CH5 networking

Network layer address

The network layer protocol used on the internet is IP, so a web address is translated into an IP address that is 4 byte long when using IPv4. This process is similar to using a phone book to go from someones name to his or her phone number.

Segment

The protocol data unit (PDU) at the transport layer.

Real-Time Transport Protocol (RTP)

a protocol that is used by QoS protocols (RSVP or RTSP) to send packets across the connection. It contains information about the sending application, a packet sequence number, and a time stamp so that the data in the packet can be synchronized with other packets by the application layer software.

Application Layer Address

a server name. When a user types an Internet address into a web browser, the request is passed to the network layer as part of an application layer packet formatted using the HTTP protocol.

Routers

are usually found at the edge of subnets because they are the devices that connect subnets together and enable messages to flow from one subnet to another as the messages move through the network from sender to receiver.

Session

can be thought of as a conversation between two computers.

Static Routing

decentralized type of routing where all computers or routers in the network make their own routing decisions following a formal routing protocol. With this type of routing, routing decisions are made in a fixed manner by individual computers or routers. The routing table is developed by the network manager, and it changes only when computers are added to or removed from the network. This type of routing is commonly used in networks that have few routing options that seldom change.

Border Gateway Protocol (BGP)

is a dynamic distance vector exterior routing protocol used on the Internet to exchange routing information between autonomous systems. It is the preferred routing protocol between Internet sections, but it is seldom used inside companies because it is large, complex, and often hard to administer.

Routing Information Protocol (RIP)

is a dynamic distance vector interior routing protocol that is commonly used in smaller networks, such as those operated by one organization. The network managers use this protocol to develop the routing table. When new computers are added, this protocol simply counts the number of computers in the possible routes to the destination and selects the route with the lease number.

Enhanced Interior Gateway Routing Protocol (EIGRP)

is a dynamic hybrid interior routing protocol that is commonly used inside organizations. It records information about a route's transmission capacity, delay, reliability, and load. It is unique in that computers or routers store their own routing tables as well as the routing tables for all of their neighbors so they have a more accurate understanding of the network.

Open Shortest Path First (OSPF)

is a dynamic hybrid interior routing protocol that is commonly used on the internet. It uses the number of computers in a route as well as network traffic and error rates to select the best route. Instead of using broadcast messages, it selectively sends status update messages directly to selected computers or routers. It is the preferred interior routing protocol use by TCP/IP.

Intermediate System to Intermediate System (IS-IS)

is a link state interior routing protocol that is commonly used in large networks. It is an ISO protocol that had been added to many TCP/IP networks.

Data link layer address

is permanently encoded in each network card. Also known as the MAC address. This address is part of the hardware and can never be changed.

autonomous system

is simply a network operated by one organization, such as IBM, or an organization that runs one part of the internet.

Internet Protocol (IP)

is the network layer protocol and performs addressing and routing.

Routing

is the process of determining the route or path through the network that a message will travel from the sending computer to the receiving computer.

Internet Control Message Protocol (ICMP)

is the simplest interior routing protocol on the Internet. It is simply an error reporting protocol that enables computers to report routing errors to message senders. It also has a very limited ability to update routing tables.

Transmission Control Protocol (TCP)

is the transport layer protocol that links the application layer to the network layer. It performs segmenting; breaking the data into smaller PDUs called segments, numbering them, ensuring each segment is reliably delivered, and putting them in the proper order at the destination.

User Datagram Protocol (UDP)

is typically used instead of TCP when the sender needs to send only a single packet to the receiver.

loopback

is used for computers to communicate with themselves. It is mainly used by developers and system administrators when testing software. It is in the 127 range of IP address.

Connection-less messaging

means each packet is treated separately and makes its own way through the network. The sender simply sends the packets as separate, unrelated entities, and it is possible that different packets will take different routes through the network. Because packets following different routes may travel at different speeds, they may arrive out of sequence at their destination. The sender's network layer, therefor, puts a sequence number on each packet. The network layer must reassemble them in correct order before passing the message to the application layer.

Segmenting

means to take one outgoing message from the application layer and break it into a set of smaller segments for transmission through the network. It also means to take the incoming set of smaller segments from the network layer and reassemble them into one message for the application layer.

exterior routing protocols

protocols that are designed to be more careful in the information they provide. Usually only provide information about the preferred or the best routes rather than all possible routes.

interior routing protocols

protocols usually designed to provide detailed routing information about all or most computers inside the autonomous systems.

name server

servers that have address databases that store thousands of Internet addresses and their corresponding IP addresses.

Connection-oriented messaging

sets up a TCP connection (also called a session) between the sender and receiver. This process starts with the sender (usually a client) sending a SYN (synchronize) to the receiver (usually a server). The server responds with an ACK (acknowledgment) for the senders SYN and then it sends its own SYN. The last step is when the client sends an ACK for the servers SYN. This is called a three-way handshake, and this process also contains the segment size negotiation.

Quality of Service (QoS)

special type of connection-oriented messaging in which different connections are assigned different priorities. With this type of routing, different classes of service are defined, each with different priorities. For example, a packet of videoconferencing images would likely get higher priority than would an SMTP packet with an email message and thus be routed first. When the transport layer software attempts to establish a connection, it specifies the class of service that connection requires. Each path through the network is designed to support a different number and mix of service classes. When a connection is established, the network ensures that no connections are established that exceed the maximum number of that class on a given circuit.

Dynamic Host Configuration Protocol (DHCP)

the most common standard for dynamic addressing. It does not provide a network layer address in a configuration file. Instead, there is a special software package installed on the client that instructs it to contact the sever to obtain an address.

address resolution

the process of translating the application layer address (or server name) of the destination into a network layer address and in turn translate that into a data link layer address.

Link state dynamic routing

type of dynamic routing in which computers or routers track the number of hops in the route, the speed of the circuits in each route, and how busy each route is. Is preferred in large networks because they spread more reliable routing information throughout the entire network when major changes occur in the network.

Distant vector dynamic routing

type of dynamic routing in which the routers count the number of hops along a route. With this approach, computers periodically exchange information on the hop count and sometimes on the relative speed of the circuits in route and how busy they are with their neighbors.

unicast message

type of message in which one computer sends a message to another computer.

multicast message

type of message in which the same message is sent to multiple computers.

Centralized Routing

type of routing where all routing decisions are made by one central computer or router. It is commonly used in host-based networks. All computers are connected to the central computer, so any message that needs to be routed is simply sent to the central computer, which in turn re-transmits the message on the appropriate circuit to the destination.

Dynamic Routing

type of routing where decisions are made in a decentralized manner by individual computers. This approach is used when there are multiple routes through a network, and it is important to select the best route. It attempts to improve network performance by routing messages over the fastest possible route, away from busy circuits and busy computers. An initial routing table is developed by the network managers but is continuously updated by the computers themselves to reflect changing network conditions. Two types: distance vector and link state.

dynamic addressing

with this approach, a server is designated to supply a network layer address to a computer each time the computer connects to the network. This is commonly done for client computers but usually not for servers. Uses DHCP to assign temporary IP addresses to a group of computers.