Q1- What are the data transmission modes ?

Ans- There are three type of transmission modes.

Simplex- It is an oneway communication where only one device can send data and other will recieve data. This type of transmission is done through a single thread of fiber optic cable. That is why we use pair of Fiber Optic Cable . One is for send and another is for recieve..

Half Duplex-

In this type of transmission both devices can send or recieve data but not at a time. Both devices will be able to send or recieve data one by one. If first device is sending data then second device will wait untill first device's transmission complete. Example of halfduplex transmission medium is coaxial cable.

Full Duplex-

In this type of transmission both devices can send or recieve data at a time.Today's Fast Ethernet or Gigabit Ethernet is based on full duplex. We can create full duplex network by using Twisted pair Cable or pair of Fibler Optic Cable.

Q2- What is Ethernet ?

Ans- Ethernet is a LAN standard given by IEEE. It is a most popular standard where data transmission rate is 10 mbps and data is transmitted in frame formate. For addressing of devices in network Ethernet Address (MAC address) is used. There are some advance version of Ethernet --

Fast Ethernet ( 100 Mbps) full duplex

Gigabit Ethernet (1Gbps) full duplex

10 Gigabit Ethernet (10Gbps) full duplex

40 Gigabit Ethernet (40 Gbps) full duplex

Q3-What is different between .pst and .ost ?

Ans- .pst and .ost both are the file extension of microsoft outlook data file. These files contains user's mail. There are two protocols to recieve mails from mail server. 1st is POP and 2nd is IMAP. If we configure email client in automatic mode (smartphones or PC) It automatically configured by using IMAP.

If we configure manually then we can choose POP or IMAP. IMAP does not store data permanently and always access data from mail server when we sync.It does not download attachments automatically on email client computer . It is good for multidivice configuration because all devices works online and sync to each other. When we use IMAP then .ost file is create for mail storage.

When mail is confugured using POP then .pst file is created to store mail. This files contains all inforamation permanently on email client computer. All attchements are downloaded on email client automatically. POP is most used protocol for PCs. We can see all previous mails and can open all attachments even when PC is offline.

Q4- What information should we have to configure outlook (Email Client) in a PC.

Ans- We should have some inforamtion related to email account which are-

1-Email ID

2-Password

3-Incomming mail server name or Address (POP or IMAP server)

4-Outgoing mail server name or Address ( SMTP server)

5-Port number for incomming and outgoing mail servers (POP-995,SMTP-465/587, IMAP-993)

These port numbers are with SSL because most of mails servers are supporting only ssl/tls connection. Which secures connection by encrypting data between mail server and clients.

DNS (Domain Naming System)

Domain Name System is the service which is use to resolve host name to IP and IP to host name. It also provides a hierarchical name space in domain environment. It has many records in a domain . It is most preferred name resolution technology over the TCP/IP network.

DNS Server Types-

1- Primary DNS server-

It is created on a first DNS server in a domain . It may integrated with ADDS or It may be different to ADDS. When we install ADDS and DNS on same server then Active Directory Integrated zone is created.Integrated zone is always made a primary zone. We don't have to create new zone. It has many records like.

• Host records (A, AAAA)- It stores host name and IP address of DNS clients.

• Pointer records ( PTR )- It stores IP address of hosts.

• Name Server Records (NS)- It stores server name on which DNS zone is delegated.

• Mail Exchanger Records (MX)- It stores mail server's record

• CName record (Alia's) - It stores an alternate name for any host

• Service Location (SRV) - It stores records about servers which hosts various services like ftp,http etc.

2- Secondary DNS Server-

Ssecondary DNS server is created for load balancing of primary . It stores all DNS records but has read only permissions . We cannot edit or create any records on Secondary DNS but it is able to resolve all clients queries. It replicates from primary server and updates all records.

3- Stub DNS server-

It is also a type of DNS zone which stores only three DNS records. These records are NS,SOA and Host records. This zone also has read only permission. It updates it's records from primary server.

4- Cache Only DNS server-

It is a type of DNS server which does not have any records but it is able to resolve all clients queries. When it receives any queries it forwards to primary DNS . Primary DNS gives reply to stub. Stub sends result to client and also stores this result in it's cache. If again same query is asked by client the Stub DNS will not forward query to primary .It will resolve from it's cache. There is no security issue in Caching Only DNS server.

There are two Look up Zones-

1- Forward Look up Zone- It is responsible for resolving host name to IP address. It contains all DNS records except PTR record.

2- Reverse Look up Zone- It is responsible for resolving IP address to host name . It stores all records except Host record.