Domain Name System

By Raul Bernardino

Introduction:

The Domain Name System (DNS) is a one of the system that transforming the host name and domain name in to the proper Internet Protocol (IP) addresses or from IP addresses translates to the resource name. Usual the internet protocol addresses are using the numeric. As human limitation it is hard to remember the IP addresses for more than 10 especially using DHCP. For example as a human being, we can’t memorize our friends phone numbers that more than 20 phone numbers, with the 10 digits numbers. We can easily remember the names of the colleagues and their addresses rather than their phone numbers. Therefore, we do have our own phone directory base on the names or addresses as a preference. This is same as in the internet protocol, we can’t remember the host IP and domain IP but we do can easily remember the host name and domain name. Each device has its own IP addresses or MAC addresses

 Mockapetris, P. (1983) “invented the Domain Name System from the original of the specifications appears in request for the comment (RFC-882). Since 1987 the publication of the RFC-1034 and RFC-1035 are an updating one of the Domain Name System specifications in which is to replace the obsolete of the RFC-882 and RFC-883.”

Domain Name System is working as follows: The domain names are consisting of parts or labels and with dots (.) as the separators. For example www.amazon.com, the top level domain is “com’, down to sub-domain which is from top level domain to left be “amazon.com”. In the older of the Microsoft windows servers’ the version was called Windows Internet Name Service (WINS). Starting from windows server 2003 the DNS becomes a part of the network infrastructure. Where, the DNS is mirrored with the active directory forests and domain.

The DNS architecture: The DNS is a hierarchical data-base distribution with set of protocols such as how to query and updates the data-base, how to replicate the information among servers, and data-base schema.

The DNS domain Names: it contains several of data including host name and domain names. It is tree structure or what so called domain namespace. The Fully qualified Domain Name (FQDN) is a unique host name among the domain names in the tree structure. Below diagram shows that mydomain is an example of FQDN.

DNS Hierarchical diagram

Therefore having a healthy DNS is important to have all communications up and running.  Otherwise it will be partial running. For example our domain is listed in spam record. We can still have access to internal emails including web browser but it is not receiving any external emails. Once our IP is release from the spam records, we will then receive again external emails.

To secure our own DNS, we do have implemented the mail filters, we called mail protectors. This software application is from the lotus notes mail protector. 

Conclusion: The DNS is an important tool in the networking infrastructure where to resolve the names in to the Internet Protocols address or from IP to the name resolve and records and updates them in the DNS data-base. It is also helping in the networks distribution points to fine the host and domain quickly.

References list:

1. Kurose J.F., Ross K.W., 2010: Computer Networking; A Top-Down Approach: 5^th Edition’; Boston, Addison-Wesley
2.  Lecture notes, CPCOMM_week2_lecture
3. DNS- Domain Name System, [on-line]. Available from: http://compnetworking.about.com/cs/domainnamesystem/g/bldef_dns.htm (Accessed date: August 12, 2011)
4.  RFC 1035 - Domain names - implementation and specification, [on-line]. Available from:  http://www.faqs.org/rfcs/rfc1035.html (Accessed date: August 12, 2011)
5.  DNS Concept, [on-line]. Available from:   http://www.zytrax.com/books/dns/ch2/ (Accessed date: August 12, 2011)
6. How DNS Works, [on-line]. Available from:   http://technet.microsoft.com/en-us/library/cc772774(WS.10).aspx  (Accessed date: August 12, 2011)

Streaming Stored Audio

 By Raul Bernardino

Introduction:

Nowadays, the audio and video streaming becomes one of the popular interactive web sites to be visited and streamed the videos and audios. For instance is a video or an audio streaming in the youtube web site and etc. The streaming are one of the process to play a file (audio or video) while it is still in the process of downloading. There are two typical problems as follows:

• The audio or video may or may not be in the compressing mode. The compressing mode audio file will be less lost tolerant in compare to the uncompressing audio file which is loss file or missing part of the audio or either video files
• The time is sensitive for storing of the audio or video file is less than that of the real-time audio where the client application can cache part of the streaming that is yet to play and for this reason have some tolerance

The streaming stored audio advantages over UDP Transport protocol as follows:

• It has better quality and have no overhead connection management like TCP does
• It can communicate with multiple ports and the speeds are faster
• The streaming stored audio disadvantage over UDP transport protocol as follows:
• It needs control protocol whereas either over UDP port or TCP connection
• If the streaming stored file is compressed it may loss or reduce the quality to below entrance
• It cannot smooth moving over firewalls, Network Address Translations (NAT), and several routers

The streaming stored audio advantages over TCP transport protocol as follows:

• It cans guarantee minimum level of the sound quality
• It cans easily moving over firewalls and NAT configuration
• It does not need control protocol like UDP does because TCP has it on control channel

The streaming stored audio disadvantage over TCP transport protocol as follows:

• The data through put may be lower or slower than UDP because every time packets delivery has to ACK or NACK
• It is not practical in the multiple connection

The RealNetworks: The RealNetworks is a company that provides internet media software services which is based in the USA. This company has created several products such as Realvideo, RealAudio, RealPlayer, and ReadDownloader. It is also including Unifi a could media services for personal, Rinse which is a digital cleap tool for the music library, and Helix which is a technology of moving digital data or media to user end (PC, mobiles, and other devices).

The Realaudio is an audio software application whereas in the compressing format. The RealVideo is a video software application whereas in the compression format. The RealPlayer is a software media where to play the audio or video. While, the RealDownloader is a software application for the downloading manager. The RealNetworks is also providing entertainment and messaging services to the mobile operators.

The Microsoft: The Microsoft media streaming protocol has two differentiate protocols as follows:

• The Real Time Streaming Protocol (RTSP)
•  Microsoft Media Services (MMS) protocol

The RSTP is one of the application protocol layers that created with the specific task where to control the moving of real time data namely data that contains video or audio. The RTSP is also use streaming video or audio contains in the client PC where it use window media player version 9 or later series. This RTSP is working the RTP (real-time transport protocol) either it uses UDP or TCP.

The MMS is a proprietary of the application protocol layer whereas it developed for windows media services earlier version.

References list:

1. Kurose J.F., Ross K.W., 2010: Computer Networking; A Top-Down Approach: 5^th Edition’; Boston, Addison-Wesley
2. Lecture notes, CPCOMM_week3_lecture
3.  DNS- Domain Name System, [on-line]. Available from: http://www.akber.com/streaming-stored-audio   (Accessed date: August 19, 2011)
4. Real Time Streaming Protocol, [on-line]. Available from:  http://en.wikipedia.org/wiki/Real_Time_Streaming_Protocol    (Accessed date: August 19, 2011)
5.  Firewall Information for Windows Media Services 9 Series, [on-line]. Available from:   http://www.microsoft.com/windows/windowsmedia/forpros/serve/firewall.aspx (Accessed date: August 19, 2011)
6. RealNetworks, [on-line]. Available from:   http://en.wikipedia.org/wiki/RealNetworks (Accessed date: August 19, 2011)

Network Address Translation

By Raul Bernardino

Introduction:
The internet protocol (IP) authorization body ICANN which is given away a block of IPs to the ISPs around the world and coordinate them. The ICANN is an abbreviation of Internet Corporation for Assigned Names and Numbers. The ICANN exist since 1998 has dedication to manage and control IPs with the participation from all over the world. The ICANN is not controlling the internet contains but it is coordinating the IP Management and top levels domain names. The main roles are developing policies for the unique identifier of the internet.  There are three main tasks besides developing the policies. They are allocating IP addresses, manage DNSs, and assigning domainnmes, and resolve the disputes. Below is diagram of the ICANN organization structure.

Without this organization, I do think today internet might not exist. The ICANN makes world connect and share the information.

How do ICANN manage the IPs throughout the world? Since IP4 is not enough to every devices that willing to connect, the ICANN manages the IPs through regional registers such as APNIC for Asia Pacific internet register, through government such as gTLD internet register, ISPs, etc as it shows in above diagram.

The internet server provider will allocate a block of IP to the companies and institution that are willing to share information over the internet. To maximize the IP allocation, the companies, institutions, or agencies are organizing themselves internally with the private IPs either use class A, B or C to accommodate the needs and put router as a gateway to translate the private IPs to public IP or from public IP to the local/private IP. Below is Network Address Translation diagram.

NATs are one of security plus for the network why is that? The local area network (LAN) users just use one internet protocol address to communication to the rest of the world. The internet services provider just need to give one IP to the agencies for all their devices in that agency. If there is a changing IP internal it does not need to tell rest of the world. The changing ISP also does not affect with the internal IP communication. NATs will responsible to make it works or translating from public to private. Below diagram will show us how it translating from public to private and from private to public.

What router does?

The outgoing data-grams will be replacing source IP and port number with new IP and new port number. And the remote client or server will be respond with NAT IP address and new port number as a destination address. In the NAT table, it remembers the NATs as a translation pairs. Therefore the incoming data-grams can be forwarded to the destination address bases on the pair translation address in the NAT table. NAT works in the 16-bit port number field, 60,000 simultaneous connections in the single LAN. NAT also controversial in which the router only works up to layer 3 and it is violated the end to end argument.

In order to overcome the shortage of the IPv4 address with NATs, the IPv6 can be a solution. The IPv6 has 32 bit address. It will be permitting more devices and users on the internet end to end communication. It will be reducing network traffic on the router site. Simplify the internet address assignment. The IPv6 also support network layer security and it is allowing network motilities.

References list:

1. Kurose J.F., Ross K.W., 2010: Computer Networking; A Top-Down Approach: 5^th Edition’; Boston, Addison-Wesley
2. Lecture notes, CPCOMM_week4_lecture
3. ICANN, [on-line]. Available from: http://www.icann.org/en/about/   (Accessed date: August 27, 2011)
4. Pasho, A. (June 2, 2011), June 8 is World IPv6 Day – Is Your Organization IPv6 Aware?, [on-line]. Available from: http://blog.getcs.com/2011/06/june-8-is-world-ipv6-day-is-your-organization-ipv6-aware/ (Accessed date: August 27, 2011)