Term
| What services does the network layer provide? |
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Definition
| Services to exchange the individual pieces of data over the network between identified end devices. |
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Term
| What are the 4 basic processes used at the network layer? |
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Definition
Addressing
Encapsulation
Routing
Decapsulation |
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Term
| What is the PDU of the network layer? |
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Definition
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Term
| What information is contained in the layer 3 PDU? |
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Definition
| Source and Destination IP address |
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Term
| What is the role of a router? |
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Definition
| To select paths for and direct packets toward their destination. This process is known as routing |
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Term
| What is it called when a packet passed through an intermediary device? |
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Definition
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Term
| What happens to the transport layer PDU as the packet moves through the network? |
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Definition
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Term
| What does the network layer protocol specify? |
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Definition
| The packet structure and processing used to carry the data from one host to another host. |
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Term
| List the 5 Network layer protocols. |
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Definition
Internet Protocol version 4 (IPv4)
Internet Protocol version 6 (IPv6)
Novell Internetwork Packet Exchange (IPX)
AppleTalk
Connectionless Network Service (CLNS/DECNet) |
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Term
| Which protocol will be the focus of this class? |
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Definition
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Term
| What are the basic characteristics of IPv4? |
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Definition
• Connectionless - No connection is established before sending data packets.
• Best Effort (unreliable) - No overhead is used to guarantee packet delivery.
• Media Independent - Operates independently of the medium carrying the data. |
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Term
| Describe what a connectionless service in networking means? |
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Definition
| It requires no initial exchange of control information to establish an end-to-end connection before packets are forwarded, nor does it require additional fields in the PDU header to maintain this connection. |
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Term
| What is the main issue that may occur in a connectionless exchange? |
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Definition
| Connectionless packet delivery may, however, result in packets arriving at the destination out of sequence. If out-of-order or missing packets create problems for the application using the data, then upper layer services will have to resolve these issues. |
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Term
| What does unreliable mean in networking? |
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Definition
| Unreliable means simply that IP does not have the capability to manage, and recover from, undelivered or corrupt packets. |
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Term
| Which layer is responsible for adding reliability to packet delivery? |
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Definition
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Term
| Describe media independent. |
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Definition
| IPv4 and IPv6 operate independently of the media that carry the data at lower layers of the protocol stack. |
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Term
| What layer is responsible for preparing a packet for the media? |
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Definition
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Term
| What is the one characteristic of the network layer that is dependent on the media? |
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Definition
| Maximum Transmission Unit MTU |
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Term
| What portion of the IP packet does a router use to make forwarding decisions? |
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Definition
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Term
| What remains untouched as packets travel through the network? |
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Definition
| In all cases, the data portion of the packet - that is, the encapsulated Transport layer PDU - remains unchanged during the Network layer processes. |
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Term
| What are the 6 key fields in an IP packet? |
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Definition
IP Source Address
IP Destination Address
Time-to-Live (TTL)
Type-of-Service (ToS)
Protocol
Fragment Offset |
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Term
| What happens to a packet if the TTL field reaches 0? |
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Definition
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Term
| What is the checksum field used for? |
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Definition
| To determine if the header has reached the destination intact. |
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Term
| What are three methods of determining how to divide your network? |
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Definition
Geographic location
Purpose
Ownership |
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Term
| Why would you group users geographically? |
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Definition
| To improve manageability and network performance. |
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Term
| Why would you group users by task? |
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Definition
| To improve performance based on network requirements of each task. |
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Term
| Why would you group networks by ownership? |
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Definition
| To maintain control and limit access. |
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Term
| What are the 3 main issues as networks grow larger? |
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Definition
Performance degradation
Security issues
Address Management |
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Term
| What is a network broadcast? |
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Definition
| A broadcast is a message sent from one host to all other hosts on the network. |
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Term
| What is broadcast domain? |
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Definition
| The network area in which all hosts receive broadcasts |
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Term
| Is it good or bad to increase the number of broadcast domains in your network? |
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Definition
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Term
| What is the major advantage of dividing networks by ownership? |
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Definition
| Access to and from resources outside each network can be prohibited, allowed, or monitored |
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Term
| What efficiency does dividing large networks into separate networks provide to the hosts? |
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Definition
| Hosts who need to communicate are grouped together reduces the unnecessary overhead of all hosts needing to know all addresses. |
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Term
| What is the device called that hosts send information to that must travel outside their network? |
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Definition
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Term
| What is hierarchical addressing? |
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Definition
| A hierarchical address uniquely identifies each host. It also has levels that assist in forwarding packets across internetworks, which enables a network to be divided based on those levels. |
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Term
| What is the example presented that describes hierarchical addressing in our daily lives? |
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Definition
| Zip codes and house addresses |
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Term
| How many bits are in an IPv4 address? |
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Definition
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Term
| How is the ip address divided? |
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Definition
| IPv4 addresses are divided in four groups of eight bits (octets) |
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Term
| What portion of the IP address does a router use? |
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Definition
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Term
| What is the actual address used for a default gateway? |
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Definition
| The router interface IP address at the edge of the network. |
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Term
| What is the route that the router forwards a packet to called? |
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Definition
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Term
| What decisions do routers make as a packet enters an interface? |
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Definition
| Is the network directly connected or not. Yes forward to that network. No forward to the next-hop router. |
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Term
| How is the default gateway configured on a host running windows? |
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Definition
| On a Windows computer, the Internet Protocol (TCP/IP) Properties tools are used to enter the default gateway IPv4 address |
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Term
| What portion of the IP address must be the same for the host and gateway? |
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Definition
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Term
| What command is issued at the command prompt of windows to see the default gateway setting? |
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Definition
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Term
| What is it called when a router makes forwarding decisions? |
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Definition
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Term
| What is the map called that a router uses to make forwarding decisions (Hint: look at the figure)? |
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Definition
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Term
| What does a routing table contain? |
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Definition
| The routing table stores information about connected and remote networks. |
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Term
| What are the 3 main features of routes in a routing table? |
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Definition
Destination network
Next-hop
Metric |
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Term
| What happens if the packet does not have an address contained in the routing table? |
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Definition
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Term
| For what is a default route used? |
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Definition
| The default route is used when the destination network is not represented by any other route in the routing table. |
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Term
| What is the command to view the routing table for a host? |
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Definition
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Term
| What is the destination network IP address and subnet mask for the default network interface? |
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Definition
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Term
| What three commands are listed that allow you to change the routing table? |
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Definition
route ADD
route DELETE
route CHANGE |
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Term
| What does the address in the routing table represent? |
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Definition
| It represents a range of host addresses and sometimes a range of network and host addresses. |
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Term
| If more than one route exists in the routing table for an address, which one will be selected? |
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Definition
If more than one route exists in the routing table for an address, which one will be selected?
The route that is most specific for that IP address. |
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Term
| When is the default route used? |
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Definition
| When the IP address does not match any other entry in the routing table. |
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Term
| Why does a directly connected device not have a next-hop? |
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Definition
| There are no intermediary devices and the packet is directly forwarded. |
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Term
| What are the three decisions a router can make about a packet? |
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Definition
Forward it to the next-hop router
Forward it to the destination host
Drop it |
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Term
| At which layer does a router process packets at? |
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Definition
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|
Term
| What layer is the packet encapsulated at before it leaves the router? |
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Definition
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Term
| What is another name for a default gateway? |
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Definition
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Term
| Why would a packet take a different route than another packet that is part of the same data stream? |
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Definition
| Routers may learn a new path between packets. |
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Term
| Why are default routes so important to routers? |
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Definition
| Because the gateway router is not likely to have a route to every possible network on the Internet. |
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Term
| What happens if a router has not route for the packet and does not have a default route? |
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Definition
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Term
| Why doesn’t IP have error notification? |
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Definition
| It would reduce efficiency and add overhead. |
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Term
| What does a router need to forward a packet? |
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Definition
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Term
| What happens if routing table are not up to date? |
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Definition
| That packets may not be forwarded to the most appropriate next-hop, causing delays or packet loss. |
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Term
| What are two ways a router can learn about routes? |
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Definition
| Route information can be manually configured on the router or learned dynamically from other routers in the same internetwork. |
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Term
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Definition
| A manually configured route |
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Term
| What must be done if the internetwork changes? |
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Definition
| Static routes must be reconfigured |
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Term
| What is the definition of a dynamic routing protocol? |
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Definition
| Set of rules by which routers dynamically share their routing information. |
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Term
| What happens when a router receives information about changes in routes? |
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Definition
| It updates its’ routing table. |
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Term
| What are 3 common routing protocols? |
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Definition
Routing Information Protocol (RIP)
Enhanced Interior Gateway Protocol (EIGRP)
Open Shortest Path First (OSPF) |
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Term
| What are the 2 costs listed with using a dynamic protocol? |
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Definition
Overhead that consumes network bandwidth
Processing capacity necessary |
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Term
| What advantages are listed for static routing? |
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Definition
No network overhead produced
No processing capacity used
Administrative distance is configured to ensure efficient and effective routing |
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