A Network Technologies And Network Control Mechanisms Computer Science Essay

A span should be able to link LANs utilizing different protocols at the informations nexus bed, such as Ethernet LAN to a radio LAN. Data bed references are used in order for a span to be able to route informations. Therefore, Bridgess make usage of MAC reference to send on the information. If a specific reference is non found in the bridging tabular array, the information is sent to all hosts found on the web. This is called crystalline bridging. If the reference is known and found in the bridging tabular array, it makes usage of beginning routing bridging in order to present the information to the right finish.

Beginning: ( FreeWiMAXInfo, n.d. )

However, there are many issues which are of significance when bridging connexions between different LANs. One of the chief issues is that different types of LANs such as Ethernet 802.3 and Wireless 802.11 contain different degrees of security. In fact, Ethernet 802.3 does non hold link layer encoding while in Wireless 802.11, link layer encoding is provided. This issue will hold a great impact when information is transmitted from the above different LANs over a span. This is because the security provided by Wireless 802.11 web will non be compatible with Ethernet 802.3 web. In fact, today, routers are being used to link different types of LANs together. On the other manus, Bridgess are now being used to link LANs of the same type together.

Beginning: ( Tanenbaum, 2003 ) ( Pg. 242 )

Another issue which is significance when bridging connexions between different LANs is the information rate. Different types of LANs might hold different types of information rates. If a LAN is directing informations at bigger sum of velocity that the other LAN can manage via a span, the span will hold to buffer the received informations, seeking non to travel out of memory. This will ensue that span will non be able to manage the standard informations every bit fast as they received.

Beginning: ( Tanenbaum, 2003 ) ( Pg. 241 )

Another major issue is that different types of LANs have different maximal frame lengths. Different frame lengths can do several jobs and there is no specific solution for this job. In fact, frames are discarded if frames size is excessively big to be forwarded.

Beginning: ( Tanenbaum, 2003 ) ( Pg. 242 )

Q2

Wireless transmittals by and large make usage of cellular service countries. Below, there is an illustration of a cell form with a frequency-reuse factor of 3.

Frequency reuse is a techniques used to better capacity and efficiency in communications systems. This technique makes usage of frequences and channels. Wireless systems are doing usage of this technique to partition an RF radiating cell into sections of a cell.

Beginning: ( Javvin web director & A ; security, n.d. )

In the above illustration, a set is divided into 3 sets which can hold an equal bandwidth and the three subaa‚¬A?bands are reused in an alternating manner. aa‚¬A“No neighboring cells have the same frequence in this constellation ensuing in it being the bunch with the least figure of cells that is provides practical frequence reuse.aa‚¬A?

Beginning: ( Abu-Al-Saud, n.d. )

There is no existent reply of which is better to utilize whether low reuse factor or high reuse factor. It all depends on what the existent demands are whether the geographical country is big or little. For illustration if one needs less intervention, hence, high reuse factor should be used. On the other manus if one needs higher capacity of the web, low reuse factor should be used.

Beginning: ( Wireless Information Transmission System Lab, n.d. )

P4.2

Q1

UDP is a message-oriented protocol while TCP is a byte-oriented protocol. Whilst TCP guarantees bringing of informations by doing usage of 3-way manus shingle, UDP does non vouch informations bringing. However, UDP is faster and is chiefly used for voice cyclosis.

Beginning: ( Laynetworks – Comparative analysis – TCP – UDP, n.d. )

If an application needs to protect the boundaries of its message, UDP should be used. This is because UDP preserves message boundaries which are set by the transmitter and receiving system. Sender can direct packages which contains informations size smaller than the MTU size, without the demand of atomization. However, if the package size is larger than the MTU size, the information has to be fragmented. If transmitter is called twice with sizes of 500 bytes and 1000 bytes severally, the two packages will be sent. When both fragmented packages arrive to finish with the sizes of 100 bytes and 200 bytes, the first call will return the first 100 bytes of the 500 bytes package, whereas the staying bytes are thrown off. The 2nd call will return the first 200 bytes of the 1000 bytes packet, whereas the staying bytes are thrown off.

On the other manus, TCP does non continue message boundaries between sends. In fact if the transmitter is called twice with sizes of 500 bytes and 1000 bytes severally, the whole 1500 bytes will be sent. Keep in head that informations can be split in more packages with a specific information size. Therefore, it is non needfully to direct the two calls in two packages merely.

Beginning: ( On Time – IP Packet Types, n.d. )

Q2

From the undermentioned gaining control, we can see that there is a TCP SYN Flooding onslaught. TCP SYN Flooding onslaught is a specific Denial-of-Service ( DoS ) onslaught which affects hosts which run TCP waiter processes.

This onslaught will impact particularly server procedures which will do them incapable to manage echt petitions from legitimate client applications for TCP connexion. TCP SYN implosion therapy onslaughts are designed to assail services that bind to and listen on a TCP socket.

Beginning: ( RFC 4987, 2007 )

Schemes which are used to relieve TCP SYN Flooding onslaughts

Firewalls and Proxies

A tactic which can be used to relieve this onslaught is the Firewall-based maneuver. This tactic is used to protect hosts from SYN deluging onslaughts. Its construct is to alleviate the connexion constitution processs onto a firewall and proctor all the connexion efforts until they are finished and so they are sent back to the defended hosts via placeholders. With this technique, hosts have non to worry about SYN deluging onslaughts, since firewalls and placeholders are covering with these jobs.

SYN Cache

SYN cache is a technique used to diminish the figure of province that a SYN allocates. Until the connexion is established, the full province allotment is delayed. The terminal hosts contains some secret spots which they choose from the incoming SYN sections which are used for SYN cache execution. These secret spots are hashed together with the IP references and TCP ports of a peculiar section. In order to find the location, this hash value has to be used. These values have certain bound. If the bound has been reached, the first entry is removed. The secret spots will support a host from being attacked. The aggressor is prevented from being able to assail some specific hash values for overruning the hash value bound.

Beginning: ( Wesley, 2006 )