Data Streaming and E-mail Technologies
Letzte Aktualisierung: März 2003
Betrifft: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2
Data Streaming and E-mail Technologies
The use of streaming video and audio media is becoming an increasingly desirable feature in network technologies. As networks become more saturated with traffic, the timely delivery of latency-sensitive data, such as the data generated by video conferencing and Internet Protocol (IP) telephony programs, becomes more problematic. ATM and QoS are two technologies that you can use to facilitate the timely delivery of latency-sensitive data.
POP3 is an e-mail protocol that can be used facilitate mail delivery to computers that are not part of a network or computers that do not have an e-mail server on the local network.
Most network technologies use variable-length packet mechanisms to transfer data, and the available network bandwidth is divided into fixed channels or slots synchronized by a timing mechanism. This method is inefficient, and as the quantity of latency-sensitive data places increasing demands on the finite network bandwidth, the inefficiency becomes more problematic.
Asynchronous transfer mode (ATM) is a recent innovation in broadband networking technology that can be used to build high-speed networks. ATM differs from other existing LAN and WAN technologies because it is specifically designed to use bandwidth resources at maximum efficiency and support high-speed communications. To do this, ATM uses small, fixed-length cells to efficiently structure and parcel data for transfer. Because devices that communicate on an asynchronous network negotiate the rate at which they will communicate, based on physical hardware limitations and the ability to maintain a reliable flow of information within the network, they do not have the same types of restrictions as most existing network technologies.
ATM has been demonstrated at data rates up to 9.6 gigabits per second (Gbps) over Synchronous Optical NETwork (SONET), an international specification for fiber-optic communication. ATM is a scalable solution that can simultaneously accommodate data, voice, audio, fax, and video information types.
ATM provides versatility by means a set of features, including ATM-LAN emulation, address resolution protocol (ARP) address resolution service (MARS), and Encapsulated Ethernet over a permanent virtual connection (PVC):
The ATM LAN emulation client enables existing programs and protocols designed for use on Ethernet and Token Ring networks to run without modification over an ATM network.
In ATM, the LAN emulation (LANE) client module conforms to the ATM Forum LANE 1.0 specification. The ARP/MARS service enables the Microsoft TCP/IP stack to resolve ATM addresses to hardware addresses for more direct and efficient use of ATM media.
Encapsulated Ethernet over PVC enables the transmission of Ethernet packets across PVC on an ATM network adapter.
Post Office Protocol version 3 (POP3) service enables a server to host e-mail accounts for subscribers of Internet service providers (ISP) or for small businesses. The most common use is for home ISP clients or small businesses that cannot locally implement and support a mail server, Simple Mail Transfer Protocol (SMTP) service, and related mail handling infrastructure. The POP3 protocol is used to retrieve mail that is being held by a mail server that offers SMTP service. The POP3 service performs the tasks of downloading messages, moving the messages from a folder in the file system of a mail server to clients on small networks, or to stand-alone home computers. Typically, after mail is downloaded from the mail server, the mail server deletes the mail from its folder.
As the finite bandwidth of a network becomes more congested with traffic, it becomes increasingly problematic to deliver latency-sensitive data in a timely manner. Quality of Service (QoS) is a set of service requirements that a network must meet to ensure an adequate service level for data transmission. The goal of QoS is a guaranteed delivery system for network traffic, such as Internet Protocol (IP) packets. A QoS guarantee indicates a service level that a program requires to transmit data at a specified rate and to deliver it within a specified time. Because QoS provides some guarantee of sufficient network resources, it gives a shared network a level of service similar to that of a dedicated network.
QoS facilitates the deployment of media-rich applications, such as video conferencing and Internet Protocol (IP) telephony, without adversely affecting network throughput. QoS achieves more efficient use of network resources by differentiating between subsets of data such as fax data and latency-sensitive streaming media. QoS can also improve the performance of mission-critical software such as Enterprise Resource Planning (ERP) applications.