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Network+ Study Guide (N10-003)

                                                                                               Index            

Protocols


Protocols are the special set of rules that end points use in a telecommunication connection when they communicate. These rules allow computers with dissimilar operating sytems, network topologies, hardware, etc. to communicate. Next is a description of some of the more common protocols:

 

  • TCP/IP - TCP/IP is the protocol suite of the internet and will be covered in the next section.
  • IPX/SPX - These protocols were developed by Novell and are/were used with Novell Netware. IPX is the fastest routable protocol and is not connection oriented. IPX addresses are up to 8 characters in hexadecimal format. SPX is connection oriented.
  • NetBeui - Stands for "NetBIOS Extended User Interface". It is a transport layer protocol mainly used for small Windows 9x and NT LANs. In reference to the NetBIOS distinction, NetBIOS is the applications programming interface and NetBEUI is the transport protocol. NetBEUI is a non-routable protocol meaning it will not allow communication through a router. It is broadcast oriented which causes it to not scale well. Although it can still be installed on newer Microsoft operating systems, it has largely been replaced by TCP/IP.
  • Appletalk - AppleTalk is the name given to the set of protocol and networking standards created by Apple Computer for use with the Macintosh family of computers. AppleTalk is routable and automatically handles such things as assigning of workstation and network addresses, message routing between networks, etc.

TCP/IP
TCP/IP Protocol Suite The TCP/IP protocol suite is made of many other protocols that perform different functions. Below is a list of some of them:

 

  • TCP - TCP breaks data into manageable packets and tracks information such as source and destination of packets. It is able to reroute packets and is responsible for guaranteed delivery of the data.
  • IP - This is a connectionless protocol, which means that a session is not created before sending data. IP is responsible for addressing and routing of packets between computers. It does not guarantee delivery and does not give acknowledgement of packets that are lost or sent out of order as this is the responsibility of higher layer protocols such as TCP.
  • UDP - A connectionless, datagram service that provides an unreliable, best-effort delivery.
  • ICMP - Internet Control Message Protocol enables systems on a TCP/IP network to share status and error information such as with the use of PING and TRACERT utilities.
  • SMTP - Used to reliably send and receive mail over the Internet.
  • FTP - File transfer protocol is used for transferring files between remote systems. Must resolve host name to IP address to establish communication. It is connection oriented (i.e. verifies that packets reach destination).
  • TFTP - Same as FTP but not connection oriented.
  • ARP - provides IP-address to MAC address resolution for IP packets. A MAC address is your computer's unique hardware number and appears in the form 00-A0-F1-27-64-E1 (for example). Each computer stores an ARP cache of other computers ARP-IP combinations.
  • POP3 - Post Office Protocol. A POP3 mail server holds mail until the workstation is ready to receive it.
  • IMAP - Like POP3, Internet Message Access Protocol is a standard protocol for accessing e-mail from your local server. IMAP (the latest version is IMAP4) is a client/server protocol in which e-mail is received and held for you by your Internet server.
  • TELNET - Provides a virtual terminal or remote login across the network that is connection-based. The remote server must be running a Telnet service for clients to connect.
  • HTTP - The Hypertext Transfer Protocol is the set of rules for exchanging files (text, graphic images, sound, video, and other multimedia files) on the World Wide Web. It is the protocol controlling the transfer and addressing of HTTP requests and responses.
  • HTTPS - Signifies that a web page is using the Secure Sockets Layer (SSL) protocol and is providing a secure connection. This is used for secure internet business transactions.
  • NTP - Network Time Protocol is a protocol that is used to synchronize computer clock times in a network of computers.
  • SNMP - Stands for Simple Network Management Protocol and is used for monitoring and status information on a network. SNMP can be used to monitor any device that is SNMP capable and this can include computers, printers, routers, mainframes, gateways and many more.

TCP/IP Ports
Ports are what an application uses when communicating between a client and server computer. Some common ports are:
 

 

  • 21 FTP
  • 23 TELNET
  • 25 SMTP
  • 69 TFTP
  • 80 HTTP
  • 110 POP3

TCP/IP Addressing
Every IP address can be broken down into 2 parts, the Network ID(netid) and the Host ID(hostid). All hosts on the same network must have the same netid. Each of these hosts must have a hostid that is unique in relation to the netid. IP addresses are divided into 4 octets with each having a maximum value of 255. We view IP addresses in decimal notation such as 124.35.62.181, but it is actually utilized as binary data.

IP addresses are divided into 3 classes as shown below:
 

Class Range
A 1-126
B 128-191
C 192-223

 NOTE: 127.x.x.x is reserved for loopback testing on the local system and is not used on live systems. The following address ranges are reserved for private networks:
10.0.0.0 - 10.254.254.254
172.16.0.0 - 172.31.254.254
192.168.0.0 - 192.168.254.254


IP addresses can be class A, B or C. Class A addresses are for networks with a large number of hosts. The first octet is the netid and the 3 remaining octets are the hostid. Class B addresses are used in medium to large networks with the first 2 octets making up the netid and the remaining 2 are the hostid. Class C is for smaller networks with the first 3 octets making up the netid and the last octet comprising the hostid. The Network ID and the Host ID are determined by a subnet mask. The default subnet masks are as follows:
 

CLASS DEFAULT SUBNET # OF SUBNETS # OF HOSTS PER SUBNET
Class A 255.0.0.0 126 16,777,214
Class B 255.255.0.0 16,384 65,534
Class C 255.255.255.0 2,097,152 254

What if you wanted more than 1 subnet? Subnetting allows you to create multiple logical networks that exist within a single Class A, B, or C network. If you don't subnet, you will only be able to use one network from your Class A, B, or C network. When subnetting is employed, the multiple networks are connected with a router which enables data to find its way between networks. On the client side, a default gateway is assigned in the TCP/IP properties. The default gateway tells the client the IP address of the router that will allow their computer to communicate with clients on other networks.

IPv6
The previous information on TCP/IP has referred to IPv4, however, this addressing scheme has run out of available IP addresses due to the large influx of internet users and expanding networks. As a result, the powers that be had to create a new addressing scheme to deal with this situation and developed IPv6. This new addressing scheme utilizes a 128 bit address (instead of 32) and utilizes a hex numbering method in order to avoid long addresses such as 132.64.34.26.64.156.143.57.1.3.7.44.122.111.201.5. The hex address format will appear in the form of 3FFE:B00:800:2::C for example.