Few n/w questions

1.DHCP ack is ?

a)unicast
b)Multicast

2.)DHCP works in which layer of OSI?

3.)Error correction done in which layer?

Please answer(with explantion) it and help me

a) unicast

dhcp works at application layer - layer 7

error correction is at layer 4 transport layer, but error detection is at layer 3 network layer

The client broadcasts a DHCPDISCOVER message on its local physical
subnet. The DHCPDISCOVER message MAY include options that suggest
values for the network address and lease duration. BOOTP relay
agents may pass the message on to DHCP servers not on the same
physical subnet.

Each server may respond with a DHCPOFFER message that includes an
available network address in the 'yiaddr' field (and other
configuration parameters in DHCP options). Servers need not
reserve the offered network address, although the protocol will
work more efficiently if the server avoids allocating the offered
network address to another client. When allocating a new address,
servers SHOULD check that the offered network address is not


Message Use

---

---

DHCPDISCOVER - Client broadcast to locate available servers.

DHCPOFFER - Server to client in response to DHCPDISCOVER with
offer of configuration parameters.

DHCPREQUEST - Client message to servers either (a) requesting
offered parameters from one server and implicitly
declining offers from all others, (b) confirming
correctness of previously allocated address after,
e.g., system reboot, or (c) extending the lease on a
particular network address.

DHCPACK - Server to client with configuration parameters,
including committed network address.

DHCPNAK - Server to client indicating client's notion of network
address is incorrect (e.g., client has moved to new
subnet) or client's lease as expired

DHCPDECLINE - Client to server indicating network address is already
in use.

DHCPRELEASE - Client to server relinquishing network address and
cancelling remaining lease.

DHCPINFORM - Client to server, asking only for local configuration
parameters; client already has externally configured
network address.

www.ietf.org/rfc/rfc2131.txt

Thx SOSE

a) unicast

dhcp works at application layer - layer 7

error correction is at layer 4 transport layer, but error detection is at layer 3 network layer

The client broadcasts a DHCPDISCOVER message on its local physical
subnet. The DHCPDISCOVER message MAY include options that suggest
values for the network address and lease duration. BOOTP relay
agents may pass the message on to DHCP servers not on the same
physical subnet.

Each server may respond with a DHCPOFFER message that includes an
available network address in the 'yiaddr' field (and other
configuration parameters in DHCP options). Servers need not
reserve the offered network address, although the protocol will
work more efficiently if the server avoids allocating the offered
network address to another client. When allocating a new address,
servers SHOULD check that the offered network address is not


Message Use

---

---

DHCPDISCOVER - Client broadcast to locate available servers.

DHCPOFFER - Server to client in response to DHCPDISCOVER with
offer of configuration parameters.

DHCPREQUEST - Client message to servers either (a) requesting
offered parameters from one server and implicitly
declining offers from all others, (b) confirming
correctness of previously allocated address after,
e.g., system reboot, or (c) extending the lease on a
particular network address.

DHCPACK - Server to client with configuration parameters,
including committed network address.

DHCPNAK - Server to client indicating client's notion of network
address is incorrect (e.g., client has moved to new
subnet) or client's lease as expired

DHCPDECLINE - Client to server indicating network address is already
in use.

DHCPRELEASE - Client to server relinquishing network address and
cancelling remaining lease.

DHCPINFORM - Client to server, asking only for local configuration
parameters; client already has externally configured
network address.

www.ietf.org/rfc/rfc2131.txt

Just want to inform that Error detection occurs at Layer 2.

Because Layer 2 ( Data Link layer ) adds footer and tailer.. In the tailer it adds FCS ( frame check sequence - 4 bytes ) which checks whether frame is error free or not.

Thanks..

woops !! error detection is done at layer 2 datalink