Configuration of a HTTP server on local computer using Dynamic DNS

Configuring a HTTP Server on your local computer using Dynamic DNS

Requirements: HTTP Server (XAMPP/LAMPP Chosen here)

Purpose:  We demonstrated how to setup a local HTTP server using Apache (preinstalled using XAMPP).

If this web page was to be accessed globally from the internet, our IP address would have to be referenced (say http://202.124.23.33/ , however if our IP is dynamic, it is difficult to keep track of our web page’s address). Even using a registered domain name would not help ( http://www.somedomain.com/ ) as it would not be able to keep track of our dynamically changing IP, which is the usual case for most home internet users.

Solution: We use a facility of our test router called dynamic DNS.

Dynamic DNS is a method, protocol, or network service that provides the capability for a networked device, such as a router or computer system using the Internet Protocol Suite, to notify a domain name server to change, in real time (ad-hoc) the active DNS configuration of its configured hostnames, addresses or other information stored in DNS.

A popular application of dynamic DNS is to provide a residential user’s Internet gateway that has a variable, often changing, IP address with a well known hostname resolvable by network applications through standard DNS queries.

Function

Dynamic DNS providers provide a software client program that automates the discovery and registration of client’s public IP addresses. The client program is executed on a computer or device in the private network. It connects to the service provider’s systems and causes those systems to link the discovered public IP address of the home network with a hostname in the domain name system. Depending on the provider, the hostname is registered within a domain owned by the provider or the customer’s own domain name. These services can function by a number of mechanisms. Often they use an HTTP service request since even restrictive environments usually allow HTTP service. This group of services is commonly also referred to by the term Dynamic DNS, although it is not the standards-based DNS Update method. However, the latter might be involved in the providers systems.

Most home networking routers today have this feature already built into their firmware. One of the early routers to support Dynamic DNS was the UMAX UGate-3000 in 1999, which supported the TZO.COM dynamic DNS service.

An example of use is a home user who wishes to access a computer on a home network while travelling. The user may be supplied with a different IP address every time an Internet connection to the service provider is made, so there is no stable address to connect to. If a DDNS service is used to associate a fixed address to a device, then the user can, for example, establish a Virtual Private Network (VPN) to the network using that address. As a detailed example, the IP address can be 123.234.111.112 one day, 123.124.45.15 the next, but the DDNS address will always be, say, myhome.ddns.org. A remote control program such as VNC server can be left running on a machine in the network; the user can connect to the network by establishing a password-protected VPN to myhome.ddns.org, then connect to the machine using a VNC client program.

In Microsoft Windows networks, Dynamic DNS is an integral part of Active Directory, because domain controllers register their network service types in DNS so that other computers in the Domain (or Forest) can access them.

Increasing efforts to secure Internet communications today involve encryption of all dynamic updates via the public Internet, as these public dynamic DNS services have been abused increasingly to design security breaches. Standards-based methods within the DNSSEC protocol suite, such as TSIG, have been developed to secure DNS updates, but are not widely in use. Microsoft developed alternative technology (GSS-TSIG) based on Kerberos authentication.

Steps to change MAC address in windows

Steps to Configure :  Change the MAC address in Windows

1. Go to Start -> Control Panel

Double click on Network Connections (inside Network and Internet Connections category in Windows XP). The, right click on the active network connection with network adapter that you want to change the MAC address (normally Local Area Network or Wireless Network Connection) and click on Properties.

Above steps work in Windows XP, Windows 2000 and Windows Server 2003. For Windows Vista, access to NIC’s properties is from Control Panel -> Network and Internet -> Network and Sharing Center -> Manage Network Connections.

Alternatively, if you already know which network adapter that’s responsible for your network or Internet connection, go to Device Manager and open the properties dialog by double click on the NIC itself.

1. In the General tab, click on the Configure button.
2. Click on Advanced tab.
3. In the Property section, select and highlight Network Address or Locally Administered Address.
4. To the right, “Not Present” radio button is by default selected as value. Change the value by clicking on radio button for Value:, and then type in a new MAC address to assign to the NIC.

The MAC address consists of 6 pairs of numbers (0 – 9) and characters (A – F) combination. For example, 88-17-E8-90-E2-0A. When entering the new MAC value, omit the dash (-), for example 8817E890E20A.

1. Click OK when done.
2. To verify the change of MAC address, go to command prompt, then type in one of the following commands:

Ipconfig /all
net config rdr

1. Reboot the computer if successful to make the change effective.

Note: To restore or reset back to original default MAC address, simply set back the option to “Not Present”.

Comparison of ARQ protocols

ARQ PROTOCOL	Stop and wait	Go-Back-N	Selective Repeat
Maximum sender size window	Not applicable	2^m -1	2^(m-1)
Maximum receiver size window	Not applicable	1	2^(m-1)
Pipelining	Not implemented	Implemented	Implemented
Bandwidth utilization	LOW	MEDIUM	HIGH
Out of order frames	Discarded	Discarded	Accepted
Cumulative ACK	Not applicable	Applicable	Applicable
NAK	Not applicable	Not applicable	Applicable

Comparison of MAC spoofing platform and method wise

Comparison of MAC spoofing platform wise & method wise:

Ease of MAC Spoofing:	Windows XP, Vista, 7	Linux	MAC
3rd Party Tools.	Easy, less unreliable.	Not needed	Required for versions of OS X before Tiger (OS X 10.4), detectable.
Manual configuration	Registry Hack, after detecting interface, unreliable	Script commands.	Easy, Reliable

	3rd party Tools			Manual Configuration
	Mac Make Up	Mad Macs	Etherspoof
Ease of Use	Fairly Easy	Extremely Easy	Extremely Easy	Easy for Linux, MAC OS X 10.4 and above, Unreliable registry hack in windows
Major Advantage	Can spoof wide range of adapters	Easy to use and revert back to original without registry damage	1 time application	Hack almost untraceable.
Major Disadvantage	Does not work in several test cases.	Bug does not allow to spoof Intel Wireless ABG/N adapters.	Unreliable (may not apply in all scenarios)	Unreliable in closed source OS.
Flexibility/ Configurability	Medium level configuration	Zero configuration, not flexible	Application of Patch	Extremely high level, and therefore difficult
Platform	Windows	Windows	MAC OS X	Any

Linksys WRT54AG Router

key specifications                                                                               Wireless-G Broadband router

Manufacturer		Linksys
Manufacturer Part #		WRT54G
Device Type		Wireless Router with Integrated 4 Port Switch
Enclosure Type		Standalone
Networking	Connectivity Technology	Wireless – 802.11g
	Data Transfer Rate	Up to 54 Mbps
	Frequency Range	2.4 Ghz
	Remote Management	Web-Based
	Status Indicators	Power, DMZ, WLAN, LAN (1, 2, 3, 4/DMZ), Internet
	Features	Auto-MDI/MDI-X Cable Detection, 128-bit WEP Encryption, DHCP, DDNS, Static and Dynamic Routing (RIP1 and 2), VPN Pass-Through (IPSec and PPTP), DMZ Hosting, Stateful Packet Inspection (SPI) Firewall, Internet Policy, Packet Filtering, WPA, MAC Filtering, Built-in 4 Port Switch
	Compliant Standards	IEEE 802.3, 802.3u, 802.11g, 802.11b
Interfaces	Interfaces	4 x 10/100 Ethernet LAN (RJ-45) 1 x 10/100 Ethernet WAN (RJ-45)
Power Requirements	Power Supply	External
	Voltage	5 V DC
Dimensions (H X W X D)	Unit	1.89″ x 7.87″ x 7.32″
Weight	Unit	1.06 lbs

Mapping logical to physical address:ARP

A host or a router has an IP datagram to send to another host or router, it has the logical (IP) address of the receiver .The logical (IP) address is obtained from the DNS if the sender is the host or it is found in a routing table if the sender is a router .But the IP datagram must be an encapsulated in a frame to be able to pass through the physical network.  This means that sender needs the physical of the  receiver .The host or the router sends an ARP query packet. The packet includes the physical and IP address of the sender and the IP address of the receiver .Because the sender does not know the physical address of the receiver, the query is broadcast over the network.

Every host or router on the network receives and processes the ARP query packet, but only on the intended recipient recognizes its IP address and sends back an ARP response packet. The response packet contains the recipient’s IP and physical addresses. The packet is unicast directly to the inquirer by using the physical address received in the query packet.

In the below fig.(a) the system on the left(A) has a packet needs to be delivered to another system (B) with IP address 141.23.56.23. System A needs to pass the packet to its data link layer for the actual delivery , but it does not know the physical address of the receipient . It uses the services of ARP by asking the ARP protocol too send a broadcast ARP request packet to ask for the physical address of a system with an IP address of 141.23.56.23.

This packet is received by every system on the physical network, but only system B will answer it, as shown in fig.b. system B sends an ARP reply packet that includes its physical address .Now system A can send all the packets it has for this destination by using the physical address it received.

comparison between TCP and UDP

	UDP	TCP
Packet Header Size	8 bytes	20 – 60 bytes
Transport Layer Packet entity	Datagram	Segment
Port Numbering	Yes	Yes
Error Detection	Optional	Yes
Reliability: Error recovery by automatic repeat request (ARQ)	No	Yes
Virtual circuits: Sequence numbering and reordering	No	Yes
Flow control	No	Yes
Congestion avoidance: Variable congestion window, slow start, time outs	No	Yes
Multiple streams	No	No
ECN support	No	Yes

Protocol stack & Addressing

CCN Question Bank for 1st Internals:

Students should not be under the impression that questions will be compulsorily set from this question bank.

Please compare this question bank with the written copy provided by Maam.

(1)    Explain the functions of application layer, presentation layer, session layer of the OSI model. Give the advantages and the disadvantages of combining these layers into 1 layer in the TCP/IP model.

(2)    The physical address will change from hop to hop but the logical addresses and port addresses usually remain the same. Justify this statement with proper examples.

(3)    Which layer is responsible for moving

1. Frames from one hop to the next.
2. Packets from source to destination host.

Explain the functions of these layers in detail.

(4)    Write if the following is true or false. Justify with suitable diagrams and examples.

1. The network layer gets each packet to the correct computer.
2. The data link layer makes the physical layer appear error free to the upper layer.
3. The transport layer gets the entire message sent to the correct process on the destination computer.

(5)    What is the criteria for a good polynomial generator, find the suitability of the following generators in relation to burst errors of different lengths.

1. x⁶ + 1
2. x¹⁸ + x⁷ + x + 1
3. x³² + x²³ + x⁷ + 1

(6)

1. There are 200 bytes in a data block, each byte being 8 bit. If the error rate is 1*10^-5 what is the probability of the block being received in error.
2. Generate the CRC code for the data word 110101010 using the divisor 10101.

(7)    Let g(x)=x³ + x + 1 consider the info sequence 1001, 110110

1. Find the code word corresponding to the info sequence given above.
2. Suppose the code word has tx error in the first bit, what does the receiver obtain when error checking is done. (Assume MSB error)

(8)    Explain the design of a CRC encoder and CRC decoder. Also give a sample example of the division performed in the encoder and decoder.

(9)    Explain the hardware implementation of the cyclic code in the encoder and the decoder.

(10) If the generator has more than 1 term and the coefficient of x⁰ is 1, all single errors can be caught. Justify the statement with suitable examples.

Problem Faced: Dynamic DNS using XAMPP and WRT54AG Router

Description:
Refer to post “Configuring a HTTP Server on your local computer using Dynamic DNS”,
We used XAMPP and our WRT54AG Wireless router to set up a HTTP server accessible from http://ninny.dyndns.org/ .

Problem Statement:

XAMPP is hosted on localhost 127.0.0.1 , however our local IP
(as provided by DHCP lease of our router) is 192.168.1.x ,
so even though Dynamic DNS was successfully configured,
accessing http://ninny.dyndns.org/ was unable to retrieve the
locally hosted web-page.

Solution: [Solved]

We tried changing the host configuration [ Open C:\WINDOWS\system32\drivers\etc\host ], which looks like this:

# Copyright (c) 1993-2006 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
#      102.54.94.97     rhino.acme.com          # source server
#       38.25.63.10     x.acme.com              # x client host

127.0.0.1       localhost
::1             localhost

(1) We changed this to 192.168.1.7 (local IP of host computer at that time) : Failed
(2) We tried changing XAMPP configurations : Failed
(3) We are now using linux and using LAMP, and should have a solution soon.

Solution:
The problem was solved by putting the localhost IP in the DMZ of the router configuration, If we are online, http://ninny.dyndns.org/ will lead you to the XAMPP restricted page.

Fun fact: Did you know?

Adobe Activation hack: You can add a line 127.0.0.1 activate.adobe.com in this host configuration file. This will trick absolutely any adobe software, registered by a fake serial key, to ask for “activation” (read “validation for piracy”) information from 127.0.0.1 (that is your own computer), since no activation information is recieved, you are free to use expensive Adobe software free of cost and with enabled updates.