orbital maneuvers must be safely executed, and any missed maneuvers should not endanger the rest of the cluster. In addition, there must be sufficient separation between the cluster and any neighboring satellites that are not a part of the cluster. That is, the space volume occupied by the cluster should not infringe on the space required for other satellites operating in the immediate vicinity. It may also be desirable to fly the mission satellites independently of the maneuvers of the hub satellite, especially if the mission satellites are owned and operated by a nongovernment entity. However, the mission satellites must still fly within the field-of-view of the antenna(s) on the hub satellite in order to maintain the inter-satellite link(s). Finally, at the end of any satellite's usable life, it must be possible to de-orbit the satellite properly. Command and Control

Command and control of the mission satellites must be securely and reliably maintained at all times. This includes mission satellite launch, arrival and insertion into the cluster, anomaly operations, and departure; and hub satellite retirement or replacement. The mission satellites, then, will likely be fitted with independent telemetry and command systems. Such a payload would have somewhat more mass and about the same power dissipation as the accompanying inter-satellite communications payload. Our studies have shown that, for high throughput applications, there are significant savings in power dissipation when using the inter-satellite communications payload in place of direct-to-ground communications hardware. Thus, the addition of an independent telemetry and command system does not diminish the benefit of having a hub satellite.

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Paper ID# 901709.PDF Fault Tolerant Operations

The hub satellite will typically be a large, expensive military or commercial satellite that hosts the SbLAN hub payload. As such, it is important that any failures of the SbLAN hub payload not impact the host satellite, and that any failures on the mission satellites not endanger the operations of the hub satellite or any of the other mission satellites. Similarly, the mission satellites should be designed to safely survive in a controlled fashion should the hub satellite fail. Use of TCP on the Ground-to-Hub Link

The current concept calls for the use of either User Datagram Protocol (UDP) or Transmission Control Protocol (TCP) between the ground station and the hub satellite. Transferring large amounts of data from a geosynchronous orbit to Earth requires attention to the long fat network (LFN) problem. Traditional TCP breaks down in the presence of the high delay-bandwidth product typical of links to and from geosynchronous orbit. Several papers address this issue and present both a detailed analysis of the problem and several suggestions on mitigation [4]-[6]. MISSIONS The SbLAN concept is not targeted at anyone particular mission. Instead, it is an enabling technology. Mission satellites can do "anything." Provided they conform to the standard, they will be able to communicate through the hub back to the ground or with one another. Nonetheless, we describe here two possible missions that we envision for SbLAN. Note that these missions, and other potential SbLAN missions like them, fall under the Operationally Responsive Space (ORS) initiative begun by the U.S. Department of Defense (DoD) in 2007 [7]. Space Environmental Sensing

One interesting application of a mission satellite is the sensing of the space environment or space "weather" by a moderate- to small-sized satellite flying in the SbLAN constellation. Such a satellite measures, for example, the flux of specific atomic particles of interest or the X-ray energy level of the sun, and transmits this information in real time to the ground through the Hub satellite. Telemetry and Command Support

A second interesting application is a mission satellite that provides a telemetry and command communication service for low-Earth-orbiting government satellites. In this concept, a mission satellite in geosynchronous orbit provides telemetry and command links to satellites flying

below it in low- or medium-Earth-orbits. Thus the mission satellite provides the same telemetry and command services as a ground-based Earth station, either substituting for that Earth station or providing a valuable back-up service. PRACTICAL ANALYSIS Wireless LAN Standards IEEE standards 802.11 [8] and 802.16 were both evaluated for use in SbLAN between the hub satellite and the mission satellites. The 802.11 standard (commercialized as "Wi-Fi'') is a widely adopted wireless LAN protocol. Its intended range is hundreds of meters, and it was designed specifically for use in the rich multi-path environment found in and around buildings. IEEE standard 802.11 systems are typically used in frequency bands near 2 and 5 GHz and typically utilize direct sequence spread spectrum or OFDM modulation schemes. IEEE standard 802.16 was originally developed to compete with cable modems and Digital Subscriber Line systems in providing broadband service to homes. Wireless networks formed on this scale are called metropolitan area networks. The standard's intended range is tens to hundreds of kilometers and is designed for use in any appropriately allocated frequency band between 2.4 and 66 GHz. There are a number of versions of the standard that have been defined, each with somewhat different characteristics, intended uses, and operations in different band segments. The various versions (amendments) are designated by an alphabetic suffix (e.g. 802.16a). Releases of groupings of amendments are given a year designation (e.g. 802.16-2004). For the purposes of SbLAN, we have selected the 802.16-2004 standard. This standard includes a version that is designed for line-of-sight signal distribution from towers to antennas mounted on buildings. Its physical layer incorporates single carrier modulation that can be efficiently used in a space application. We selected 802.16-2004 because this standard readily supports the throughput needs of a useful SbLAN network and is designed to operate over the required distances. Although existing commercial off-the-shelf 802.16 hardware does not have the required radiation hardening for a space environment, a radiation-hardened FPGA implementation is executable. In addition, the QoS features of the 802.16 standard are significantly more sophisticated than those of the 802.11 family. Protocol Stack

We now describe one possible network protocol stack. For the transport layer between the ground station and the

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Paper ID# 901709.PDF hub satellite, UDP or TCP with LFN extensions is used. This will accommodate the high delay-bandwidth product of the ground station to hub link. The datalink layer uses the HDLC protocol, and at the physical layer some type of phase shift keying modulation (e.g. QPSK or 8PSK) is used with the radio frequency carrier operating in one of the commercial Fixed Satellite Service (FSS) bands (e.g. 11.7 to 12.2 GHz downlink, 14.0 to 14.5 GHz uplink). Between the hub and mission satellites, IEEE standard 802.16-2004 is used, employing the single carrier physical layer. The physical layer is QPSK modulation with an appropriate forward error correction code to work in the space communication environment. To comply with U.S. and international frequency allocations, the radio frequency carrier will be in one of the ISS bands (e.g. 22.55 to 23.55 GHz). Internet Protocol (IP) is used at the network layer, with the hub satellite containing a lightweight IP router. This router provides services such firewalls, address resolution protocol, and higher-layer TCP and UDP management functions. IPv4 is all that is necessary for this small LAN, though IPv6 would not be a problem.

EXPERIMENTS Purpose

In order to learn more about the characteristics of IEEE standard 802.16 and how such a standard would support and enable the SbLAN concept, we purchased commercial off-the-shelf WiMAX equipment. We are performing both wired and wireless experiments with this equipment, using a base station (as would be present in the hub satellite) and up to six subscriber units (one subscriber unit would be present in a mission satellite). Equipment

The equipment used for the experiments consists of a Redline Communications RedMax™ ANI00U base station and Redline Communications RedMax™ SU-O subscriber units [9], [10]. Figure 2 shows the equipment in the laboratory as set up for the wired experiments. This equipment is certified for WiMAX Wave 2, profile 3.5Tl. This profile defines sets of features of IEEE standard 802.16 that must be implemented. Notably, the physical layer implemented is the OFDM physical layer. Licensing

To conduct wireless experiments in this band, we applied to the Federal Communications Commission for an experimental "Special Temporary Authority" (STA) license. The STA was granted for a period of 6 months, from March 1, 2009 through August 31, 2009. The base station location is

TABLE I WIMAX EQUIPMENT PARAMETERS

Parameter Carrier frequency BS output power (wired) BS output power (wireless) Duplex technique Uplink:downlink ratio Channel bandwidth Subscriber unit service class Subscriber unit traffic priority

Value 3.74 GHz o dBm 23 dBm Time division duplexing 70:30 7 MHz Best Effort 0

in Rancho Palos Verdes, CA, at 33° 46' 31" north latitude, 118° 22' 6" west longitude. This site is located on the side of a hill at about 300 meters elevation, overlooking the Los Angeles basin (including Los Angeles Air Force Base and The Aerospace Corporation's campus). The subscriber units (representing the mission satellites) are located within a 50 Ian radius of the base station. Basic Connectivity Experiments

Our first experiments, both wired and wireless, were to ensure that the equipment closed the RF link and to ascertain the maximum throughput achievable. Some of the key parameters of the equipment and the values to which they were set during the experiments are shown in Table I. Note that the stations were communicating using OFDM during all the experiments. The base station was connected to a computer through a 100 Mbps Ethernet connection. Likewise, the subscriber unit under test was connected to a computer through a 100 Mbps Ethernet connection. After we configured the base station and subscriber units for use in the wired testbed, the RF link closed. The base station and subscriber unit automatically select a modulation based on the quality of the link. When the devices are connected by cable, the quality of the link is quite high, so the base station and subscriber unit selected the highest throughput modulation, 64 QAM (3/4), for both the uplink (subscriber unit to base station) and downlink (base station to subscriber unit) directions. With the link closed, our next goal was to test the maximum throughput. Since we envision the majority of data in the SbLAN flowing in the uplink direction, we focused on sending network traffic in that direction. To generate the traffic, we used the Iperf traffic generation tool and its graphical front-end, Jperf [11], [12]. The computer connected to the base station functioned as the Iperf server, while the computer connected to the subscriber unit functioned as the Iperf client. We estimated the maximum throughput to be the highest throughput rate at which UDP traffic sent from the computer connected to the subscriber

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Fig. 2.

Wired WiMAX testbed

TABLE II BASIC CONNECTIVITY EXPERIMENTAL RESULTS

Configuration Wired Wireless (long range)

Uplink Modulation 64 QAM(3/4) 16 QAM(l/2)

Max. Throughput 13 Mbps 6 Mbps

unit to the computer connected to the base station did not experience significant packet loss. For the wired testbed, this was 13 Mbps. We repeated this basic connectivity experiment for a wireless configuration in which the base station and subscriber unit were approximately 17 km apart. The results are shown in Table II. In this wireless configuration, the average latency for uplink communication was 13.3 ms and the average jitter was 0.9 ms. Multi-Subscriber Unit Experiments

We have also begun experimenting with multiple subscriber units. An important issue for SbLAN is that mission satellites are able to join the network, transmit, and leave the network without interrupting the operation of other mission satellites already in the network. To experiment with such a scenario, we added a second subscriber unit (Subscriber 2) to the wireless configuration described above. Subscriber 2 also was placed approximately 17 km from the base station and has the same uplink modulation and maximum throughput as the first subscriber unit (Subscriber 1). The results of one multi-subscriber unit experiment are shown in Figure 3. In this experiment, we used Iperf to generate TCP traffic and sent it through Subscriber 2 to for 600 seconds. During that transmission, Subscriber 1 joined the network, transmitted various traffic generated by Iperf, and then left the network. As can be seen in Figure 3(a) and (e), Subscriber 1's joining and leaving the network caused minimal disruption to Subscriber 2's transmission. The traffic from each subscriber unit was in the Best Effort service class and had the same priority. So, bandwidth

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Fig. 3. Multiple subscribers transmitting at the same time (a) Subscriber I joins the network (b) Subscriber I transmits UDP packets at 3 Mbps (c) Subscriber I transmits UDP packets at 6 Mbps (half are dropped) (d) Subscriber I transmits TCP packets (e) Subscriber I leaves the network

was shared when both subscriber units transmitted at the same time. In particular, note that when Subscriber 1 tried to transmit at the full available bandwidth (Figure 3(c)), it was still only given half the bandwidth; half its packets were dropped. It can also be seen in the figure that when one subscriber unit was not transmitting, the other was free to use all the available bandwidth. Future Experiments

The experiments described above are only the first steps in evaluating the WiMAX equipment. There are many other experiments we plan to pursue, as detailed presently. The following experiments are planned: 1) Test with a mix of realistic traffic that would be representative of an operational SbLAN; 2) Test with multiple subscriber units at varying distances from the base station, and include a QoS evaluation; 3) Assess the information security built into the 802.16 standard; 4) Use a transmit amplifier representative of those typically used in a space application and judge the

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Paper ID# 901709.PDF performance of commercial off-the-shelf hardware transmitting in OFDM mode; 5) Convert the transmitted waveform from OFDM to single carrier modulation and judge performance through the same transmit amplifier; 6) Emulate the end-to-end system by adding a network link with a long delay between the base station and another test router to represent the link between the hub satellite and the ground station. RELATED WORK SbLAN is closely related to two other projects sponsored by DoD. These are the Cisco Systems IRIS project and the DARPA System F6 project. IRIS is sponsored by the DoD as a Joint Capability Technology Demonstration (JCTD) [13]. It was developed through a partnership of Cisco Systems, Inc. and Intelsat General, Corp., and is scheduled for launch at the end of 2009 [14]. IRIS consists of a Cisco router hosted on the Intelsat IS-14 satellite, with the goal of demonstrating the feasibility and utility of operating a satellite-hosted router and investigating the convergence of satellite services at the IP layer in space. System F6 is a DARPA-sponsored program with the overarching goal of investigating the feasibility of breaking down large monolithic satellites into smaller satellites in hopes of reducing satellite-system risks [3]. A critical piece for the success of System F6 is investigating and implementing the technology to form a collaborative high speed wireless network amongst all the smaller satellites. Routing in space is an essential part of the System F6 project, just as it is for SbLAN. IRIS is focused on serving ground-based customers with space-based IP router capability. This is significantly different than the SbLAN concept, which is focused on forming a network of satellites. The focus of System F6 is much broader than that of SbLAN. System F6 is focused on empowering communications amongst the cluster of satellites as a necessary component to deliver collaboration. SbLAN is interested in evaluating the use of a common space-based network communication hub to ease the downlinking of information from non-related mission satellites to the ground. CONCLUSION We have presented the Space-based Local Area Network concept, in which a group of satellites forms a local area network in space. We have described one possible incarnation of the SbLAN concept and its possible missions. We have also addressed both the benefits and challenges of

the concept. Finally, we discussed experiments that we are conducting to evaluate existing communications standards for use in SbLAN. The SbLAN concept presents many exciting opportunities for space communications and networking, enabling highly flexible communications for mission satellites that can be launched, maintained, and retired independent of each other and of the hub satellite. In addition, the focus on standards-based communication will allow for reduced cost and simpler operation of the mission satellites. Thus, while we acknowledge that there are challenges for the SbLAN concept, we believe that the benefits outweigh them. ACKNOWLEDGMENTS We wish to thank Alexander Utter, Mitchell Marosek, Joseph Kim, and Eugene Grayver for their contributions to the project. REFERENCES [1] R. W. Clark and M. A. Florio, "Demonstration and assessment of an on-orbit internet protocol routing capability," in Proceedings of the 26th International Communications Satellite Systems Conference, San Diego, CA, June 2008. [2] "IEEE standard for local and metropolitan area networks part 16: Air interface for fixed broadband wireless access systems," 2004. [3] "System F6," 2009. [Online]. Available: http://www.darpa.mil/tto/ Programs/sf6.htm [4] R. Braden, "Requirements for communication hostscommunication layers," in IETF Request for Comments 1122, 1989. [5] V. Jacobson, R. Braden, and D. Borman, "TCP extensions for high performance," in IETF Request for Comments 1323, 1992. [6] T. Dunigan and F. Fowler, "A TCP-over-VDP test harness," ORNUI'M-2002/76, 2002. [7] "Plan for operationally responsive space: A report to congressional defense committees," April 2007. [Online]. Available: http: //www.acq.osd.miVnss0/ors/ors.htm [8] "IEEE standard for information technology-telecommunications and information exchange between systems-local and metropolitan area networks-specific requirements-part 11: Wireless LAN medium access control (MAC) and physical layer (PHY) specifications," 2007. [9] RedMAX™ Base Station (AN-100U). [Online]. Available: http://www.redlinecommunications.com/news/ resourcecenter/productinfo/RedMAX_AN1OOu_ds.pdf [10] RedMAX™ Subscriber Unit (SU-O). [Online]. Available: http://www.redlinecommunications.com/news/ resourcecenter/productinfo/RedMAX_S VO _ds.pdf [11] "Iperf." [Online]. Available: http://sourceforge.net/projects/iperf [12] "Jperf." [Online]. Available: http://sourceforge.net/project/ showfiles.php?group_id=128336&package_id=268197 [13] "Internet routing in space (IRIS)," 2009. [Online]. Available: http: //www.cisco.com/web/strategy/government/space- routing.html [14] S. Lawson, "Cisco's new-market ambitions extend Network World, Jui. 2009. [Oninto orbit," line]. Available: http://www.networkworld.com/news/2009/ 070709-ciscos-new-market-ambitions-extend-into.html

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