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TCP/IP

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Figure 24-1

An Internet According to TCP/IP

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Figure 24-2TCP/IP and the OSI Model

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Comparison between OSI and TCP/IP

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Figure 24-3

IP Packet

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Figure 24-4

Internet Address

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Figure 24-5

Internet Classes

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Figure 24-6

IP Addresses in Decimal Notation

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Figure 24-7

Class Ranges of Internet Addresses

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Figure 24-8Network and Host Addresses

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Figure 24-9

A Network with Two Levels of Hierarchy

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Figure 24-10

A Network with Three Levels of Hierarchy

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Figure 24-11

Addresses with and without Subnetting

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Figure 24-12

Masking

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Figure 24-12

Private and Reserved Addresses

The following addresses are reserved for private use. They are typically non-routing.

Network address Default mask 10.0.0.0 255.0.0.0 172.16.0.0 255.240.0.0 192.168.0.0 255.255.0.0

127.0.0.0 is reserved for loopback and is used for internal testing on the local machine.

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Figure 24-12

Where Do I Get an IP Address?

Three regional Internet registries assign Internet Protocol addresses – •ARIN•RIPE •NCC •APNIC

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Figure 24-12

Where Do I Get an IP Address?

Because IP addresses are in such short supply due to inefficient assignment of addresses,it’s nearly impossible anymorefor anyone but an Internet Service Provider to get an address from one of these agencies. We now get our addresses from our Internet Service Providers.

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Figure 24-12

Classes and Classless

Class A - supports 16 million hosts on eachof 127 networks Class B - supports 65,000 hosts on each of 16,000 networks Class C - supports 254 hosts on each of 2 million networks

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Figure 24-12

Classes and Classless

Of the total address space:50% is assigned to class A networks25% is assigned to class B networks12.5% is assigned to class C networks

A very small fraction of class A addresseshave been assigned to workstations.

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Figure 24-12

Classes and Classless

Because of this inefficient assignment of addresses, longer addresses and the idea ofclassless addresses was developed.

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Figure 24-12

IPv4 vs IPv6

IPv6 was developed because of the shortage of IP addresses.

IPv4- 32 bit addresses, about 4 billionIPv6- 128 bit addresses, about 4 billion billion

However, if these addresses are not assignedefficiently, even this may not be enough

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Figure 24-12

IPv4 vs IPv6

Along with IPv6, a classless structure was proposed. Networks were defined on the bitlevel, rather than at a multibit level

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Figure 24-12

CIDR

CIDR stands for Classless InterDomain Routing.It is also sometimes called Supernetting.

The idea is to subnet based at the bit.CIDR notation looks like this:•Class A = /8•Class B = /16•Class C = /24)

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Figure 24-12

CIDR

The number after the “/” is the number of bitsin the subnet maskClass A = /8For example: 9.0.0.0, with subnet mask of 255.0.0.0, or 11111111.0.0.0

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Figure 24-12

CIDR

The number after the “/” is the number of bitsin the subnet maskClass B = /16129.233.0.0, subnet mask 255.255.0.0, 11111111.11111111.0.0Class C = /24) 192.60.128.0, subnet mask 255.255.255.0,11111111.11111111.11111111.0

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Figure 24-12

CIDR

What happens if you want a network largerthan 254 nodes? Say, about 1000?You can combine 4 class C addresses, 192.60.128.0-192.60.131, and change the subnet mask. 192.60.128.0 /22, subnet mask 255.255.252.0,11111111.11111111.11111100.00000000

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Figure 24-12

CIDR

The network address is calculated by ANDing the associated class C IP addresses.

192.60.128.0 (11000000.00111100.10000000.00000000)192.60.129.0 (11000000.00111100.10000001.00000000)192.60.130.0 (11000000.00111100.10000010.00000000)192.60.131.0 (11000000.00111100.10000011.00000000) 192.60.128.0 (11000000.00111100.10000000.00000000)

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Local Login

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Remote Login

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Telnet

Telnet is a terminal emulation program for TCP/IP networks such as the Internet. The Telnet program runs on your computer and connects your PC to a server on the network. You can then enter commands through the Telnet program and they will be executed as if you were entering them directly on the server console. This enables you to control the server and communicate with other servers on the network. To start a Telnet session, you must log in to a server by entering a valid username and password. Telnet is a common way to remotely control Web servers.

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FTP

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FTP

File Transfer Protocol, or FTP, is a protocol used to upload files from a workstation to a FTP server or download files from a FTP server to a workstation. It is the way that files get transferred from one device to another in order for the files to be available on the Internet. When ftp appears in a URL it means that the user is connecting to a file server and not a Web server and that some form of file transfer is going to take place. Most FTP servers require the user to log on to the server in order to transfer files.

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HTTP

In contrast, Hyper Text Transfer Protocol, or HTTP, is a protocol used to transfer files from a Web server onto a browser in order to view a Web page. Unlike FTP, where entire files are transferred from one device to another and copied into memory and then disk, HTTP only transfers the contents of a web page into a browser for viewing. FTP is a two-way system as files are transferred back and forth between server and workstation. HTTP is a one-way system as files are transported only from the server onto the workstation's browser. When http appears in a URL it means that the user is connecting to a Web server and not a file server.

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SNMP Concept

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SNMP Messages

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Figure 24-13ARP

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TFTP

Abbreviation of Trivial File Transfer Protocol, a simple form of the File Transfer Protocol (FTP). TFTP uses the User Datagram Protocol (UDP)and provides no security features. It is often used by servers to boot diskless workstations, X-terminals, and routers.

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NFS

Abbreviation of Network File System, a client/server application designed by Sun Microsystems that allows all network users to access shared files stored on computers of different types. NFS provides access to shared files through an interface called the Virtual File System (VFS) that runs on top of TCP/IP. Users can manipulate shared files as if they were stored locally on the user's own hard disk. Originally called Yellow Pages.

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SMTP

• Short for Simple Mail Transfer Protocol, a protocol for sending e-mail messages between servers.

• Most e-mail systems that send mail over the Internet use SMTP to send messages from one server to another; the messages can then be retrieved with an e-mail client using either POP3 or IMAP.

• In addition, SMTP is generally used to send messages from a mail client to a mail server. This is why you need to specify both the POP3 or IMAP server and the SMTP server when you configure your e-mail application.

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DNS

Short for Domain Name System. It translates domain names into IP addresses. Because domain names are alphabetic, they're easier to remember. A network however,is really based on IP addresses. Every time you use a domain name, therefore, a DNS service must translate the name into the corresponding IP address. For example, the domain name www.example.com might translate to 192.0.34.166

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Bootp or Bootstrap

Short for Bootstrap Protocol, an Internet protocol that enables a diskless device to discover its own IP address, the IP address of a BOOTP server on the network, and a file to be loaded into memory to boot the machine. This enables the workstation to boot without requiring a hard or floppy disk drive. The protocol is defined by RFC 951. It uses TFTP, and thus UDP

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DHCP

Short for Dynamic Host Configuration Protocol, a protocol for assigning dynamic IP addresses to devices on a network. With dynamic addressing, a device can have a different IP address every time it connects to the network. In some systems, the device's IP address can even change while it is still connected. DHCP also supports a mix of static and dynamic IP addresses.A DHCP server may also provide subnet mask, domain Name, default gateway and DNS server

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Figure 24-15

UDP Datagram Format

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Figure 24-16

TCP Segment Format

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Ports

• Ports are the addresses for a process in the TCP/UDP layer of the TCP/IP protocol stack.

• When a workstation makes a request across the network, it’s not enough that the reply comes back to the same workstation. It must also come back to the same process

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Ports

• For example, you may decide to start downloading a file using FTP (port 21). While doing so you also decide to look at web pages using HTTP (port 80). The replies will come back to the same machine, but will be dealt with by a different process.

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Figure 24-14

Port Addresses

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Ports

• http://support.fishnetsecurity.com/scripts/fishnet/portnumbers/portnumbers.asp allows you to enter a protocol and get the port associated with that protocol.

• http://www.iana.org/assignments/port-numbers is the site of the organization, IANA, that assigns port numbers. It has a complete list of ports in ASCII format

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Ports

• Ports are broken up into three sections:– The Well Known Ports are those from 0

through 1023.– The Registered Ports are those from 1024

through 49151– The Dynamic and/or Private Ports are those

from 49152 through 65535

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Ports

• The Well Known Ports are assigned by the IANA and on most systems can only be used by system (or root) processes or by programs executed by privileged users.

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Ports

• The Well Known Ports are assigned and controlled by IANA. Some UDP ports you may be familiar with include:– 69 TFTP– 111 RPC– 161 SNMP– 162 SNMP trap

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Ports

• Some well-known TCP ports you may be familiar with include:– 20 FTP data– 21 FTP control– 23 Telnet– 53 DNS– 80 HTTP

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Ports

• The Registered Ports are those from 1024 through 49151

• The Registered Ports are listed by the IANA and on most systems can be used by ordinary user processes or programs executed by ordinary users.

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Ports

• The Dynamic and/or Private Ports are those from 49152 through 65535. These can be used by any process or user at any time, without restriction.

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Ports

• Ports are used in the TCP [RFC793] to name the ends of logical connections which carry long term conversations. For the purpose of providing services to unknown callers, a Service Contact Port is defined. This specifies the port used by the server, such as a NAT server, as its contact port.

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Ports

• Ports are assigned at each end of the conversation by the software.

• Some protocols use the same port every time, while others choose a different port for each conversation.

• Although both ends must assign a port number, they don’t necessarily have to assign the same port number.

• Both UDP and TCP use ports.

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Sockets

• A socket is a combination of the IP address from the packet and the port number from the TCP or UDP address field. Together they uniquely define both the client and process.

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IP

• Internet Protocol provides a way to get data from network to network.

• The IP packet contains the IP address. • It provides for a variable length data field• It specifies which protocol it will

encapsulate (eg TCP, UDP, etc)• It has provision to limit the life of the

packet

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IP

• It provides for fragmentation of packets as they go from network to network

• It can handle a maximum datagram size of 65,535 bytes, which can be broken down for other network types including FDDI (4,352), Ethernet (1500), and X.25 (576).

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PING

• Ping is a protocol hacked together early on in the development of networking

• Its function is to check to see if a network device is up and running

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PING

• Ping is popularly defined as standing for Packet INternet Groper, is the definition given by Dave Mills, author of NTP and claimed author of PING

• Mike Muus, (died Oct. 2000 in a traffic accident), also claimed authorship. He said that the name had no such origin. He named it after the echolocation method used by submariners, which, in turn, was named after the sound the method made.

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PING

• Whoever originally wrote it, ICMP is a protocol in the TCP layer which uses two types of messages: Error-Reporting and Query

• Query uses one of four types of messages, including Echo Request and Reply.

• Ping combines the Echo Request and Reply function of ICMP with UDP in an IP packet to validate whether a node is functioning

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PING

• Ping Time is the time it takes for a packet to go from the source to destination and back again, including all delays from intermediate routers, processing delays, and network congestion delays.

• The ping protocol is not a single protocol. It uses a combination of protocols; ICMP and UDP