Subnet to the left consists of: Router R1, Wireless router W, PC P, Mobilephone

Question

Subnet to the left consists of:

Router R1,

Wireless router W,

PC P,

Mobilephone M

Subnet to the right consists of:

Router R2,

Ethernet switch E,

(web)server S

In addition, there's a DNS-server D

a) Mobile phone M comes into the network. Which of the following alternatives best describe which processes M must go through to be able to use WiFi-router W to communicate with the internet?

1)Associate with access point, get IP-address and router- and DNS information via DHCP, register its homeaddres through a foreign agent in R1, get new IP-address from DNS-server D

2)Associate with the acces spoint, get the IP-address and router- and DNS-information via DHCP

3)Associate with access point, get IP address and router- and DNS-information via DHCP, register its homeadress through foreign agent in R1

4) Associate with an accesspoint via ALOHA, get IP-address and router- and DNS-infprmation via DNS server D.

b)

Assume that RTT between R1 and D is 150ms, RTT between R1 and R2 is 400ms, link capacity between R1 and R2 is 2Mbit/s both ways, that link between R1 and R2 is 1000 km long and that there is little queue at R1 and R2, that node processing in R1 and R2 is irrelevant and that local networks have little traffic and that transfer cpacity is many times as big as access link R1-R2

We have not communicated with S befoe, but we communicate with other nodes on the internett. We now wish M to download fraom a website S. http-response, which contains whole html-description of website, get space in the IP-datagam equal to 1500byte and html-description does not refer to any other objects. How much time does it take for the browser to start a process with the download until the website can be shown in M's browser?

Alternatives:

1)400ms

2)550ms

3)800ms

4)1100ms

5)950ms

333 333 333.333 CC-49-DE-D0-AB-7E E6-E9-00-17-BB-4B 74-29.9C-E8-FF-55 W: F8-E9-39-71-AB-44 R2 222.222222.222 111.111.111.000 CC-49-DE-DO-AB-7D 222.222.222000 88-82-2F-54140F 4S-BD-D2-C7-56-2A 444 444 444.444 88-B2-2F-54-1A-0E 1A-23-F9-CD-06-9B

Explanation / Answer

a) Associate with access point, get IP address and router- and DNS-information via DHCP, register its homeadress through foreign agent in R1

b)
This is the first communication between M and S thus to get host details of S, M will request DNS server : 150 ms
Send http request to S (R1->R2): 400ms
Send http response to D (R2->R1): 400ms

Time when first byte of response arrives at M = 950ms

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