Digital Telecommunications and Networks - Assignment Example

Executive Summary This report has provided us through knowledge on Hubs – the types, their use and the advance features that they support. The report has discussed two major devices – Modems and Routers – and has highlighted use of each device for gaining Internet connectivity either through wired or wireless medium. It has also discussed the latest advances in the routers manufacturing and has also explained most of the commonly used routing table terminologies. Then the report has focused on the advantages and disadvantages of the Static Routing and Dynamic Routing. Finally, the report has explained the criterions for selecting the specific routing protocol. Contents 1.1Definition of Hubs 4 1.2Types of Hubs 4 2. Intelligent hubs 4 2.1Popularity of Intelligent hubs over the other types of hubs 4 2.2Working Principle of Intelligent Hubs 5 3. Routers and Modems 5 3.1Difference between routers and modems 5 3.2Requirements for a home internet connection 5 4.Advances and trends in router device 6 5.Routing Table Terminology 7 A.Mask: Webopedia (1996) has defined Mask as “A filter that selectively includes or excludes certain values”. To better understand this definition, let’s consider the example of database. When defining a databases field, it is possible to assign a mask that indicates what sort of value the field should hold. Values that do not conform to the mask cannot be entered. 7 B.Network Address: This address serves as a unique identifier for a node or a station in a network and allows computers to send messages to other computers on the network. One of the best known forms of addressing is the Internet Protocol (IP) address. 7 C.Next-hop address: Whenever a data packet passes through a router a hop occurs. For example, if someone is sending data from Asia to America then the delay is must as the data passes through multiple routers and routers also take time to process the packet to the destination. Basically Next-hop address is the address of the next router through which the data packet passes. 7 D.Interface: Interface of a router is basically the medium that we use to connect a router. Few examples are BRI (Basic Rate interface), Serial, and Fast Ethernet 10/100/1000 connections that are used for connecting the router to the WAN or from Router to router or switch. 7 E.Flags: Flag is basically used for advertisement of the router. According to Haberman and Hinden (2008), there are six different types of flags: 7 M - Managed Address Configuration Flag [RFC4861] 7 O - Other Configuration Flag [RFC4861] 7 H - Mobile IPv6 Home Agent Flag [RFC3775] 7 Prf - Router Selection Preferences [RFC4191] 7 P - Neighbor Discovery Proxy Flag [RFC4389] 7 R - Reserved 7 F.Reference Counts: 7 G.Use: 7 6.Advantages and disadvantages of Static vs. Dynamic Routing 8 6.1Advantages 8 6.2Disadvantages 8 7.Criteria for selecting a Routing Protocol 8 According to Ballew (1997), following are the criterion for selecting the best suitable routing protocol: 8 Criteria 1: Model of the Router 8 Hubs 1.1 Definition of Hubs Hubs are a network device which uses to connect one or more computers. It passes the data packet to the destination through broadcasting the packet on each available node. For example, if there are 8 computers attached on an 8 port hub it will amplify and copy the data packet on other available 7 ports as well. On an OSI model, Hub is considered to be a layer one device means physical layer device. Hubs are not preferable for a large network as they do not monitor and control the traffic. 1.2 Types of Hubs A. Active Hub: These hubs, also popularly known as ‘Repeaters’, actually boost the data packet signals in order to make them reach the destination, therefore, they can play important role in case if the network has been implemented over a large geographical area. B. Passive Hub: Passive Hubs are basically the normal operating hubs and unlike Active Hubs, these hubs are not capable of re-generating the signals and therefore, do not amplify the data packets. Due to this limitation, Passive Hubs are only considered to implement small networks with few computers. C. Intelligent Hub: Intelligent Hubs are the most advanced form of hubs. They contain extra features which help in managing the network on a large scale. They can be used instead of a switch and can be a safe choice as compared to Active and Passive Hubs. 2. Intelligent hubs 2.1 Popularity of Intelligent hubs over the other types of hubs Following is the list of extra features and functionalities that makes Intelligent Hubs more popular over other types of hubs: It supports SNMP (Simple Network Management Protocol) through which we can access this hub and monitor its uptime and downtime in case of any power failure. It also supports VLAN (Virtual Local Area Network) which makes the network more manageable. For example, if a computer moves from one location to another within the same VLAN, then there is no need to change the configuration of the network like gateway, subnet mask etc. It can also be used as a bridge between two networks as it is capable to amplify the data transmission, similar to Active Hubs. It allows switching. It supports a number of technologies; for example, WAN, FDDI and Token Ring. 2.2 Working Principle of Intelligent Hubs In Figure 1, we assume that there are four departments and each department’s node is attached to a separate Intelligent Hub in order to implement the VLAN and ensure better management of the users. Since, each department users have their own hub; therefore, the traffic would be very low, hence, resulting in less network congestion. However, it is worth to be noted that hubs cannot manage the traffic. As we can see that all hubs are connected to the backbone routers, therefore, users can even access both the Campus Servers. However, to restrict or limit user’s access to Campus Servers, ACLs (Access Control List) can be defined on the routers. 3. Routers and Modems 3.1 Difference between routers and modems S. No. Router Modem 1 Acts as an interface between two networks. Acts as a bridge between the PC and the ISP. 2 Forwards packets based on IP addresses between ISP’s router and either LAN or single PC. Forwards the packets based on hardware-level MAC addresses between ISP’s router (and the Internet) and the PC. 3 Used for network traffic management. Used for modulating/de-modulating the signals for the transmission of data to telephone exchange. 3.2 Requirements for a home internet connection For Wired Connection: This type of connection can be established by using either of the two – either the router or the modem. A modem can be used by connecting the RJ-11 telephone line in to it. It modulates and de-modulates the analogue and digital signals and sent them to the telephone exchange from where they are redirected to the ISP to provide internet connectivity. Router can also be used for wired connection to the Internet at home and to do so, all what is needed is a public IP through which we can connect to WAN (Internet); however, their use for solely this purpose is not recommended due to their cost and complex configuration. For Wireless Connection: This type of connection can only be established by using the router. One way to provide wireless Internet connectivity is to connect DSL line into the wireless DSL router and all the laptops and desktop PCs, within the certain range, with a wireless LAN card installed will able to use Internet through the wireless DSL router. Another approach for obtaining the wireless Internet connectivity can be through using a new technology called WiMax. 4. Advances and trends in router device The recent advances and current trends of router device are: Capability to operate at high speeds: Shared port adapters are integrated in Cisco state-of-the-art Routers for controlling voice, video and data experience. They minimize the lagging and congestion while operating at very high link speeds of above 500 Gbps. Support of VoD (Video on Demand): User can now watch the video or hear the audio real time and can even download them on a computer. Support of MPLS (Multi Protocol Label Switching): Data packets are tagged with labels in MPLS and are transmitted on a very high speed not worrying much about which data they are carrying. Integrated session border control for VOIP (Voice Over IP): It controls the signaling and maintains the quality for the transmission of VOIP transmissions. Integration of video call admission control: It prevents the real time data transmission from being congested as it rejects the request if there is no sufficient downstream or upstream which is required for the transmission. It can help to prioritize the traffic on the basis of their importance from the organization’s perspective. 5. Routing Table Terminology A. Mask: Webopedia (1996) has defined Mask as “A filter that selectively includes or excludes certain values”. To better understand this definition, let’s consider the example of database. When defining a databases field, it is possible to assign a mask that indicates what sort of value the field should hold. Values that do not conform to the mask cannot be entered. B. Network Address: This address serves as a unique identifier for a node or a station in a network and allows computers to send messages to other computers on the network. One of the best known forms of addressing is the Internet Protocol (IP) address. C. Next-hop address: Whenever a data packet passes through a router a hop occurs. For example, if someone is sending data from Asia to America then the delay is must as the data passes through multiple routers and routers also take time to process the packet to the destination. Basically Next-hop address is the address of the next router through which the data packet passes. D. Interface: Interface of a router is basically the medium that we use to connect a router. Few examples are BRI (Basic Rate interface), Serial, and Fast Ethernet 10/100/1000 connections that are used for connecting the router to the WAN or from Router to router or switch. E. Flags: Flag is basically used for advertisement of the router. According to Haberman and Hinden (2008), there are six different types of flags: M - Managed Address Configuration Flag [RFC4861] O - Other Configuration Flag [RFC4861] H - Mobile IPv6 Home Agent Flag [RFC3775] Prf - Router Selection Preferences [RFC4191] P - Neighbor Discovery Proxy Flag [RFC4389] R - Reserved F. Reference Counts: G. Use: 6. Advantages and disadvantages of Static vs. Dynamic Routing 6.1 Advantages S. No. Static Routing Dynamic Routing 1 Suitable for small networks. Suitable for large networks. 2 Routes are defined manually in the routers which are easy to manage and remember. Ensures the reliable delivery of data by providing an alternative path for transferring in case if the primary link becomes unavailable. 3 Needs to be defined only once in the ACL of the router which is easy and simple. Data transmission is robust. 6.2 Disadvantages S. No. Static Routing Dynamic Routing 1 Not suitable for large networks. Not suitable for small networks. 2 In case of failure, there is no alternative path for transferring data. Requires more processing power as the routing information update intervals are shorter 3 Not fault-tolerant Choosing the best alternative route is in the hand of routing protocol; the network admin cannot edit the path nor do anything from his own. 7. Criteria for selecting a Routing Protocol According to Ballew (1997), following are the criterion for selecting the best suitable routing protocol: Criteria 1: Model of the Router Explanation: First factor will be the model of the router which might be provided to us by the vendor or existing hardware. We have to check which routing protocols it supports. What are the interface and how many interfaces it provides? We have to also see the requirements of the company. Interface also depends which type of information will flow to and from the organization. Bandwidth also plays a very important role. Criteria 2: Hardware of the Router Explanation: How the current router hardware will support the emerging trends of the technology. How easy will be the changes to be implemented taking very less time for updating the current network IP sub netting scheme etc. The router must support the emerging trends of technology because to make the network more secure for the upcoming threats and to secure the organization network. Criteria 3: Number of end users Explanation: The next factor will be the end users. The number users will decide whether to do VLSM sub netting. Routing protocol must support VLSM sub netting. We must also consider that the employees will increase by the time passes and IP requirements will also increase. To consider the fact that we only have limited public IP addresses we have to do VLSM (Variable Length Subnet Masking) to overcome this issue. Criteria 4: Criticality of the applications Explanation: What will be the critical systems and will the organization afford the downtime of these systems? If no then we have to implement dynamic routing scheme using smart routing protocol. There are critical live application for downtime cannot be afforded at all. If the primary link goes down there should be alternative paths which may replace it and make the system live once again. Criteria 5: Support for multiple vendors Explanation: If there are multiple vendors providing different brands of devices and routers than we must consider the open standard, this fact must be considered as we all know there are many vendors of network devices and we have to manage our network by making standards for protocols, network devices models so that there must be no complexity for configuring the routers and the configuration at client end. Criteria 6: Type of Information Explanation: The routing protocol selection also depends on the type of information passes between different sites of the organization. The information might need to be encrypted using encryption algorithms as data might be confidential. If the organization does not have a hardware based firewall, then the network administrator can suggest for a firewall based router to make the network more secure and robust. References Ballew, S 1997, Managing IP Networks with Cisco Routers, viewed 7 May 2009, http://oreilly.com/catalog/cisco/chapter/ch05.html#28417 Haberman, B & Hinden, R 2008, RFC5175 - IPv6 Router Advertisement Flags Option, viewed 7 May 2009, http://www.faqs.org/rfcs/rfc5175.html Webopedia 1996, mask, viewed 7 May 2009, http://webopedia.com/TERM/M/mask.html Read More