DCE, DTE, CPE, Topologi Fisik

Data terminal equipment

(February 2008)

Data terminal equipment (DTE) is an end instrument that converts user information into signals or reconverts received signals. These can also be called tail circuits. A DTE device communicates with the data circuit-terminating equipment (DCE). The DTE/DCE classification was introduced by IBM.
Basically, V.35 is a high-speed serial interface designed to support both higher data rates and connectivity between DTEs (data-terminal equipment) or DCEs (data-communication equipment) over digital lines.
Two different types of devices are assumed on each end of the interconnecting cable for a case of simply adding DTE to the topology (e.g. to a hub, DCE), which also brings a less trivial case of interconnection of devices of the same type: DTE-DTE or DCE-DCE. Such cases need crossover cables, such as for the Ethernet or null modem for RS-232.
A DTE is the functional unit of a data station that serves as a data source or a data sink and provides for the data communication control function to be performed in accordance with the link protocol.
The data terminal equipment may be a single piece of equipment or an interconnected subsystem of multiple pieces of equipment that perform all the required functions necessary to permit users to communicate. A user interacts with the DTE (e.g. through a human-machine interface), or the DTE may be the user.
Usually, the DTE device is the terminal (or a computer emulating a terminal), and the DCE is a modem or another carrier-owned device.
A general rule is that DCE devices provide the clock signal (internal clocking) and the DTE device synchronizes on the provided clock (external clocking). D-sub connectors follow another rule for pin assignment.

• 25 pin DTE devices transmit on pin 2 and receive on pin 3.
• 25 pin DCE devices transmit on pin 3 and receive on pin 2.
• 9 pin DTE devices transmit on pin 3 and receive on pin 2.
• 9 pin DCE devices transmit on pin 2 and receive on pin 3.

This term is also generally used in the Telco and Cisco equipment context to designate a network device, such as terminals, personal computers but also routers and bridges, that's unable or configured not to generate clock signals. Hence a PC to PC Ethernet connection can also be called a DTE to DTE communication. This communication is done via an Ethernet crossover cable as opposed to a PC to DCE (hub, switch, or bridge) communication which is done via an Ethernet straight cable.

Sumber : http://en.wikipedia.org/wiki/Data_terminal_equipment\

Distributed Computing Environment

From Wikipedia, the free encyclopedia

The Distributed Computing Environment (DCE) is a software system developed in the early 1990s by a consortium that included Apollo Computer (later part of Hewlett-Packard), IBM, Digital Equipment Corporation, and others. The DCE supplies a framework and toolkit for developing client/server applications. The framework includes a remote procedure call (RPC) mechanism known as DCE/RPC, a naming (directory) service, a time service, an authentication service and a distributed file system (DFS) known as DCE/DFS. DCE was a big step in direction to standardisation of architectures, which were manufacturer dependent before. Transforming the concept in software for different platforms has been given up after a short period. Similar to the OSI model DCE was not granted success, the underlying concepts however prevailed.

History

Open Software Foundation (OSF) came about to a large degree as part of the Unix wars of the 1980s. After Sun Microsystems and AT&T worked together to produce UNIX System V Release 4 (SVR4) and refused to commit to fair and open licensing of Unix source code, many of the other Unix vendors felt their own market opportunities were unduly disadvantaged. The Distributed Computing Environment is a component of the OSF offerings, along with Motif and Distributed Management Environment (DME).
As part of the formation of OSF, various members contributed many of their ongoing research projects as well as their commercial products. For example, HP/Apollo contributed its Network Computing Environment (NCS) and CMA Threads products. Siemens Nixdorf contributed its X.500 server and ASN/1 compiler tools. At the time, network computing was quite popular, and many of the companies involved were working on similar RPC-based systems. By integrating security, RPC and other distributed services on a single "official" distributed computing environment, OSF could offer a major advantage over SVR4, allowing any DCE-supporting system (namely OSF/1) to interoperate in a larger network.
The DCE system was, to a large degree, based on independent developments made by each of the partners. DCE/RPC was derived from the Network Computing System (NCS) created at Apollo Computer. The naming service was derived from work done at Digital. DCE/DFS was based on the Andrew File System (AFS) originally developed at Carnegie Mellon University. The authentication system was based on Kerberos, and the authorization system based on Access Control Lists (ACLs). By combining these features, DCE offers a fairly complete C-based system for network computing. Any machine on the network can authenticate its users, gain access to resources, and then call them remotely using a single integrated API.
The rise of the Internet, Java and web services stole much of DCE's mindshare through the mid-to-late 1990s, and competing systems such as CORBA muddied the waters as well.
One of the major uses of DCE today is Microsoft's DCOM and ODBC systems, which use DCE/RPC (in MSRPC) as their network transport layer.
OSF and its projects eventually became part of The Open Group, which released DCE 1.2.2 under a free software license (the LGPL) on 12 January 2005. DCE 1.1 was available much earlier under the OSF BSD license, and resulted in FreeDCE being available since 2000. FreeDCE contains an implementation of DCOM.

Architecture

The largest unit of management in DCE is a cell. The highest privileges within a cell are assigned to a role called cell administrator, normally assigned to the "user" cell_admin. Note that this need not be a real OS-level user. The cell_admin has all privileges over all DCE resources within the cell. Privileges can be awarded to or removed from the following categories : user_obj, group_obj, other_obj, any_other for any given DCE resource. The first three correspond to the owner, group member, and any other DCE principal respectively. The last group contains any non-DCE principal. Multiple cells can be configured to communicate and share resources with each other. All principals from external cells are treated as "foreign" users and privileges can be awarded or removed accordingly. In addition to this, specific users or groups can be assigned privileges on any DCE resource, something which is not possible with the traditional UNIX filesystem, which lacks ACLs.
Major components of DCE within every cell are:

1. The Security Server that is responsible for authentication
2. The Cell Directory Server (CDS) that is the respository of resources and ACLs and
3. The Distributed Time Server that provides an accurate clock for proper functioning of the entire cell

Modern DCE implementations such as IBM's are fully capable of interoperating with Kerberos as the security server, LDAP for the CDS and the Network Time Protocol implementations for the time server.
While it is possible to implement a distributed file system using the DCE underpinnings by adding filenames to the CDS and defining the appropriate ACLs on them, this is not user-friendly. DCE/DFS is a DCE based application which provides a distributed filesystem on DCE. DCE/DFS can support replicas of a fileset (the DCE/DFS equivalent of a filesystem) on multiple DFS servers - there is one read-write copy and zero or more read only copies. Replication is supported between the read-write and the read-only copies. In addition, DCE/DFS also supports what are called "backup" filesets, which if defined for a fileset are capable of storing a version of the fileset as it was prior to the last replication.
DCE/DFS is believed to be the world's only distributed filesystem that correctly implements the full POSIX filesystem semantics, including byte range locking. DCE/DFS was sufficiently reliable and stable to be utilised by IBM to run the back-end filesystem for the 1996 Olympics web site, seamlessly and automatically distributed and edited worldwide in different timezones.


Sumber: http://en.wikipedia.org/wiki/Distributed_Computing_Environment

Customer-premises equipment

From Wikipedia, the free encyclopedia

Customer-premises equipment or customer-provided equipment (CPE) is any terminal and associated equipment located at a subscriber's premises and connected with a carrier's telecommunication channel(s) at the demarcation point ("demarc"). The demarc is a point established in a building or complex to separate customer equipment from the equipment located in either the distribution infrastructure or central office of the Communications Service Provider.
CPE generally refers to devices such as telephones, routers, switches, RGs, set-top boxes, fixed mobile convergence products, home networking adaptors and internet access gateways that enable consumers to access Communications Service Providers' services and distribute them around their house via a LAN (Local Access Network).
Also included are key telephone systems and most private branch exchanges. Excluded from CPE are overvoltage protection equipment and pay telephones.
CPE can refer to both devices purchased by the subscriber and provided by the operator or service provider.

History

The two phrases, "customer-premises equipment" and "customer-provided equipment", reflect the history of this equipment.
Under the Bell System monopoly in the United States (post Communications Act of 1934), the Bell System owned the phones, and one could not attach one's own devices to the network, or even attach anything to the phones (a popular saying was "Ma Bell has you by the calls"). Thus phones were property of the Bell System, located on customers' premises – hence, customer-premises equipment. In the U.S. Federal Communications Commission (FCC) proceeding the Second Computer Inquiry, the FCC ruled that telecommunications carriers could no longer bundle CPE with telecommunications service, uncoupling the market power of the telecommunications service monopoly from the CPE market, and creating a competitive CPE market.^[1]
With the gradual breakup of the Bell monopoly, starting with Hush-A-Phone v. United States [1956], which allowed some non-Bell owned equipment to be connected to the network (a process called interconnection), equipment on customers' premises became increasingly owned by customers, not the telco. Indeed, one eventually became able to purchase one's own phone – hence, customer-provided equipment.
In the Pay TV industry many operators and service providers offer subscribers a set-top box with which to receive video services, in return for a monthly fee. As offerings have evolved to include multiple services [voice and data] operators have increasingly given consumers the opportunity to rent additional devices like access modems, internet gateways and video extenders that enable them to access multiple services, and distribute them to a range of Consumer Electronics devices around the home.

Technology Evolution

 

Hybrid devices

The growth of multiple-service operators, offering triple or quad-play services, required the development of hybrid CPE to make it easy for subscribers to access voice, video and data services. The development of this technology was led by Pay TV operators looking for a way to deliver video services via both traditional broadcast and broadband IP networks. Spain’s Telefonica was the first operator to launch a hybrid broadcast and broadband TV service in 2003 with its Imagineo DTT/IPTV offering^[2], while Polish satellite operator 'n' was the first to offer its subscribers a [Three-way hybrid]] (or Tri-brid) broadcast and broadband TV service^[3], which launched in 2009

Set-back Box

The term Set-Back Box is used in the digital TV industry to describe a piece of consumer hardware that enables them to access both linear broadcast and internet-based video content, plus a range of interactive services like Electronic Programme Guides (EPG), Pay Per View (PPV) and Video on Demand (VOD) as well as internet browsing, and view them on a large screen television set. Unlike standard set-top boxes , which sit on top of or below the TV, a set-back box has a smaller form factor to enable it to be mounted to the rear of the display panel flat panel TV, hiding it from view.

Home Gateway

A residential gateway is a home networking device used to connect devices in the home to the Internet or other WAN. It is an umbrella term, used to cover multi-function networking appliances used in homes, which may combine a DSL modem or cable modem, a network switch, a consumer-grade router, and a wireless access point. In the past, such functions were provided by separate devices, but in recent years technological convergence has enabled multiple functions to merged into a single device.
One of the first home gateway devices to be launched was selected by Telecom Italia to enable the operator to offer triple play services in 2002 . Along with a SIP VoIP handset for making voice calls, it enabled subscribers to access voice, video and data services over a 10MB symmetrical ADSL fiber connection.

Virtual Gateway

The virtual gateway concept enables consumers to access video and data services and distribute them around their homes using software rather than hardware. The first virtual gateway was introduced in 2010 by Advanced Digital Broadcast at the IBC exhibition in Amsterdam^[4][5][6]. The ADB Virtual Gateway uses software that resides within the middleware and is based on open standards, including DLNA home networking and the DTCP-IP standard, to ensure that all content, including paid-for encrypted content like Pay TV services, can only be accessed by secure CE devices^[7].

Broadband

A subscriber unit, or SU is a broadband radio that is installed at a business or residential location to connect to an access point to send/receive high speed data wired or wirelessly. Devices commonly referred to as a subscriber unit include cable modems,, access gateways, home networking adapters and mobile phones.
 

WAN

The terms “customer-premises equipment,” “Customer-provided Equipment,” or “CPE” may also refer to any devices that terminate a WAN circuit, such as an ISDN, E-carrier/T-carrier, DSL, or metro Ethernet. This includes any customer-owned hardware at the customer′s site: routers, firewalls, switches, PBXs, VoIP gateways, sometimes CSU/DSU and modems.
Application Areas

• Connected Home
• Pay TV
• Over-The-Top Video services
• Broadband
• IP Telephony
• Fixed Mobile Convergence [FMC]

Other uses

• Cellular carriers may sometimes internally refer to cellular phones a customer has purchased without a subsidy or from a third party as "customer provided equipment."
• It is also notable that the fully qualified domain name and the PTR record of DSL and cable lines connected to a residence will often contain 'cpe'.

Sumber : http://en.wikipedia.org/wiki/Customer-premises_equipment

Topologi fisik jaringan

Topologi fisik jaringan adalah bentuk fisik bagaimana komputer terhubung antara satu dengan lainnya. Jika Anda perhatikan kembali pada gambar 4, Anda dapat membayangkan bagaimana bentuk hubungan antar komputer pada masing-masing ruangan di sekolah.

Secara umum ada tiga macam topologi fisik yang sering digunakan dalam LAN, yaitu:
A. Topologi Bus
B. Topologi Ring (Cincin)
C. Topologi Star (Bintang)

A. Topologi Bus
Pada topologi bus biasanya menggunakan kabel koaksial. Seluruh jaringan biasanya merupakan satu saluran kabel yang kedua ujungnya diterminasi dengan alat berupa Terminator.
Topologi ini mempunyai keuntungan dan kerugian sebagai berikut:
Keuntungan
- Hemat kabel
- Layout kabel sederhana
- Mudah dikembangkan
Kerugian
- Deteksi dan isolasi kesalahan sangat kecil
- Kepadatan lalu lintas data
- Bila salah satu client rusak, maka jaringan tidak bisa berfungsi.
- Diperlukan repeater untuk jarak jauh

B. Topologi Ring (Cincin)
Pada topologi ini kabel yang digunakan akan membentuk lingkaran tertutup sehingga mengesankan cincin tanpa ujung. Secara umum layout topologi ring juga relatif sederhana.
Keuntungan
- Hemat kabel
Kerugian
- Peka kesalahan
- Pengembangan jaringan lebih kaku

C. Topologi Star (Bintang)
Pada topologi star setiap node pada jaringan akan berkomunikasi melalui sebuah pusat atau konsentrator. Aliran data setiap node akan menuju konsentrator (HUB) terlebih dahulu sebelum ke node tujuan.
Dengan menggunakan topologi jenis ini maka jaringan mudah dikembangkan dengan menarik kabel ke konsentrator/node pusat.
Keuntungan
- Paling fleksibel
- Pemasangan/perubahan stasiun sangat mudah dan tidak mengganggu bagian jaringan lain
- Kontrol terpusat
- Kemudahan deteksi dan isolasi kesalahan/kerusakan
- Kemudahaan pengelolaan jaringan
Kerugian
- Boros kabel
- Perlu penanganan khusus
- Kontrol terpusat (HUB) jadi elemen kritis
Selain topologi di atas ada beberapa topologi yang ada antara lain topologi mesh dan tree (pohon).
Pada topologi mesh tiap komputer saling terhubung dengan banyaknya komputer yang ada, sedangkan pada Tree tiap komputer terhubung secara bebas ke dalam jaringan.


Sumber : http://prihadipati.blogspot.com/2010/07/topologi-fisik-jaringan.html