Chapter 5, BDC

loopback

(an address starting with 0 is not allowed) the 127 address range is reserved for a computer to communicate with itself, used to test software

exterior routing protocols

Protocols used between autonomous systems, provide information about only the preferred or the best routes rather than all possible routes.

address resolution

To send a message, the sender must be able to translate 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. DNS for app to network- 1= resolving name server if it doesnt know then 2 = root servers if it doesnt know gives you the IP for top level domain TLD server (.edu server) then it responds saying ask the authoritative name server for gatech.edu and provides its IP address

routing protocol

a protocol that is used to exchange information among computers to enable them to build and maintain their routing tables

dynamic addressing

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. DHCP

broadcast messages

addresses starting with 225, every computer on network

subnets

addressing hierarchy, first part of address defines the network and the second part of the address defines a particular computer or host on the network, but its not efficient to assign every computer to the same network, subdivide the network into logical pieces, assign all computers in the same LAN numbers that start with the same first 3 digits (128.192.56.x) everything but the x is the _____

centralized routing

all routing decisions are made by one central computer or router. commonly used in host-based networks and in this case, routing decisions are rather simple. 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 retransmits the message on the appropriate circuit to the destination.

link state dynamic routing

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. In other words, rather than knowing just a route's distance, link state routing tries to determine how fast each possible route is. Each computer or router periodically (usually every 30 seconds or when a major change occurs) exchanges this information with other computers or routers in the network (not just their neighbors) so that each computer or router has the most accurate information possible. Link state protocols are preferred to distance vector protocols in large networks because they spread more reliable routing information throughout the entire network when major changes occur in the network. Drawbacks: more processing by each computer or router in the network (slows down network), wastes network capacity transmitting routing information

session

conversation between 2 computers, establish a ___ between computers and the sender sends all segments until done and ends the ___ (connection oriented), if UDP (one quick message) then connectionless messaging

UDP (user datagram protocol)

datagrams, sender needs to send single small packet to the receiver (ping), no segmenting required

static routing

decentralized, which means that all computers or routers in the network make their own routing decisions following a formal routing protocol. In MANs and WANs, the routing table for each computer is developed by its individual net- work manager, In LANs or back- bones, the routing tables used by all computers on the network are usually developed by one individual or a committee. Most decentralized routing protocols are self-adjusting, meaning that they can automatically adapt to changes in the network configuration, 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, the computer will update the rout- ing table to indicate the failed circuit. If an alternate route is available, it will be used for all subsequent messages. Otherwise, messages will be stored until the circuit is repaired, commonly used in networks that have few routing options that seldom change.

DHCP (dynamic host configuration protocol)

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 a DHCP server to obtain an address. DHCP server can be configured to assign the same network layer address to the computer (on the basis of its data link layer address) each time it requests an address, or it can lease the address to the computer by picking the "next available" network layer address from a list of authorized addresses. Addresses can be leased for as long as the computer is connected to the network or for a specified time limit

border gateway protocol (BGP)

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

routing information protocol (RIP)

dynamic distance vector interior routing protocol that is commonly used in smaller networks, such as those operated by one organization. The network manager uses ___ to develop the routing table. When new computers are added, ___ simply counts the number of computers in the possible routes to the destination and selects the route with the least number. Computers using ___ send broadcast messages every minute or so (the timing is set by the network manager) announcing their routing status to all other computers. used by both TCP/IP and IPX/SPX.

Enhanced Interior Gateway Routing Protocol (EIGRP)

dynamic hybrid interior routing protocol developed by Cisco and is commonly used inside organizations. Hybrid means that it has some features that act like distance vector protocols and some other features that act like link-state protocols. records information about a route's transmission capacity, delay, reliability, and load, all computer and routers store their own routing tables as well as the routing tables for all their neighbors

Open Shortest Path First (OSPF)

dynamic hybrid interior routing protocol that is commonly used on the Internet. It uses the number of computers in a route as well as net- work traffic and error rates to select the best route. more efficient than RIP because it normally doesn't use broadcast messages. Instead, it selectively sends status update messages directly to selected computers or routers. preferred TCP/IP method of routing

port address

each application layer software package has a unique one with the TCP/IP, Any message sent to a computer must tell TCP (the transport layer software) the application layer port address that is to receive the message. Therefore, when an application layer program generates an outgoing message, it tells the TCP software its own port address (i.e., the source port address) and the port address at the destination computer (i.e., the destination port address). These two port addresses are placed in the first two fields in the TCP segment, 16-bit (2 byte) number

connectionless messaging

each packet is treated separately and makes its own way through the network. Unlike connection-oriented routing, no connection is established. The sender simply sends the packets as separate, unrelated entities, and it is possible that different packets will take different routes through the network, depending on the type of routing used and the amount of traffic. Because packets following different routes may travel at different speeds, they may arrive out of sequence at their destination. The sender's network layer, therefore, puts a sequence number on each packet, in addition to information about the message stream to which the packet belongs. The network layer must reassemble them in the correct order before passing the message to the application layer.

data link layer address

ethernet address, needed only on multipoint circuits that have more than one computer on them, physical address because permanently encoded in each network card (MAC address) and can never be changed

subnet mask

every computer in a TCP/IP network is given a _____ to enable it to determine which computers are on the same subnet (LAN) that it is on and which ones are outside of it

intermediate system to intermediate system (IS-IS)

link state interior routing protocol commonly used on large networks

transport layer

links the application software in the application layer with the network and is responsible for the end-to-end delivery of the message. accepts outgoing messages from the application layer and segments them for transmission, accept incoming messages from the data link layer and organize them into coherent messages that are passed to the application layer, PDU = segment

IP

network layer protocol and performs addressing and routing. IP software is used at each of the intervening computers through which the message passes; it is IP that routes the message to the final destination, packets, IPv4 - decimals for address and IPv6 uses hexadecimal

ACL (access control List)

network security, defines what packets should be routed and what types of packets should be discarded

routing

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

TCP/IP (transmission control protocol/internet protocol)

reasonably error free transmission because it performs error checking so it can send large files across sometimes unreliable networks with great assurance that the data will arrive uncorrupted, transport and network layer protocol

ICANN (internet corporation for assigned names and numbers)

responsible for managing the assignment for network layer addresses (IP addresses) and application layer addresses (www.gatech.edu) and internet domains (.edu, .org)

auxiliary port

router port, allows the admin to log via a direct network connection (modem), not used today really

console port

router port, used to configure the router

distance vector dynamic routing

routers count the number of hops along a route. A hop is one circuit, 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.

dynamic routing

routing 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. 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 manager but is continuously updated by the computers themselves to reflect changing network conditions

interior routing protocols

routing protocols used inside an autonomous system, provide detailed routing information about all or most computers inside the autonomous system

QoS (quality of service)

routing, special type of connection oriented messaging in which connections are assigned different priorities, classes of service, RSVP and RTSP allow this, RTP to send packets across the connection

ARP (address resolution protocol)

sends out a broadcast message with whoever is IP address x.x.x.x please send me your DLL address and then the right computer responds and the original broadcaster saves it to its address table and sends the message it wanted

application layer address

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, assigned by software configuration file (all servers have but most clients do not), can have more than one for the same computer (www.gatech.edu and www.georgiatech.edu)

connection oriented messaging

sets up a TCP connection (also called a session) between the sender and receiver. To establish a connection, the transport layer on both the sender and the receiver must send a SYN (synchronize) and receive a ACK (acknowledgement) segment, three-way handshake to begin and four-way handshake to end, full duplex so both side of the session has to terminate the connection independently

internet control message protocol (ICMP)

simplest interior routing protocol on the Internet, simply an error-reporting protocol that enables computers to report routing errors to message senders, limited ability to update routing tables

autonomous system

simply a network operated by one organization, such as IBM or Indiana University, or an organization that runs one part of the Internet. computers within each system know about the other computers in that system and usually exchange routing information because the number of computers is kept manageable. interior v exterior routing protocols

reserved addresses

starting from 224 and should not be used on IP networks because 224-239 are used for multicasting (broadcast or group)

segmenting

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

network layer

takes messages from the transport layer and routes them through the network by selecting the best path from computer to computer through the network (and adds an IP packet). accept incoming messages from the data link layer and organize them into coherent messages that are passed to the application layer.

unicast message

the most common type of message in a network is the transmission between two computers

address space

total number of addresses available, if a protocol uses N bits to define an address then the available space is 2^N

TCP

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, 192-bit header of control information, destination port tells the software at the destination to which application layer program the application layer packet should be sent, source port tells the receiver which application layer program the packet is from, sequence number so segments are assembled correct order and all there, UDP

multicast message

used to send the same message to a group of computers

IOS (cisco internetwork OS)

uses a command line interface rather than a graphical user interface. The network manager uses ___ commands to create a configuration file (also a config file) that defines how the router will operate. The config file can contain the type of routing protocol to be used, the interfaces that are active/enabled and those that are down, and what type of encryption is used.

routers

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. each connection is called an interface, routing table, have CPU/memory/ports(interfaces)

network layer address

web address is translated to IP address, assigned by software, each computer on a network needs a unique one