CareerCup

1.) What is difference between IPv4/IPv6 protocol
Ans: IPv4 stands for 4 byte IP address and IPv6 is version 6 for six byte IP address, giving more addresses as networks grow around the world with more machines.
2.)OSI & TCP/IP stack layers + protocols at each layer.
OSI-> Application->Presentation->Session->Transport->Network->Logical->Link Layer
TCP/IP -> App (FTP/HTTP)->Transport(TCP/UDP) -> Network (ICMP/IP/IGMP) -> MAC (802.3/802.16) -> PHY (OFDM/etc)..
3.)What is network/subnet mask. Explain how a host A sends a message/packet to host B
You need to explain which layer takes routing decision and how.
3a.) When both are on same network
Ans: Host has IP routing table which matches destination host IP to be in same subnet, so Host makes an ARP request if it doesnt have MAC address of dest host and then sends packets to the dest IP address.

3b.) When both are on different networks
Ans: Hosts IP routing table would have default gateway IP to which the destination host packets would be routed and so on, until the network with dest host is found, and the above procedure is repeated.

4.) What is TCP/UDP. Difference between both. And explain how TCP handles reliable delievery(explain ACK mechanism), flow control(explain TCP sender's/receiver's window) and congestion control.
Ans: TCP :- Transmission control protocol receiver ACKS every packet to ensure reliable delivery from transmitter. If sender transmits more data than receiver can read flow control is used to rate limit the sender and avoid congestion by reducing the transmission Window. Connection make and break is synced between sender and receiver.
UDP:- User datagram protocol:- has lesser overhead compared to TCP and packets are not acknowledged so sender cannot ensure at transport layer if the delivery was successful.

difference between IPv4/IPv6 protocol:
IPV4 is 32 bits while IPV6 is 128bits.
IPV4 IPSec is optional and should be supported externally ,IPV6 IPsec is compulsory.
IPV4 Headers include checksum.not in IPV6.
IPV4 Configured either manually or through DHCP.IPV6 Does not require manual configuration or DHCP.
Header includes options.in IPV6 headers options are supported as extension headers.

Flow control is used to balance the rate at which bits are produced by the sender with the rate at which bits are consumed by the receiver. This matches the speed of a sender with the capabilities of a receiver. Congestion control is used to regulate the rate at which senders generate traffic in order to avoid the over-utilization of the resources available within network. This prevents network congestion which if pronounced, could lead to a network collapse.

what is the difference between IP and IPV6