Question

What are the layers of the TCP/IP protocol stack, the function, protocols and PDU of each layer

What is the difference of throughput and bandwidth?

Calculate throughput, transmission, propagation and queuing and error checking delays.

Calculate RTT’s and total delays

What are three types of transmissions?

Which services would use TCP? UDP?

Explain how cookies and the website backend database work,

Identify parts of a http send/response messages

Explain the differences between TCP and UDP.

What is the difference between network core and network edge?

What is the difference between Go Back N and Selective Repeat?

What are the problems with Stop and Wait?

Under what conditions does P2P faster than Client/Server when there are multiple clients and peers?

How does web caching reduce the latency for web requests?

How is it that web caches avoid the problem of stale wev pages(pages that our out of date)

How can the local DNS server reduce network congestion and delays when accessing a website.

Identify the different DNS Resource Records.

Describe how an email message from Alice gets to Francis.

What are the different types of DNS query? Describe difference between iterated and recursive?

What does it mean to “maintain the state.”

How does encapsulation work at the transport layer? What happens to the packet from the sender to the receiver?

Answer 1

Q1)Different layers of TCP/IP protocol suite are :-

1. Application layer-

• Top most layer.
• Equivalent to Application, Presentation and Session layer of OSI model.
• Acts as an interface between the application programs
• Capable of performing features of Application, Presentation and Session layer of OSI model.
• Protocols like SMTP, HTTP, HTTPS, FTP ,NTP , SSH, Telnet SNMP etc all works on this layer
• Protocol Data Unit (PDU) at this layer is data .

2. Host-to-Host layer

• Equivalent to transport layer of OSI model.
• Responsible for delivery of data
• Depends which type of protocol is use -TCP or UDP

1. If reliable delivery of data is needed then TCP will be used
2. If fast delivery, without reliability,is needed then UDP will be used

• TCP and UDP are the protocols used in this layer.
• Protocol Data Unit (PDU) at this layer is Segment.

3. Internet layer

• Equivalent to Network layer of OSI model
• Logical addressing and routing is performed at this layer using IP address of a device.
• Routers forward the packet on the basis of IP addresses of device at this layer.
• IP is the most important protocol at this layer
• ICMP, IGMP are the protocols works at this layer.
• PDU at this layer is Packet.

4. Network Access layer

• Equivalent to Data link layer and Physical layer of OSI model.
• Hardware addressing is done at this layer.
• Defines protocols for physical transmission of data
• Ethernet is the most important protocol used at this layer.
• Fast Ethernet, Token Ring and FDDI are other protocols at this layer.
• PDU at this layer is called frame.

Q2) Bandwidth is the amount of data that can be transferred on a given time .It is measured in bits per seconds

Throughput is the actual amount of data transferred at a given amount of time ,over a communication channel. If throughput is higher than the network system is working properly.Throughput can be reduced by certain factors like latency, data loss etc.

Q3) Transmission delay is the amount of time required to put all the bits ,to be transferred, on to the wire

Transmission delay= Data Size/ Bandwidth

Therefore it depends on the size of the data to be transmitted and bandwidth.

Propogation delay is the time required to reach first bit from sender to receiver.

Propogation delay=Distance /transmission speed

Therefore,it depends upon the distance to be travelled and the transmission speed.

Processing delays are the time required to process the data by the router. It should be lower for faster transmission.

Queuing delay is time between the originator generates a signal that it has send all the data and receiver's signal that it has received all the data.It is caused by originating switch,intermediate switch or the receiver switch

Queuing delay=( (N-1)*L/2R)

Where N= number of packets

L=Size of packet

R= bandwidth

Q4) Total delay =( transmission time + propogation delay+processing delay + queuing delay)

RTT is the total time taken to signal to be sent and the acknowledgement to be received.

Q5) There are 3 types of transmission modes:-

• Simplex mode -In this mode,data can be sent in one direction only.e.g-T.V broadcasting
• Half duplex- In this mode,data can be sent in both directions but only one direction at a time .e.g- walkie-talkie
• Full duplex- In this mode, data can be send in both directions at a time .e.g- Telephone communication.