Residential Gateway
Having discussed Access Networks and home media, now comes the problem of how to connect the Access Network to the Home Network to provide an end-to-end solution. This is essentially the same problem businesses have in connecting LANs to wide-area networks: Doing so involves having an intelligent device that copes with networking problems. In the case of residential service, there are additional problems in handling video and supporting a consumer market.
Several home media standards will survive for long transition periods, creating interoperability challenges. For example, how will a TV monitor connected to Firewire obtain images from a PC connected to phone wire? Or how will a wireless Personal Digital Assistant direct printer output to a Category 5 connected printer? Important questions arise regarding addressing, signaling, system management, and the like.
Residential Gateway Functions
Figure 7-5 illustrates the functions and interfaces of a Residential Gateway (RG).
Figure 7-5. Residential Gateway Interfaces
Keep in mind that these represent a superset of potential RG functions. In different network configurations, some of these tasks could be unnecessary or performed by other components. First we discuss network problems:
Packet forwarding
Media translation
Speed matching
IP address acquisition
Network address translation
MPEG and IP coexistence
Packet filtering
Authentication and encryption
System management
Packet Forwarding
To address the previous problem in which a TV monitor connected to Firewire obtains images from a PC connected to phone wire, or in which a wireless Personal Digital Assistant directs printer output to a Category 5-connected printer, some form of intelligent packet forwarding, or routing, is indicated. It is possible that traffic from all devices can be broadcast on the internal LAN, but this has scaling and congestion problems because there is expected to be video on the home LAN.
Likewise, there are the cases shown back in Figure 7-1. A TV and PC can be connected to the same or different access networks. At the same time, there is traffic within the home. An RG is the device that arbitrates various types of traffic to ensure fairness and quality of service. As the number of potential Access Networks and Home Networks proliferates, connecting them all with common addressing and service characteristics becomes an issue for a rather intelligent Home Networking device.
Media Translation
In some cases, the physical wiring of the Access Network is identical to that of the internal network. Cable TV networks, for example, use coaxial cable on the drop wire and inside the home. Media translation is not needed in such cases.
However, in most cases the Access Network physical medium differs from the Home Network medium. The Access Network might be wireless, for example, as with LMDS or DBS, but internal distribution might be handled over a wired infrastructure. Similarly, new forms of inside wiring, such as a home's AC power circuits, might be used. Whenever the inside and outside wiring differ, they likely could use different frequencies, have different modulation schemes, and require retransmission. The dissimilarity of the networks forces the need for media translation at the RG, where the networks couple.
Speed Matching
In addition to the problem of media translation, the various media operate at different speeds. The Home Network might be faster than the Access Network, or vice versa. Whenever speed mismatches occur, buffering is required so that the higher-speed network does not overwhelm the lower-speed network. The RG performs the buffering.
IP Address Acquisition
Terminal equipment accessing the Internet requires IP addresses so that packets originating on the Internet or corporate networks can unambiguously address the home TE. Readers familiar with the IP protocol suite will recognize that several options exist. Among these are DHCP Server and DHCP Relay. Manual, static IP addressing is another option. It remains to be seen which of these functions will be performed by the RG.
For readers less familiar with these protocols, the rest of this section provides a brief overview. Packets from the Access Network do not say "Jimmy's TV" or "Rosie's PC" in the packet header. Some form of globally significant addressing is required, such as an IP address or an ATM address. A mechanism is required to associate the IP address in the packet header with the home device. What IP address is to be used by the consumer, and by what mechanism is it to be applied to the PC and advertised to the rest of the world? The consumer can manually configure his own IP address, but this is error-prone and highly consumer-unfriendly.
A more user-friendly way to enable address acquisition for the home TE is to have the RG operate the Dynamic Host Configuration Protocol (DHCP) server function. With the RG acting as a DHCP Server, it can supply IP addresses to multiple home computers from a pool of addresses provided to it by the carrier. These addresses can be advertised by the gateway throughout the Access Network and to the Internet at large.
However, having the RG perform DHCP Server functions imposes some processing and storage requirements that might not be desirable. Another possibility is to perform DHCP Relay. In this technique, the TE broadcasts a request for an IP address. The RG recognizes DHCP requests and relays them to a server in the Access Network or content provider network specifically addressed in the RG to provide IP addresses. The DHCP Server returns the address to the RG, which in turn relays it to the TE. This centralizes the role of dynamic address assignment in the network.
Network Address Translation
The IP address provided by the Internet service provider may or may not be globally unique. An example of a globally unique identifier is a telephone number. If your phone number were not globally unique, someone else could be getting your phone calls. So, within the global telephone system there is a hierarchical format that begins at the top with the country code, then the area code, then the serving office number, and finally a suffix identifying your telephone number. It is possible—even likely—that someone else in the country has the same serving office number and suffix as you, but the two numbers are differentiated by the area code. Likewise, internationally, two phone numbers are differentiated by the country code.
The Internet does not have this luxury because there are not enough IP addresses. The current IP version 4 (IPv4) standard, used around the world today, has only 32 bits. While it is possible to sequentially number all the computers in the world (perhaps 32 bits implies about 4 billion), doing so would preclude a numbering hierarchy such as we have with telephone numbers. So, IP service providers typically allocate private addresses, out of their own imagination.
The problem of global address ambiguity is solved by a function called network address translation (NAT). The function of NAT is to convert the private address used locally by a consumer Home Network to a public, globally unique IPv4 address. This seems to be a rather straightforward table lookup that matches private to public addresses. However, because of some functions of certain IP protocols, such as the File Transfer Protocol (FTP), some care must be taken to determine which are protocol-specific. FTP, for example, does some tricks with the IP address before a file transfer is enabled.
NAT also creates problems of network security. Some security protocols depend on having a static IP address. Some firewalls are keyed according to a specific IP address. If a user's IP address changes because the NAT translates to a different IP address at a later date, penetration though a firewall is blocked. This is the equivalent of having your area code change, which happens from time to time in the telephone world. Here, when your IP address changes, there may be some firewall somewhere that is dependent on having your previous address.
Finally, it may be necessary to translate the port address (which identifies a particular IP application). This function is called port address translation (PAT), or port following.
If NAT/PAT translation is required, a logical place for it will be in the RG.
Residential Networking and IPv6
Because of the problems created by address depletion and NAT, some Internet experts, including the late Jon Postel, Research Director of the University of Southern California Information Sciences Institute and author of the seminal specifications of the Internet, believe the migration to a new IP protocol is needed. The successor to IPv4 is IPv6, which provides for a 128-bit address space. This is enough addressing to individually address every molecule on Earth, and some not on Earth as well. Certainly, as IP devices become smaller, more numerous, and embedded in our environment, the proliferation of addressing becomes a more difficult problem. It is simply not cost-effective to have a NAT/PAT translator on my wristwatch, with the attendant service provider protocol handling.
Today Internet service providers are reluctant to implement IPv6. It involves work, and their networks must cope with IPv4-to- IPv6 translation during a transition period. There is also no global czar of IPv6 addressing, a global agency that doles out codes and enforces etiquette.
However, for the Internet to scale to billions of low-cost devices, as it must for the consumer and embedded environment, that transition must be made. Waiting until later would only make the transition more painful.
MPEG and IP Protocol Coexistence
The emergence of digital TV raises the likelihood that both MPEG and IP traffic will be networked to the home. MPEG will convey digital TV, and IP will convey Web pages. Datacasting moves IP packets inside MPEG frames. Internet providers want to encapsulate MPEG inside IP. Another way to convey both protocols is to use some form of time-division or frequency-division multiplexing.
Whether encapsulation or multiplexing is performed, the multiprotocol case raises the possibility that the RG will be responsible for protocol handling. In the case that one protocol is encapsulated inside the other, for example, a device that de-encapsulates the inside protocol is required. If the protocols are multiplexed, demultiplexing is required.
Packet Filtering
The gateway can perform a firewall function to prevent unauthorized packets from entering the home. The packet filters might be controlled by the consumer or the carrier. The consumer, for example, might want to restrict the flow of adult material into the home. Similarly, the carrier might want to prevent the flow of premium programming to customers who don't pay for it.
It is also possible to perform filtering in the access node (such as DSLAM or CMTS). By filtering packets in the network rather than in the RG, costs associated with filtering (such as memory and processing) are reduced, which is an important consideration for consumer-purchased equipment. However, distributing functions such as filtering into the RGs generally makes the functions more scalable.
Authentication and Encryption
Carriers might require customers to authenticate themselves to receive service. Encryption would be required for carriers and consumers who want to keep their transmissions private. Both authentication and encryption require some form of intelligent device that can apply relevant protocols, such as Radius or TACACS, and that can manage passwords and keys. The RG is a logical place for these processes.
One open issue is whether to authenticate the residence or the device. Authentication to the residence would require only one password for the entire home, whereas device authentication requires a password for each device. It is unclear whether the additional complexity is worth the additional security.
System Management
The RG is a relatively complex piece of consumer equipment, more complex in terms of software than any device currently in the home. For this reason, it is unreasonable to ask the consumer to assume the role of administrator for the gateway. This role is likely to be assumed by the service provider or content provider. The following list details some system-management functions:
Automatic configuration
Installation and management of applications
Alarm monitoring and surveillance
Fault management and recovery
Software updates and fixes
Performance management
Accounting
Apart from networking functions, other candidate functions specific to applications can reside in the RG. Some examples include these :
MPEG Decoding
Normally, MPEG decoding is performed in a digital STB. However, because the gateway must provide for IP coexistence, it is also possible—and sometimes logical—to co-locate the decoder with the IP stack in the same box. Because many CE vendors do not want to put the decoder into the TV monitor, for modularity and cost reasons, a separate decoder is needed anyway. Integrating a decoder with the IP stack saves some shelf space in the home.
Personal Video Recorder
Taking video one step further, it is possible to integrate a hard disk drive with the MPEG decoder to store video programming, just as one would record onto videotape. TiVo and ReplayTV are competing in this new consumer electronics space. The personal video recorder (PVR) also has a program guide and a feature to bypass commercials. When coupled with a CD-ROM burner attached to Firewire, interesting networking problems arise. (Also, scary piracy scenarios arise for content developers.)
It is also likely that Web caches will proliferate at home. This is to enable consumers to be content providers, allowing the world to see such personal things as their baby pictures. This, too, would require a hard disk connected to a network.
Web Browser/E-mail Client
If an IP stack is required in the set-top box, why not include the Web browser and e-mail client? Portal service providers would like this because it can create a hermetically sealed environment to completely surround the viewers' Internet/TV experience. This environment is sometimes called a Walled Garden. Service providers that provide an RG will likely provide the user interface as well.
RG Attributes
Based on its likely functions, some of the RG's necessary characteristics begin to emerge. Let's take a look at some of these.
Operating Systems
The RG is certainly a computer, and thus it requires an operating system (OS) to regulate resource allocation such as memory and processor utilization. Because computer memory is responsible for a large part of the cost of a computer, and because the market for consumer electronics is highly cost-sensitive, the OS is required to have a small footprint. That is, the OS should occupy the smallest amount of memory practical. The OS also should accommodate real-time operation and multitasking.
Challenge to Microsoft?
Because Microsoft's Windows 95 requires a considerable amount of memory and does not support multitasking, it is not viewed as appropriate for RG use. This has given rise to new developments in the OS and middleware product development space. Many vendors see the RG as an opportunity to compete against Microsoft's Windows in an emerging OS space. Among the more prominent of these is Sun, with the Java/Jini environment.
Other OS and middleware offerings targeted at digital set tops and consumer electronics include OpenTV, by OpenTV ; David, by Microware ; and PowerTV, by PowerTV . Basic OS kernels are offered, such as VxWorks, by Wind River ; pSOS, by ISI; and QNX.
Of course, Microsoft has not sat idly by. It has responded with a small footprint offering of its own, called Windows CE (some would say Wince). But Microsoft has made important agreements and acquisitions with digital set-top providers and consumer electronics vendors. The company will continue to be a force in this emerging market.
It remains to be seen how the developments of new OSs that provide real-time operations and multitasking on a small footprint will evolve. Specifically, it will be interesting to watch the impact, if any, this market will have on the pervasiveness of the Windows/Intel (Wintel) architecture.
Carrier Management
It is likely that the RG will be under some form of carrier management, at least during early product introduction. This means that the Access Network provider will remotely control the RG. Carriers would be responsible for handling software downloads, extracting invoicing information, and providing customer configuration. Carrier management is motivated by the complexity of the device and the desire for user-friendliness. The RG thereby would fall under the model the cable operators use for the set-top box: The box is owned and maintained by the carrier and is rented to the subscriber. This is different from the consumer electronics model, in which the item is owned and maintained by the consumer.
Standardization
For the RG to be as low-cost as possible, many parts of it require standardization. This particularly applies to the Access Network and Home Network interfaces. Standardization includes modulation components, forward error correction, and MAC protocols. However, it also includes standardization of the software environment. A number of industrial consortia are emerging to address the software environment. Among the prominent of these are the following:
Open Service Gateway Initiative , which is pushing the Java/Jini/HAVi story; no sign of Microsoft here. OSGI necessitates the existence of at least one Java Virtual Machine (JVM) in the home network. This JVM can be in the home PC, a set-top box, a TV, or a VCR. Other home devices that cannot run Java will use the central JVM processor as a proxy to obtain services, such as name service, application installation, and application management.
Universal Plug and Play Forum , which is promoting the Windows CE story; no sign of Sun here. This is basically the same story as OSGI, but it requires Windows in the home.
Home API Working Group , which is developing a software developer's kit (SDK) running on Microsoft Windows that will let software developers write programs that can connect to home appliances as well as entertainment devices. Largely, more push comes from Microsoft and Intel.
Video Electronics Standards Association (VESA), which is specifying the use of IEEE 1394b as the home backbone protocol and is capable of connecting to other networks, such as Ethernet, HomePNA, CEBus, and X-10. The push largely comes from consumer electronics vendors emphasizing systems aspects of the delivery of home video. However, Intel has provided important contributions, specifically managing the specification of IP over 1394 in the IETF. IP is specified as the network layer, and Web servers and browsers are used to access devices over the network with an XML interface for device-to-device control. The VESA Home Network Committee is coordinating its work with EIA/TIA TR 41.5, EIA/TIA 42.2, IEEE 1394b, the DAVIC physical layer technical committee, the 1394 Trade Association, the Consumer Electronics Manufacturers Association (CEMA, part of EIA), UPnP Forum, and CableLabs.
Cisco IOS Involvement
Whatever the outcome of the OS and API wars, it is likely that the Cisco Internetworking Operating System (IOS) will be the networking software component of many RGs. Cisco provides the majority of the routing equipment used in the public Internet and supplies private networking equipment as well. Given Cisco's presence in cable, xDSL, wireless, and routing, it makes sense that Cisco would extend its influence into the home.
RGs will have IP stacks, packet filters, network translation software, and other pieces of networking software. To capture this market, Cisco has established its Consumer Line of Business.
An important question on the evolution of Residential Gateways is how the internetworking operating system will interact with the computing operating system. This remains to be seen.
Examples/Possibilities
The variety of Access Networks, in-home networks, and user functions gives rise to many possible RG configurations. A few alternatives are presented here, with the caveat that other configurations will be marketed and that, on the flip side, none of these may happen.
The Telecommunications Industry Association (TIA) TR41.5 committee has been working on a Residential Gateway project for some time. The organization completed work on a proposed Technical Systems Bulletin (TSB) providing "Recommended minimum application, feature and operational requirements" of an RG at a meeting in November 1998. (Details can be found at the Web site www.tiaonline.org .)
A home networking control platform is under development between Matsushita Electric and Nintendo using Nintendo's next-generation Dolphin video game console. The combined development is called the Home Information Infrastructure (HII) system, a networking architecture for connecting and controlling domestic audio and video equipment. Rival architectures include Sony Corp's HAVi specification.
The cable industry is well under way with the standardization of DOCSIS and DVB for data and OpenCable and DVB for digital TV over cable. A device is in development that takes in digital TV and DOCSIS data and emits digital TV over an RGB cable or IEEE 1394 and emits data over an Ethernet cable. In theory, the box will use the DOCSIS channel for TV conditional access as those conditional access systems become ready. The box has a built-in Web browser that uses TCP/IP over the DOCSIS data channel and an Ethernet port on the back for use by the consumer. It is also possible to add voice ports to this gateway. The voice ports connect to voice encoders in the gateway so that the DOCSIS channels can be used for digital telephony. The consumer only needs to plug in his RJ-11 cable from the phone into the gateway. Some other kind of home networking will be needed to send data around the house.
Residential Gateway Issues
Before home networking becomes commonplace, issues apart from technology must be addressed by vendors and carriers.
Copy Protection
The new generation of audiovisual digital terminal equipment (such as digital video cassette recorders and DVDs) will provide high-quality displays of sight and sound. Furthermore, with digital technology, it is possible to make copies of content indefinitely without loss of quality. That is, one can make copies of copies, and the last copy will look and sound as good as the original.
This concerns content developers—namely, film studios and the music recording industry. An informal, broad-based group called the Copy Protection Working Group (CPTWG) is addressing the issue of copy protection. The group is comprised of the major motion picture studios, CE firms, computer companies, and the music recording industry. CPTWG is investigating the following three aspects of copy protection:
Device authentication, by which physical devices such as DVDs, digital TV sets, and VCRs are certified as compliant with copy protection. A compliant device will send content only to another compliant device.
Content encryption, which provides for the encryption of content on the digital medium using techniques that are permitted for export by the United States and other governments. Most governments, including the United States, have rules forbidding the export of high-grade encryption technology. CPTWG encryption must be exportable because of the worldwide trade in consumer electronics (mostly from Asia) and content (mostly from the United States and Europe).
Copy control information (CCI), which includes rules that control the number of copies of a particular piece of content that can be made by a specific device. The content, for example, would specify that zero, one, or an indefinite number of copies can be made by a particular device.
Without stringent copy protection, content providers believe that they cannot enforce their copyrights and will be reluctant to provide their best content in digital form.
Partnering
The Home Network is the turf on which many industries will converge. Individually, none of them so far seems to have all the requisites to succeed. Table 7-3 indicates some industries and their strengths and weaknesses with respect to home networking.
The CE industry, for example, has strong consumer channels, understands consumer-support issues (such as how to deal with returns), and implements excellent branding. This industry also has strong computer processing experience with recent success in games. The problem is networking. Products of the CE industry do not require addressing, software management, filtering, and other functions familiar to networking vendors and carriers.
Networking vendors face marketing challenges when dealing with the consumer market. They are accustomed to higher margins on hardware products because they do not sell disposables to subsidize equipment sales. As a contrasting example, video game vendors recover the cost of the game players by selling game cartridges. Networking vendors have few consumer channels, no infrastructure for customer support, and therefore little consumer branding.
Given their complementary weaknesses and strengths, as well as the scale of investment in product development and risk, different industries are likely to form new alliances to address the Home Network problem. The key to winning in the home market is the development of strong partnerships. Exactly which partnerships will be formed and for which markets remains to be seen.
Fixed RG Versus Modular RG
For homes attaching to multiple Access Networks, each Access Network will require a network-specific NT and NIU. A cable modem, for example, cannot be used for xDSL systems. This raises an important packaging question for the RG: How will it accommodate multiple Access Networks? In a related question, if a consumer changes Access Networks, is he required to change the RG, or will the RG have a modular design that can accommodate multiple Access Networks with the addition of a PC card or a similar attachment?
The flexibility of a modular design will increase the cost of the RG. Additionally, a modular RG will do little to reduce churn. Carriers must consider, for strictly commercial reasons, whether they need to retain the account control that a carrier-specific NIU will provide.
Rewiring the Home
Notwithstanding the improvement in the home rewiring situation noted previously under Category 5 wiring, rewiring a home is nonetheless a big problem for most homeowners. Renters could be precluded entirely. Old homes could have asbestos problems. High-quality homes have lath and plaster and real wood, which are difficult to penetrate. Proponents of Category 5 wiring and Firewire must confront arguments against rewiring when constructing their business case. Most leading-edge users of Home Networks simply leave their cables dangling.
The marketing imperative is to get to market fast, so there is much interest in reusing legacy wiring (phone wire, powerline) or using wireless solutions. In any case, the carrier installing the Access Network probably will be responsible for the Home Network. As such, the carrier likely will perform some form of installation for a fee. Whether or not the carrier's responsibility for installation makes rewiring scenarios untenable from a business perspective remains to be seen.
Installation Services
Because Access Network operators are frequently responsible for inside wiring, some have decided to outsource the installation. An interesting development is the role IBM Corp. ( www.ibm.com , NYSE: IBM) has decided to play. IBM has rarely been considered as a residential service or equipment provider, but a new service called IBM Home Director establishes IBM in the residential broadband service arena.
IBM Home Director has teamed with Bell Atlantic and Ameritech to provide installation of coaxial cable and various telephone wires, depending on their needs. IBM is also developing a series of computer applications that will run on the new infrastructure, including a home management application.
The foundation for the Home Director system is the Home Network Connection Center, the in-home hub for a complete structured wiring solution. The Connection Center brings together various types of wire in the home, including coaxial, Category 5, and telephone, into a central location so that video, data, and telephony can be distributed throughout the home.
Without such installation services, the installation of high-speed home networking is largely a do-it-yourself effort.
Full-Service Home Networking
Because separate networks exist for phone, cable, power, and home automation, the question arises whether there is a strong market need to integrate services on a single Home Network architecture—that is, a full-service home network.
The perceived advantages of full-service home networking to the customer are simplified ordering, wiring, and maintenance. The disadvantage to the consumer is that a single network makes the consumer vulnerable to a single-network outage and possibly could make the customer captive to a single Access Network provider.
The candidates for full-service Home Networks are coaxial cable and Firewire. Only cable would not require home rewiring, but use of it requires subscription to cable or FTTC Access Networks.
The advocates of full-service networking include the ATM Forum, the cable industry, and supporters of Fiber to the Home. The ATM Forum sees ATM as the best way to offer latency control to applications. The cable industry's interest is motivated by the fact that it has the most widespread physical infrastructure to offer both digital TV and data services to the home.
ADSL and various wireless local loop technologies do not offer the prospect of full-service home networking for both broadcast video and data. This might not be a disadvantage to these industries, because the economic case for a full-service network in the home is not yet established.