Author Archive for skapoor

Node Offline Responses

Published by skapoor June 1st, 2009 in FieldServer and Uncategorized. 0 Comments

When a Client Node on the FieldServer goes offline the corresponding data objects on the FieldServer are also marked offline. If a client polls a virtual FieldServer node for this particular data, an offline response will be returned by the FieldServer. If the client then requests the FieldServer to identify itself, a valid response will be provided in spite of the data being offline. This results in status toggle, with the Server side Client receiving no replies to data requests and marking the Node offline and then again marking the node online after a successful identification poll, then again receiving no replies to data requests and marking the node offline and so on.

The Server Node must therefore be capable of deciding the nature of its response based on the status of relevant Client Nodes. This can be accomplished using responsible Map Descriptors (RDBC, WRBX, and WRBC). In case no acknowledgement of these functions is received, the device is identified as offline and a flag is placed at the data array offset. The virtual FieldServer can be configured using the Offline_Method option to respond to identification requests in one of the following ways:

  1. Ignore_Clients/No Setting (default) – The kernel ignores the status of Client side Nodes and uses only the online/offline status of relevant data objects to decide on the type of response.
  2. Any_Offline – If any relevant Client Node is offline the Server Node will respond with a node offline message as defined by the Server protocol. This option is available for selected drivers only.
  3. All_Offline – If all relevant Client Nodes are offline the Server Node will respond with a node offline message as defined by the Server protocol. This option is available for selected drivers only.
  4. Always_Respond – A response with data currently in the FieldServer is always sent, without considering the online/offline status of the relevant Client Nodes. This option is available for all drivers.

Offline Server Nodes are treated differently by different protocols. Some protocols will have an explicit offline response, while others will simply not respond.

If configured, the node offline response will take priority over the data offline response.<-->

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Timing Parameters

Published by skapoor June 1st, 2009 in FieldServer. 0 Comments

Normally a FieldServer sends a poll request to a Server device and that device gives a response back to the FieldServer.

Following are the timing parameters considered important in the fieldserver’s operation:

 

Scan_interval: It is the amount of time between successive poll requests. Its default value is 2 seconds and it belongs to Map descriptors, nodes and connections.

 

Poll_delay:  It is the time between receiving a response from a server device and the next poll request. Its default value is 0.05 seconds and it belongs to Connections only.

 

Timeout: If the FieldServer sends a poll request, and the Server device does not send a response, it is considered a timeout. The time for which the FieldServer waits before declaring a timeout can be adjusted by the timeout parameter. Its default value is 2 seconds and it belongs to Map descriptors, nodes and connections.

 

ic_timeout:  This parameter monitors the time between characters in a response. If the time exceeds the ic_timeout, the response is discarded and is considered a timeout. Its default value is 0.5 seconds and it belongs to Map descriptors, nodes and connections.

 

 

Retries: If a timeout occurs, then the FieldServer will retry the poll request a few more times. Number of times tried is specified by the retries parameter. Its default value is 3 times and belongs to nodes only.

 

Retry_interval: The interval between retries is specified by the retry_interval. The Fieldserver will send poll requests at the end of each retry_interval. Once the specified numbers of retries have been sent, the FieldServer will mark the node offline. Its default value is 10 seconds and belongs to nodes only.

 

Recovery_interval: Once a node has been marked offline, it will wait for a period specified by recovery_interval before sending another poll request. Its default value is 30 seconds and it belongs to nodes only.

 

Probation_delay: Once the communications have been re-established, the FieldServer will wait for a period called probation_delay, before marking the node as online. Its default value is 1 minute and it belongs to nodes only.

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Tags v/s Categories

Published by skapoor June 1st, 2009 in Uncategorized. 0 Comments

Earlier, WordPress.com used only categories and no tags. A tag is a new breed of search engine optimization i.e. SEO. Tags are fundamentally keywords for each page or article created by us. It is a non-hierarchical keyword or term assigned to a piece of information such as an internet bookmark, digital image, or computer file. This type of metadata helps depict an item and facilitates it to be found again by browsing or searching. Tags are chosen easily and personally by the item’s creator or by its viewer, depending on the system. Tags are “free-form” words means there is no formal restriction on tags we attach.

Long tag lists should be generally avoided. Tag pages are somewhat like category pages.  We can assign related posts the same tag, and then all those posts appear on the same tag page. During the design stages of the site, make a list on a piece of paper of all the tags we want to use on our site.  These will be the most important keywords for the niche, but they should be keywords that are different to the categories which we have setup for the site.  Tags can be considered as additional pages that WordPress will create offering us a secondary way of filing our posts.

Although, usage of tags made broad grouping of post topics possible yet to describe a post in more specific terms, more categories are needed. A category is an exclusively defined division in a system of classification. A system of classification here refers to a highly structured, possibly hierarchical system. For example, to borrow from the classification system for living things, we have a tree like “Animals -> Vertebrates -> Mammals -> Horses”. Any of these terms can be considered to be a category, and they fall into a strict structure.

The basic difference between categories and tags is that categories are structured and tags are unstructured. Categories organize, hierarchically. Tags need not. Tags provide meta-information, Categories need not. Tags cross-connect, Categories do not. <–>

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FieldServer 485 Connection Diagram to Isolator ICD102A (Black Box)

Published by skapoor May 25th, 2009 in RS485. 0 Comments

fieldserver-485-to-485-isolator

This diagram shows how to connect a FieldServer FS20 series to an ICD102A optical isolator using a 2-wire RS 485 connection. FieldServer’s only support 2 wire connections.

Datasheet for the Black Box RS485 Isolator/Repeater can be found here: Blackbox Network  Services

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Google Page Rank

Published by skapoor May 24th, 2009 in Uncategorized. 0 Comments

PageRank is a link analysis algorithm used by the Google Internet search engine that assigns a numerical weighting to each element of a hyperlinked set of documents, such as the World Wide Web. The purpose behind this is to measure the relative importance of the element within the set. It is a probability distribution check which represents the possibility that a person randomly clicking on links will arrive at any particular page.

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Google Adwords

Published by skapoor May 24th, 2009 in Google AdWords campaign info. 0 Comments

AdWords is Google’s flagship advertising product and main source of revenue. AdWords offers pay-per-click (PPC) advertising, and site-targeted advertising for both text and banner ads. The AdWords program consists of local, national, and international distribution. Google’s text advertisements are short and contain one title line and two content text lines whereas Image ads can be one of several different Interactive Advertising Bureau (IAB) standard sizes. Main competitors of Google AdWords are Yahoo! Search Marketing and Microsoft adCenter. Advertisers specify the words that should trigger their ads and the maximum amount they are willing to pay per click. When a user searches Google’s search engine on www.google.com or the relevant local/national google server ads for relevant words are shown as “sponsored links” on the right side of the screen, and sometimes above the main search results. These ads are also known as creatives by Google.

The ordering of the paid-for listings depends on other advertiser’s bids and the “quality score” of all ads shown for a given search. The quality score is calculated by historical click-through rates, relevance of an advertiser’s ad text and keywords, an advertiser’s account history, and other relevance factors as determined by Google. The quality score is also used by Google to set the minimum bids for an advertiser’s keywords. The minimum bid reflects on the quality of the landing page also, which includes the relevancy and originality of content, navigability, and transparency into the nature of the business.

All AdWords ads are eligible to be shown on www.google.com. Another option available for advertisers is of enabling their ads to show on Google’s partner networks. The “search network” includes AOL search, Ask.com, and Netscape. Like www.google.com, these search engines show AdWords ads in response to user searches. The “content network” shows AdWords ads on sites that are not search engines. These content network sites are those that use AdSense, the other side of the Google advertising model. AdSense is used by website owners who want to earn money by displaying ads on their websites.

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