How does NDN differ from CDNs?

A content distribution network (CDN) is a good example of service that is implemented as an overlay on today’s TCP/IP architecture to meet the demand for scalable content distribution, when the same content is requested by many users. CDN customers tend to be relatively large content owners who are willing to pay for higher performance delivery of their content. Content producers without CDN services would face load and performance challenges if/once their content becomes popular.

CDNs operate at the application layer, which gives rise to two issues: how to get customer content requests into the CDN system (a common solution is for the CDN provider to host DNS service for the domain name of the content it serves); and mapping each request to the nearest CDN node serving the content. NDN works directly at network layer and naturally forwards Interest packets along the best paths to the desired data.

Are there any commonalities between IP and NDN architectures?

Both architectures share the same hourglass shape, with the IP/NDN layer as the narrow waist.
Both send datagrams.
Both follow end-to-end principle.
Both use their own namespace for data delivery (i.e. IP uses IP addresses to deliver datagrams between IP nodes; NDN uses the application name space to deliver datagrams between NDN nodes).

What will the role of ICN be on the Internet in 20 years? Will it be the dominant paradigm of communications?

It’s the dominant paradigm now. YouTube, Netflix, Amazon, iTunes, …, are pure ICN and account for more than half of the world’s internet traffic. But today’s ICN-over-IP is inefficient and unsecure because the information-centric overlay is a poor match to the Internet’s conversationally-oriented underlay. The Internet is also already mostly mobile devices (whose users are also content-focused), which the IP architecture does not support well.  Finally, the IP architecture was not designed to naturally support secure communication or secure data distribution. Rather than ignore the growing incongruity between the architecture and global use of the Internet, we are inspired to design, develop, and incrementally deploy an architecture that `catches up’ with the dominant paradigm of communications today.

This architectural incongruity is analogous to the one between packet-oriented IP overlay and circuit-oriented telephony underlay during the Internet’s first 20 years. Imagine the 1990 question “What will be the role of the internet in the global telephony system 20 years from now?”  We now know the answer was “the global telephony system became just one of many applications running over IP internet,” i.e., the overlay became the underlay because it did more, better. We predict we could substitute `Internet’ for `telephony system’ and `NDN/ICN’ for `IP internet’ to move the clock forward 20 years.


10.19 reading

The Billion Dollar Startup Club


Screenshot from 2015-10-19 10:46:17

snapchat: video or pic msg, destroyed once read.

palantir: data analysis

WeWork is an American company which provides shared workspace, community, and services for entrepreneurs, freelancers, startups and small businesses.

lufux:Shanghai Lujiazui International Financial Asset Exchange Co:peer to peer lending for startup

spotify: music


10.19 reading




So basically netcat is a tool to do some bidirectional network communication over the TCP/UDP protocols.

ncat <host> [<port>]

<host> may be a hostname or IP address, and <port> is a port number. Listen mode is the same, with the addition of the --listen option (or its -l alias):

ncat –listen [<host>] [<port>]
ncat -l [<host>] [<port>]

1. Telnet

The very first thing netcat can be used as is a telnet program. Lets see how.

$ nc -v google.com 80

Now netcat is connected to google.com on port 80 and its time to send some message. Lets try to fetch the index page. For this type “GET index.html HTTP/1.1” and hit the Enter key twice. Remember twice.

$ nc -v google.com 80
Connection to google.com 80 port [tcp/http] succeeded!
GET index.html HTTP/1.1

HTTP/1.1 302 Found
Location: http://www.google.com/
Cache-Control: private
Content-Type: text/html; charset=UTF-8
X-Content-Type-Options: nosniff
Date: Sat, 18 Aug 2012 06:03:04 GMT
Server: sffe
Content-Length: 219
X-XSS-Protection: 1; mode=block

<HTML><HEAD><meta http-equiv="content-type" content="text/html;charset=utf-8">
<H1>302 Moved</H1>
The document has moved
<A HREF="http://www.google.com/">here</A>.

The output from google.com has been received and echoed on the terminal.

2. Simple socket server

To open a simple socket server type in the following command.

$ nc -l -v 1234

The above command means : Netcat listen to TCP port 1234. The -v option gives verbose output for better understanding. Now from another terminal try to connect to port 1234 using telnet command as follows :

$ telnet localhost 1234
Connected to localhost.
Escape character is '^]'.
ting tong

After connecting we send some test message like abc and ting tong to the netcat socket server. The netcat socket server will echo the data received from the telnet client.

$ nc -l -v 5555

Connection from port 5555 [tcp/rplay] accepted
ting tong

This is a complete Chatting System. Type something in netcat terminal and it will show up in telnet terminal as well. So this technique can be used for chatting between 2 machines.


monitor system

My goal is to build a cloud monitor system in one year.


  1. the goal of MS(monitoring system)/ difference with others
  2. the architecture and  function of MS/difference with others
  3. how to realize it
  4. refinements

1. the goal

provide complete and real time info about system, including resource, workload, forecast and etc.

2. function


  • alerts and alarms:Being able to set up alerts so that the proper administrator is notified depending on the issue is important. If a storage alert goes out to a server admin, the response may not be as fast as it would be had the alert gone out to a storage administrator.                             different alerts go to different administrator
  • resource management
  • user count
  • failover capabilities
  • roles and privileges:This isolation of roles creates effective audit trails. It also greatly reduces the risk that a team member will make the wrong changes to the system.
  • SLA considerations:This means monitoring uptime and environment usage. Depending on the type of SLA, different metrics are important to the administrator. This might mean monitoring the number of VMs working or adjusting downtime requirements
  • Testing and maintenance

samples of monitoring system




monitor system

website building

download sublime, responsive web template, and start with w3c tutorial about html

alt: provide the info about element in case the element itself can’t display

HTML elements are written with a start tag, with an end tag, with the content in between:

Some HTML elements do not have an end tag.

HTML Tip: Use Lowercase Tags

Single or Double Quotes?

Double style quotes are the most common in HTML, but single style can also be used.

In some situations, when the attribute value itself contains double quotes, it is necessary to use single quotes:

<p title=‘John “ShotGun” Nelson’>

Or vice versa:

<p title=“John ‘ShotGun’ Nelson”>

The <hr> tag creates a horizontal line in an HTML page.


<p>This is a paragraph.</p>
<p>This is a paragraph.</p>

The HTML <head> element has nothing to do with HTML headings.

The HTML <head> element contains meta data. Meta data are not displayed.

The HTML <head> element is placed between the <html> tag and the <body> tag:


<!DOCTYPE html>
<title>My First HTML</title>
<meta charset=“UTF-8”>

More Meta Elements

In the chapter about HTML styles you discover more meta elements:

The HTML <style> element is used to define internal CSS style sheets.

The HTML <link> element is used to define external CSS style sheets.

Attribute Description
alt Specifies an alternative text for an image
disabled Specifies that an input element should be disabled
href Specifies the URL (web address) for a link
id Specifies a unique id for an element
src Specifies the URL (web address) for an image
style Specifies an inline CSS style for an element
title Specifies extra information about an element (displayed as a tool tip)
value Specifies the value (text content) for an input element.
Tag Description
<html> Defines an HTML document
<body> Defines the document’s body
<head> Defines the document’s head element
<h1> to <h6> Defines HTML headings
<hr> Defines a horizontal line

HTML Line Breaks

The HTML <br> element defines a line break.

Use <br> if you want a line break (a new line) without starting a new paragraph:


<p>This is<br>a para<br>graph with line breaks</p>

The HTML <pre> Element

The HTML <pre> element defines preformatted text.

The text inside a <pre> element is displayed in a fixed-width font (usually Courier), and it preserves both spaces and line breaks:

Tag Description
<p> Defines a paragraph
<br> Inserts a single line break
<pre> Defines pre-formatted text

HTML Styling

Every HTML element has a default style (background color is white and text color is black).

Changing the default style of an HTML element, can be done with the style attribute.

This example changes the default background color from white to lightgrey:


<body style=“background-color:lightgrey”>

<h1 style=“color:blue”>This is a heading</h1>
<p style=“color:red”>This is a paragraph.</p>


The HTML Style Attribute

The HTML style attribute has the following syntax:


The property is a CSS property. The value is a CSS value.

  • Use the style attribute for styling HTML elements
  • Use background-color for background color
  • Use color for text colors
  • Use font-family for text fonts
  • Use font-size for text sizes
  • Use text-align for text alignment

HTML Text Formatting Elements

Tag Description
<b> Defines bold text
<em> Defines emphasized text
<i> Defines italic text
<small> Defines smaller text
<strong> Defines important text
<sub> Defines subscripted text
<sup> Defines superscripted text
<ins> Defines inserted text
<del> Defines deleted text
<mark> Defines marked/highlighted text

HTML Quotation and Citation Elements

Tag Description
<abbr> Defines an abbreviation or acronym
<address> Defines contact information for the author/owner of a document
<bdo> Defines the text direction
<blockquote> Defines a section that is quoted from another source
<cite> Defines the title of a work
<q> Defines a short inline quotation

HTML Computer Code Elements

Tag Description
<code> Defines programming code
<kbd> Defines keyboard input
<samp> Defines computer output
<var> Defines a mathematical variable
<pre> Defines preformatted text

HTML Comment Tags

You can add comments to your HTML source by using the following syntax:

<!– Write your comments here –>
Note Note: There is an exclamation point (!) in the opening tag, but not in the closing tag.

Inline Styling (Inline CSS)

Inline styling is useful for applying a unique style to a single HTML element:

Inline styling uses the style attribute.

This inline styling changes the text color of a single heading:


<h1 style=“color:blue”>This is a Blue Heading</h1>

Internal Styling (Internal CSS)

An internal style sheet can be used to define a common style for all HTML elements on a page.

Internal styling is defined in the <head> section of an HTML page, using a <style>element:


<!DOCTYPE html>
body {background-color:lightgrey}
h1   {color:blue}
p    {color:green}

<h1>This is a heading</h1>
<p>This is a paragraph.</p>


The id Attribute

All the examples above use CSS to style HTML elements in a general way.

To define a special style for one special element, first add an id attribute to the element:

<!DOCTYPE html>
p#p01 {
color: blue;

<p>This is a paragraph.</p>
<p>This is a paragraph.</p>
<p>This is a paragraph.</p>
<p id=”p01″>I am different.</p>


The class Attribute

To define a style for a special type (class) of elements, add a class attribute to the element:

<!DOCTYPE html>
p.error {

<p>This is a paragraph.</p>
<p>This is a paragraph.</p>
<p class=”error”>I am different.</p>
<p>This is a paragraph.</p>
<p class=”error”>I am different too.</p>


Use id to address single elements. Use class to address groups of elements.

HTML Style Tags

Tag Description
<style> Defines style information for a document
<link> Defines a link between a document and an external resource
website building