TCP/IP architecture model was initially designed as DARPA model by the US government agency by that name. There were four layers in the DARPA model. Those were, application layer, transport layer, Internet layer and network interface layer. Each of those layer used to correspond to one or more layers in the OSI model with seven layers.
In the TCP/IP protocol architecture, there are four layers or sets of protocols, similar to the DARPA model. TCP/IP protocol architecture works as protocol stack. Each layer of TCP/IP protocol stack, has its own set of functionalities and provides a set of services to the next layer. The descriptions of these layers are, (Blank, TCP/IP Foundations, 2006)
Network interface layer or network access layer is the lowest layer in the TCP/IP protocol stack. It places TCP/IP packets on the network and receives the same from the network. TCP/IP protocol stack is independent of different network access methods, medium, frame formats etc. Thus it supports different types of networks, different types of LAN technologies like token ring, Ethernet etc., different types of WAN technologies like frame relay, X.25 etc. This layer is independent from different network technologies. It gives the TCP/IP protocol stack the ability to adapt any new networking technology, for example, ATM or Asynchronous Transfers Mode networks. (Blank, TCP/IP JumpStart, 2006)
Internet layer sits on the top of network interface layer in the TCP/IP protocol stack. Internet layer is responsible for packaging, addressing and routing of packets. There are some core protocols in this later. These protocols are important for internetworking. The protocols are IP or Internet Protocol, ARP or Address Resolution Protocol, ICMP or Internet Control Message Protocol, IGMP or Internet group management protocol. Each of these protocols performs different types of responsibilities and collectively all these are the responsibilities of internet layer. (Comer, 2006)
Internet protocol is responsible for routing packets. Thus functions like routing, IP addressing, packet fragmentation and reassembly are provided by this layer.
Address resolution protocol provides services like IP to MAC address translation etc. The main function is to provide address resolution services to the network layer.
Internet control message protocol provides different types of diagnosis and error handling services that may occur from erroneous packet delivery.
Internet group management protocol manages groups of IP multi-casting.
Transport layer provided host to host service on the top of internet layer. It consumes services from the internet layer and provide service to the application layer that is on the top of it. Mainly it provides services related to transmission of data packets successfully over the internet. There are two protocols in this layer. Those are TCP or Transmission Control Protocol and UDP or User Datagram Protocol. (Alani, 2014)
Transmission Control Protocol is responsible for providing a connection- oriented, one to one and reliable communication service. It arranges the sequences of packets, acknowledges the packet transmissions, and provides recovery of packets lost during transmission.
On the other hand, user datagram protocol is a connectionless, one to many (may be one to one), unreliable service for communication over the internet. Generally, UDP is used to transfer smaller amount of data or data where security or data loss is not a big issue.
TCP provides secure and better service than UDP, but there is some additional overhead of TCP services, when some application does not want to have these overhead and still want to have a data transmission, then it selects UDP instead of TCP. (Blank, TCP/IP JumpStart, 2006)
Application layer is the topmost layer on the TCP/IP protocol stack. It directly interacts with the applications on a computer or system. It provides abilities to the applications to consume services from other layers of the TCP/IP protocol stack. Application layer has a bunch of protocol and new protocols evolve frequently. (Reynders & Wright, 2003)
Some of the widely used application layer protocols and the services provided by those protocols are,
Some examples of application layer interfaces for TCP/ IP protocol stacks may be NetBIOS, Windows Sockets etc. In Windows operating system environment, Windows Socket helps in having a standard API. NetBIOS helps in managing sessions, name resolutions, datagram related protocol services.
The illustration of TCP/ IP protocol stacks along will different sets of protocols for each of the layers, has been given as,
There are different types of networks used for different organizations, the networks differ in structures, services, interfaces, technologies. Connecting all these networks to have an interconnected network or Internet required some uniformity and platform independent protocols. OSI model was built to abstract the diverse nature of the network. OSI model provides enough abstractions to hide the complexities of networking and internetworking and gives enough scope to the programmer to build specific programs to each layer. Then programs from different layers of OSI model then work with one another.
There were several flaws in OSI model. There were no details about the protocols or how to implement the functions of each layer. On the contrary, TCP/IP model gives details about the protocols from each layer. A programmer can implement those protocols from different layers and the job is done. (Held, 2002)
OSI model has total 7 layers. Those layers are categorized into two category of layers as given in the following picture. The layers in the OSI model as, Application layer. Presentation layer, Session layer. Transport layer, Network layer, Data Link layer, Physical layer. First three layers belong to the application layer category and rest of the layers belong to the data flow category.
On the other hand, there are four layers on the TCP/IP model. Those are application layer, transport layer, internet layer, and network access interface layer. These four layers covers the seven layers of OSI mode. The layers on the TCP/IP model are again divided into two categories. Application and transport layers are categorized as protocols layers and rest two belongs to networks layers.
The comparison between OSI model and TCP/IP model are summarized as, (Alani, 2014)
|
Open System Interconnection (OSI) Model |
TCP /IP Model |
|
This is more focused on architectural aspects of a network model and provides an idealistic view. |
It is more focused on the implementation aspects and provides some realistic view. |
|
OSI model is developed by a horizontal approach. |
It is developed based on a horizontal approach. |
|
The basic assertion behind the OSI model is that operation of distributed applications is laid upon a strict hierarchy of layers and standardisation. |
The basic assertion of TCP/IP model is that any application is composed of a set of functions over an end to end distributed communication service. |
|
There is a ‘pool’ of application service elements or ASEs a distributed application selects an element from such pool and performs functions that is specific to the end to end service. |
Abstraction is the fundamental characteristic here. Every application assumes that services from lower layer will be available at any point of time. |
|
The session layer controls the sessions, presentation layer controls the representation of data etc. and the application layer communicated with the application on the host system. In OSI model, all these are different layers. Some examples of functions of OSI application layer are, VT, FTAM ,MHS, CMIP, DS etc. |
In the TCP/IP model, application, session and transport layers of the OSI model have been clubbed into application layer of TCP/IP model. Some example of protocols from application layer of TCP/IP model are, FTP. HTTP, DNS. Telnet etc. (Alani, 2014) |
|
The transport layer of OSI is responsible to deliver information from source system to destination system. |
The transport layer communicates from source to destination, performs flow control, error checking etc. |
|
The network layer provides connection oriented and connectionless services. |
The internet layer on the TCP/IP provides only connectionless service. |
|
Data link layer prepares the streaming of data, handles flow control, error control. Whereas data is transmitted through the physical media as a raw bit stream. The later part is handled by physical layer. |
Here data transmission is handled by network access layer only. Services provided by data link and physical layers in the OSI model are provided by the network access layer in the TCP/IP model. |
|
While implementation of the OSI model, the emphasis is on reliability of data transfer. |
The reliability is handled as an individual cases of end to end delivery. |
|
Detection and handling of errors is performed in each layer using checksums. |
Detection and handling of errors is done by the transport layer only. |
OSI model is most of the time a theory based description of an ideal network model, whereas TCP/IP model is a model that is being used in practice for long time.
IPv4 or Internet Protocol version 4 is a widespread and currently used internet addressing scheme. A network connects different types of devices as hosts. An internet is an interconnection of different types of networks across the globe. It is necessary to uniquely address each of the host connected to the internet. For that purpose internet address or IP addresses are used.
There are different schemes of IP addressing. IPv4 is a 32 bit IP addressing scheme. With 32 bits, possibly there will be 232 unique IP addresses. IPv4 addressing uses a class-full addressing.
Implementation of IP addresses in private and public networks has some challenges. One is, there is scarcity of addresses that can serve need of the networks and devices. Thus, there are two types of addressing used in private and public network.
The addressing scheme used within a private network is not visible from the public network. Masquerading, NAT etc. are used to implement it. However, it increases overhead on routers. (Comer, 2006)
On the other hand, there are two types of IP addresses, static and dynamic. ISPs use a pool of available IP addresses, when some client logs on to their network and request some IP address, then the ISP allocates one IP address from the address pool. The IP address is valid for that client for that session only. When the client logs off, the address will be de-allocated and will go back to the address pool. This scheme is known as dynamic IP address. Where the IP address is not tied to some device. The same client may get different IP address when it logs in again. And the same IP address may be allocated to other client next time.
On the other hand, there are other types of IP addresses that are tied to a particular device. These are called static IP addresses. (Held, 2002)
NAT or Network Address Translation is used to bridge the gap between private and public network. A NAT table is kept on the router. There may be at least two attribute for each entry of the NAT table, the IP addresses of a device in the private network and the IP address of the destination of the packet. The router checks the NAT table, replaces the source address as the public address of the network and forwards the packet to the destination. When it receives some packet from the Internet or other network, then it checks the NAT table again and forwards the packet to the destination. For public networks, there is no existence of the private network, they communicate with the public IP address of the network.
There are RIR or Regional Internet Registry that are organizations for handling registration and allocation of IP addresses in different parts of the world. There are 5 RIRs currently for different regions of the world.
Following picture illustrates the RIRs and operating domains. Each of the RIR has 16 millions of IP addresses to allocate.
In IPv4 scheme, the whole address space is divided into 5 categories those are,
|
Class |
Address Range of first Octet |
Network and Host octets |
|
Class A |
1 to 126 |
N.H.H.H |
|
Class B |
128 to 191 |
N.N.H.H |
|
Class C |
192 to 223 |
N.N.N.H. |
|
Class D |
NA |
Reserved for Multi casting |
|
Class E |
NA |
Reserved for Research and Future use. |
There are several disadvantages of IPv4 addressing scheme. The blocks don’t have equal number of networks or hosts. For example, there is huge numer of hosts possible for a Class A IP address but in reality no class A IP address contains that many hosts. On the other hand very few hosts are possible for a Class C IP address. So, there is a mismatch between the requirement and availability. Here comes the major disadvantage of IPv4 addressing schemes. There are unused IP addresses but those can’t be allocated. The available IP addresses are depleting and has failed to cater the requirement of growth of internet. (Reynders & Wright, 2003)
As a result IPv6 has been developed.
The aim of this report is to discuss and highlight the key issues in implementation of IPv6 protocol for the organization TCS Ltd.
In the rest of the parts of the report the discussion will focus on different aspects of implementing IPv6 in the organization, the benefits and drawback of the implementation, explanation and evaluation of other alternative transition mechanisms, analysis and evaluation of possible improvement in QoS or Quality of Service and security.
IPv6 or Internet Protocol version 6 is the latest and updated version of the communication protocol IP in the TCP/IP model. It helps in identification and location of a host system in the internet uniquely and routing traffic from source to destination on the Internet. IPv6 has been developed by IETF or Internet Engineering Task Force. One of the major issue with IPv4 is rapid depletion of the available IP addresses and poor distribution of the same. To deal with this problem IPv6 has come into the picture. It is slowly replacing IPv4. IPv6 is a 128 bit addressing protocol and holds almost 2128 unique addresses into its address space. IPv6 is not interoperable with IPv4. Thus one is needed to be replace by other. There are various transition mechanisms from going to IPv6 from IPv4. (Hagen, 2014)
A 128 bits IPv6 address is broken down into 8 groups of four hexadecimal digits in each group. Each of the group is separated by a colon. There are compression methods available to shrink or expand representation of an address.
One of the major benefits of IPv6 is the larger address space and classless distribution of addresses. The address allocation methods of IPv6 facilitates route aggregation and limits extensions of routing table. It support multicasting in a simpler and extended way. There are several optimizations for delivery of services. It enhances mobility, configuration and security of the devices.
So, other benefits of IPv6 for an organization are, (Johnson, Perkins, & Arkko, 2004)
Apart from the benefits there are few drawbacks of IPv6. Those are,
Some alternative transition mechanisms to transit to IPv6 from IPv4 are,
In this method, the encapsulation is done at the source and the destination encapsulates it. A private IPv4 network without any information about the IPv6 protocol, is used to transfer the datagrams from the source to the destination. In the following picture, the illustration has been shown, including two hosts with dual IPv4 and IPv6 stacks. These stacks are used for encapsulations. IPv6 datagrams are sent as IPv4 packets. On the destination end, the hosts are updated to IPv6 protocol and will be able to de-capsulate the packets. (John J. Amoss, 2007)
This transition mechanism does not require to change the existing IPv4 network, rather it use encapsulation to transit to the IPv6 network.
In this mechanism, a tunneling method connecting routers of the organization will be used along with the encapsulation schemes. On the originating host, the edge router will be placed. Another edge router on the destination host will be responsible for the de-capsulation. (Raicu & Zeadally, 2003)
There will be a tunnel between the edge routers at two ends. Again there will be two protocol stacks of IPv4/ IPv6 at two ends. These stacks will be supported by the hosts at both ends. Again, the source will encapsulate the packets, that will flow through the tunnel and the destination will de-capsulate the packets.
Following picture illustrates the idea.
The dual stacks at the both ends are needed to be supported by the edge routers.
IPv6 provides better QoS and Security compared to the same in IPv4.
IPv6 protocol helps in identifying payload that are time sensitive or not. A network can have two types of these packets. It helps in reducing the time in retransmission. IPv6 helps in setting priorities for data transmissions that provide low latency. Applications can select from the priority list as per requirement.
A source of significant delay in packet transmission is fragmentation of packets. In IPv6 fragmentation is handled in different way. There is a negotiation between the source and the destination devices about the maximum size of the payload and other parameters are adjusted accordingly.
It reduces latency and fragmentation significantly thus helps in better utilization of the network resources. There is QoS implementations on each of the networking device.
On the other hand, security of IPv6 protocol is more stringent than the same in the IPv4 protocol. IPSec is an important part of the security mechanisms in IPv6. End to end security is ensured in IPv6. (Li, Jinmei, & Shima, 2010)
Conclusion
In this report IPv6 and different aspects of IPv6 implementation have been discussed. There is a brief description of IPv6 along with discussion on benefits and drawbacks of IPv6, transition mechanisms, QoS and security etc. have been also discussed.
The aim of this report is to provide information of VoIP and MIP as requested by the TCS Ltd. The organization wants to implement these protocols and technologies for their employees. The organization wants to focus on the reduction of operational cost and modifying efficiency of network.
VoIP or Voice over IP is a technology that helps a group of people to deliver voice and multimedia based communication over IP based networks like Internet. It is also called IP telephony.
It supports services like voice communication, SMS, fax etc. over the Internet unlike traditional telephony system, it does not use circuit switching. Rather internet telephony or VoIP uses packet switching networks and packetization of data. An example of VoIP is Skype. (Porter, 2006)
There are underlying technologies like session control, signaling control, setting up the call, tearing down the call etc. There are special medial delivery protocols to encode audio, video etc. as digital and streaming data.
VoIP can be used by computers, laptops, smart phones etc. SMS service is available over WiFi or 3G connections. (Goode, 2002)
Quality of Service or QoS of VoIP has several issues. VoIP is implemented over the Ip networks. IP networks are best effort networks and there may be loss of data, untimely deliver, latency related problem etc.
VoIP will use time sensitive communication data. There is no provision of identifying and handling time sensitive data. Network traffic is handled by a first come first serve basis. There is no way to control fixed delays etc.
The end points of a VoIP communication path may have to wait for the completion of the transmission of packets from one end to other, then one end will be able to send more data.
Security is another consideration of VoIP. There are risks of DoS attacks, stealing of information, eavesdropping etc. There are other technical consideration related to security. For example, VoIP traffic also passes through the firewalls, NATs etc. so, there are chances that communication may get blocked. Encryption is always not supported by VoIP. (Wallingford, 2005)
Some of the security measurements and protocols available for the VoIP are, SRTP or Secure Real time Transport Protocol. Also there are implementation of IPSec for the point to point communications.
MIP or Mobile IP is based on the idea of mobile computing and mobility of devices in a network. It helps a mobile device to keep its IP address same while moving around networks. A mobile node is allowed to have two types of address a care of address and a home address. The care of address changes whenever it moves to some other network, on the other hand the home address is remained same.
Thus the computing activities based on the IP addresses are not hampered even there is a change in the network. (Raab, 2007)
There are several security and QoS considerations. Most of the times mobile nodes use wireless connectivity options. These links are highly susceptible to vulnerabilities and information security risks. The risks may be active replay attacks, eavesdropping etc.
These vulnerabilities cannot be eliminated. But use of encryption etc. can help. Tunneling used in MIP has some serious vulnerability. Thus authentication is always needed here. It also used ARP in case of tunneling. But it is hard to implement authentication for ARP. Thus, there will be some inherent vulnerability. (James, 2008)
Conclusion
In this report VoIP and MIP has been discussed. There is discussion on what are VoIP, MIP along with security, QoS issues and how enterprise networks are using those.
References
Ahmed, A., Madani, H., & Siddiqui, T. (2010). VoIP Performance Management and Optimization. Cisco Press.
Ahson, S. A., & Ilyas, M. (2008). VoIP Handbook. CRC Press.
Alani, M. M. (2014). Guide to OSI and TCP/IP Models. Springer.
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Blank, A. G. (2006). TCP/IP JumpStart. John Wiley & Sons.
Comer, D. (2006). Internetworking with TCP/IP: Principles, protocols, and architecture. Prentice Hall.
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Goralski, W. (2009). The Illustrated Network. Morgan Kaufmann.
Graziani, R. (2012). IPv6 Fundamentals. Cisco Press.
Hagen, S. (2014). IPv6 Essentials. O’Reilly Media, Inc.
Held, G. (2002). The ABCs of TCP/IP. CRC Press.
James, S. (2008). Mobile Ip: The Internet Unplugged. Pearson .
John J. Amoss, D. M. (2007). Handbook of IPv4 to IPv6 Transition. CRC Press.
Johnson, D., Perkins, C., & Arkko, J. (2004). Mobility support in IPv6.
Karas, J., & Peschke, R. (2002). TCP/IP Tutorial and Technical Overview. Prentice Hall PTR.
Kozierok, C. M. (2005). The TCP/IP Guide. No Starch Press.
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Loshin, P. (2004). IPv6. Morgan Kaufmann.
Mondal, A. S. (2012). Mobile IP. Springer .
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Perkins, C. E. (2005). Mobile IP. Pearson .
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Raab, S. (2007). Mobile Ip Technology And Applications. Pearson .
Raicu, I., & Zeadally, S. (2003). Evaluating IPv4 to IPv6 Transition Mechanisms. IEEE.
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