fnal_ppt

Address Resolution Protocol (ARP):

Address Resolution Protocol (ARP) SANCHITA SEN 1337,ECE

Overview:

Overview

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Figure 7.1 ARP and RARP

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Position of ARP and RARP in TCP/IP protocol suite Notice that ARP and RARP are supplemental to IP.

Slide 5:

ARP ARP associates an IP address with its physical address. On a typical physical network, such as a LAN, each device on a link is identified by a physical or station address that is usually imprinted on the NIC. Address resolution provides a mapping between the two different forms of address. 32-bit Internet address 48-bit Ethernet address

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Figure 7.3 ARP operation

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Figure 7.4 ARP packet

ARP and RARP:

ARP and RARP ARP ARP provides a dynamic mapping from an IP address to the corresponding hardware address. We use the term dynamic since it happens automatically and is normally not a concern of either the application user or the system administrator. RARP (Reverse Address Resolution Protocol) RARP is used by systems without a disk drive but requires manual configuration by the system administrator.

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Figure 7.5 Encapsulation of ARP packet The ARP packet is encapsulated within an Ethernet packet. Note: Type field for Ethernet is x0806

Reverse Address Resolution Protocol (RARP):

Reverse Address Resolution Protocol (RARP)

Slide 11:

RARP RARP finds the logical address for a machine that only knows its physical address. This if often encountered on thin-client workstations. No disk, so when machine is booted, it needs to know its IP address. RARP requests are broadcast, RARP replies are unicast . If a thin-client workstation needs to know its IP address, it probably also needs to know its subnet mask, router address, DNS address, etc. So we need something more than RARP. BOOTP, and now DHCP have replaced RARP.

ARP and RARP:

ARP and RARP Note: The Internet is based on IP addresses Protocols (Ethernet, FDDI, ATM) may have different (MAC) addresses The ARP and RARP protocols perform the translation between IP addresses and MAC layer addresses We will discuss ARP for broadcast LANs, particularly Ethernet LANs

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RARP RARP finds the logical address for a machine that only knows its physical address. The topics discussed in this section include: Packet Format Encapsulation

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The RARP request packets are broadcast; the RARP reply packets are unicast . Note:

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RARP operation

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RARP packet

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Encapsulation of RARP packet

Internet Control Message Protocol:

Internet Control Message Protocol ICMP

ICMP:

ICMP ICMP has two major purposes: To report erroneous conditions To diagnose network problems

ICMP Message Format:

ICMP Message Format Type Code Checksum Data 1 byte 1 byte 2 bytes ? Which type of message? Which sub-type of message? Checksum of entire ICMP message Extra data (specific to the type of message)

Important ICMP Messages ERROR REPORTING MESSAGES: :

Important ICMP Messages ERROR REPORTING MESSAGES: Destination Unreachable Source quench message Time Exceeded message Parameter Problem message Redirection message

QUERY MESSAGES::

QUERY MESSAGES: Echo request reply Time stamp request and reply Address mask request and reply Router solicitation and advertisement

Echo Request/Reply:

Echo Request/Reply This is a pair of two messages namely echo request and echo reply and they are used for diagnosis purpose Echo Request : Requests that the receiving host send a copy (echo) of the request back to the sender Echo Response : The response from the receiving host. THIS PAIR OF MESSAGES DETERMINES WHETHER TWO SYSTEMS(HOSTS OR ROUTERS) CAN COMMUNICATE WITH EACH OTHER.

TIME STAMP REQUEST AND REPLY:

TIME STAMP REQUEST AND REPLY This pair of messages can be used by the hosts and routers to determine the round trip time needed for an IP datagram to travel between them

ADDRESS MASK REQUEST AND REPLY:

ADDRESS MASK REQUEST AND REPLY The IP address of a host contains a network address,subnet address and host identifier. A host may know its full IP address but may not know its bifurcation. So it can send an address mask request messae to the router. The router then sends back the address mask reply message.

ROUTER SOLICITATION AND ADVERTISEMENT:

ROUTER SOLICITATION AND ADVERTISEMENT A host that wants to send data to a host on another network must know the address of router connected to its own network. In such situations the router solicitation and advertisement messages can help . A host can broadcast or multicast a router solicitation message. The routers receiving this message can broadcast their routing information using the router advertisement message.

Destination Unreachable:

Destination Unreachable Network Unreachable: The network of the packet’s destination address field could not be reached Network Unknown: The network of the packet’s destination address field could not be located Host Unreachable: The host specified by the destination address could not be reached Host Unknown: The host specified by the destination address could not be located Protocol Unreachable: The specified protocol (e.g. TCP or UDP) could not be established with the specified host Port Unreachable: The specified port number could not be reached

Redirection message:

Redirection message If a router or host wants to send a packet to another network then it should know the IP address of the next router. The routers and hosts must have a routing table to find the address of the next router and the routing table has to be updated constantly. For such an updating, the ICMP sends a redirection message back to its host.

Time Exceeded:

Time Exceeded This is generated in two cases: If a router recieves a datagram with a 0 in the ttl field then it discards that datagram and sends a time exceeded message back to the original source. If all the fragments which make up message do not arrive at the destination host within a certain time limit then time exceeded message is sent back.

Parameter Problem:

Parameter Problem There should not be any ambiguity in the header part of the diagram. If a router or destination host finds any such ambiguity or missing value in any field of the datagram then it discards that datagram and sends the parameter problem message back to the source.

SOURCE QUENCH MESSAGE:

SOURCE QUENCH MESSAGE Used to report congestion to original source and to request it to reduce its current rate of packet transmission. This message serves two purpose: Tells the source that the datagram has been discarded ; Gives a warning to the source that the source should slow down(quench) because congestion has taken place somewhere.

THANK YOU:

THANK YOU .