WIRELESS NETWORKING EVOLUTION AT THE APPLICATIONS LEVEL The Web is driving fundamental changes to application design, and it is becoming the standard for the construction of networked applications. Most networked applications have shifted from simple transaction processing to Web-based communication on the front end, and extensive multi-application processing on the back end. This is increasing network complexity, impacting network design and causing performance concerns, especially in wireless environments. Three significant trends are emerging. 1. Communication is increasing between Web browsers and applications. Also, inter-application communication is increasing as the applications themselves are becoming more and more distributed. 2. Clients are containing less and less application processing and focusing more on convenience, browsing and display (witness the trend towards thin clients, skinny clients, possibly anorexic clients with extensive proxy processing in the network to support them). This perspective becomes obvious when you look at browsing the wireless Web with cell phones and PDAs. 3. Because of performance concerns and the wide range of wireless mobile station capabilities, network devices that on-the-fly assist the rendering of data and improve wireless infrastructure performance is a growing market. Also, expect future networking product directions to provide capabilities to accelerate the proliferation of wireless applications and services. While these three trends are occurring, network bandwidth continues to grow and the network continues to evolve with new capabilities like QoS, policy, NAT, VPN, and mobile wireless, which further increase network design flexibility, new technology usage and extend the reach of World Wide Web. Web-based networking is all about accelerating the creation of new applications and driving new services out to the networked user, including a growing number of wireless data users. To many, the term "Web based application" means Markup Language (ML) based browsers communicating with HTTP servers (and possibly using FTP and other protocols). One major factor driving network evolution is: Web-based applications are changing the way networks need to behave to support them. Within change is always opportunity for new products and services. Today, the wireless Web is a great example of ongoing technology evolution and revolution. The World Wide Web (WWW) system could be viewed as being composed of two major pieces: network transport and application processing. Although the OSI model is becoming less and less relevant, it is possible to view network trends and directions as two pieces of the OSI model, shown in Figure 1. An inner core, consisting of the OSI layers 1,2,3 and 4, which is the network transport. The outer layers, consisting of the OSI layers 5,6,7, and beyond (e.g., back-end databases), which either support or directly perform application processing.
The inner core, or network transport, is a shared physical entity comprised of nodes, links and algorithms that actually move data. The major responsibility of the network transport is to supply capacity and enable connectivity between users and applications. This area of the network typically focuses on packet header processing (forwarding decisions and header enveloping/de-enveloping) shown in the Figure 2. At the core, network-based technology is often deployed to reduce costs (muxing, higher speeds, line aggregation, VPNs, etc.), and it is becoming increasingly important in supporting complex inter-application flows and the huge numbers of wireless connected devices expected in the future.
Traditionally, application-based technology has been deployed directly from business requirements to generate or enable revenue. Today, networking products and solutions are beginning to make decisions on the application's behalf to improve perceived application performance and assist in rendering information to the user (e.g., content caching). An "application assist function" performed on the content in the packet located farther back from the packet headers is shown in Figure 3. Markup languages, such as HTML and XML (along with MIME information) are located here. They are making it easier to identify content and process packets accordingly. That means that packets on the fly through the network can be intercepted and modified to solve both rendering and infrastructure optimization issues.
What's Changing? The Internet has evolved considerably over the years. Some innovation such as queueing techniques, tagging and logical partitioning through VPNs is occurring in the core. But, by far, most innovation today seems to be focused at the outer ring (the higher layers of the OSI architecture). This is the networking area where content is important and we can refer to this area as Web networking, since technology changes seem to be driven by Web activity. Processing packets in the network based on content information is part of a growing trend. Markup languages are driving network evolution by allowing network nodes to look deeper into the packets to provide valuable functions, such as traffic distribution, security and various forms of content manipulation (e.g., to satisfy wireless environment constraints). These functions are also considered network services in behalf of Web applications. This trend of providing more application assistance in the network is part of the overall movement of function between the outer ring and inner core of the network This area of innovation (or change) is depicted in Figure 4. For example, Web-based networking is generating a requirement for a "distribution layer" to efficiently locate and direct server traffic. As Web traffic increases, redundancy and scalability become increasingly important. Today, both problems are addressed by the same solution: more servers and other equipment. As the number of servers at a site grows, load distribution becomes an issue in that load needs to be allocated among available resources and networks need to provide paths around detected failures.
Load distribution today is typically done using connection information, but a more intelligent approach would be to balance traffic flows to servers based on making their available capacity known to the network. This trend is now resulting in the balancing of requests for content and also the consideration of where the data is destined (e.g., a wireless device). Security could be considered "another layer" with similar issues. Unfortunately, "The Wireless Web" remains slow for conducting serious transaction application processing. The reason is that application traffic flows are becoming more complex and, at the same time, they are attempting to utilize limited bandwidth resources. For example, when a user requests information from a server, the transaction (data fetched due to the initial request) is becoming a smaller part of the Web page. The Web page is often assembled using the dynamic information from the server (usually from where the initial URL request was made; for example, for a stock quote). Static aspects of the page, such as graphics and advertising text, are often sent from other servers or nearby caches. Distributing content over a number of servers allows the servers with dynamic content (or the content of value) to conserve capacity and focus on transaction processing (or making money). In addition, static content is viewed as very manageable and easily replicated and distributed throughout the network. When this is done, availability, reliability, efficient distribution of content, and finding static as well as dynamic content become networking issues and drive an expanding network services and application market. In Web networking, the concept of a session, used by the OSI model, is merely one of many "threads" of information flow to get the user a "completed" Web page. In this sense the "super transaction" of assembling dynamic and static content is what the user would view as his "transaction" or unit of work. Processing to satisfy the Web page request is typically distributed around the network. Figure 5 shows a typical HTTP 1.1 Web browser page assembly process. It begins with clicking on a URL and usually ends with "Document: Done" being displayed by the browser. During this time, multiple TCP sessions (from SYN to FIN) are established and terminated (other traffic flows using UDP could occur as well). The distributed nature of Web networking is clear. Note that the DNS activity is usually recursive and by itself is capable of generating significant network traffic.
The process of fulfilling a user's Web application request requires sophisticated communication, synchronization and distributed processing. In a very real sense the network is becoming the computer. These (network is the computer) functions, today, are continuing to evolve to provide additional capabilities to deal with the proliferation of diverse wireless devices and effectively utilize limited bandwidth through the exploitation of Markup language capabilities in general and XML in particular. The expanding use of XML is a monument to the power and effectiveness of standardization, institutionalized by the Internet. XML, a standard for structuring and representing information, is quickly becoming the new high-level language of choice on the Internet. The next step for XML is to capture semantics as well as syntax. Semantic information is currently being defined and identifiable through the DARPA Agent Markup Language (DAML). With the evolution of the use of XML to standardize semantic information, XML will assist completing the transition of the Web to a fully machine-readable form and open up enormous future opportunities for the core and edge networking devices to participate in the Internet revolution at the application level.
Mobile Wireless Internet Forum
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