Architectural Internet

Architectural Internet

ARP:-Address Resolution Protocol

Network Layer

Q:-Why ARP Packet are not Encapsulation into IP data grams ?

-Because ARP packets Never Leave LAN.

Q:-Explain in details the need for ARP Protocol?

Before The IP Protocol can deliver a packet form a source HOST to the

Destination HOST. -

It Need to New How to Deliver it to the next HOP first

Q:-What is the size of an ARP request and reply packet?

-The size of an ARP request or reply packet is 28 Bytes.

Q:- in Proxy ARP Routers . if a router receive can an ARP request for HOST on

another network. The router will send an ARP reply message announcing .

-It's Own Hardware (physical) address.

Q:- Explain The Step of ARP Request and reply?

if system A need to Communication with system B it first send an ARP

request Packet to all Host on the network to obtain the physical address of B

but only system B will reply to that massage with an ARP reply packet

stating its physical address.

-solution

a-ARP request is broad cast

b.ARP reply is unicast

Broadcast:-

Unicast :-PTP

Physical Address Data

Link:-

TTL:-Time To Live

No. of Hops Available

Q:-A Host with IP address 130.13.43.10 and physical address 0xb23455102210

Host Packet to send to another host with IP address 130.23.13.15 and physical

address 0XAU6EF45983AB. The two Hosts are on the same Ethernet network.

Show the ARP Request and Reply packets encapsulation in Ethernet frame

ARP Request From A to B

ARP Reply From B to A

...130.23.43.20 4 bit 130

128 + 2

23222120 0 0 1 0

27262524 1 0 0 0

2 8

Q:-Show by Diagram the format of ARP packet and compare between ARP

request and reply.

Solution

ARP packet

Hardware type Protocol Tope

Hardware

Length

Protocol

Length

Opcode

(1=request , 2=reply)

Sender Hardware address

Sender Protocol address

Target Hardware address

Target Protocol address

Request Reply

1- A host requesting the destination

physical address

1-The host replies with hardware

address

2- Operation filed value = 1 2- Operation filed value = 2

3-Target hardware address = all zero

(because it is known)

3-Target hardware address is the

physical address of request host

Q: Explain with diagram the proxy ARP

The proxy ARP Router

Replies To Any ARP request

received for destination

192.168.0.1, 192.168.0.2 and 192.168.0.3

Example:-

State Queue Attempt Time out Protocol address Hardware address

R

P

F

P

12

5

--

7

--

2

--

1

900

--

--

--

10.0.0.1

192.168.0.1

--

192.168.7.3

AF:FC:33:00:56:66

--

--

--

Sol:

1-ARP Output model Receive an IP data gram to Destination IP 10.0.0.1

After 200MS.


R

P

F

P

12

5

--

7

--

2

--

1

700

--

--

--

10.0.0.1

192.168.0.1

--

192.168.7.3

AF:FC:33:00:56:66

--

--

--

2-ARP Input model Receive an ARP packet with largest IP address 192.168.0.1

and (AC:AE:32:45:73:42)


R

R

F

P

12

5

--

7

--

--

--

1

700

900

--

--

10.0.0.1

192.168.0.1

--

192.168.7.3

AF:FC:33:00:56:66

AC:AE:32:45:73:42

--

--

3-After 700 MS ARP Output Model Receive an IP Data gram with destination IP

(192.168.7.4).


F

R

P

P

-

5

15

7

--

--

1

1

-

900

900

--

-

192.168.0.1

192.168.7.4

192.168.7.3

-

AC:AE:32:45:73:42

--

--

R=Resolved P=Pending F=Free

Queue=Number of Queue where packet are wailing For address resolution

Attempt=Number of ARE request Sent

Time Out= Life time of the entry (sec)


F

R

P

Q:-Show by Diagram the process of encapsulation the ARP packet into farm?

Solution

Q:-What are the four cases of using the ARP protocol ?

Case 1:-

A Packet Same network

Case 2:-

A Packet Another network

Case 3:-

Router A Packet Host Another network

Case 4:-

Router A Packet Host Same network

ICMP | Internet Control Message Protocol

ICMP go to Source

Datagram PCKET

Network Layer

Q:-if the port on the destination HOST is unreachable the type and code for this

ICMP Message.

-Type 3 Code 3.

Q:Show how the encapsulation of ICMP packet contains bath ip header first 8

byte 8 datagram data?

Or (contents of data field for error messages)

IP

Header

8byte IP Data

ICMP

Header

IP

Header

8byte ICMP

Packet

Sent IP

Datagram IP

Header

ICMP

Header

IP

Header

8byte

Q: For the following network diagram show the needed temp message to be

generated .

(if Host A send data to D)

Solution:- Destination Host D will send to informs the source host that the

destination unicast address is unreachable.

Q:Why is that an ICMP packet descend have source and destination port number?

-ICMP does not use a port ; it is an echo reply protocol communication protocol .

ICMP Echo Protocol

Not Communication Protocol

Time stamp

Synchronization of both ends clocks

Time difference = receive time stamp = original time stamp

One way = Synchronization One-way (delay)

Checksum *

ICMP Network Layer

ICMP:-is a message control and error-reporting between a Host server and get

way to the internet.

Function :- Manages network communication and error reporting mechanisms.

Q:-Why ICMP is Considered to be the IP companion ?

-Because message not send of through encapsulation IP Header

Q:-Compare Between ICMP and ARP in terms of message

ARP ICMP

Address resolution protocol ,it is

helping which IP address is

working on which MAC address.

trace or ping are using ICMP when

you send ping Host needs to find

get way MAC

Q:- Sketch the general ICMP message format and label?

32 Bit

Type code Checksum

Data length depends on type

and code

Q:- Error reporting message ? ICMP handles five (5) type of error

1-Destination unreachable.

2-source Quench.

3-Time exceeded.

4-Parameter problem.

5-redirection.

Q: Show By proper Diagrams the Encapsulation of ICMP into Frame?

Q:-sketch the source Quench error reporting format and give Example?

Solution:

Type Code Checksum

Unused (A11 0)

ICMP

-Type:-Type of Message

-Code :- Subtype of Message

-Checksum:-1's compliment

computed over entire ICMP message- The rest of the ICMP data depends

on the type and code

Error Reporting Message :Report Problems

Query Massage:- GET Specific Information

Q:-List type of ICMP Message .

Category Type Message

Error Reporting

Message

3

4

5

11

12

Des. unreachable

Sour. Quench

Redirection

Time exceeded

Parameter Problem

Query Massage 0 or 8

13 or 14

Echo request or reply

Time stamp request or reply

Q: What are the necessary Step Calculations for synchronization of clocks?

Original Time=39|Receive Time =45|Time the packet retuned = 56 |Transmit time=46

Sending Time = Receive time Original time == 45-39=6

Receiving Time = return time-Transmit Time stamp == 56-46=10

Round trip time=6+10=16

Time Difference =Receive time (original Time+ one way)== 45-(39+1)=85

Q/ What is difference between intra-domain and inter-domain ?

Intra- domain Inter-domain

- Distance vector - Path vector

- Popular protocol are : - Routing protocol:

RIP - EGP

OSPF - BGP (more recent)

- Protocol for intra domain -Protocol for inter domain

routing are also called IGP routing called EGP

- Routing within AS - Routing between AS

23

Q/Compare between static and dynamic routing table?

Sol//

1- Static routing:- - Minimal CPU / memory overhead - No bandwidth -Granular control on how traffic is routed - Impractical on large network

2-Dynamic routing:- - Simpler to configure on large network -will dynamically choose different - Ability to load balance between multiple links - Update are shared between routers

Q/What are the four type of links?

Sol// 1- Point to point link : connect two router without any other host.

2- Transient link : is a network with several routers.

3- Stub link: is a network that is connected to only router.

4- Virtual link : when the link between two routers is broken.

Q/ What are the five type of OSPF?

Sol//1-Hello packet

2-Data base description packet

3-Link state request

4-Link state update

5-Link state acknowledgment

Hello packet: is used to discover neighbor and maintain relationship with other router.

Q/ Sketch the RIP message format and explain the function of each one of its fields ?

Q/ There are five type of link-state update message

Sol// 1- Router link: send this to describe neighbor and own interface

2- Network link: for broadcast network only

3- Summary link to network

4- Summary link to AS boundary router

5- External link

Command Version Reserved

Family All 0s

Network address

All 0

All 0

Distance

8-bit 8-bit

16-bit

32-bit

24

Q/What is the difference between routing table and route protocol ?

Sol// -Routing table : is to put the packet into route to it is find destination .

-Routing protocol : to create mange update the routing table in any network .

Q/ What is an autonomous system ?and what is area ?

Sol// AS : is a collection of routers under one persons or more network operator

-So you are responsible for area 0 and area 1 there fore it is on AS

*Although routing is within area there is default route sending it to area 0

Q/ What are the three timers in RIP explain the need for each one of them and give simple

example ?

Sol// 1- Periodic Timer : control the advertising of regular update message .

2- Expiration Timer : governs the validity of a route .

3- Garbage Collection Timer : when the information about a route becomes invalid .

Q/RIP V1 RIP V2

1- class full RIP 1- classless RIP 2- use broad cast to send periodic update 2- use multicast to send periodic update 3- no support authentication 3- support authentication 4- no support VLSM/CIDR 4- support for VLSM/CIDR Q/ Define the BGP and outline its use ?

Sol// BGP : Border Getaway Protocol is an inter domain routing protocol using path vector

routing .

Q/ What are four type of message in BGP ?

Sol// 1- open 2- update 3- keep alive 4- notification

Q/ Type of system BGP

Sol// 1- stub AS 2- multi homed AS 3- transit AS 4- CIDR

Q/ How RIP pocket are encapsulated in the internet? What layer ?and what port ?

Sol// layer 3 - Port 520

Q/ Define link-state routing and what is protocol currently being use that conforms to link-

state routing

Sol// link-state : is a complex routing technique in which each router share information with

other router a bout reach ability of other network and metric .

Protocol : OSPF (Open Short Path First )

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Architectural Internet