PPP support different option that can be configured optionally. One of these options is authentication. The authentication option provides a method to negotiate the use of a particular protocol for Authentication. By default, authentication is not required. Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP) can be used for PPP links authentication which is defined in RFC 1334
Password Authentication Protocol is a basic two-way process used to authenticate a user’s password. The username and password are sent in plain text without any encryption. If it is accepted, the connection is allowed. As an authentication protocol, PAP is the least secure because the password is sent in plain text.
The figure below illustrates the process of PAP. R1 sends its PAP user name and password to R2. R2 evaluate R1’s user name and password against its local database. If it matches, it accepts the connection and accepts the message. If not, it rejects the connection and sends a reject message.
The command “ppp authentication pap” is used for PPP authentication. When the command is entered, the username and password are sent as one LCP data packet. After PPP completes the link establishment phase, the remote node constantly sends a username with password across the link until the receiving node acknowledges the connection or terminates the connection.
The receiving node checked the username-password using an authentication server that either allows or denies the connection. If the connection is accepted, it sends the connection acknowledgement message otherwise it returned the reject message. Password Authentication Protocol authenticates only during establishing a connection, it never re-authenticate after connection establishment. This is a network vulnerability to the attacker; they can attack using this area.
Password Authentication Protocol can be used where a large installed base of client applications that do not support CHAP. Password Authentication Protocol can also be important between different vendor equipment, where implementations of CHAP are not compatible. It is also used where a plaintext password is necessary to simulate a login at the remote host
Configuring PAP Authentication
Now we know the basic information about PAP. We know that PAP is a two-way authentication protocol. Both routers authenticate and are authenticated. The PAP username and password that each router sends must match those configured with the username name password password command of the other router.
PAP only did authentication during initial link establishment. The hostname on one router must match the username the other router has configured for PPP. The passwords must also match. Specify the username and password parameters, The PAP configuration for the above topology is the following:-
Router R-1 (Remote Site)
Router>enable
Router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname R1
R1(config)#username R2 password ccna12345
R1(config)# interface serial0/0/0
R1(config-if)#no shut
R1(config-if)# ip address 192.168.10.1 255.255.255.252
Excel formulas are difficult tasks for users of this software. Learning Excel formulas is very important to help use Excel more effectively. In the previous lesson, I discussed the methods of entering a formula. In this lesson, I am going to teach you basic formulas.
SUM
The SUM function is the most basic formula in Microsoft Excel. Using this formula, we can find the sum of two or more values in the cells. All formulas in Excel start with the equals sign “=” followed by a specific text formula. The SUM function is the must-know formula in Excel.
To perform this formula, enter the values to add together using the format =SUM(number1, [number2], …). The values, we need to enter into the formula can either be actual numbers or equal to the number in a specific cell of the spreadsheet. The example usage of this formula is:
=SUM(A2: H2) –Selection that sums the values of a row from A2 to AH.
=SUM(A2: A15) – Selection that sums the values of a column from A2 to A15.
=SUM(A2: A5, A9: A15, A20) – A complicated collection that sums values from range A2 to A5, skip A6, A7 and A8, adds A9 to A15, and then jumps to A20.
=SUM(A2: A10)/5 – Shows you can also turn your function into a formula.
Subtraction
We can subtract multiple values from one another using the SUM formula, for example, “=SUM(A1, -B1, -C1)” with a negative sign before the cell whose value we need to subtract. The Figure below illustrates the output of the formula.
We can also use the format “=A1-B1” for subtraction. To subtract multiple values from one another we can just enter the formula “=A1-B1-C1”, the figure below illustrates the output of this command.
AVERAGE
The AVERAGE formula simply calculates the averages of data, such as the average number of shareholders in a given shareholding. To perform the average formula in Excel, enter the values, cells, or range of the cells you need to calculate the average.
The format of the formula is “=AVERAGE (number1, number2, etc.) or =AVERAGE (Start Value: End Value) for example “=Average(B2: B15). This formula will calculate the average of all the values or range of cells included in the B2 to B15 cells range. The figure below illustrates the average command.
We can find the average using the formula =SUM(B2: B15)/14). B2 to B14, these are a total of 14 cells. The formula will divide the total B2 by B14 by the number 14.
Remember that HDLC is the default encapsulation protocol for Cisco routers. If PPP configuration is not done on Cisco routers, the default encapsulation will be used. To set PPP as the encapsulation method used by a serial interface we need PPP configuration on the serial interfaces. The PPP configuration for the below topology is following.
Router1
Router1#configure terminal
Router1(config)# interface serial 0/0/0
Router1(config-if)# encapsulation ppp
Router2
Router2#configure terminal
Router2(config)# interface serial 0/0/0
Router2(config-if)# encapsulation ppp
The encapsulation ppp interface command has no arguments. The figure billow illustrates that Router1 and Router2 have been configured with both an IPv4 and an IPv6 address on the serial interfaces. PPP is a Layer 2 encapsulation that supports different Layer 3 protocols.
Compression Configuration
The command syntax for compression configuration is “compress”. Compression can be configured after enabling PPP encapsulation on the serial interface of a Cisco router. This option invokes a software compression process; therefore it can affect system performance. If the traffic already contains compressed files, such as .zip, .tar, etc, never use this option. The command for configuration is as under:
Two keywords are available for “compress” command. With predictor keyword, the predictor algorithms are used. While stac is used for LSZ algorithms.
Link Quality PPP Configuration (LQM)
Quality is also the option of the LCP phase. LCP tests the link to verify whether the link quality is sufficient to use Layer 3 protocols or not. After configuring this option, the percentages are calculated for both incoming and outgoing directions. If the link quality percentage is not maintained, the link is supposed to be of poor quality and is taken down. The “ppp quality percentage” command is used to ensure that the link meets the quality requirement set; otherwise, the link closes down. The percentage range is from 1 to 100. The LQM configuration for the above network is as under:
PPP support different option than can be configured optionally. Authentication using PAP or CHAP, Compression using either Stacker or Predictor and Multilink that combines two or more channels to increase the WAN bandwidth. To negotiate these PPP options, the LCP link-establishment frames contain option information in the data field of the LCP frame, as shown in Figure 1. If LCP frame has no configuration option, then the default value for that configuration option is assumed. This phase is complete when a configuration acknowledgement frame has been exchanged. The configurable LCP options for specific WAN connection may include the following LCP options:
Authentication
This 16 bits long field with a code value of 0x03. This Configuration Option provides a method to negotiate the use of a particular protocol for Authentication. By default, authentication is not required. Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP) can be used for authentication.
Compression
Compression option is used to Increases the effective throughput on PPP links. Increasing throughput is possible due to reducing the amount of data in the frame that must travel across the link. The protocol decompresses the frame at the receiving side. Stacker and predictor protocols are used for this purpose.
Magic Number (Error Detection)
The Magic Number field is used for detecting links that are in a looped-back condition. It is responsible to ensure a reliable, and loop-free data link. Until the Magic-Number Configuration Option has been successfully negotiated, the Magic-Number must be transmitted as zero. Magic numbers are randomly generated number used to identify one end of a point-to-point connection. Each side of the link negotiates its magic number. If both sides discover that the magic numbers they are negotiating are the same, both side attempts to change its magic number. If the magic number remains the same after changing, the session terminates because of the loopback that is found.
PPP Callback
PPP callback option is used to improve security the in PPP links. Cisco router can act as a callback client or a callback server in the LCP option. The call back occurs at the beginning of a new PPP session. LCP includes the callback option and its settings. The client makes the opening call, requests for server call back, and terminates its call. The callback router answers the call and makes the return call to the client based on its configuration statements. The command is PPP callback [accept | request]. RFC-1570 further describes PPP callback.
Multilink
The multilink option is used for load balancing over the router interfaces that PPP uses. It is also referred to as MP, MPPP, and MLP. It provides a method for spreading traffic across multiple physical WAN links. Multilink indicates to its peers that it is capable of combining multiple physical links into a single bundle. A system indicates to its peer that it is prepared to do multilink by sending the multilink option as part of the initial LCP option negotiation.
According to the details, the Speaker of the National Assembly Asad Qaiser, who fell victim to the corona virus a few days ago, fell ill due to the corona virus and was shifted to the hospital in critical condition.
According to sources close to the family of National Assembly Speaker Asad Qaiser the speaker of the National Assembly isolated himself at home after testing positive for the corona virus, His condition started deteriorating some time ago and he has been shifted to hospital in critical condition.
On the other hand, health officials said that the Speaker of the National Assembly Asad Qaiser has been admitted to the intensive care unit and his treatment has been started on an emergency basis. However, it would be premature to say more about his condition.
It may be recalled that the Speaker of the National Assembly Asad Qaiser had isolated himself at home after testing positive for the corona virus.
In addition to the Speaker of the National Assembly, his children were also infected with the corona virus, which isolated them at home. However, the condition of their children is out of danger.
When a PPP link has been initiated, the LCP passes control to the appropriate Network Control Protocol (NCP). NCP is a set of protocols that form part of PPP. PPP is a data link layer protocol that can transmit multiprotocol data between two point-to-point.
PPP’s modular model allows LCP to set up the link and then transfer the details of a network protocol to a particular NCP. Each network protocol has a corresponding NCP and corresponding RFC. For example, IPv4, IP6, IPX, and many others have corresponding NCPs. These NCPs use the same packet as the LCPs.
After the LCP configuration and authentication in the basic link, the inappropriate Network Control Protocol is called on to complete the particular configuration of the network layer protocol. After the network layer protocol’s successful Network Control Protocol configuration, the network protocol is in the open state on the established LCP link. From there, PPP can carry the corresponding network-layer protocol packets.
Internet Protocol Control Protocol (IPCP)
When LCP has established the link, the routers exchange IPCP messages for option negotiation. IPCP is responsible for configuring, enabling, and disabling the IPv4 modules on both ends of the PPP link. The same responsibilities are allocated to IPV6CP for IPv6 addresses. IPCP negotiates two options:
Compression—The compression protocol allows devices to negotiate an algorithm to compress TCP and IP headers and save bandwidth. For compression, the Van Jacobson TCP/IP header compression is used. The Van Jacobson TCP/IP header compression compresses the size of the TCP/IP headers to 3 bytes. Which is the important improvement on slow serial lines, particularly for interactive traffic?This compression method is similar in concept to the Protocol-Field-Compression and Address-and-Control-Field-Compression (ACFC) options in LCP.
IP-Address-IP address allows the initiating device to send the Configure-Request. To specify an IP address, it needs to be used for routing IP over the PPP link or to request that the other device supply it with one. This is most commonly used for dial-up networking links before the advent of broadband technologies such as DSL and cable modem services.
After the Network Control Protocol process is completed, the link goes into the open state, and LCP gets the link in the maintenance phase. Link traffic contains possible LCP, NCP, and network-layer protocol packet combinations. After the data transfer is completed, the Network Control Protocol terminates the protocol link, and the LCP terminates the PPP connection. The different NCPs are;
When two devices are first turned on, there is no physical layer connection between them. Once the connection is made, the link can continue to establish a PPP session. There are three phases of establishing a PPP session:
Phase 1: Link establishment and configuration negotiation
Before PPP exchanges any network layer datagrams, such as IP, the LCP must first perform the basic setup of the link. The sending device sends an LCP configuration request to a receiving device. Suppose sending device is A and receiving device is B. The B receive the configuration request message over the physical link, containing the parameters wishes to use.
If device B agrees with the parameters, it replies with an acknowledgement (Ack) otherwise sends negative acknowledgement (NACK) message. In the case of NACK, sending device tries different parameters with a new request. This phase is complete when the negotiation between both is successful. After the successful completion of Phase 1, the status goes to LCP open and proceed to the authentication phase.
Phase 2: Link quality determination
Link Quality determination is the second phase of the PPP session establishment. It as an optional phase in the PPP session. The LCP check the link quality to decide that the link is sufficient to bring up network-layer protocols. The LCP can delay data sending of network layer protocol information until this phase is complete.
After the link quality determination, the specific configuration of the appropriate network layer protocol is performed by invoking the suitable NCP, such as IPCP, IPXCP etc. If the LCP terminate the link, it informs the network-layer protocols so that they can take appropriate action. More than one NCP can be run on a particular PPP link, and each NCP can be terminate independently when it is no longer needed. The PPP link remains configured for communications until explicit LCP or NCP frames terminate the link, or until some outside event occurs.
LCP Operation
Link Control Protocol (LCP) is the main part of the PPP session. It is responsible for controlling the links in Point-to-Point Protocol (PPP) suite. It is implemented at Data Link Layer in the OSI model. LCP is used to automatically agree upon the encapsulation format, sizes of packets, looped-back link, and common misconfiguration errors. It is also responsible for connection termination. LCP operation uses three classes of LCP frames to accomplish the work of each of the LCP phases:
Link-establishment frames
Link-maintenance frames
Link-termination frames
Link Establishment
Link establishment is the first phase of LCP operation that must complete successfully, before exchanging any network layer packets. During link establishment, the LCP opens the connection and negotiates the configuration parameters. The initiating device starts link establishment by sending a Configure-Request frame to the responder. The frame contains a variable number of configuration options needed to set up on the link. The initiator includes the options for how it wants the link created, including protocol or authentication parameters.
The responder processes the request. If the options are not suitable or not recognized the responder sends a Configure-NAK or Configure-Reject In case if the negotiation fails, the initiator must restart the process with new options. If the options are suitable and acceptable, the responder replies with a Configure-Ack message and the process moves on to the next stage. Next stage is NCP operation. When NCP has completed configurations, authentication if configured, the line is available for data transfer. During the data exchange, LCP transitions into the link maintenance phase. Figure 1 illustrates the Link Establishment phase of LCP.
Link Maintenance
When the link is in the maintenance phase, LCP can test the link using test and feedback messages as shown in Figure 2.
Test Messages Frame. Echo-Request, Echo-Reply, and Discard-Request can be used for testing the link.
Feedback Messages Frame. Code-Reject and Protocol-Rejectframe types provide link feedback when one device receives an invalid frame due to unrecognized LCP code or a bad protocol identifier. Code-Reject packet is sent in response. The sending device will resend the packet.
Link Termination
The link remains open until the LCP terminates the link. If the LCP terminates the link before NCP, the NCP session is also terminated. NCP only terminates the network layer and NCP links. PPP can terminate the link at any time. PPP link termination can occur because of the loss of the carrier including authentication failure, link quality failure, the expiration of an idle-period timer, or the administrative closing of the link. For closing the link, LCP exchanged the Terminate packets.
The device that starts the shutdown process sends a Terminate-Request message. The other device replies with a Terminate-Ack. When the link is closing, PPP informs the network-layer protocols so that they may take suitable action.
LCP Packet
Figure 1 shows the fields in an LCP packet:
Code – This field is 8 bits long and identifies the type of LCP packet.
Identifier – The identifier is also 8 bits (one octet) long field in length and is used to match packet requests and replies.
Length – The length field is 16 bits long field in length and indicates the total length (including all fields) of the LCP packet.
Data – The data field is 0 or more bits in size as indicated by the length field. The format of this field is determined by the code field. Data field contains the information associated with the frame, which may be configuration options, frame information, or data.
Each LCP packet is a complete LCP message containing an LCP code, an identifier field, a length field indicating the size of the LCP packet and LCP packet type-specific data. Each LCP packet has a specific function in the exchange of configuration information depending on its packet type. The code field of the LCP packet defines the type of the packet. Different LCP packet types are:
Configure-Request – When the LCP Code field value is 0x01, it shows that the packet is the configure-request frame. This frame is used for opening or resetting a PPP connection. It contains a list of LCP option with changes to default values.
Configure-Ack – When the code field value is 0x02, it means that the frame is Configure-Ack field. This frame is sent when all of the value of the last configure-request received is recognized and acceptable. When both PPP peers send and receive Configure-Acks, the LCP negotiation is complete.
Configure-Nak – If the code field value is 0x03, it’s mean that the frame is Configure-NAK frame. This frame is sent When some LCP option is not acceptable and some option is acceptable. The frame includes the mismatching option and their acceptable values.
Configure-Reject – If the code field value is 0x04, the frame type is a Configure-Reject frame. This type of frame is sent when any LCP option is not recognized or accepted. This frame also includes the unrecognized or non-negotiable option.
Terminate-Request – if the code field value is 0x05, the frame is Terminate-Request frame. This frame is sent optionally for closing the PPP session.
Terminate-Ack – if the code field value is 0x06, the frame type is Terminate-Ack. This frame is sent in response to the Terminate-Request frame in PPP session.
Code-Reject – If the code field value is 0x07, the frame type is a Code-Reject frame. This frame is sent when the LCP code is unknown. The Code-Reject message also includes the rejected LCP packet.
Protocol-Reject – When a code field value is set to 0x08, the frame type is Protocol-Reject frame. It is sent when the PPP frame includes an unknown protocol ID. The Protocol-Reject message also includes the rejected LCP packet.
Echo-Request – If the code field value is 0x09, the frame type is Echo-Request. Echo-Request frame is sent optionally to test the PPP connection.
Echo-Reply – When a code field value is 0x0a, the frame type is Echo-Reply. This frame is sent in response to the Echo-Request frame. PPP Echo-Request and Echo-Reply frame are not related to the ICMP Echo-Request and Echo-Reply messages.
Microsoft Excel is one of the important family members of Microsoft office. It is in industry-standard software for data analysis. Bankers and financial analysts also use Microsoft Excel for data processing, calculations and presentation. The excel formula is a difficult task for the users of this software. There are two ways to perform data processing and calculation in Microsoft Excel:
Formulas
The formula is an expression that operates on different values in a range of cells or a cell. For example, =A1+A2+A3+A4, which finds the sum of the values from cell A1, A2, A3and A4.
Functions
Another way to perform this calculation is the function method. It is a predefined formula in Excel. Functions eliminate manual entry of formulas which is too much difficult. The function has also human-friendly names. For example: =SUM(A1:A10). The function sums all the values from A1 to A10. You can see that in with just a small piece of command we have sums 10 cells.
How can Enter formula in Excel
There are five different methods for inserting formulas in the workbook and sheets. Each method has its advantages. So, before starting into the formula learning, it is important to learn the way of inserting formulas into excel workbook.
Typing a formula inside the cell
Typing a formula in a cell is the very basic way of inserting formula in Excel. The formula insertion is usually started with typing an equal (=) sign, followed by the name of an excel function. We can see the formula in the formula bar. Microsoft Soft Excel is very intelligent software, so when we start typing the name of the function, the software displays a pop-up hint.
The pop-up lists all possible values, from where we can select the preferred function. While selecting the function never press the Enter Key, instead press the Tab key to the continuous selection of more function. If you enter If you press enter you may find the “#NAME?” error. To fix this error just re-select the cell and go to the formula bar to complete the function.
Insert Function Option from Formulas Tab
This is the tool for those who have full control over excel formula. The Excel Insert Function dialogue box is everything you need in data processing and calculations. To start this function, just click on the Formulas tab and select the first menu labelled Insert Function. We can start this function anywhere on clicking the “fx” just at the beginning of formula bar. The opening dialogue box will contain all the functions you ever need to complete your analysis. The figure below illustrates this function starting.
Selecting a Formula from Groups in Formula Tab
These are reached function formula group. To find formula group, navigate to the Formulas tab and select favourite group. Click on the preferred group to display a sub-menu filled with a list of different functions.
AutoSum Option
AutoSum option is the most used function of Microsoft Excel. For a quick sum, this function is very useful. The figure below illustrates the AutoSum option in Microsoft Excel. This tab is available in the Home tab in the far-right corner. This option is also available in the Formulas tab.
Use Recently Used Tabs
This option is available in the formula tab. In this option, we can re-use the most recent used formula. This option is just next to the AutoSum option.
جواب – کلمہ شہادت کا ترجمہ ہیں کہ ” میں گواہی دیتا /دیتی ہوں کہ اللہ تعالیٰ کے سوا کوئی معبود نہیں وہ اکیلا ہے۔ اس کا کوئی شریک نہیں اور میں اس بات کی بھی گواہی دیتا/دیتی ہوں کہ بے شک محمد ﷺ( اللہ) اس کے بندے اور اس کے (آخری) رسول ہیں “
٢ – کلمہ شہادت کی اہمیت بیان کریں۔
جواب – کلمہ شہادت کا زبان سے اقرار کرنا اور دل سے تسلیم کرنا اسلام میں داخل ہونے کا اعلان ہے۔ اس پر ایمان لانے سے انسان کفر و شرک سے بچ جاتا ہے۔ اس کے پہلے حصےمیں عقیدہ توحید کی گواہی کا ذکر ہے – کہ اللہ تعالیٰ کے سوا کوئی عبادت کے لائق نہیں ۔ وہی خالق و مالک ہے رزاق ہے ۔ تمام صفات اُسی کی ہیں وہی زندگی و موت کا مالک ہے –
کلمہ شہادت کے دوسرے حصے میں عقیدہ رسالت کا ذکر ہے جس کا مطلب ہے کہ حضرت محمدﷺ اللہ تعالیٰ کے بندے اور آخری رسولؐ ہیں۔ جن کو انسانوں کی ہدایت اور راہنمائی کیلئے بھیجا گیا ہے۔ یہ کہ ان کے بعد کوئی نبی اور رسول آیا ہے اور نہ قیامت تک کوئی نبی اور رسول آئےگا۔
٣۔ کلمہ شہادت دنیا اور آخرت کی کامیابی کیلئے کیوں ضروری ہے؟ وضاحت کریں۔
جواب – کلمہ شہادت کا اقرار کرنے والا ہر حال میں اللہ تعالی کی عبادت اور بندگی کرتا ہے۔ اسی سے اپنی حاجت کا طلبگار رہتا ہے۔ اسی کو تمام صفات کے لائق سمجھتا اور مانتا ہے۔ اور پنی زندگی اللہ تعالئی کو معبود مان کر اور رسول کریم ﷺ کو آخری نبی مان کراپنی زندگی کو اسلام کے مطابق گزارتا ہے جس دنیا اور آخرت دونوں کامیابی اور سکون حاصل کرتا ہے ۔
Four soldiers, including a colonel and a major, were killed during a clash between Mujahideen and Indian Army in Handwara area of Kupwara district of Occupied Kashmir.
According to Kashmir Media Service, the Indian Army occupying Chhanji Mola in Handwara area of Kupwara cordoned off the area and started house to house search.
KMS said that Col. Ashutosh Sharma, who was leading the Indian Army operation, entered the house along with four other personnel to search the house and was killed by Mujahideen who had taken shelter in the house.
Later, the occupying Indian forces called in more troops and surrounded the house. However, clashes broke out between the Mujahideen and the occupying forces which lasted for several hours.
Later, the Indian Army sprayed gunpowder on the house and set it on fire, as a result of which both Mujahideen were martyred.
According to KMS, four Indian military personnel, including a colonel and a major, and a sub-inspector of Indian police were killed in a clash with Mujahideen.
Among the Indian soldiers killed were Col. Ashutosh Sharma and Major Anoop Sood.
It may be recalled that the brutal operations by the Indian occupying forces in the occupied valley have intensified and in the last two weeks, the occupying forces have martyred 20 Kashmiri youths in the name of fake operations.
In addition, the occupying forces have destroyed the houses of many Kashmiris during Ramadan.
