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1.a How network managers benefit from network management tools
1.b Role of SMI in network management
2.a Advantages of using UDP as a transport-layer protocol
2.b Application-layer protocols employing UDP as the transport-layer
2.c UDP and streaming multimedia applications
3.a IP assignment by DHCP to clients
3.b Router components
3.c IPv4 vs. IPV6
1.a How network managers benefit from network management tools
It is the responsibility of a network manager to plan, design, implement, admnister and
manage a computer network. Depending on the requirements they may have to deal with
various types of scenarios.
Mainly,there are four types of networks and others may arise from different combinations
of these. They are:
i) Local area network (LAN): local area networks are a collection of computers interconnected within the framework of a building etc. certain limitations apply as far as distance is concerned.
ii) Metropolitan area network (MAN): metropolitan area networks are simply two or more LANs linked together for information exchange etc. within a city or town
iii) Wide area network (WAN) : wide area networks are formed by connecting LANs and MANs to work in a much larger area e.g. within many cities or even a whole country.
iv) Global area network (GAN) -a framework of inter-connected networks spreading across the globe.
All the above network types may be implemented using a number of technologies depending on the requirements.
Network Management Tools are being used extensively these days at every stage in all types of networks .It may not be all wrong to say that network managers today feel handicapped without them.The more a setup becomes reliant on its data network the more important is the proper management of this network for its smooth operation. Network Management tools help network managers in many different ways.They have made it possible to monitor connectivity,data I/O,errors,system failures which in turn help problem diagnosis,keeping logs,performance monitoring and evaluating.
Network managers benefit from various management tools in different areas of their work some of which are:
Perormance management tools are important because they help network managers monitor and manage the performance of a network system and thus maintain the standard performance level required for the network to provide maximum efficiency possible.A network may consist of different hardware and software components,different protocols and standards being implemented and various technologies and platforms being used.These tools enable managers to harmonize the mutual working of these components and thus improve performance.
It is not unfamiliar in large networks to allocate account quotas for different users and allocate bandwidth usages.The reason for this is to avoid bottlenecks or congestion and allow only as much use of network resource as required or permitted for certain tasks to specific users.There are many accounting management tools available to managers nowadays to achieve such tasks.
Security is one aspect of the the networked world we live in which is becoming more important by the second.The more sensitive the function of a system,as important it is to secure it from any unwanted influence.This is why there are millions of software and hardware tools for network security.The importance of network security in today's world is evident from the fact that large company's hire teams of security experts to monitor and test their networks and certified security specialists are well in demand. Security management tools help network managers in this ever important field.
Fault management tools enable managers to moitor,identify, log and troubleshoot problems that hinder smooth operation of a network.
- This type of management tools are one of the most common and extensively used in the networking field.As a large number of applications are used by network users. Application management tools help managers in achieving this task by prioritizing, providing needed resources and bandwidth etc. to applications. Below is a list and brief introduction of some popular application monitoring tools:
- Alviasprovides free monitoring of HTTP, TCP/IP port, ping, SMTP, web page defacements from multiple networks around the world, besides that H.323.Beacon is a network tool that can be used to measure, qualify and troubleshoot performance of Videoconference sessions both at the and host levels (end-to-end) and a network manager can benefit from this tool and manage in any kind of websites or programming involving video conference calling etc.
- Hobbit Monitor monitors hosts, network services, and anything else that is configured it to do via extensions. Hobbit periodically generates requests to network services For Example - http, ftp, SMTP and so on - and record if the service is responding as expected. Through the use of agents installed on the servers, Network managers can also configure local disk utilization, log files and processes.
- Open SMART (Open Source System Monitoring and Reporting Tool) is a tool to monitor applications with only one agent. A network manager will report all the results to a central monitoring console for displaying and alerting. Open SMART network managers can fix some errors (like not running processes) on their own and Open SMART knows about conditional monitoring (e.g. in a cluster: An application will be monitored only, if that particular file system is available on this cluster node, too).
Apart from these there are many other kinds of management tools that network managers benefit from like bandwidth management, authorization, load balancing, traffic routing, troubleshooting tools, planning and deployment tools etc.
Case I: In my own experience while working for a network services provider there have been many cases where we have greatly benefitted from network management tools. In one certain case in a network of 40 nodes, the network was always getting choked and it was becoming impossible to trace the systems and departments responsible for this. The solution was achieved by using an snmp based third party bandwidth monitoring tools called “toolset” which monitors and displays bandwidth used in different easily understandable visual forms.
The systems responsible for the problem were traced and then given separate controlled Linksys gateways with built-in bandwidth restriction tools to make it impossible for them to use excessive network resources.
Case II: The Advanced Host Monitor is a system management tool that continuously monitors servers' availability and performance. In the event of network errors, Host Monitor will alert the network administrator (or even correct the problem when possible) before problems get seriously out of hand. This helps protect data and reduces the likelihood of costly network failures.
Host Monitor is network administration software; it provides different ways to respond on failed services. Host Monitor can perform tasks that are designed to recover from a failure automatically without any intervention e.g. restart the service, reboot machine and dial-up to the network actions.
An example of a host monitor alert can be when the exchange server of an organization disconnects, or the disk capacity of a critical server reaches its limit. The host monitor tool will then generate alerts and send them to the Network Administrator to work on. In the mean while, it will also be working to recover from the failed service without any human intervention. When some critical service fails Host Monitor may reboot the server. If that does not help, Host Monitor will send e-mail to the on-call technician.
Case III:In a call center, the agents complain that they are getting static voice quality or poor voice quality, the data monitoring tools help the Network Administrator to analyze where the data is being utilized and where it should be utilized. It will also notify the administrator about the bandwidth being used which in turn will show if proper bandwidth is being provided to the call flow. The bandwidth needed for voice over IP is at least 56Kbps, so this tool will help the administrator to negotiate further about the data flow.
1.b Role of SMI in network management
In the early days of networks when the internet in its present form had not yet evolved,managing networks and network devices was not as complex as it is today.However, after the birth of internet in its current form the need for a standard in network management gave birth to the SNMP(simple network management protocol) in 1990.
“SNMP (Simple Network Management Protocol) is the standard management of Internet Protocol (IP)”
The basic components of of a network running SNMP are managed devices, agents and
network management systems.
The core components that the in the working of SNMP are:
Management Information Base (MIB): the MIB consists of variables required for device operation and management.They are extensively used in all network communication. It is essentially a collection of all objects managed by SNMP .All objects are grouped in categories.
Abstract Syntax Notation One (ASN.1): ASN is a standard containing data structures to encode, decode, transmit and represent data over a network. It is SNMP's source of standard rules for describing objects.
Structure of Management Information (SMI): The SMI, an adapted subset of ASN.1, operates in Simple Network Management Protocol (SNMP) to define sets or modules of related managed objects in a Management information base (MIB).
- SMI stands for Structure of Management Information (SMI) .The SMI defines the rules for describing management information.
- SMI comprises the provision for parameters or codes to indicate experimental or private data structures. The data structure is the "Structure and Identification of Management Information for TCP/IP-based Internets" (SMI), and the "Management Information Base for Network Management of TCP/IP-based Internets" (MIB-II).
- SMI specifies how data types are to be used by SNMP.The two main data types defined by SMI are: Simple and Application-wide are defined by SMI.
- The management of hosts and gateways on the Internet is a difficult task and requires a complicated system to secure the data and information that is being transferred over the internet. For this purpose a data structure for such information that is being transferred over the internet has been defined. This data structure can be used with any of the management protocols, like the "Simple Network Management Protocol" (SNMP), or the "Common Management Information Protocol over TCP" (CMOT).
- Until now, network managers have been looking after multivendor storage-area networks (SAN) and have required a series of independent management applications, developed by a number of different dealers and tied to multiple hardware management APIs, to keep their systems running effectively.
The simple network management protocol is basically a framework of rules and information required for all different kinds of devices on a network to be able talk to each other and also understand each other.
2.a Advantages of using UDP as a transport-layer protocol
Although TCP is commonly thought to be better of the two.TCP vs. UDP debate depends on the requirements of the task at hand. Four main advantages of UDP over TCP are:
i) UDP is much more efficient than TCP because it has fewer headers and no acknowledgements.
ii) UDP quickly forms a connection without much negotiation while TCP using a 3-way handshake is not much favoured in applications exchanging low data volumes.
iii) UDP is used in voice communication and games etc. owing to lower latency.A packet that gets through in a TCP connection will still have to wait if the one before it was lost until it is re-transmit causing delay. However, with UDP there is no such issue and thus is preferred for lower latency applications. iv) Although UDP is said to be the less reliable protocol of the two, this can be an advantage if the designers want to implement their own choice and level of error control and reliability into their applications.This would also, to some extent, reduce network constraints on the application.
iv) (Transmission Control Protocol) TCP suffers on multihop wireless routes, managing to deliver minimum amount of packets on destination. Therefore, fewer data packets can be sent over the multihop wireless routes compared to (User datagram protocol) UDP protocol.
2.b Application Layer Protocols using UDP
The Application Layer Protocols using UDP as transport layer are:
a.DNS (Domain Name Service):
The internet domain name service(DNS)uses UDP as its network layer protocol.The reason UDP is preferred over TCP is that unlike TCP,it does not have to perform a three way handshake,send and receive acknowledgements,maintain connection state,care for congestion control and error checksetc.
There is almost no time wasted in communication using UDP. DNS supports a very large number of users and time constraint is important. Reliability, however, is not as critical.If DNS ran over TCP it would be far more slower.This is the main reason DNS uses UDP rather than TCP.
b. TFTP(Trivial File Transfer Protocol):
TFTP uses UDP over TCP as its network layer protocol because it was basically designed for small file transfers and low memory consumption environments. It is also used for booting devices that have no storage media over a network.Without much security or any advanced file transfer and directory listing features unlike FTP,the TFTP protocol makes a good example of an application layer protocol employing UDP.
c.RIP (Router Information Protocol):
The routing information protocol(RIP) is another application layer protocol employing UDP at transport layer.It does not require establishing a connection. Any loss of information can be updated again later as RIP keeps updating router information so reliability is not a critical issue.Because of its simple request/reply structure RIP prefers UDP over TCP.
d.SNMP(Simple Network Management Protocol):
A slightly more complex UDP application is Simple Network Management Protocol (SNMP). It allows applications to assemble information about how various elements of the network are performing, and to control the network by means of commands sent over it rather than by physical configuration of equipment.SNMP's use of UDP avoids the overhead of having to maintain connections between the SNMP manager and each agent as the data contains mainly of requests and simply a reply which contains requested data.
2.c UDP controversial for streaming multimedia
Multimedia applications on the internet nowadays widely use. It is used for all multimedia by VoIP (internet telephony) sites, for audio/video streaming (sites such as youtube etc. are quite popular), audio/video conferencing. In the use of all such applications, if data loss or any sort of disruption occurs, no harm is done as they are not critical applications. The congestion control built in to TCP is not well suited for real time processes. Another reason is that TCP can not be used to multicast whereas the use of UDP bears no such problems. On the other side UDP lacks any kind of congestion control and links may be choked and networks congested bringing performance levels near zero. All these make the use of UDP for streaming multimedia applications controversial at the same time.
2.d Adaptive congestion control in UDP
Congestion control is a technique of controlling data transfer over a connection in order to avoid the network from being congested by all its resources bein used up.
A scheme that could force UDP to use an adaptive congestion control is the streaming of multimedia. User Datagram Protcol does not have any sort of congestion control mechanism built in.If used without any sort of congestion control,the risks of the link being congested and the network efficiency being greatly reduced are evident.The network in such a state can not perform necessary tasks for its operation.This is where an adaptive congestion control can help.If large amount of audio or video data is being transported over UDP in a network without any such control,no audio or video communication can take place.
With the availability of high speed internet,the internet community these days benefits from audio/video conferencing,streaming multimedia and voip.These are only possible if there are adaptive measures of congestion control governing the communication.So such a scheme can give the internet users the following benefits:
i. Improved quality in sound and video applications
iv.lesser load on gateways/routers
3.a Dynamic Host Configuration Protocol (DHCP)
The Dynamic Host Configuration Protocol (DHCP) provides configuration parameters to Internet hosts. DHCP consists of two components: a protocol for delivering host-specific configuration parameters from a DHCP server to a host and a mechanism for allocation of network addresses to hosts.
DHCP is built on a client-server model, where designated DHCP server hosts allocate network addresses and deliver configuration parameters to dynamically configured hosts. Throughout the remainder of this document, the term "server" refers to a host providing initialization parameters through DHCP, and the term "client" refers to a host requesting initialization parameters from a DHCP server.
A host should not act as a DHCP server unless explicitly configured to do so by a system administrator. The diversity of hardware and protocol implementations in the Internet would preclude reliable operation if random hosts were allowed to respond to DHCP requests.
For example, IP requires the setting of many parameters within the protocol implementation software. Because IP can be used on many dissimilar kinds of network hardware, values for those parameters cannot be guessed or assumed to have correct defaults. Also,distributed address allocation schemes depend on a polling/defense
mechanism for discovery of addresses that are already in use. IP hosts may not always be able to defend their network addresses, so that such a distributed address allocation scheme cannot be guaranteed to avoid allocation of duplicate network addresses.
DHCP supports three mechanisms for IP address allocation. In "automatic allocation", DHCP assigns a permanent IP address to a client. In "dynamic allocation", DHCP assigns an IP address to a client for a limited period of time (or until the client explicitly
relinquishes the address). In "manual allocation", a client's IP address is assigned by the network administrator, and DHCP is used simply to convey the assigned address to the client. A particular network will use one or more of these mechanisms, depending on the
policies of the network administrator.
Dynamic allocation is the only one of the three mechanisms that allows automatic reuse of an address that is no longer needed by the client to which it was assigned. Thus, dynamic allocation is particularly useful for assigning an address to a client that will be connected to the network only temporarily or for sharing a limited pool of IP addresses among a group of clients that do not need permanent IP addresses. Dynamic allocation may also be a good choice for assigning an IP address to a new client being permanently
connected to a network where IP addresses are sufficiently scarce that it is important to reclaim them when old clients are retired. Manual allocation allows DHCP to be used to eliminate the error-prone process of manually configuring hosts with IP addresses in
environments where (for whatever reasons) it is desirable to manage IP address assignment outside of the DHCP mechanisms.
b) major components of a router
Generally,a router has four major components:
- Input ports
- Output ports
- Switching fabric
- Router Processor.
- INPUT PORT:
An input port is the point of attachment for a physical link and is the point of entry for incoming packets. Ports are instantiated online cards, which typically support 4, 8, or 16 ports.
- OUTPUT PORT:
The input port performs many functions mainly encapsulation and decapsulation.It also tracks the destination for incoming data packets.
- SWITCHING FABRIC:
The switching fabric interconnects input ports with output ports. If the switching fabric has a bandwidth greater than the sum of the bandwidths of the input ports, then packets are queued only at the outputs, and the router is called an output-queued router.
- THE ROUTER PROCESSOR:
The routing processor participates in routing protocols and creates a forwarding table that is used in packet forwarding. The routing processor computes the forwarding table, implements routing protocols, and runs the software to configure and manage the router. It also handles any packet whose destination address cannot be found in the forwarding table in the line card.
c) Using appropriate diagrams compare the structure of an IPv6 datagram with that of IPv4. Detail TWO advantages of IPv6 over IPv4. (6 Marks)
c) Using appropriate diagrams compare the structure of an IPv6 datagram with that of IPv4. Detail TWO advantages of IPv6 over IPv4.
IPv6 DATAGRAM TAKEN FROM WWW.TCPIPGUIDE.COM
IPv4 DATAGRAM TAKEN FROM WWW.WIKIMEDIA.ORG
COMPARISON OF STRUCTURE OF IPv4 AND IPv6 DATAGRAM:
The difference between IPv4 and IPv6 lies in the following aspects
- Network addresses translation.
- Administrative workload
- Support to mobile devices
TWO ADVANTAGES OF IPv6 OVER IPv4:
- The IPv6 has a simpler format.
- The IPv6 has a basic header with fixed length and zero or more extension headers. This solution presents great flexibility, because each datagram includes only the necessary headers for the corresponding communication