Cisco 1 CH6

a hop

A packet may cross many intermediary devices before reaching the destination host. Each router a packet crosses to reach the destination host is called

Differentiated Services (DS)

An IPv4 header 8-bit field used to determine the priority of each packet.

IP header

At the network layer, this header is used to deliver the packet to the destination host and remains in place from the time the packet leaves the source host until it arrives at the destination host.

IP is inherently unreliable because packet delivery is not guaranteed.

Describe the *best effort* characteristic of the IP protocol.

No connection with the destination is established before sending data packets.

Describe the *connectionless* characteristic of the IP protocol.

Operation is independent of the medium (i.e., copper, fiber optic, or wireless) carrying the data.

Describe the *media independent* characteristic of the IP protocol.

Internet Header Length (IHL) Total Length Header Checksum

Fields used to identify and validate an IPv4 packet.

Identification Flags Fragment Offset

Fields used to reorder a fragmented IPv4 packet

default gateway

The router connected to the local network segment is referred to as

Logical Link Control (LLC)

This IEEE 802.2 sublayer communicates between the networking software at the upper layers and the device hardware at the lower layers. It places information in the frame that identifies which network layer protocol is being used for the frame. This information allows multiple Layer 3 protocols, such as IPv4 and IPv6, to use the same network interface and media.

connectionless best effort media independent

What are the characteristics of the IP protocol at the network layer?

enables the services at the different layers to develop and scale without affecting the other layers.

What is one of the main purposes of encapsulation?

IP is Unreliable meaning that it does not have the capability to manage and recover from undelivered or corrupt packets. The IP protocol does not guarantee that all packets that are delivered are, in fact, received.

What is one weakness of IP ?

de-encapsulation

When the packet arrives at the network layer of the destination host, the host checks the IP header of the packet, If the destination IP address within the header matches its own IP address, the IP header is removed from the packet. This process is known as:

Ctrl-C

Which key combination allows a user to abort setup mode?

network portion

Which portion of the network layer address does a router use to forward packets?

Network Address Translation (NAT) (a technology commonly implemented within IPv4 networks. because the public IPv4 address is shared, the IPv4 address of an internal network host is hidden. This can be problematic for technologies that require end-to-end connectivity.)

a technology commonly implemented within IPv4 networks and provides a way for multiple devices to share a single public IPv4 address.

fragmenting

an intermediate device, usually a router, must split up a packet when forwarding it from one medium to another medium with a smaller MTU. This process is called

route print or netstat -r

command can be used to display the host routing table on a windows host

Addressing end devices Encapsulation Routing De-encapsulation

the network layer uses four basic processes:

Internet routing table

used by routers to make best path determinations

itself local host remote host

A host can send a packet to

version

IPv4 header field that contains a 4-bit binary value set to 0100 that identifies this as an IP version 4 packet.

Protocol

IPv4 header field that has a 8-bit binary value indicates the data payload type that the packet is carrying, which enables the network layer to pass the data to the appropriate upper-layer protocol. Common values include ICMP (1), TCP (6), and UDP (17).

Time-to-Live (TTL)

IPv4 header that contains an 8-bit binary value that is used to limit the lifetime of a packet. The packet sender sets the initial TTL value, and it is decreased by one each time the packet is processed by a router. If the TTL field decrements to zero, the router discards the packet and sends an Internet Control Message Protocol (ICMP) Time Exceeded message to the source IP address.

IP address depletion Internet routing table expansion Lack of end-to-end connectivity

IPv4 still has three major issues:

MAC sublayer

Implements this sublayer (IEEE 802.3, 802.11, or 802.15) in hardware. It is responsible for data encapsulation and media access control. It provides data link layer addressing and it is integrated with various physical layer technologies.

Increased address space Improved packet handling Eliminates the need for NAT

Improvements that IPv6 provides include:

tests the TCP/IP protocol stack on the host.

Pinging the loopback interface:

default gateway functions

Routes traffic to other networks Has a local IP address in the same address range as other hosts on the network Can take data in and forward data out

maximum transmission unit (MTU) (The data link layer passes the MTU value up to the network layer.)

one major characteristic of the media that the network layer considers: the maximum size of the PDU that each medium can transport.

Routing

process that selects the best path and direct packets toward the destination