Month: December 2012

NDP – Neighbor Discovery Protocol

IPv6 Neighbor Discovery Protocol

In IPv6 we do not have ARP (address resolution protocol) anymore. ARP is replaced with ICMP based NDP protocol. NDP or ND protocol uses special IPv6 ICMP messages to find and resolve L2 neighbours IPv6 addresses.

It’s a simple way for hosts to learn IPv6 addresses of neighbours on L2 subnet around himself. That includes learning about other hosts and routers on local network. That is the biggest difference between IPv4 and IPv6, there’s no ARP but ICMP takes the function.

NDP is defined in RFC 2461 and this article will introduce you to NDP functions, main features’ lists, and the related ICMPv6 message types.

As the most precise description of NDP is that it belongs to the Link layer of the Internet Protocol suite in TCP/IP model. We can say that Link layer of TCP/IP model is basically a direct combination of the data link layer and the physical layer in the OSI Open Systems Interconnection protocol stack. As in this blog I always try to use OSI model this article was inserted both to Data-link and Physical layer category.

NDP function

In case of IPv6 networks, the NDP Protocol make use of ICMPv6 messages and solicited-node multicast addresses for operating its core function, which is tracking and discovering other IPv6 hosts that are present on the other side of connected interfaces. Another use of NDP is address autoconfiguration.

Let’s discuss some major roles of IPv6 NDP:

  • Stateless address autoconfiguration – SLAAC
  • Duplicate address detection DAD
  • Router discovery
  • Prefix discovery
  • Parameter discovery link MTU, hop limits 
  • Neighbor discovery
  • Neighbor address resolution – replaces ARP in IPv6
  • Neighbor and router reachability verification

In order to carry out work NDP uses five types of ICMPv6 messages. In the following list you can find the function as well as summary of their goals.

NDP message types:

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PNRP Name Resolution – How it works?

PNRP name resolution protocol uses this two steps:

  • Endpoint determination – In this step the peer is determining the IPv6 address of the computer network card on which the PNRP ID service is published.
  • PNRP ID resolution – After locating and testing the reachability of the peer with the PNRP ID with desired PNRP service, the requesting computer sends a PNRP Request message to that peer for the PNRP ID of the desired service. Other side is sending a reply in which it confirms the PNRP ID of the requested service. It also sends a comment, and up to 4 kilobytes of additional information in that reply. Using the comment and additional 4 kilobytes there can be some custom information sent back to the requestor about the status of server or computer services.

In the process of discovering needed neighbor, PNRP is making an iterative process in which it locates all nodes that have published their PNRP ID. The node performing the resolution is in charge of communicating with the nodes that are closer to the target PNRP ID.

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PNRP the New DNS – Peer Name Resolution Protocol

PNRP – The Peer Name Resolution Protocol is new protocol made by Microsoft which is one of the first technology that will change the way we think about naming resolution in computer networking and possibly be the next DNS – Domain Name System like technology. PNRP is the new DNS but there are so much differences between them that it deserves an article on this blog.

Just to remind, is few simple words, DNS is a technology that enables us to type the domain name in the browser and leaves to Domain Name System to translate the domain name to IP address of the server where the web page is published.

As we are stepping forward to IPv6 implementation in the whole world in next years, there are technologies and future services that will not function at their best using DNS. In this case Microsoft was one of the first to develop a new technology, decentralized technology that will rely on neighbor computer for the name resolution and completely rely on IPv6 addressing. The Per Name Resolution protocol was the answer.

In case of DNS, it depends on a hierarchical structure of naming, while PNRP depends on peer systems in order to resolve the computer system’s location. Mainly, PNRP is a referral system that operates lookups on the basis of data it is familiar with.

PNRP - Peer Name Resolution ProtocolHere is a simple example, if you require to search Computer 1 and you are close to Computers 2 and 3, it is important for your system to know whether Computer 2 knows Computer 1 or not. If the response of Computer 2 is positive, only then a a link to Computer 1 is provided to you. If the reply is in negative, then the system asks Computer 3 whether it knows Computer 1 and the same method is used with Computer 2. If none of the computers knows Computer 1, then the request is sent to other computers close to the system till it successfully finds the one that is familiar with Computer 1.

There are number of ways in which PNRP is different from the DNS service:

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Next project was one of my first networking Science articles. It is a short look at latest achievements from some of the biggest networking scientists today with some short comments from my mentor and me. The work was presented at 19. International scientific conference of International Federation of Communication Associations. International scientific conference “DIT 2012” accepts and publishes scientific and professional papers and the results of interdisciplinary scientific research, whose area of interest is the development of society, education, science and technology.

Okaj, let’s go on…


dr. sc. Božidar Kovačić & Valter Popeškić (me)
University of Rijeka – Department of Informatics
Theme: 3. New ICT technology, media and e-education;

Abstract or simply, intro…

Today’s computer networks will not be able to resolve the tangled problems that emerge from increasingly throughput-demanding services after their need for resources exceed the capabilities of today’s networking technologies. Cognitive networks have the means to resolve this issue incorporating intelligence to the network functions. Introduction to Cognitive network as a concept brings the view into the future of communication, information and learning using modern technology.

A cognitive network is a network consisting of elements that reason and have the ability to learn. In this way they self-adjust according to different unpredictable network conditions in order to optimize data transmission performance. In a cognitive network, judgments are made to meet the requirements of the network as an entire system, rather than the individual network components. The main reason of the emergence of cognitive networks is to achieve the goal of building intelligent self-adjustable networks and in the same time improve the performance. Intelligent self-adjustable networks will be able to use intelligence to determine ideal network operating state for many tunable parameters.

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