Communication System
The key elements of a data communication system are the source, the transmitter, the transmission system, the receiver and the destination. The source will be used in the generation of the data to be transmitted. The transmitter has a purpose of transforming and encoding the data into signals that can be transmittable for example the transformation from a digital bit stream to the corresponding analogue signal. The transmission system serves the purpose of carrying the data and it can be in terms of a transmission line or a complex network connecting the source and the destination. The receiver will be used for the purpose of accepting the signal transmitted from the transmission system and will convert it into a form that is compatible with the destination device. The destination will then take the incoming data from the receiver
This key elements performs the tasks of transmission system utilization, interfacing and signal generation. It also synchronises the data between receiver and transmitter, exchange management, error detection, recovery, message formatting, security management and network management in the data communication
Overall architecture of the internet
The internet consists of interconnected packet network supporting host computer communication using and single internet protocol. The protocols in the internet include IP, Internet Control Message Protocol and the Internet Group Management Protocol. All internet protocols will use IP as the basic data transport mechanisms. The IP is a connectionless, internetwork service and will provision for addressing fragmentation and reassembly. ICMP will be used for error reporting, first hop-router redirection and flow control. It will also carry out other control and maintenance functions. The IGMP will be used as a mechanism of leaving and joining an IP multicast group by the hosts and the routers .
The internet architecture is basically made up of the protocol layering, networks, router, autonomous system, addressing system, and IP multicasting. The protocol layering can be application layer which can provide services directly to the users. Sample protocols used in the internet are the Telnet for remote login, FTP for file transfer and SMTP for electronic mail delivery. The second layer is the transport layer provide the end-to-end connection in the communication system and can implement TCP or UDP protocols. The next layer is the internet layer which implements IP, ICMP and IGMP protocols in the communication. The last layer of the internet is the link layer that will be used in the direct communication. It will have media connectivity like electrical or optical which will encode and transport the messages .
The second constituent of the internet is the networks which provide packet connection. The networks can be LAN which cover a small geographical areas like ATM or Ethernet. The second one can be WAN which will cover a geographical diverse area and are called the long haul networks.
TCP/IP architecture and explain function of each layer
TCP/IP is a layered communication that has the following layers. It is broken down into application, transport, network, links and physical layers. The application and transport layers are for communication while the network and link layers are for interconnection. The physical layers represents the distance of the communication
The application layers assists people and machine to communicate using well defined protocols like HTTP. A sample is the webpage communication.
The transport layer provides the programming interface to the application layer. In TCP/IP protocols, the transport protocol can be either User Datagram Protocol, UDP, or the Transmission Control Protocol, TCP. The programming interface of the given application layer is called a socket API.
The network layer provides full connectivity in the communication system. It may use intermediate systems like the routers and can be implemented in packet switching in the case of the internet uses.
The link layer will define how several hosts will use the same radio frequency for communication.
The physical layer will transform the given bits and bytes into the electromagnetic waves. It performs the encoding of bits as physical signals.
IEEE 802 reference model
IEEE 802 reference model is used in the development of the MAN and LAN standards. This will involve only the physical and link layer of the OSI model. It will provide a complete standard for carrying IP and currently has incorporated the mobile internet access. The model will be made up of two separate layers that are the Medium Access Control, MAC, and the Logical Link Control layer. The third component in the IEEE 802 reference model is the physical layer. The MAC layer will be used to interface to the physical layer. It will also manage the LAN transmission, frame synchronisation and the error detection modules. The LLC layer will be used in the provision of an interface to higher layers. The physical layer of the IEEE 802 reference model will be used in the specification of the medium of transmission and the given topology, decoding and encoding of the signals and for but reception and transmission. There are various models in the IEEE 802 references for wireless communication and they include the use of 802.2 for CSMA/CD, 802.11 for wireless LAN, 802.16 for Wireless PAN, 802.16 for Wireless MAN, 802.20 for Wireless Mobility, 802.2 for logical link control and 802.21 for handoff. The final part is the 802.1 protocol of bridging and management internetworking .
IPv4 and IPv6
IPv6 is used for the enhancement and is primarily used for the design of the extended address space. It provides a platform for the new internet functionality that is needed in the immediate future and will be used in the provision of flexibility for the expansion and growth of the internet. It has the features of a header, addressing, security, privacy, auto configuration, routing and QoS. It has a 128-buit addressing, supports multicast routing and a simplified header format with some IPv4 fields dropped. It will have an extension on the headers and required authentication and privacy for data integrity. It has an auto-configuration that will be self-configuring, uses DHCPv6 for management. It also supports source routing that supports Source Demand Routing Protocol thus the destination can return packet via same route
For IPv4 there is broadcast while in IPv6, there is no broadcast but instead uses multicast for flexibility. There is uncontrolled fragmentation in IPv4 and only a source can fragment IPv6 since there is a limited size of minimum MTU. IPv6 is an extension headers that supports multiple headers that will include the upper layer. This provides for future enhancement. Also IPv6 supports security encryption, header encryption, sender authentication and privacy that is not permitted in IPv4 .
Operation IP
IP provides the communication between hosts on different kinds of networks for example data-link implementation like Ethernet. It is a connectionless and unreliable delivery service. It is unreliable since there is no guarantee that the packets sent will be delivered. There is no handshaking in the transmission of the packets thus each given packet is very independent of any other packet
IP is a layer 3 network layer protocol that will have addressing information that will enable packets to be routed. It will provide connectionless, through internetwork and will provide fragmentation and reassembly of the given datagrams. IP packet will be described as a version, IP header length, total length, identification and flags. TTL, protocol and header checksum, source address and the destination address. The 32-bit IP address format is grouped into 8-bits at the time and is divided into a host and a network. The IP address classes are A, B, C, D and D .
Digital and analogue information sources
TCP and UDP transport protocol
There are various differences between TCP and UDP transport protocol in the communication system. This include the following:
TCP is a connection oriented protocol, thus a given connection has to be established before any data is transmitted. This is called 3-way handshaking. On the other hand, the UDP is a connectionless protocol thus no connection will need to be established before data is sent. In UDP, data is sent directly over the given network
In TCP Connection, because a connection has to be established before transmission of the data, it takes more time for the data transfer than the UDP connection. The 3-way handshaking will be done for the establishment a connection and then removing the connection .
Data transfer using TCP is reliable than the one using UDP system. TCP is an acknowledgement based system since a connection is established before the transfer is done. In UDP, since connection is not made before transmission, the sender does not know whether the packets actually reached the destination or not.
The header size of the packet in the TCP system is bigger than the UDP header.
TCP supports error checking while UDP does not support error checking.
The transmitted packets are received in the same order that they are sent and thus is very ordered. For UDP, it is not ordered.
Application layer protocols that uses TCP include HTTP, FTP, and Telnet to transmit data. Whereas UDP is used by protocols like VoIP, SNMP and DHCP.
Overview of IEEE 802.1 Q VLAN standard
This utilises VLAN tagging which is defined as a multiple bridged network that allows for transparent sharing of the same physical link without having leakages of the information between the networks. This standard deals with the MAC bridges and Virtual Bridged LANs. This standard has a MAC address identifier followed by a bridge forwarding that will have a destination MAC and a VLAN ID for operation. Then there is the frame filtering for proper forwarding of the outbound ports. This is done through the forwarding of the frames to every port except the reception one. The last step in this standard model is the QoS implementation that is based on priority, drop eligibility and time after the forwarding decision .
This standard also specifies the control plane and the data planes separated by a bridge. The basic bridge tis used to specify the operation in the given steps, used as a description language and the ports within the bridge have their role depending on the components types. In this standard, the network virtualisation is based on data plane and can be Q-in-Q bridging and MAC-in-MAC for provider bridge. It will have mapping of all the virtual networks to each other at the given edges. The QoS is enhanced by the allocation of bandwidth to traffic of the link and coexists with priority and data centre bridging .
BGP and OSPF routing
Border gateway protocol is used to route traffic between autonomous systems. An autonomous system will have a common routing policies. It exchanges routing information for the internet and is the protocol used between Internet Service Providers. When the BGP is used between autonomous systems, it is called External BGP. BGP is a robust routing protocol that achieves high scalability and is the routing protocol employed in the internet. It uses many route parameters called attributes for the definition of the policies and maintenance of a stable routing environment. BGP neighbours will exchange full routing information whenever a TCP connection is established. In case any changes in the routing table occurs, the BGP routers send only those routes that will have changed to the neighbours. BGP routers will not send the periodic update but is used to only advertise the optimal destination path
The Open Shortest Path First, OSPF, is the routing protocol for IP networks. It is developed by the IGP group of the IEFT, Internet Engineering Task Force. It is an open protocol and thus its specification is in the public domain. It is based on the shortest path first algorithm called the Dijkstra algorithm. It is a link-state routing protocol that will use the sending of the link-state advertisement to other routers in the same hierarchical area. The metrics, information on the attached interface and all other variables will be attached to the OSPF link-state advertisement. As the OSPF accumulate the link-state information, they will make use of the shortest path first algorithm for the calculation of the shortest path to each of the nodes .
Functionalities of SMTP
Simple Mail Transfer Protocol is used for the provision of a simple way of transfer of electronic mails between the hosts. It has the roles of the sender and the receiver. The sender establishes the two-way transmission channel using TCP connection to the receiver. The receiver can be a real host or an intermediate host on the path to the real receiver. The SMTP protocol can be modelled as a message transfer agents
The MTA will pass the given mail directly to the receiver by taking direct contact to the receiver host’s MTA. For simple local configuration, the mail is relayed through a relay MTA to hide the individual mail servers.
The commands for the protocols can include HELO, MAIL, DATA, EXPN and SEND. These commands are for sending the mail while others for reply like the 1yz, for positive preliminary reply can be used. The basic sequence of the mail sending sequence starts with the announcement of the receivers name to host, then sender to host and the identification of the source of the message. The sender will then do the identification of the recipient, transmission of the mail then finally transmitting complete sequence code CR/LF. The mal route and time stamp is added to the mail message sent out .
Operation of DNS
The DNS functional elements is the resolver which is simple, recursive thus a very simple query can be used to assemble the whole answer. The server is authoritative and will have a zone file and some implementation can be used as both the resolver and the server roles. It is a lookup service thus simple queries can be used to provide simple answers. It is successful because it is simple, clean and can record resources. It has a Time To Live that is the maximum Resource Record Set that can be cached by a non-authoritative servers .
The DNS protocol on wire can be UDP for transport and retransmission that sends a timed-out-query. The data operation in the DNS is sync using information in SOA during DNS zone loading. There will also have DNS cache that will store data for a short time and DNS resolver that start at longest match on the given query. They will have cache when looking for the given data and will follow the delegation until an answer is found .
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