1.15.2010

Ubuntu Security

The Windows Mindset

If you are coming from a Windows background you are used to terms like antivirus, spyware, and firewalls. Linux is different and these are not as important.

Viruses

The fact of the matter is: viruses/worms take advantage of flaws or holes in the code. There are no significant Linux viruses "in the wild". Linux boxes are no less targets than any other OS.

Do not believe the suggestion that the Linux community is complacent or "behind the times" in terms of viruses, or any other security issue. Linux developers have not "ignored" viruses, rather the OS is built to be highly resistant to them and since the code is "Open" there are literally thousands of eyes watching .

For the most part, Linux anti-virus programs scan for Windows viruses which do not run on Linux.


Reasons AGAINST antivirus on Ubuntu:
  1. They scan primarily for Windows viruses.
  2. There is a high rate of false positives.
  3. Isolation/inoculation is poor.
  4. And currently there are no known active Linux viruses (so there is essentially nothing to detect).

Reasons FOR antivirus on Ubuntu:
  • You are running a file or mail server with Windows clients.
  • You wish to scan files before transferring them, by email, flash drive, etc., to a Windows machine.

Running antivirus can make some sense if you are intending to "protect" Windows users, however, for a variety of reasons, it is best if Windows users learn to protect themselves.

Note: There have been many documented cases in Windows and Linux that a buffer overflow in an antivirus product has been an attack vector!

If you would like to run an antivirus program on Ubuntu you have several choices :

Comments on wine

Discussions about running Windows viruses on wine crop up from time to time and it is possible to run some Windows viruses on wine.

See these links :

Take the same precautions with wine as you would with Windows. Do not install untrusted applications from untrusted sources.

Windows viruses will be confined to ~/.wine and they do not have permission to change system files. This means to remove them you simply:

Code:
rm -rf ~/.wine
Please take care, this command deletes everything in your wine directory including all data and all applications.

You then need to restore your wine directory from a known good backup (you do keep backups ?).


Firewall

GUFW (gui)

UFW - Desktops

UFW - Servers

Ubuntu includes a firewall, iptables, but by default nothing is engaged. This is reasonable as a default Ubuntu install opens zero ports to the outside world, so a firewall is redundant. However, installing "server software" will cause ports to open, so some people like to use a firewall as a catch-all layer to find mistakes in their configuration.

Another use for firewalls is for the administrator to forcibly impose network policies on the user.Also, a periodic audit of the system for open ports is a good practice. Running the "nmap" command from another machine, or using one of many online port scanners:

http://nmap-online.com/
https://www.grc.com/x/ne.dll?bh0bkyd2

Remember, what you care about are open ports. Closed ports and stealth ports are equally secure, in that they are inaccessible to the public.

Iptables references :

The "problem" with iptables is that it is not particularly friendly to new users. Fortunately, there are several more user friendly interfaces available to allow you to manipulate your firewall (UFW, Firestarter, and Guarddog) :


A source of confusion sometimes occurs when users feel the need to be running firestarter/Guarddog for their firewall to be active. This is untrue ! Keep in mind that these applications are not firewalls, but rather configuration tools for ip tables. These applications should be run only to configure your firewall. Once configured, IP tables (the actual firewall) is active (at boot) without having to run firestarter/guarddog. firestarter will monitor traffic, but it runs as root and there are better monitoring programs, so configure you firewall, shut down firestarter/grauddog, and let IP tables do the rest


Browser / Spyware : Java/Flash/Ad-ware/Trackers/Cookies

This is where most users will have the most risk.
We all want Java/Flash, but our Internet browser opens us to attacks.

  1. Deny all cookies and add trusted sites, allowing only for session.
  2. Install NoScript. Again block all and add trusted sites to a white list.
  3. Install Safe History
  4. Adblocking : I block with a hosts file rather then Adblock Plus or Adblock Filterset.G because a hosts file protects more then just firefox.



See this link for additional information : How to Secure Firefox


The Ubuntu Mindset


Permissions and Encryption

The first layer of defense is file permissions. Permissions are used to set access and thus protect both system and user files.

Basic permissions
FilePermissions

See also umask at the bottom of that link. The umask value can be set in ~/.bashrc.

To set a "private home", as a user,
Code:
chmod 700 $HOME

How to's:

Running Server(s)

Common servers include NFS, Samba, FTP, SSH, VNC, RDP, and HTTP. Desktops become Servers if server software is installed.

Questions to ask yourself include:
  1. What port(s) or services does this software provide?
  2. Who will be able to connect to this? (i.e. is it restricted to a range of IP addresses Password protected?)
  3. What level of access will the visitor have to the system? (i.e. does the server run under a restricted user, or the root account? What can this restricted user do in a worst case scenario?)
  4. Does this service expose any additional information that's useful to a hacker? (i.e. does it allow users to transmit their passwords in cleartext? Does it have a 'statistics' view that reveals logged-in users, ip addresses, network configuration, or other potentially helpful information?)
  5. What is the security history of this software? Does it have a history of vulnerability and patch after patch? Or has it had a relatively unmarred history?

Examples :

SSH
VNC
Apache


Forensics


What to do when you think you have been cracked :
  1. Power off.
  2. Disconnect/disable your Internet connectivity.
  3. Now take a deep breath, re-boot, and read the logs. Ask for help if needed, but you really need to confirm that your system has been compromised.
  4. If you have been compromised, and have the time and interest, boot a live CD and image your hard drive. This image can then be used for forensic analysis.
  5. Re-install. Unfortunately, there is no way to trust a compromised system.
  6. When you install, be sure to install off line, use a stronger password, and research intrusion detection.

Intrusion References
CERT® Coordination Center (CERT/CC)
CERT® Coordination Center ~ Intruder Detection Checklist


My goodness ...


Further Reading:

Ubuntu wiki ~ Security page

Ubuntu wiki ~ Installing Security Tools

UDSF Security Analysis Tools

The Big Ol' Ubuntu Security Resource

Locking Down Ubuntu

Ubuntu geek ~ Security category

Security references Topics include Basics, firewall, Intrusion detection, Chroot, Forensics/Recovery, and Securing networked services.


Changing poison into medicine,
Nam-myoho-renge-kyo
 Technicowl
A person with ubuntu is open and available to others, affirming of others, does not feel threatened that others are able and good, for he or she has a proper self-assurance that comes from knowing that he or she belongs in a greater whole and is diminished when others are humiliated or diminished, when others are tortured or oppressed. ~ Archbishop Desmond Tutu, 1999
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1.14.2010

President Obama tells Haiti

Video: You will not be forsaken
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1.13.2010

Haiti's Other Earthquake

Restavek and Child Slavery: Haiti's Other Earthquake

Haiti holds a romantic and tragic place in the historical imagination -- a nation birthed by a successful slave rebellion, it was the first to abolish slavery in the Western hemisphere and briefly served as a beacon of hope for American abolitionists. However, it never realized its promise, for reasons that scholars and analysts can debate ad infinitum.

Perhaps most egregiously, its grinding poverty is so pervasive that an estimated 300,000 children have been given up by their parents to become restavèks -- a creole term for children sent to become house servants to wealthier Haitians. According to human rights workers and survivors of the child-slavery system, these children are forced to work long hours, are often kept out of school, are barely fed and clothed, and are routinely abused physically, emotionally and sexually.


Now, professional recruiters have made the situation even worse by making a business out of the longstanding informal practice. Last June, a United Nations expert on contemporary forms of slavery, Gulnara Shahinian, visited Haiti at the invitation of the government and issued a report that included the recommendations summarized below:

Since it is still struggling to recover from devastating storms in 2008 and will now be focusing effort on earthquake rescue, relief and repair, it's not likely that Haiti will have the resources to enact the reforms advocated by the UN, so private efforts such as Cadet's take on greater significance. Other high-profile philanthropic efforts include Haitian American musician Wyclef Jean's Yele Foundation. In 2008, Jean spoke to Al Jazeerah about his efforts to combat Haiti's food crisis:
Jean also sprang into action about the earthquake via Twitter,tweeting a way to contribute to the relief effort via text message.

Jean's efforts to combat poverty in Haiti are complemented by the work of other philanthropists, including former Pres. Bill Clinton, who serves as the UN special envoy to Haiti. He toured the island in March, 2009 with UN Secretary Ban Ki-Moon to survey efforts by his foundation and other organizations to expand education and nutrition programs. Clinton has been upbeat about Haiti's future, saying it...
"...offers unique opportunities for public and private investment to improve health and education in ways that will be good for Haitians and all their partners in our interdependent world."

Now that the earthquake has delivered to the country what Mr. Ban has called "catastrophic" and Haitian President Rene Preval has called "unimaginable," considerably more effort will be required to ensure that those investments are made and the benefits trickle down to the poorest Haitians so that they will be able to feed and care for their own children. Ultimately, only economic development and sustained human rights activism will finally allow the island to realize the dream that its founders fought so desperately to achieve more than 200 years ago.
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How to help - Haiti- Charitable Organizations

A list of charitable organizations active in the nation


msnbc.com
updated 11:11 p.m. CT, Tues., Jan. 12, 2010

The U.S. State Department Operations Center said Americans seeking information about family members in Haiti should call 1-888-407-4747. Due to heavy volume, some callers may receive a recording. "Our embassy is still in the early stages of contacting American citizens through our Warden Network," the U.S. State Department said in a statement. "Communications are very difficult within Haiti at this time."

For those interesting in helping immediately, simply text "HAITI" to "90999" and a donation of $10 will be given automatically to the Red Cross to help with relief efforts, charged to your cell phone bill
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1.12.2010

Toshiba Satellite E205 with Intel 802.11n Wireless Display Technology



The E205 will be available for $999 on Best Buy’s site on January 12, (TODAY) and will appear in retail stores several days later.



The coolest feature of the E205? With the push of a button you can beem wirelessly whatever you're watching then stream 720p video from the notebook to (like Hulu) to your big-screen TV, courtesy of Intel’s new Wireless Display technology. The video is carried over 802.11n to the Netgear box, and is then converted to a wired HDMI signal. Best Buy bundles a special box from Netgear that acts as a wireless receiver and plugs into your HDTV via HDMI.

 
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1.11.2010

Wi-Fi Alliance

 The Wi-Fi Alliance is a global, non-profit industry trade association formed in 1999 to certify interoperability of Wireless Local Area Network products based on the IEEE 802.11 standard and amendments with more than 200 member companies devoted to promoting the growth of WLANs. Certification programs ensure the interoperability WLAN products from different manufacturers, with the objective of enhancing the wireless user experience.


Wi-Fi Alliance Certification Programs address: Wi-Fi products based on IEEE radio standards 802.11a/b/g/n Wi-Fi Protected Access certification , wireless network security(WPA, WPA2 and WPS for personal and enterprise deployments), authentication mechanisms used to validate the identity of network devices (EAP), and support for multimedia content over Wi-Fi networks (WMM and WMM Power Save. (WPS) Wi-Fi Protected Setup certification.
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1.10.2010

802.11n is Ratified - Cisco Celebrates with New Lower Prices


The Industry's Favorite 802.11n AP Now at a Fraction of the Cost
Your users want a wireless network that can provide 7x more video and 9x the speed. Your business needs the investment protection that comes with the fastest-growing and most widely deployed 802.11n technology. You want the confidence that comes from deploying a ratified standard, but for a low price.

Cisco is leading the market transition toward 802.11n and for a limited time only, we're offering an exclusive deal that removes the barriers to adoption of the industry's most powerful wireless technology.
Take advantage of the 11n Acceleration Kit, which includes:
» Learn more about Cisco 802.11n
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Accelerate your adoption of 802.11n technology by taking advantage of this exclusive deal.
1-877-330-3409
When calling, use code:
"Celebrate"
Register for the
11n Acceleration Kit promotion.
Register Now https://apps.cisco.com/gdrp/coiga/showsurvey.do?surveyCode=5016&keyCode=184584_5

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1.09.2010

Wireless Networking

Wireless Networking Is the New Cellular.


Remember back in the day when we had a brick Motorola cellular phone. My mom had one in the car so she could call me to come pick her up from the post office. Anyone over 29 will remember.




I remember the time because at the time I was a telecommunications specialist in the
 army with a green brick phone at my disposal during field exercises.

 I also remember thinking this cell phone is eventually going to replace my home phone. In 2001 I reduced my home plan down to (no kidding) $23.00 dollars a month basic service and used my cell phone as my house phone. I should have invested in stocks. Motorola stock went up and like most people I never saw that coming.

Like cell phones just about everything connected to a network will eventually be wireless. It won't be long before network servers and high throughput devices go wireless.

We are seeing devices that transmit Hi-Def TV and DVD signal from AV receiver to a monitor. Wireless networking technology has changed the face of enterprise, small-to-medium, and SOHO Biz and personal networking.

CWNA Certified Wireless Network Administrator Official Study Guide: Exam PW0-104 (CWNP Official Study Guides)Now is the time to capitalize on the opportunities that wireless networking
 brings to Information Technology careers. The Certified Wireless Network
 Administrator-CWNA certification is the first step in the Certified Wireless
 Network Professional-CWNP line of certifications and is focused on
 administering an enterprise 802.11 WLAN. CWNA includes topics such as
 802.11 standards, security, management, protocol analysis, QoS, site
 surveying,  and radio frequency.




Instek GSP-827 Spectrum AnalyzerAdditional certifications focus more intensely on security, protocol analysis, Instek GSP-827 Spectrum Analyzer $4, 2300.00
  • Frequency Range: 9kHz~2.7GHz
  • Input Range: -100dBm~+20dBm
  • Average Noise Floor: -130dBm/Hz
  • Power Measurements: ACPR/OCBW/CH Power
  • Split Window: Simultaneous Measurements in Two Separate Frequency Spans
QoS, design, advanced surveying, VoWiFi, location tracking, and RF spectrum management.
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1.03.2010

Dell XPS 8000 Discontinued? What The Hell Dell?

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Nook e-reader gains new appeal as 'rooted' wireless tablet

Appeal as unhacked e-book reader also strong judging by faithful user raves. http://bit.ly/63qGBa



Barnes and Noble NOOK ebook readerNook devotees, including wants the Nook despite negative reviews, mainly because it has many features not always available on competing devices including Wi-Fi, a replaceable battery, the open Android OS, and one that reads the ePub format.

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1.02.2010

Information Technology Jobs In America: Corporate and Government




http://www.computerworld.com/s/article/9139190/Salary_Survey_2009
Information Technology Jobs in America: Corporate & Government Career Guide (Information Technology Jobs in America: Corporate & Government)
The information technology industry continues to grow in the U.S. and globally. Information Technology Jobs in America: Corporate & Government Career Guide shows where the jobs are, in the U.S. IT Services Sector and in U.S. Federal and State and Municipal government agencies and departments. The book covers new territory – not a technical guide – this career guide goes beyond, to show Americans the largest source of jobs in the U.S. in this growing industry. Section I Good News – Companies Keep Hiring as Demand Grows. Why ‘Outsourcing’ May Lose Its Power as a Scare Word. Shifting Occupations in the Industry. More Managing - Less Programming. Tech Jobs with Government Are Lively Stable, Secure, and Well-Paid. Salaries show a Higher Paid Class of Employees. Experience Is an Acceptable Substitute for Education. Core Skills Include Business-Process Understanding.
Section II Explains how to make contact with this special sector for IT jobs, IT service providers, and how to build a career in the IT services sector.
Section III Explains Technology in Government, public unionism for emerging technology jobs and the desirable salaries of these emerging technology titles. The authors describe the technological developments that make technology in government possible. They define the modified processes that now call for staff in Relational Databases, Web Portal Development, Infrastructure Development and Maintenance, Network Computing, Data Security, e-Government, and e-Commerce.

Section IV "What Jobs Are Available in Federal, State and City Government," brings to the forefront the thousands of information technology jobs that exist in all 101 Federal agencies, and in U.S. State and Municipal government agencies and departments. Detailed Tables show current Information Technology Job Titles for Federal and State and City information technology jobs, Salaries, 5-year Salary Projections, and Estimated Pensions. Financial facts explain why, in today’s global economy, an IT career in government is a desirable choice.

Section V Provides a Step-by-Step guide to "Completing the Application & Hiring Process" for an information technology job in both the Federal and State and City government personnel hiring systems. It explains why a Civil Service Exam is not required in most cases; why experience is an acceptable substitute for education in most government jobs, how to fill out an Experience and Education paper or Knowledge-Skills and Abilities Statement, and Factors for Job Class Salary Ranking and Candidate Ranking. Appendices include Sample Federal IT Job Announcements, and Sample State & City IT Job Descriptions with Qualifications Required, and Required Application Forms.

Section VI Provides Analytical Articles on Today’s Tech Jobs: C++ Computer . Java and JavaScript . Visual Basic . Sun Solaris, Unix, Linux, Network Tech Jobs . Oracle, SQL, FoxPro, Sybase, Database Management . Software Programmer; Software Engineer . Network Programmer, Network Systems . Telecommunications . Web Developer . IT Procurement, IT Training, Project Management and more.

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1.01.2010

2010 Predictions: What's on Deck for Cameras?




Flip Video camcorders  From Cisco. Simple, pocketable, and sharing-friendly video cameras.. Here's how 2009's major camera trends will continue in 2010's Consumer Electronics Show announcements...or so we think.
Fujifilm FinePix F70 EXR 10X-optical-zoom lens adaptable EXR sensor in a 0.9-inch-thick frame, making it one of the most versatile pocket cameras currently available
camcorder, the excellent Kodak Zi8.

 See all Best Prices on Digital Cameras
See also: Flash Memory, Graphics & Publishing Software, Lenses, Bags & Cases


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12.24.2009

LinuxCertified.com


Linux Training and Linux Certification
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Linux Laptop




Fully Supported & Configured Linux Laptops and Netbooks | LinuxCertified
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12.23.2009

Day of reckoning for startups, consolidation of network security appliances

VCs get out of the security game? "We're going to see some shakeups. It might very well be the year that a lot of venture capital firms try to recoup some of their investments," Kindervag said. "So you'll see a lot of VC-backed companies merging together or being bought by larger companies. I think a lot of [them] have run out of cash, and there's not much of an appetite to pour more money into some of these things."


Super network security devices: Kindervag said 2010 could bring a new generation of network security appliances that do -- well -- just about everything. "If there is any hot technology for next year, it will probably be security devices that are uber-intelligent and extremely fast – a cross between unified threat management and what some people are calling next-generation firewall architectures. These will be devices where a tremendous amount of intelligence is applied to the packet, all the way up to Layer 7, in near real time at any speed, whether it is a 10 Gb core or better. That's where everything is moving to – this consolidation of multiple technologies which will just be features on more robust security gateways. So you can turn on the firewall feature, you can turn on the IPS feature. They will all be embedded into this codebase and they will all be able to function within a single clock cycle.

VoIP and unified communications security awareness: Enterprises will play catch up with securing newly installed IP telephony and collaboration technologies that were deployed without a proper network security vetting, Kindervag said. "There's all this new stuff and we haven't implemented it securely. We've implemented it in an ad hoc way, and we need to secure it. This is something that hasn't happened before," he said. "It used to be you had to go through a long process to determine whether something is secure and then implement it. Now we're looking at whether it's secure long after it's been in general usage. Everything changed so quickly, with the rise of social networking and Web 2.0 that the demand from the user side was so great and it couldn't be controlled by a small group of 'paranoid' security types."
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Cisco-EMC-VMware, oh my! And more options for virtualization, automation, mobility, and video management

Cisco-EMC-VMware: Cisco's alliance with EMC and VMware to form the Virtual Computing Coalition, announced in November, signified "the next step of how Cisco is going to try to move into the computing marketplace more aggressively," Frey said. The coalition's products marked "the first time a complete turnkey modular solution has come from someone other than the major systems vendors," said Frey, who predicted that it would propel a simpler network management environment.

Virtualization management gets easier: Application-based vendors will continue to add support for and recognize more virtualized infrastructure, Frey said, lowering capital expenses and deployment times for enterprises. "Everything's going virtual," he said. "I know this is not new, but especially in the second half of next year … all the management tool [vendors will be] either adding support for virtual components … or recognizing virtual components."

Mobility: Wireless LAN is here to stay, and not all enterprises are prepared. "There's no slowing the pace of growth in the use of mobile endpoints, and a number of times they're showing up as the preferred end client." "The challenge around this is the more and more people want to use those as their primary computing device, you've got a whole new set of challenges for measuring and [securing] the user experience."

Video on the network: Cisco's acquisition of Tandberg will translate into "a lot more aggressive deployment of video conferencing," Frey said. "Cisco does this for a reason -- it requires a lot bigger network. You need more bandwidth." Many enterprises have yet to embrace video conferencing and won't have their networks prepared for the rush, he added. "It will be sort of like voice over IP in its first years of existence." . "Once they started to roll [VoIP] out over their entire organizations, they realized how many skeletons they had in the proverbial wiring closet." If enterprises aren't prepared, he said, they can expect 10 times the wiring challenges they faced with VoIP.
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HP-3Com affects prices, rise of the two-tiered data center network

HP-3Com shakeup will drive down prices: The merger between HP and 3Com will push up HP ProCurve far enough to be nipping at Cisco's heels, with Juniper Networks picking up the rear. "We'll now have a market where there are a number of large viable competitors."  "We're going to see a lot more competition, and for folks who do a good job doing competitive sourcing with pricing, they will save a lot of money."

From three to two: "We will see networks evolve," Skorupa said. "Today, typically they're built in three tiers -- core, aggregate and edge -- and the new networks being built will collapse." In an effort to simplify network management, ease troubleshooting and lower costs, networks will fall back to two tiers.
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Wireless LAN predictions: Cheaper access points, more robust and reliable networks

802.11n prices will drop: "We saw a beginning to that in 2009 with Aruba, Aerohive and Meraki all having a little more pricing competition," DeBeasi said. "We're going to continue to see that. And the silicon vendors, their next-generation silicon will be lower power, lower cost."

WLAN vendors strive to make wireless more robust, reliable: Every vendor will continue to introduce techniques aimed at making wireless networks more reliable and robust, DeBeasi said. "The throughput [of 802.11n] is better, but can [enterprises] depend on it? There are lots of techniques that vendors are adding." Current techniques from vendors include beamforming, airtime fairness and bandwidth steering. "We're going to see improvements in beamforming [and other techniques] in 2010," he said.
Expect 1x1 MIMO, 4x4 MIMO and everything between: DeBeasi said most of the 802.11n products on the market so far have utilized 3x3 or 2x3 MIMO (multiple input, multiple output). He expects vendors to offer a full range of receiver and transmitter arrays in 2010. "I think we'll see some 1x1 products, lower-power and lower-cost products. The throughput will be lower, too, of course. I think the iPhone might come out with a 1x1 802.11n capability this year. And at the high end, we'll probably begin to see, near the end of the year, 4x4 MIMO in enterprise access points to offer better throughput."
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OSI Reference Model


OSI divides telecommunication into seven layers. The layers are in two groups. The upper four layers are used whenever a message passes from or to a user. The lower three layers are used when any message passes through the host computer. Messages intended for this computer pass to the upper layers. Messages destined for some other host are not passed up to the upper layers but are forwarded to another host. The seven layers are:

Layer 7: The application layer ...This is the layer at which communication partners are identified, quality of service is identified, user authentication and privacy are considered, and any constraints on data syntax are identified. (This layer is not the application itself, although some applications may perform application layer functions.)

Layer 6: The presentation layer ...This is a layer, usually part of an operating system, that converts incoming and outgoing data from one presentation format to another (for example, from a text stream into a popup window with the newly arrived text). Sometimes called the syntax layer.

Layer 5: The session layer ...This layer sets up, coordinates, and terminates conversations, exchanges, and dialogs between the applications at each end. It deals with session and connection coordination.

Layer 4: The transport layer ...This layer manages the end-to-end control (for example, determining whether all packets have arrived) and error-checking. It ensures complete data transfer.

Layer 3: The network layer ...This layer handles the routing of the data (sending it in the right direction to the right destination on outgoing transmissions and receiving incoming transmissions at the packet level). The network layer does routing and forwarding.

Layer 2: The data-link layer ...This layer provides synchronization for the physical level and does bit-stuffing for strings of 1's in excess of 5. It furnishes transmission protocol knowledge and management.

Layer 1: The physical layer ...This layer conveys the bit stream through the network at the electrical and mechanical level. It provides the hardware means of sending and receiving data on a carrier.

Open Systems Interconnection ( OSI ) is a standard reference model for communication between two end users in a network. The model is used in developing products and understanding networks.
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The Data-Link Layer | OSI

Layer 2 refers to the Data Link layer of the commonly-referenced multilayered communication model, Open Systems Interconnection (OSI). The Data Link layer is concerned with moving data across the physical links in the network. In a network, the switch is a device that redirects data messages at the layer 2 level, using the destination Media Access Control (MAC) address to determine where to direct the message.

The Data-Link layer contains two sublayers that are described in the IEEE-802 LAN standards:

* Media Access Control (MAC) sublayer
* Logical Link Control (LLC) sublayer

The Data Link layer ensures that an initial connection has been set up, divides output data into data frames, and handles the acknowledgements from a receiver that the data arrived successfully. It also ensures that incoming data has been received successfully by analyzing bit patterns at special places in the frames.The OSI seven-layer model – What is a layer?

* The Application Layer (Layer 7)
* The Presentation Layer (Layer 6)
* The Session Layer (Layer 5)
* The Transport Layer (Layer 4)
* The Network Layer (Layer 3)
* The Data Link Layer (Layer 2)
* The Physical Layer (Layer 1)
* Putting all the layers together
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