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Showing posts with label Networking. Show all posts
Showing posts with label Networking. Show all posts

Tuesday, 17 March 2020

March 17, 2020

नेटवर्क विश्वसनीयता की जांच करने के लिए मानदंड क्या है?

 नेटवर्क विश्वसनीयता: नेटवर्क विश्वसनीयता का अर्थ है नेटवर्क के माध्यम से संचार जैसे नेटवर्क के माध्यम से वांछित संचालन करने की क्षमता।


नेटवर्क विश्वसनीयता नेटवर्क कार्यक्षमता में महत्वपूर्ण भूमिका निभाती है। नेटवर्क निगरानी प्रणाली और उपकरण नेटवर्क को विश्वसनीय बनाने के लिए आवश्यक आवश्यकताएं हैं। नेटवर्क मॉनिटरिंग सिस्टम नेटवर्क में होने वाली समस्याओं की पहचान करता है जबकि नेटवर्क डिवाइस यह सुनिश्चित करते हैं कि डेटा उचित गंतव्य तक पहुंचना चाहिए ।


एक नेटवर्क की विश्वसनीयता निम्नलिखित कारकों से मापा जा सकता है:


  • डाउनटाइम: डाउनटाइम को ठीक होने के लिए आवश्यक समय के रूप में परिभाषित किया गया है।
  • विफलता आवृत्ति: यह आवृत्ति है जब यह जिस तरह से यह इरादा है काम करने में विफल रहता है ।
  • तबाही: यह इंगित करता है कि नेटवर्क आग, भूकंप जैसे कुछ अप्रत्याशित घटना से हमला किया गया है ।

March 17, 2020

वितरित प्रसंस्करण के फायदे क्या हैं?

 वितरित प्रसंस्करण के फायदों की एक सूची:


  1. सुरक्षित
  2. एनकैप्सुलेशन का समर्थन करें
  3. वितरित डेटाबेस
  4. तेजी से समस्या को हल करने
  5. अतिरेक के माध्यम से सुरक्षा
  6. सहयोगी प्रसंस्करण

March 17, 2020

What is the network? || नेटवर्क क्या है?

 

  • A network is a set of devices that are connected with a physical media link. In a network, two or more nodes are connected by a physical link or two or more networks are connected by one or more nodes.
  • A network is a collection of devices connected to each other to allow the sharing of data.
  • Example of a network is an internet. An internet connects the millions of people across the world.
  • एक नेटवर्क उपकरणों का एक सेट है जो भौतिक मीडिया लिंक से जुड़ा हुआ है। एक नेटवर्क में, दो या अधिक नोड्स एक भौतिक लिंक से जुड़े होते हैं या दो या अधिक नेटवर्क एक या अधिक नोड्स से जुड़े होते हैं।
  • एक नेटवर्क डेटा के बंटवारे की अनुमति देने के लिए एक दूसरे से जुड़े उपकरणों का संग्रह है।
  • एक नेटवर्क का उदाहरण एक इंटरनेट है। एक इंटरनेट दुनिया भर में लाखों लोगों को जोड़ता है ।

Monday, 18 March 2019

March 18, 2019

HMAC Algorithm in Computer Network

 HMAC algorithm stands for Hashed or Hash based Message Authentication Code. It is a result of work done on developing a MAC derived from cryptographic hash functions. HMAC is a great resistant towards cryptanalysis attacks as it uses the Hashing concept twice. HMAC consists of twin benefits of Hashing and MAC, and thus is more secure than any other authentication codes. RFC 2104 has issued HMAC, and HMAC has been made compulsory to implement in IP security. The FIPS 198 NIST standard has also issued HMAC.

Objectives –

  • As the Hash Function, HMAC is also aimed to be one way, i.e, easy to generate output from input but complex the other way round.
  • It aims at being less effected by collisions than the hash functions.
  • HMAC reuses the algorithms like MD5 and SHA-1 and checks to replace the embedded hash functions with more secure hash functions, in case found.
  • HMAC tries to handle the Keys in more simple manner.

HMAC algorithm –
The working of HMAC starts with taking a message M containing blocks of length b bits. An input signature is padded to the left of the message and the whole is given as input to a hash function which gives us a temporary message digest MD’. MD’ again is appended to an output signature and the whole is applied a hash function again, the result is our final message digest MD.

Here is a simple structure of HMAC:



Here, H stands for Hashing function,
M is original message
Si and So are input and output signatures respectively,
Yi is the ith block in original message M, where i ranges from [1, L)
L = the count of blocks in M
K is the secret key used for hashing
IV is an initial vector (some constant)
The generation of input signature and output signature Si and So respectively.

To a normal hash function HMAC adds a compression instance to the processing. This structural implementation holds efficiency for shorter MAC values.

March 18, 2019

How message authentication code works?

 Apart from intruders, the transfer of message between two people also faces other external problems like noise, which may alter the original message constructed by the sender. To ensure that the message is not altered there’s this cool method MAC.

mac value generation

MAC stands for Message Authentication Code. Here in MAC, sender and receiver share same key where sender generates a fixed size output called Cryptographic checksum or Message Authentication code and appends it to the original message. On receiver’s side, receiver also generates the code and compares it with what he/she received thus ensuring the originality of the message. These are components:

  • Message
  • Key
  • MAC algorithm
  • MAC value

There are different types of models Of Message Authentication Code (MAC) as following below:

  1. MAC without encryption –
    This model can provide authentication but not confidentiality as anyone can see the message.


  2. Internal Error Code –
    In this model of MAC, sender encrypts the content before sending it through network for confidentiality. Thus this model provides confidentiality as well as authentication.
    M' = MAC(M, k)

  3. External Error Code –
    For cases when there is an alteration in message, we decrypt it for waste, to overcome that problem, we opt for external error code. Here we first apply MAC on the encrypted message ‘c’ and compare it with received MAC value on the receiver’s side and then decrypt ‘c’ if they both are same, else we simply discard the content received. Thus it saves time.
    c = E(M, k')
    M' = MAC(c, k)

Problems in MAC –
If we do reverse engineering we can reach plain text or even the key. Here we have mapped input to output, to overcome this we move on to hash functions which are “One way”.

Note – symbol “E” denotes symmetric key encryption.

March 18, 2019

Message Authentication Codes

 Message Authentication Codes are the codes which plays their role in two important functions : Authentication Detection and Falsification Detection.

Where do we need these codes ?
Suppose a User A send message to user B with message – ‘abc’. A encrypts the message using Shared – Key Cryptosystem for encrypting the message. A sends the key to B using a source key. Key exchange is based on different protocols such as Public – Key Cryptosytem. B uses the key to decrypt the Ciphertext and obatins the message.
a

All this does not happen so easily. There lies a problem.
If a malicious user X has falsified the ciphertext during the transmission. Then in that case, B has no way to realize that it has been falsified.When B decrypts the message, it will get the wrong message. Unknown to the fact B will think wrong information to be the right. Although you can decrypt or encrypt the data later on but these operations, you are applying on the wrong data.
b

Here we need to detect the falsification in the message B has got.
Here A will create a key (used to create Message Authentication Code) and sends the key to B. A will create a value using Ciphertext and key and the value is obtained. This value Created by Cipertext + Key = Message Authentication Code. B has to check whether the ciphertext is falsified or not using Message Authentication Code. Now B can clearly know that whether the ciphertext is falsified or not.
c


March 18, 2019

Zone-based firewall

 A firewall is a network security system which monitors and takes actions on the ingoing or outgoing packets based on the defined rules. It can be a hardware device or a software.

An organisation that cannot afford a hardware firewall device uses an alternative i.e implementing firewall features on Cisco IOS router by using CBAC or by using Zone-based firewall.CBAC is a predecessor to Zone-based firewall.

Zone-based Firewall –
A Zone-based firewall is an advanced method of stateful firewall. In stateful firewall, a stateful database is maintained in which source IP address, destination IP address, source Port number, destination port number is recorded. Due to this, only the replies are allowed i.e if the traffic is Generated from inside the network then only the replies (of inside network traffic) coming from outside the network is allowed.

Cisco IOS router can be made firewall through two methods:

  1. By using CBAC: create an access-list and apply it to the interfaces keeping in mind what traffic should be allowed or denied and in what direction. This has an extra overhead for the administrator.
  2. Using a Zone-based firewall.

Terms:



  1. Zone – A zone is a logical area in which the devices having same trust levels resides. After creating a zone, an interface is assigned to a zone.By default, traffic is not allowed from one zone to another.

    For example, first we create a zone called inside then if the router interface fa0/0 resides on the most trusted network which we name as inside, then fa0/0 is assigned to inside zone.

  2. Zone-pair – Policies are defined in which traffic is identified (what type of traffic) then what action should be taken (Inspect Denied, permit). Then we have to apply this policies to a zone-pair. A zone-pair is always unidirectional. If we want to make it bidirectional then we have to create another zone-pair.

    For instance, we want to allow the traffic from inside to outside network then we have to create a zone-pair. If we have chosen the action inspect then the reply is permitted from outside the network if the traffic is generated from the inside network (stateful filtering).

    Now, if we want to allow outside traffic to be able to reach inside network then we have to make a separate zone-pair. This zone-pair will allow the traffic to reach the inside network if the traffic is generated from the outside network.

  3. Self-zone – Traffic destined to the router itself, irrespective of which device has send, is known as self zone. The traffic generated from router is known as traffic coming from self-zone. Traffic going to router is considered as traffic going to Self-zone. By default, the traffic to or from the Self-zone is allowed however it can be changed according to the policies applied.

Working:
First, the zones are defined and named. Although, we can give any name but by naming convention that makes sense, name the zones as inside, outside and DMZ.

  • inside: The most trusted (private) network.
  • outside: The most untrusted (public) network.
  • DMZ: (public zone) contains devices like servers.

Now, as zones have been named, policies are created which will include what type of traffic is allowed to be generated and allowed to go through from inside network to outside network and what actions (such as inspect [stateful inspection]) should be taken on the traffic.
The actions can be:

  • inspect: an entry will be made in stateful database for the protocols (for which the policies has been applied) so that the replies (for inside network) can come back.
  • drop: default action if the traffic does not match the policies.
  • pass: the traffic will be allowed from one zone to another but no session is maintained.

The traffic which will not match the policies will be dropped due to default policy. This policies will be defined for one direction (such as inside to outside) in a zone pair.

If conditions requires to allow initial traffic to be generated in both directions (inside to outside network and outside to inside network), then two separate zone-pairs will be created and separate policies are applied.

Advantages – Some of the advantages are:

  1. By default, the traffic is blocked unlike CBAC. In Zone-based firewall, no traffic is allowed from one zone to another while in CBAC, all traffic is allowed if no explicit ACL is applied.
  2. Unlike CBAC, Zone-based firewall is no heavily dependent on ACL.
  3. It is easy to add another interface as only the zone has to be declared to which the interface belongs as all the policies will be same as applied explicitly before for that zone.
March 18, 2019

Firewall methodologies

 A firewall is a network security system which monitors and takes actions (permit or deny traffic) on the basis of policies defined explicitly.It can be performed by a single device, group of devices or by software running on a single device like server.

Cisco ASA has the biggest share in the market while there are other vendors of firewall also like checkpoint, Juniper etc.

Firewall Methodologies –
There are certain methods through which firewall can be implemented. These are as follows:

  1. Static packet filtering – Packet filtering is a firewall technique used to control access on the basis of source IP address, destination IP address, source Port number and destination port number. It works on layer 3 and 4 of OSI model.Also, an ACL doesn’t maintain the state of session. A router with ACL applied on it is an example of static packet filtering.

    Advantages –

    • If the administrator has a good knowledge of network, it is easy to implement.
    • It can be configured on almost all routers.
    • It has minimal effect on network performance.

    Disadvantage –



    • Large amount of ACLs are difficult to maintain.
    • ACLs uses IP address for filtering. If someone spoofs the same source IP address then that will be allowed by ACL.
  2. Stateful packet filtering –
    In stateful packet filtering, the state of the sessions are maintained i.e when a session is initiated within a trusted network, it’s source and destination IP address, source and destination ports and other layer information are recorded. By default, all the traffic from untrusted network is denied.

    The replies of this session will be allowed only when the IP addresses (source and destination IP address) and port numbers (source and destination )are swapped.

    Advantages –

    • Dynamic in nature as compared to static packet filtering.
    • Not susceptible to IP spoofing.
    • Can be implemented on routers.

    Disadvantage –

    • Might not be able to prevent application layer attack.
    • Some applications open dynamic ports on the server side, if the firewall is analysing this, it can cause application failure. This is where application inspection comes into use.
  3. Proxy firewalls –
    These are also known as application layer firewalls. Proxy firewall acts as an intermediary between the original client and the server. No direct connection takes place between the original client and the server.

    The client, who has to establish a connection directly to the server to communicate with it, now have to establish a connection with proxy server. The proxy server then establishes a connection with the server on the behalf of client. Now, the client sends the data to the proxy server and proxy server forwards it to the server. Proxy server can operate upto layer 7 (application layer).

    Advantage –

    • Difficult to attack server as proxy server is the intermediate between the client and the server.
    • Can provide detailed logging.
    • Can be implemented on common hardware.

    Disadvantage –

    • Processor intensive
    • Memory and disk intensive
    • Single point of failure in network security
  4. Application inspection –
    These can analyze the packet upto layer 7 (deep inspection) but can’t act as a proxy server. These can deeply analyze conversation between a client and server even when the server is assigning a dynamic port to the client therfore it doesn’t fail in these cases (which can occur in stateful firewall).

    Advantages –

    • Can analyze deeper into the conversation between the server and the client.
    • If there is a protocol anamoly happening from standard then it can deny the packets.
  5. Transparent firewall –
    By default, the firewall operates at layer 3 but the benefit of using transparent firewall is that it can operate at layer 2.It has 2 interfaces which will act like a bridge so can be configured through a single management IP address. Also, users accessing the network will not even know about that a firewall exists.

    The main advantage of using transparent firewall is that we don’t need to re-address our networks while putting up a firewall in our network. Also, while operating at layer 2, it can still perform functions like building stateful database, application inspection etc.

  6. Network Address Translation (NAT) –
    NAT is implemented on a router or firewall. NAT is used to translate private IP address into a public IP address through which we can hide our source IP address.
    And if we are using dynamic NAT or PAT, an attacker will not be able to know that what devices are dynamically assigned which IP address from the pool. This makes difficult to make a connection from outside world to our private network.
  7. Next-Generation Firewalls –
    NGFWs are third generation security firewall that is implemented in either in software or device. It combines basic firewall properties like static packet filtering, application inspection with advanced security features like integrated intrusion prevention system. Cisco ASA with firePOWER services is an example of Next-Generation firewall.
March 18, 2019

Types of firewall and possible attacks

 No one can deny the fact that the dynamic rise of the Internet has brought the world closer. But at the same time, it has left us with different kinds of security threats. To ensure the confidentiality and integrity of valuable information of a corporate network from the outside attacks, we must have some robust mechanism. This is where the Firewall comes into picture.

It can be compared with a security guard standing at the entrance of a minister’s home. He keeps an eye on everyone and physically checks every person who wishes to enter the house. It won’t allow a person to enter if he/she is carrying a harmful object like a knife, gun etc. Similarly, even if the person doesn’t possess any banned object but appears suspicious, the guard can still prevent that person’s entry.

The firewall acts as a guard. It guards a corporate network acting as a shield between the inside network and the outside world. All the traffic in either direction must pass through the firewall. It then decides whether the traffic is allowed to flow or not. The firewall can be implemented as hardware and software, or a combination of both.

Types of Firewalls:



  1. Packet Filters –
    It works in the network layer of the OSI Model. It applies a set of rules (based on the contents of IP and transport header fields) on each packet and based on the outcome, decides to either forward or discard the packet.

    For example, a rule could specify to block all incoming traffic from a certain IP address or disallow all traffic that uses UDP protocol. If there is no match with any predefined rules, it will take default action. The default action can be to ‘discard all packets’ or to ‘accept all packets’.

    Security threats to Packet Filters:

    1. IP address Spoofing:
      In this kind of attack, an intruder from the outside tries to send a packet towards the internal corporate network with the source IP address set equal to one of the IP address of internal users.
      Prevention:
      Firewall can defeat this attack if it discards all the packets that arrive at the incoming side of the firewall, with source IP equal to one of the internal IPs.
    2. Source Routing Attacks:
      In this kind of attack, the attacker specifies the route to be taken by the packet with a hope to fool the firewall.
      Prevention:
      Firewall can defeat this attack if it discards all the packets that use the option of source routing aka path addressing.
    3. Tiny Fragment Attacks:
      Many times, the size of the IP packet is greater than the maximum size allowed by the underlying network such as Ethernet, Token Ring etc. In such cases, the packet needs to be fragmented, so that it can be carried further. The attacker uses this characteristic of TCP/IP protocol. In this kind of attack, the attacker intentionally creates fragments of the original packet and send it to fool the firewall.
      Prevention:
      Firewall can defeat this attack if it discards all the packets which use the TCP protocol and is fragmented. Dynamic Packet Filters allow incoming TCP packets only if they are responses to the outgoing TCP packets.
  2. Application Gateways –
    It is also known as Proxy server. It works as follows:
    1. Step-1: User contacts the application gateway using a TCP/IP application such as HTTP.
    2. Step-2: The application gateway asks about the remote host with which the user wants to establish a connection. It also asks for the user id and password that is required to access the services of the application gateway.
    3. Step-3: After verifying the authenticity of the user, the application gateway accesses the remote host on behalf of the user to deliver the packets.
  3. Stateful Inspection Firewalls –
    It is also known as ‘Dynamic Packet Filters’. It keeps track of the state of active connections and uses this information to decide which packets to allow through it, i.e., it adapts itself to the current exchange of information, unlike the normal packet filters/stateless packet filters, which have hardcoded routing rules.
  4. Circuit-Level Gateways –
    It works at the session layer of the OSI Model. It is the advanced variation of Application Gateway. It acts as a virtual connection between the remote host and the internal users by creating a new connection between itself and the remote host. It also changes the source IP address in the packet and puts its own address at the place of source IP address of the packet from end users. This way, the IP addresses of the internal users are hidden and secured from the outside world.
March 18, 2019

Introduction of Firewall in Computer Network

 A firewall is a network security device, either hardware or software-based, which monitors all incoming and outgoing traffic and based on a defined set of security rules it accepts, rejects or drops that specific traffic.

Accept : allow the traffic
Reject : block the traffic but reply with an “unreachable error”
Drop : block the traffic with no reply

A firewall establishes a barrier between secured internal networks and outside untrusted network, such as the Internet.

History and Need for Firewall



Before Firewalls, network security was performed by Access Control Lists (ACLs) residing on routers. ACLs are rules that determine whether network access should be granted or denied to specific IP address.
But ACLs cannot determine the nature of the packet it is blocking. Also, ACL alone does not have the capacity to keep threats out of the network. Hence, the Firewall was introduced.

Connectivity to the Internet is no longer optional for organizations. However, accessing the Internet provides benefits to the organization; it also enables the outside world to interact with the internal network of the organization. This creates a threat to the organization. In order to secure the internal network from unauthorized traffic, we need a Firewall.

How Firewall Works

Firewall match the network traffic against the rule set defined in its table. Once the rule is matched, associate action is applied to the network traffic. For example, Rules are defined as any employee from HR department cannot access the data from code server and at the same time another rule is defined like system administrator can access the data from both HR and technical department. Rules can be defined on the firewall based on the necessity and security policies of the organization.
From the perspective of a server, network traffic can be either outgoing or incoming. Firewall maintains a distinct set of rules for both the cases. Mostly the outgoing traffic, originated from the server itself, allowed to pass. Still, setting a rule on outgoing traffic is always better in order to achieve more security and prevent unwanted communication.
Incoming traffic is treated differently. Most traffic which reaches on the firewall is one of these three major Transport Layer protocols- TCP, UDP or ICMP. All these types have a source address and destination address. Also, TCP and UDP have port numbers. ICMP uses type code instead of port number which identifies purpose of that packet.

Default policy: It is very difficult to explicitly cover every possible rule on the firewall. For this reason, the firewall must always have a default policy. Default policy only consists of action (accept, reject or drop).
Suppose no rule is defined about SSH connection to the server on the firewall. So, it will follow the default policy. If default policy on the firewall is set to accept, then any computer outside of your office can establish an SSH connection to the server. Therefore, setting default policy as drop (or reject) is always a good practice.

Generation of Firewall

Firewalls can be categorized based on its generation.

  1. First Generation- Packet Filtering Firewall :  Packet filtering firewall is used to control network access by monitoring outgoing and incoming packet and allowing them to pass or stop based on source and destination IP address, protocols and ports. It analyses traffic at the transport protocol layer (but mainly uses first 3 layers).
    Packet firewalls treat each packet in isolation. They have no ability to tell whether a packet is part of an existing stream of traffic. Only It can allow or deny the packets based on unique packet headers.

    Packet filtering firewall maintains a filtering table which decides whether the packet will be forwarded or discarded. From the given filtering table, the packets will be Filtered according to following rules:

    1. Incoming packets from network 192.168.21.0 are blocked.
    2. Incoming packets destined for internal TELNET server (port 23) are blocked.
    3. Incoming packets destined for host 192.168.21.3 are blocked.
    4. All well-known services to the network 192.168.21.0 are allowed.
  2. Second Generation- Stateful Inspection Firewall : Stateful firewalls (performs Stateful Packet Inspection) are able to determine the connection state of packet, unlike Packet filtering firewall, which makes it more efficient. It keeps track of the state of networks connection travelling across it, such as TCP streams. So the filtering decisions would not only be based on defined rules, but also on packet’s history in the state table.
  3. Third Generation- Application Layer Firewall : Application layer firewall can inspect and filter the packets on any OSI layer, up to the application layer. It has the ability to block specific content, also recognize when certain application and protocols (like HTTP, FTP) are being misused.
    In other words, Application layer firewalls are hosts that run proxy servers. A proxy firewall prevents the direct connection between either side of the firewall, each packet has to pass through the proxy. It can allow or block the traffic based on predefined rules.

    Note: Application layer firewalls can also be used as Network Address Translator(NAT).

  4. Next Generation Firewalls (NGFW) : Next Generation Firewalls are being deployed these days to stop modern security breaches like advance malware attacks and application-layer attacks. NGFW consists of Deep Packet Inspection, Application Inspection, SSL/SSH inspection and many functionalities to protect the network from these modern threats.

 Types of Firewall

Firewalls are generally of two types: Host-based and Network-based.

  1. Host- based Firewalls : Host-based firewall is installed on each network node which controls each incoming and outgoing packet. It is a software application or suite of applications, comes as a part of the operating system. Host-based firewalls are needed because network firewalls cannot provide protection inside a trusted network. Host firewall protects each host from attacks and unauthorized access.
  2. Network-based Firewalls : Network firewall function on network level. In other words, these firewalls filter all incoming and outgoing traffic across the network. It protects the internal network by filtering the traffic using rules defined on the firewall. A Network firewall might have two or more network interface cards (NICs). A network-based firewall is usually a dedicated system with proprietary software installed.

Both types of firewall have their own advantages.

References:
https://en.wikipedia.org/wiki/Firewall_(computing)
https://www.cisco.com/c/en_in/products/security/firewalls/what-is-a-firewall.html
http://nptel.ac.in/courses/106105084/31

   
This article is contributed by Abhishek Agrawal. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

Thursday, 25 February 2016

February 25, 2016

Difference between Stop and Wait protocol and Sliding Window protocol

 Both Stop and Wait protocol and Sliding Window protocol are the techniques to the solution of flow control handling. The main difference between Stop-and-wait protocol and Sliding window protocol is that in Stop-and-Wait Protocol, the sender sends one frame and wait for acknowledgment from the receiver whereas in sliding window protocol, the sender sends more than one frame to the receiver and re-transmits the frame(s) which is/are damaged or suspected.

Difference between Stop and Wait protocol and Sliding Window protocol:

S.NOStop-and-Wait ProtocolSliding Window Protocol
1.In Stop-and-Wait Protocol, sender sends one frame and wait for acknowledgment from receiver side.In sliding window protocol, sender sends more than one frame to the receiver side and re-transmits the frame(s) which is/are damaged or suspected.
2.Efficiency of Stop-and-Wait Protocol is worse.Efficiency of sliding window protocol is better.
3.Sender window size of Stop-and-Wait Protocol is 1.Sender window size of sliding window protocol is N.
4.Receiver window size of Stop-and-Wait Protocol is 1.Receiver window size of sliding window protocol may be 1 or N.
5.In Stop-and-Wait Protocol, sorting is not necessary.In sliding window protocol, sorting may be or may not be necessary.
6.Efficiency of Stop-and-Wait Protocol is
1/(1+2*a)
Efficiency of sliding window protocol is
N/(1+2*a)
7.Stop-and-Wait Protocol is half duplex.Sliding window protocol is full duplex.
February 25, 2016

Difference between BISYNC and HDLC features

 BISYNC:

BISYNC stands for Binary Synchronous Communication. It is a half-duplex link protocol that replaces the SRT which stands for Synchronous transmit-receive.

HDLC:
HDLC stands for High-Level Data Link Control. It works on the data link layer of the OSI reference model. It supports both connection-oriented and connection less services.

Features of HDLC and BISYNC :

BISYNC FeaturesHDLC Features
It supports serial transmission.It also supports serial transmission.
Communication mode of BISYNC is synchronous.Communication mode of HDLC is both synchronous and asynchronous.
It uses TWA directional mode.It uses TWA and TWS directional mode.
It supports both point to point and point to multipoint configuration.It also supports both point to point and point to multipoint configuration.
It follows stop and wait flow control protocol.It follows sliding window flow control protocol.
To content errors it uses LRC/CRC method.To content errors it uses CRC method.
It uses SYN SYN frame identifier in framing.It uses Flag frame identifier in framing.
EBT/ETX frame delimiter in framing.Flag frame delimiter in framing.
Multiple bytes information field in framing.Multiple bits information field in framing.
For Framing transparency it follows DLE stuffing.For Framing transparency it follows ZERO stuffing.
February 25, 2016

Difference between File Transfer Protocol (FTP) and Secure File Transfer Protocol (SFTP)

 FTP stands for File Transfer Protocol. It is a protocol which is used to transfer or copies the file from one host to another host. But there may be some problems like different file name and different file directory while sending and receiving file in different hosts or systems. And in FTP, secure channel is not provided to transfer the files between the hosts or systems. It is used in port no-21.

SFTP stands for Secure File Transfer Protocol. It is a protocol which provides the secure channel, to transfer or copies the file from one host to another host or systems. SFTP establishes the control connection under SSH protocol and It is used in port no-22.

There are some difference between them which are given below:

S.NOFTPSFTP
1.It stands for File Transfer Protocol.It stands for Secure File Transfer Protocol.
2.In FTP, secure channel is not provided to transfer the files between the hosts.In SFTP, secure channel is provided to transfer the files between the hosts.
3.It is a part of TCP/IP protocol.It is a SSH protocol.
4.It usually runs on port no-21.It runs on port no-22.
5.It establishes the connection under TCP protocol.It establishes the control connection under SSH protocol.
6.It does not encrypt the data before sending.It encrypted data before sending.
7.It works on direct method for file transfer.It works on tunelling method for transferring of files.
8.It makes uploading and downloading of files without any security.It maintains full security of the data by using SSH keys.