Please Whitelist This Site?

I know everyone hates ads. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. And I have a family to support, just like you. :)

If you like The TCP/IP Guide, please consider the download version. It's priced very economically and you can read all of it in a convenient format without ads.

If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. To do so, just open the Adblock menu and select "Disable on tcpipguide.com". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||tcpipguide.com^$document". Then just click OK.

Thanks for your understanding!

Sincerely, Charles Kozierok
Author and Publisher, The TCP/IP Guide


NOTE: Using software to mass-download the site degrades the server and is prohibited.
If you want to read The TCP/IP Guide offline, please consider licensing it. Thank you.

The Book is Here... and Now On Sale!

Searchable, convenient, complete TCP/IP information.
The TCP/IP Guide

Custom Search







Table Of Contents  The TCP/IP Guide
 9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)
      9  TCP/IP Network Interface Layer (OSI Data Link Layer) Protocols
           9  TCP/IP Serial Line Internet Protocol (SLIP) and Point-to-Point Protocol (PPP)
                9  Point-to-Point Protocol (PPP)
                     9  PPP Feature Protocols

Previous Topic/Section
PPP Feature Protocols
Previous Page
Pages in Current Topic/Section
1
2
Next Page
PPP Compression Control Protocol (CCP) and Compression Algorithms
Next Topic/Section

PPP Link Quality Monitoring/Reporting (LQM/LQR)
(Page 1 of 2)

PPP includes optional authentication in recognition of the varying security needs of the many different kinds of links over which PPP may operate. These links also differ greatly in terms of their quality. Just as we don't need to worry about authentication much when two machines are linked with a short cable, we also can feel pretty confident that data sent between them is going to arrive intact. Now, contrast that to a PPP session established over a long-distance telephone call. For that matter, how about PPP over a dial-up call using an analog cellular phone?

PPP includes in its basic package a provision for detecting errors in sent frames (a CRC field), and higher-layer protocols like TCP also include methods of providing robustness on noisy lines. These techniques allow a link to tolerate problems, but provide little in the way of useful information about what the status of the link is. In some situations, devices may want to be able to keep track of how well the link is working, and perhaps take action on it. For example, a device experiencing too many errors on a dial-up connection might want to cut off and retry a new call. In some cases a device might want to try an alternate method of attachment if the current physical link is not working well.

Recognizing this need, the PPP suite includes a feature that allows devices to analyze the quality of the link between them. This is called PPP Link Quality Monitoring or LQM. PPP is set up generically to allow any number of different monitoring functions to be used, but at present there is only one, called Link Quality Reporting (LQR). LQR works by having a device request that its peer (the other device on the link) keep track of statistics about the link and send them in reports on a regular basis.

LQR Setup

Before LQR can be used it must be set up, which is done by LCP as part of the negotiation of basic link parameters in the Link Establishment phase. The device opening the link requests link monitoring by including the Quality-Protocol configuration option in its Configure-Request frame. Again, LQR is the only quality protocol presently defined. The configuration option also specifies a reporting period that indicates the longest period of time the requesting device wants to go between receiving reports.


Previous Topic/Section
PPP Feature Protocols
Previous Page
Pages in Current Topic/Section
1
2
Next Page
PPP Compression Control Protocol (CCP) and Compression Algorithms
Next Topic/Section

If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. Thanks for your support!
Donate $2
Donate $5
Donate $10
Donate $20
Donate $30
Donate: $



Home - Table Of Contents - Contact Us

The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005

Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
Not responsible for any loss resulting from the use of this site.