Packet Switching and Advance Techniques used for data transfer.

1.Analyze packet switching techniques with respect to:

· Delay

· Reliability

· Data transmission

· Implementation

· Error handling

Ans:

Packet Switching transmits data across digital networks by breaking it down into blocks or packets for more efficient transfer using various network devices. Each time one device sends a file to another, it breaks the file down into packets so that it can determine the most efficient route for sending the data across the network at that time. The network devices can then route the packets to the destination where the receiving device reassembles them for use.

DELAYS:

· Transmission Delay :
Time taken to put a packet onto link. In other words, it is simply time required to put data bits on the wire/communication medium. It depends on length of packet and bandwidth of network.

Transmission Delay = Data size / bandwidth = (L/B) second

· Propagation delay :
Time taken by the first bit to travel from sender to receiver end of the link. In other words, it is simply the time required for bits to reach the destination from the start point. Factors on which Propagation delay depends are Distance and propagation speed.

Propagation delay = distance/transmission speed = d/s

· Queuing Delay :
Queuing delay is the time a job waits in a queue until it can be executed. It depends on congestion. It is the time difference between when the packet arrived Destination and when the packet data was processed or executed. It may be caused by mainly three reasons i.e. originating switches, intermediate switches or call receiver servicing switches.

· Processing Delay :
Processing delay is the time it takes routers to process the packet header. Processing of packets helps in detecting bit-level errors that occur during transmission of a packet to the destination. Processing delays in high-speed routers are typically on the order of microseconds or less.
In simple words, it is just the time taken to process packets.

RELIABILITY:

A reliable service is one that notifies the user if delivery fails. In computer networking, a reliable protocol is a communication protocol that notifies the sender whether or not the delivery of data to intended recipients was successful. Reliable messaging is the concept of message passing across an unreliable infrastructure whilst being able to make certain guarantees about the successful transmission of the messages. For example, that if the message is delivered, it is delivered at most once, or that all messages successfully delivered arrive in a particular order.

And now in case of packet switching Reliability is related to packets that packets had reached at the destination correctly or any packet is missing. In packet switching techniques missing packets are identified at the destination and then the it sends message to sender to retransfer those packets.This technique is very efficient in data transmission.

DATA TRANSMISSION:

Packet switching is a method of data transfer where the data is broken into small pieces of variable lengths and then transmitted to the network line. Broken pieces of data are called as packets. After receiving those broken data or packets, all are reassembled at the destination and thus making a complete file. Due to this method, the data gets transferred fast and in an efficient manner. In this method, no pre-setup or resource reservation is required like circuit switching method.

This method use Store and Forward techniques. So each hop will store the packet first and then forward the packets to the next host destination. Each packet contains control information, source address and destination address. Due to this packets can use any route or paths in an existing network.

IMPLEMENTATION:

In packet switching information for forwarding traffic is contained in the destination address of every datagram or packet.Similar to how you would write a letter and specify the destination where you want to send letter and that letter might went its way through multiple intermediate post offices en-route to recipient ,packet switching works much the same way.So how does packet switching enable sharing.Just as if you are sending a letter ,many senders can send over same network at the same time.Effectively sharing the resources in the network .A similar phenomenon occurs in packet switching ,when multiple senders send network traffic or packets over the same set of shared network links.

ERROR HANDLING:

Packets contain checksum, parity bits or cyclic redundancy checks. These each detect errors that may occur during transmission.

A preliminary calculation is performed before the packet is sent, at the transmitter. Once the packet is received, the checksum is recalculated and compared with the first calculation that is contained in the packet. If any discrepancies are noticed the packet can be corrected or discarded. Any discarded information is known as packet loss and will be dealt with by the network protocol.

2.Is internet using packet switching as a default transmission technique?is there any advanced option available to communicate data on internet?Explain with example.

Ans: Packet switching is used in the Internet and most local area networks. The Internet is implemented by the Internet Protocol Suite using a variety of Link Layer technologies. For example, Ethernet and Frame Relay are common.

Internet uses packet switching to transmit data. technique used for sending data over Internet. Messages are separated into small units (packets) which contain info about sender and receiver, messages data, and how to reassemble packets.

But with time and necessity more advancement in this field new techniques should be available.

MPLS:

Multiprotocol Label Switching (MPLS) is a protocol-agnostic routing technique designed to speed up and shape traffic flows across enterprise wide area and service provider networks.

MPLS allows most data packets to be forwarded at Layer 2 — the switching level — of the Open Systems Interconnection (OSI) model, rather than having to be passed up to Layer 3 — the routing level. For this reason, it is often informally described as operating at Layer 2.5.

In an MPLS network, the first router to receive a packet determines the packet’s entire route upfront, the identity of which is quickly conveyed to subsequent routers using a label in the packet header.

While router hardware has improved exponentially since MPLS was first developed — somewhat diminishing its significance as a more efficient traffic management technology — it remains important and popular due to its various other benefits, particularly security, flexibility and MPLS traffic engineering.

How an MPLS network works:

In an MPLS network, each packet gets labeled on entry into the service provider’s network by the ingress router, also known as the label edge router (LER). This is also the router that decides the LSP the packet will take until it reaches its destination address.

All the subsequent label-switching routers (LSRs) perform packet forwarding based only on those MPLS labels — they never look as far as the IP header. Finally, the egress router removes the labels and forwards the original IP packet toward its final destination.

When an LSR receives a packet, it performs one or more of the following actions:

Push: Adds a label. This is typically performed by the ingress router.

Swap: Replaces a label. This is usually performed by LSRs between the ingress and egress routers.

Pop: Removes a label. This is most often done by the egress router.