Matthew 7:21

Matthew 7:21

Proxy Server

A proxy server, also known as a "proxy" or "application level gateway", is a computer that acts as a gateway between a local network (e.g., all the computers at one company or in one building) and a larger-scale network such as the Internet. Proxy servers provide increased performance and security. In some cases, they monitor employees' use of outside resources.

A proxy server works by intercepting connections between sender and receiver. All incoming data enters through one port and is forwarded to the rest of the network via another port. By blocking direct access between two networks, proxy servers make it much more difficult for hackers to get internal addresses and details of a private network.

Some proxy servers are a group of applications or servers that block common Internet services. For example, an HTTP proxy intercepts web access, and an SMTP proxy intercepts email. A proxy server uses a network addressing scheme to present one organization-wide IP address to the Internet. The server funnels all user requests to the Internet and returns responses to the appropriate users. In addition to restricting access from outside, this mechanism can prevent inside users from reaching specific Internet resources (e.g., certain web sites). A proxy server can also be one of the components of a firewall.

Proxies may also cache web pages. Each time an internal user requests a URL from outside, a temporary copy is stored locally. The next time an internal user requests the same URL, the proxy can serve the local copy instead of retrieving the original across the network, improving performance.

Note: Do not confuse a proxy server with a NAT (Network Address Translation) device. A proxy server connects to, responds to, and receives traffic from the Internet, acting on behalf of the client computer, while a NAT device transparently changes the origination address of traffic coming through it before passing it to the Internet.

For those who understand the OSI (Open System Interconnection) model of networking, the technical difference between a proxy and a NAT is that the proxy server works on the transport layer (layer 4) or higher of the OSI model, whereas a NAT works on the network layer (layer 3).

source: http://kb.iu.edu/data/ahoo.html

related source: http://www3.rad.com/networks/1998/proxy/proxy.htm

Asynchronous Transfer Mode

Asynchronous transfer mode (ATM) is a switching technology that facilitates the movement of data from one point to another. It is one of the preferred technologies because of its efficiency of use, especially with different hardware components. Unlike other types of technology, the speed and efficiency used in asynchronous transfer mode makes it one of the most common network protocol standards in use today.

The main advantage of asynchronous transfer mode technology is the ability to transfer many different types of data at the same time. This is because all bandwidth is utilized, as long as it is available. Other types of technologies will often not allow all the bandwidth to be used once a particular function is started. Therefore, it makes for a very efficient way to transfer video files, pictures, e-mail and even live streaming audio and video.

Encoding data in asynchronous transfer mode is remarkably consistent, with each cell being 53 bytes in length. This helps during the processing of the data because there is no need to worry about where each cell starts and ends, unlike what is required with TCP/IP. Therefore, dealing with more known factors means there is a greater ability to contribute resources to to encoding and decoding, thus speeding up the data transmission.

The cells of asynchronous transfer mode are broken down into two main parts. There is a five bit header, which helps identify the routing the cell will take to reach its destination. The other part is known as the payload. This is the practical information that is supposed to be conveyed. There is no information marking the end of the cell because, as stated previously, the hardware is set up to automatically "know" when the cell ends.

The speed of asynchronous transfer mode can reach up to 10 billion bytes per second, also written as 10 Gbps. This makes it one of the fastest network protocols in existence. Thus, in addition to general internet use, it can also be used to transfer very large amounts of data over wide area networks and local area networks. Asynchronous transfer mode can also be used between the two types of networks as well.

There are two major divisions of asynchronous mode. Which one is used is determined by the type of data. For example, constant bit rate is used to stream live video and audio over the internet. Unspecified bit rate can be used when there is no critical time element involved. This, however, does not necessarily mean the transfer of unspecified bit rate will seem slower than constant bit rate to the end user.

source: http://www.wisegeek.com/what-is-asynchronous-transfer-mode-atm.htm

T1 and E1 Circuit

T-1 is a digital circuit that uses the DS-1 (Digital Signalling level 1) signaling format to transmit voice/data over the PSTN network at 1.544 Mbps. T-1 can carry up to 24 uncompressed digital channels of 64 Kbps (DS0) for voice or data. E-1 is the European equivalent of the T-1, except E-1 carries information at the rate of 2.048 Mbps. E-1 is used to transmit 30 64Kbps digital channels (DS0) for voice or data calls, plus a 64Kbps channel for signaling, and a 64Kbps channel for framing and maintenance.

A T1/E1 circuit is a dedicated circuit and is always composed of two parts: the local loop and the carrier circuit. A T1/E1 circuit is the first multiplexed level of the digital signalling multiplexing scheme. T1s use what is called a Stratum 3 clock to maintain what is called clocking on the line.

Within the communications network, copper twisted pairs are used. One pair for transmit, and another for receive making four wires for each T1. This allows T-carrier systems to transmit and receive simultaneously in both directions at full speed (full duplex). T1 trunk cables are made in bundles of 25 pairs of 22 AWG copper wires designed for carrying multiple T1's. A T1 uses a bipolar signalling method where voltage states range between +/- 12 volts. A binary zero is signaled with zero voltage; binary ones are signalled using either positive or negative voltage.

A T1 service is provided by three ways: full T1/Bustable T1 Service, channelized T1 and fractional T1.

• Full T1 Service - A full T1 service provides a complete circuit of up to 1.544Mbps total speed. This communications channel is often referred to as a digital trunk line. The full circuit can be either data or voice, but not both.
• Burstable T1 Service - This is a full T1 with some sort of measuring technology attached at the ISP's end. Customer gets an amount of bandwidth for each month and pays a premium when their T1 exceeds this level of data.
• Channelized T1 - A channelized T1 contains 24 individual DS0 channels, each capable of carrying voice or data. The full set of channels has the same speed as a full T1, but the individual channels may be split into voice lines or data lines using a device called a Channel Service Unit/Data Service Unit or CSU/DSU. The CSU/DSU allows the voice channels to be connected to a phone system or PBX. The data lines are then connected to a router serial interface and often are used to provide Internet connectivity.
• Fractional T1 - A fractional T1 is one or more channels bundled together and sold to a customer as a set. This allows a consumer to purchase less than a full T1's bandwidth at a lower cost. Like the channelized T1, individual channels can be voice or data and a CSU/DSU is used to split the channels, however less than the full set of 24 channels is available to the customer for use.

source: http://www.networkdictionary.com/telecom/T1andE1Circuit.php

T1 Circuit

Description

A T1is sold one of three ways, full T1, channelized T1 and fractional T1. A T1 circuit is a dedicated circuit and is always composed of two parts: the local loop and the carrier circuit. The local loop is provided by the local telephone company because they are the ones that put the wire that is conncted to the site into the ground. If the T1 is for Internet service, the other end of the circuit will be routed to the telecommunications provider of your choice and Intenret service will be turned on. Thus, your Internet T1 contains a local phone company portion of the circuit closest to you and an Internet provider part of the circuit owned by your ISP. Always remember that when troubleshooting an Internet T1, you need to get both the local phone company and the Internet provider on the phone at the same time to do any work on the circuit.

In some places, long distance companies (who are usually the big ISP's) also own the local circuits and are the local telecommunications provider. This is very rare. More often when you buy a T1, you are buying a T1 where the local phone company's part of the circuit is being resold by the ISP to you as a complete T1. This is a better way to purchase it if you can because you can hold the ISP accountable for all problems in the local phone company portion of the circuit. However, it will be more expensive.

Full T1 Service

A full T1 service is usually sold as a complete circuit of up to 1.544Mbps total speed. This communications channel is often referred to as a digital trunk line. A T1 is a dedicated circuit from the telecommunications provider to the customer and is not shared with any other customers. This is why it is often referred to as a 'dedicated' line. The full circuit can be either data or voice, but not both.

Burstable T1 Service

This is a full T1, sold with some sort of measuring technology attached at the ISP's end. You purchase an ammount of bandwidth that you receive each month and pay a premium when your T1 exceeds this level of data.

Channelized T1

A channelized T1 contains 24 individual channels, each capable of carrying voice or data. The full set of channels has the same speed as a full T1, but the individual channels may be split into voice lines or data lines using a device called a Channel Service Unit/Data Service Unit or CSU/DSU. The CSU/DSU is used to split off the voice channels from the data channels, allowing the voice channels to be connected to a phone system or PBX. The data lines are then connected to a router serial interface and often are used to provide Internet connectivity.

Fractional T1

A fractional T1 is one or more channels bundled together and sold to a customer as a set. This allows a consumer to purchase less than a full T1's bandwidth at a lower cost. The price of T1's has fallen significantly however and fractional T1 service is becoming ever more rare. Like the channelized T1, individual channels can be voice or data and a CSU/DSU is used to split the channels, however less than the full set of 24 channels is available to the customer for use.

PHYSICAL SPECIFICATIONS

GENERAL

A T1 circuit is an always on connection. It in no way resembles a voice circuit which only generates expenses when a call is placed. For this reason, T1's are sometimes referred to as private lines or dedicated data line because they are always in use (whether data is being transmitted or not) and thus, can never be used for carrying traffic from multiple subscribers. It is because T1's are dedicated circuits that they cost more than ISDN or Frame Relay circuits which assume that the customer's connection is shared with other subscribers. T1's are 'always on' and thus must be a dedicated data line.

A T1 circuit is the first multiplexed level of the digital signalling multiplexing scheme. T1s use what is called a Stratum 3 clock to maintain what is called clocking on the line. Devices supporting a T1 estimates its synchronization with the T1 based on the data received over the link. Thus, T1 communication is not always fully synchronous (this is one cause of frame slips). T1's are more properly called pleisiosynchronous connections.

T1s are often referred to as DS1 (Digital Signalling level 1). A T1's speed can reach as high as 1.544 Mbps on the circuit. T1's are the most common high speed circuit provided by telecommunications carriers because a T1 can be regenerated and extended to reach any location. Other solutions such as DSL do not have the same total reach as standard T-carrier services. T1's carry 24 channels of digital information and must maintain a certain level of 1's density in order to assure the clock is maintained at both ends of the circuit.

ELECTRICAL

A T1 uses a bipolar signalling method where voltage states range between +/- 12 volts. A binary zero is signaled with zero voltage; binary ones are signalled using either positive or negative voltage. This positive and negative value is refered to as polarity. When a series of 1's are received on a T1 link, the voltage is alternated from positive to negative voltage. From this change in voltage, the receiving equipment can detect and synchronize with the remote device's clocking. Zeroes are indicated by zero voltage on the line. Because clocking is derived by detecting changes in voltage, a long stream of zeroes from an inactive line would cause problems.

CABLING

Within the communications network copper twisted pairs are used. One pair for transmit, and another for receive making four wires for each T1. This allows T-carrier systems to transmit and receive simultaneously in both directions at full speed (full duplex). T1 trunk cables are made in bundles of 25 pairs of 22 AWG copper wires designed for carrying multiple T1's. Most carriers today (as of 2004) use fiber optics wherever possible between central offices and have been using T3's for many years. This type of physical plant is slowly fading out of use and will probably be completely gone by the turn of the next century; at least at the rate most carriers currently perform upgrades. The trunk cables carry multiple bundles of 25 pairs and the standard method used for carrying transmission is to separate transmit from receive on each pair into separate bundles to reduce cross talk. Occasionally a few extra pair are added to these bundles for line management functions such as fault location or provisioning.

source: http://www.inetdaemon.com/tutorials/telecom/t-carrier/T1/

Digital Signalling

Digital Signaling level zero (DS0)

Definition

A Digital Signalling level zero (DS0) connection is the smallest and simplest digital signalling connection. The DS0 is the basic level of communication upon which all the other Digital Signalling levels (DS1, DS2, DS3 etc.) are built. The DS0 is often erroneously called the local loop. The local loop is only the analog portion of a voice circuit between the central office and the subscriber. A DS0, being digital, is not actually part of the loop because it is on what is referred to as the trunk side of a Digital Cross Connect Switch (DCCS). The local loop is on the line side of the DCCS. DS0's are used to physically connect calls between end users through a Digital Cross Connect Switch (DCCS). If the user is communicating by voice on a telephone line, then the encoding on the signal that the DCCS receives is analog. That analog signal is converted to digital pulse codes at the switch and then multiplexed into a higher speed link such as a DS1 or DS3.

Voice vs. Data

Residential voice calls start at your phone as an analog call. The analog signal is converted by your phone into an electrical signal on a copper wire. This wire carries the voice portion of your call are encoded into the central office where they are converted to digital pulse codes. DS0 as digital pulse codes. However, it is still possible to encode computer data into a DS0 if you have a device called a Data Service Unit (DSU). The DSU accepts a serial connection from a computer system and can encode that data into a DS0. A DS0 cannot carry voice and data concurrently but it can carry one or the other. This is changing, but not because the telephone system is changing, but because users are purchasing equipment that utilizes what is called IP Telephony which encodes both data and voice into a single multiplexed communications path.

Lines vs. Trunks

Lines are the analog voice connections to end phones. Trunks, also called tie trunks (or sometimes tie lines), are digital. However, trunks carry multiple DS0's and are designed to carry traffic from a large number of subscribers. DS0's are not trunks, though they do exist on the trunk side of the DCCS.

Digital Cross-Connect Switch (DCCS)

This device has several names which depend upon the vendor. Called variously a Digital Access Crossconnect Switch (DACS) or a Digital Cross-Connecting switch (DCCS) the switch connects calls between end users. It performs A/D encoding, circuit switching of calls as well as multiplexing and demultiplexing trunks into individual DS0 circuits.

Digital Signaling level 1 (DS1)

DS1

Digital Signalling Level 1 (DS1) is a North American telecommuncations scheme consiting of 24 voice channels time-division multiplexed (TDM) into 192-bit frames across single physical connection providing 1.544 Mbps data throughput across a T1 Physical Layer digital voice connection.

DS1 is the oldest digital multiplexing system in use in the North American Public Switched Telephone System (PSTN).

Digital Signaling level 3 (DS3)

The term DS3 is used to describe a digital telephone company circuit that carries multiple calls from one central office to another. These high-capacity circuits are called 'trunk lines' or sometimes 'tie trunks' or 'tie lines'. A DS3 carries the equivalent of 28 T1/DS1 circuits by decreasing the time slice alotted for each sample of data and multiplexes the T1's together to form the final DS3 data stream. The T1's are multiplexed together to form a single data channel on the DS3. The Digital Signalling protocol allows for the data on individual T1's or even DS0's to be extracted from the DS3 stream by any Digital Cross Connecting Switch containing a demultiplexor.

The phrase "level 3" indicates a level of multiplexing and should not be confused with the company of the same name.

source: http://www.inetdaemon.com/tutorials/telecom/ds/ds0/

JUDE 1:3

ST. JUDE THADDEUS

New International Version (©1984)

Dear friends, although I was very eager to write to you about the salvation we share, I felt I had to write and urge you to contend for the faith that was once for all entrusted to the saints.


PARALLEL COMMENTARIES

Geneva Study Bible

{1} Beloved, when I gave all diligence to write unto you of the {d} common salvation, it was needful for me to write unto you, and exhort you that ye should {e} earnestly contend for the faith which was {f} once delivered unto the saints.

(1) The goal of this epistle, is to affirm the godly as opposed to certain wicked men both in true doctrine and good conduct.

(d) Of those things that pertain to the salvation of all of us.

(e) That you should defend the faith with all the strength you can muster, both by true doctrine and good example of life.

(f) Which was once given, that it may never be changed.

People's New Testament

Jude 1:3 When I gave all diligence to write unto you. His thought was that when he proposed to write diligently and carefully some need impelled him to write at once, more briefly perhaps than he had purposed.

Earnestly contend for the faith which was once delivered unto the saints. He exhorts to contend for the faith delivered once for all, the faith without innovation, the gospel of the apostles in distinction from the adulterations of false teachers. The doctrine of a progressive revelation after the apostles is not found in the New Testament.

Wesley's Notes

1:3 When I gave all diligence to write to you of the common salvation - Designed for all, and enjoyed by all believers. Here the design of the epistle is expressed; the end of which exactly answers the beginning. It was needful to exhort you to contend earnestly - Yet humbly, meekly, and lovingly; otherwise your contention will only hurt your cause, if not destroy your soul. For the faith - All the fundamental truths. Once delivered - By God, to remain unvaried for ever.

Scofield Reference Notes

Margin salvation

See Scofield Note: "Rom 1:16".

Margin it was needful

Lit. constraint was upon me, i.e. of the Spirit.

Jamieson-Fausset-Brown Bible Commentary

3. Design of the Epistle (compare Jude 20, 21).

all diligence-(2Pe 1:5). As the minister is to give all diligence to admonish, so the people should, in accordance with his admonition, give all diligence to have all Christian graces, and to make their calling sure.

the common salvation-wrought by Christ. Compare Note, see on [2664]2Pe 1:1, "obtained LIKE precious faith," This community of faith, and of the object of faith, salvation, forms the ground of mutual exhortation by appeals to common hopes and fears.

it was needful for me-rather, "I felt it necessary to write (now at once; so the Greek aorist means; the present infinitive 'to write,' which precedes, expresses merely the general fact of writing) exhorting you." The reason why he felt it necessary "to write with exhortation," he states, Jude 4, "For there are certain men crept in," &c. Having intended to write generally of "the common salvation," he found it necessary from the existing evils in the Church, to write specially that they should contend for the faith against those evils.

earnestly contend-Compare Php 1:27, "striving together for the faith of the Gospel."

once, &c.-Greek, "once for all delivered." No other faith or revelation is to supersede it. A strong argument for resisting heretical innovators (Jude 4). Believers, like Nehemiah's workmen (Ne 4:17), with one hand "build themselves up in their most holy faith"; with the other they" contend earnestly for the faith" against its foes.

the saints-all Christians, holy (that is, consecrated to God) by their calling, and in God's design.

Matthew Henry's Concise Commentary

1:1-4 Christians are called out of the world, from the evil spirit and temper of it; called above the world, to higher and better things, to heaven, things unseen and eternal; called from sin to Christ, from vanity to seriousness, from uncleanness to holiness; and this according to the Divine purpose and grace. If sanctified and glorified, all the honour and glory must be ascribed to God, and to him alone. As it is God who begins the work of grace in the souls of men, so it is he who carries it on, and perfects it. Let us not trust in ourselves, nor in our stock of grace already received, but in him, and in him alone. The mercy of God is the spring and fountain of all the good we have or hope for; mercy, not only to the miserable, but to the guilty. Next to mercy is peace, which we have from the sense of having obtained mercy. From peace springs love; Christ's love to us, our love to him, and our brotherly love to one another. The apostle prays, not that Christians may be content with a little; but that their souls and societies may be full of these things. None are shut out from gospel offers and invitations, but those who obstinately and wickedly shut themselves out. But the application is to all believers, and only to such. It is to the weak as well as to the strong. Those who have received the doctrine of this common salvation, must contend for it, earnestly, not furiously. Lying for the truth is bad; scolding for it is not better. Those who have received the truth must contend for it, as the apostles did; by suffering with patience and courage for it, not by making others suffer if they will not embrace every notion we call faith, or important. We ought to contend earnestly for the faith, in opposition to those who would corrupt or deprave it; who creep in unawares; who glide in like serpents. And those are the worst of the ungodly, who take encouragement to sin boldly, because the grace of God has abounded, and still abounds so wonderfully, and who are hardened by the extent and fulness of gospel grace, the design of which is to deliver men from sin, and bring them unto God.