What are the different memories used in a CISCO router?

- NVRAM stores the startup configuration file

- DRAM stores the configuration file that is being executed

- Flash Memory – stores the Cisco IOS.

How does RIP differ from IGRP?

RIP relies on the number of hops in order to determine the best route to a network. On the other hand, IGRP takes consideration many factors before it decides the best route to take, such as bandwidth, reliability, MTU and hop count.

What is the role of the LLC sublayer?

The LLC sublayer, short for Logical Link Control, can provide optional services to an application developer. One option is to provide flow control to the Network layer by using stop/start codes. The LLC can also provide error correction.

Does a bridge divide a network into smaller segments?

Not really. What a bridge actually does is to take the large network and filter it, without changing the size of the network.

What is a Window in networking terms?

A Window refers to the number of segments that is allowed to be sent from source to destination before an acknowledgement is sent back.

When does network congestion occur?

Network congestion occurs when too many users are trying to use the same bandwidth. This is especially true in big networks that do not resort to network segmentation.

What is the key advantage of using switches?

When a switch receives a signal, it creates a frame out of the bits that was extracted from that signal. With this process, it gains access and reads the destination address, after which it forwards that frame to the appropriate port. This is a very efficient means of data transmission, instead of broadcasting it on all ports.

What is the purpose of the Data Link?

The job of the Data Link layer is to check messages are sent to the right device. Another function of this layer is framing.

What is Routing?

Routing is the process of finding a path on which data can pass from source to destination. Routing is done by a device called routers, which are network layer devices.

Computer network topologies

There are different network topologies that we can use to connect network devices to each other.

Bus network topology

In this network topology, we use a bus – usually a copper cable or an optical fiber cable to connect between network devices. This bus connects to the network devices through connectors that exit from it.

Ring network topology

In the ring topology, we connect every network device to its neighbor devices;in order to make all thenetwork devices form a ring.

Mesh network topology

In the full mesh topology, we connect every network device to all the network devices that exists in the network.The advantage of this topology is the very high redundancy that it has Very high redundancy means that, if a path to a certain device became unavailable, there still an alternative path that can be used to reach this device.

The disadvantage of the full mesh topology is that, it requires extensive number of connections between the devices.

Partial mesh topology

In the partial mesh topology, every device is connected to some of the devices that exist in its 

network, not all devices like the full mesh topology.

The partial mesh topology requires fewer connections than the full mesh topology, which is 

considered an advantage. However, its redundancy is less than the full mesh topology.

Tree network topology

device B’ is a central device, called the ‘hub device’, while ‘device A’ and ‘device C’ are called the  ‘spoke devices’.

In this topology, the spoke devices talk to each other through the hub device.

The disadvantage of this topology is that, if the hub device became unavailable for any reason, the

communication between spoke devices will not be possible. This is called ‘single point of failure’.

Star network topology

This is the most widely used network topology.

In this topology, we use a central networking device to connect between all the end devices.

Hybrid network topology

This topology contains more than one of the previously illustrated network topologies connected to  each other.

An example of this topology is connecting a star network topology to a ring network topology.

IPV4 ADDRESSING

IP address are of two types-
Public and private.
PUBLIC IP ADDRESS- They are meant to routable (used for internet), they are registered and paid too. 
PRIVATE IP ADDRESS- They are meant to non-routable, unregistered and available free of cost.
IP addresses are divided into five classes—

A to E
Private IP addresses are declared-
Range of Private IP addresses—

1. A-  10.0.0.0 to 10.255.255.255
   
2. B-  172.16.0.0 to 172.31.255.255
   
3. C-  192.168.0.0 to 192.168.255.255
   
4. D-  Used as multicast address only
   
5. E-  Reserved for research and documentation. 
   
   
   The range of first octet (public +private)—
   A- 1-126 
   B- 128-191 
   C- 192-223 
   D- 224-239 
   E- 240-255
   Note- Usable IP address classes are A to C. DEFAULT SUBNET MASKS
   A- 255.0.0.0
   B- 255.255.0.0 
   C- 255.255.255.0
   Subnet masks are assigned to with IP address of its classes, they are very important. 

AAA

 Authentication, Authorization, and Accounting: A system developed by Cisco to provide network security. 

A&B bit signaling

 Used in T1 transmission facilities and sometimes called “24th channel signaling.” Each of the 24 T1 subchannels in this procedure uses one bit of every sixth frame to send supervisory signaling information. 

100BaseTX

Based on the IEEE 802.3u standard, 100BaseTX is the 100Mbps baseband Fast Ethernet specification that uses two pairs of UTP or STP wiring. The first pair of wires receives data; the second pair sends data. To ensure correct signal timing, a 100BaseTX segment cannot be longer than 100 meters.

100BaseT

Based on the IEEE 802.3u standard, 100BaseT is the Fast Ethernet specification of 100Mbps baseband that uses UTP wiring. 100BaseT sends link pulses (containing more information than those used in 10BaseT) over the network when no traffic is present. 

10BaseT

Part of the original IEEE 802.3 standard, 10BaseT is the Ethernet specification of 10Mbps baseband that uses two pairs of twisted-pair, category 3, 4, or 5 cabling—using one pair to send data and the other to receive. 10BaseT has a distance limit of about 100 meters per segment.

End-to-End Communication

• Connection Less Transmission

• UDP is used

• Not reliable

• Faster

• Connection Oriented Transmission

• TCP or SPX is used

• Reliable

• Slower

Connection Oriented Protocol

•        These protocols relies on Acknowledgement.

•        Positive acknowledgement means data has been received.

•        Negative acknowledgement means data is lost no further

data is sent till positive acknowledgement is received.

•        It is slow but Reliable.

•        E.g.. TCP and SPX

Connection Less Protocol

• They do not provide acknowledgement neither sequence numbers.

• It is faster but not reliable

• E.g.. UDP and IPX

Segmentation

• This is a mechanism wherein the data is divided into

multiple segments and sent over the network.

• By doing this different segments can use different links for

traveling across the network.

• If one segment is lost the only segment is required to be

re-sent and not the entire data.

• Once all segments reach to the destination the received

segments have to be sequenced back, which is also done at

transport layer.