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Chapter 11. Introduction to TCP/IP. TCP/IP. DARPA is an extension of the Department of Defense assigned to fund basic research. ARPA was its original name, then it was renamed DARPA (for Defense) in 1972, then back to ARPA in 1993, and then back to DARPA again on March 11 1996 .

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chapter 11

Chapter 11

Introduction to TCP/IP

tcp ip
  • DARPA is an extension of the Department of Defense assigned to fund basic research.
  • ARPA was its original name, then it was renamed DARPA (for Defense) in 1972, then back to ARPA in 1993, and then back to DARPA again on March 111996.
  • ARPA was responsible for funding development of ARPANET (which grew into the Internet), as well as the Berkeley version of Unix (BSD) and TCP/IP.
  • Request for Comments – beginning development of protocols
  • Handled by the IETF
  • RFC 791 Internet Protocol released in 1981
tcp ip protocol stack
TCP/IP Protocol Stack
  • 4 layers
  • Process/Application app/pres/sess
  • Host to Host transport
  • Internet network
  • Network Access datalink/physical
  • IP V4 uses a 32 bit address in 4byte divisions
  • Each byte has 256 possibilities
  • 0 and 255 reserved for network broadcast
  • 127 is a loop back
  • 1-254 are used to denote networks or hosts
ip addressing
IP Addressing
  • Logical Address assigned to each host
  • IP locates the network of a device
  • Once the network is located the network will find the device by the host portion of the address
subnet mask
Subnet Mask
  • Used to denote which part of the address Is the network and which is the node
  • 1 masks the network
ip addressing ver 4


IP Addressing (Ver. 4)

First octet denotes class A, B, C, D, E

Class A,B,C are network classes

Class D is multicast addresses

Class E is experimental

Class A 1-126 16,387,064 hosts

(254*254*254 hosts)

Class B 128-191 64,512 hosts

(254*254 hosts)

Class C 192-223

254 hosts per network

class a
Class A
  • 1st octet is supplied by INTERNIC
  • Must begin with 0
  • 1 network 1-126
    • Mask
    • 16 million nodes
    • 254x254x254
class b
Class B
  • 2 octets assigned by INTERNIC
  • Must begin with 10
  • 1 network 128-191
    • Mask
    • 16,384 networks
    • @65000 nodes
    • 254x254
class c
Class C
  • 3 octets to define network
  • Must begin with 110
  • Network 192-223
  • Mask
  • 254 nodes
  • 2,097,152 networks
class d
Class D
  • Starts with 1110
  • Range from to
  • Does not use subnet mask
  • Dynamically allocated by the application or protocol
class e
Class E
  • Starts with 11110
  • Range of to
  • Not useable by the public
  • Account for 6% of IP addresses
reserved addresses
Reserved Addresses
  • Class A
    • 10
    • 1 network
  • Class B
    • 172.16- 172.31
    • 16 networks
  • Class C
    • 192.168.0 – 192.168.255
    • 256 networks
tcp ip internet protocol ip


TCP/IP (Internet Protocol - IP)

Most commonly used protocol suite

Allows for easy cross-platform communications

Scalable and superior functionally over WANs for connecting different types of computers and networks

tcp ip protocol suite1


TCP/IP Protocol Suite

Utilizes small, specialized protocols more than any other protocol suite.

process application



Direct support for end user








Most are associated with a front-end utility or application with which the user interfaces

ftp tftp
  • FTP (File Transport Protocol)
    • Connection oriented protocol for transferring files over the network
    • upper layer protocol that works cooperatively at the Session, Presentation, and Application layers (5-7) RFC 454
    • provides services for file transfer as well as directory and file-manipulation services (DIR, Delete, etc…) via port 20 (data) and 21 (control)
      • Command line interface
  • TFTP (Trivial file transport protocol)
    • Connectionless protocol
    • No interface
http https
  • HTTP– Protocol of the Internet
  • Designed to collect hypermedia over a network
    • Hypermedia – form of communication that allows a dynamic link to another location
  • Uses port 80
  • Works in client/server mode
  • HTTPS– connections using secure socket layer protocol
    • Encrypts transmissions
    • Requires a secure server and login



a remote terminal emulation protocol, also operating at all upper layers (5-7)

Data remains on the remote system

remote equipment can be operated and configured

Uses port 23

mostly used to provide connection between dissimilar systems (PC and VMS, PC and router, UNIX and VMS)

smtp and pop



SMTP (Simple Mail Transport Protocol)

Uses port 25

used for messaging services in the TCP/IP suite

basis for e-mail across the Internet

POP (Post Office Protocol)

Uses port 110(POP3) and 109(POP2)

Distributes mail to the users

  • Internet Message Access Protocol Version 4
  • E-mail protocol for retrieving messages that supports advanced features
    • Allows the user to create and maintain folders on the remote server
    • allows the user to perform remote searches of messages using different parameters
  • Uses port 220
  • Simple Network Management Protocol
  • Manager – interface through which the administrator can gather information
  • Agent– utility that fulfills the request from the manager
  • Stores the information in a file or database
  • Can be configured to send critical updates or alerts to the manager
  • Network File System
  • Port 2049
  • Locate and access remote files
  • Locking mechanism to protect data
  • Permission checks
host to host protocols
Host to Host Protocols
  • Perform all the functions of the transport layer
    • TCP (Transmission Control Protocol)
    • UDP (User Datagram Protocol)
    • DNS (Domain Name System)
tcp transmission control protocol


TCP (Transmission Control Protocol)

the primary Internet transport protocol (layer 4)

accepts messages of any length from the upper-layer protocols

provides transportation to a TCP peer

Connection oriented (more reliable than IP)

Port address is used to determine which connection a packet is destined

responsible for message fragmentation and re-assembly

uses a sequencing function to ensure correct packet re-assembly

udp user datagram protocol


UDP (User Datagram Protocol)

Connectionless Transport layer protocol

Faster, but less reliable than TCP

No virtual link

Flow control and data recovery are provided by the application


dns domain name system
DNS (Domain Name System)
  • Transport layer, name-to-address resolution protocol
  • DNS server keeps a list of system’s names and their IP addresses.
    • Can use a system’s logical name ( rather than its numerical address when communicating
the dns tree
The DNS Tree
  • The set of IP addresses and names in DNS is called a namespace
  • Structured in a tree structure starting at the root
  • Subsections can be located by branching down the tree
  • Namespace = any bounded area in which a name can be resolved
fully qualified domain name
Fully Qualified Domain Name
  • Unique computer name within a DNS namespace
    • Example—
  • Read from left to right
  • More specific information is on the left
public and private dns roots
Public and Private DNS Roots
  • Root of a namespace is where the server starts looking
  • The Internet also contains DNS roots, but these are not owned by any one company
  • Private DNS roots are maintained by a company for their internal use
  • Public DNS roots are maintained by Internet organizations for public use
public roots
Public Roots
  • A public root is used to access computers on the Internet
  • There are 13 authoritative root servers
    • An authoritative DNS server is responsible for their namespace
  • Currently, the top level domains are fall under
    • Country code domains
      • Us, uk, jp
    • Generic domains
      • com, org, net, mil, edu, gov
      • Soon to be released domains areint, aero, biz, coop, info, museum, name, pro
    • Infrastructure
      • .arpa used by IANA exclusively
maintaining public root servers
Maintaining Public Root Servers
  • Maintained by the InterNIC organization
  • Assigns IP addresses and domain names
  • Has licensed other organizations to also assign names and IP addresses
name resolution in dns
Name Resolution in DNS
  • A resolver (client computer requesting a name) must contact a DNS server
  • The resolver wants the IP address for a specific name
  • The DNS server can respond to the request in several ways
    • Return the IP address
    • Send the resolver the IP address of another DNS server that might have the requested address
name resolution steps
Name Resolution Steps
  • Resolver contacts DNS server with a name to be resolved.
  • The DNS server asks a local DNS server for the IP address of the root server.
  • The DNS asks the root server for the IP address of the authoritative server for the requested address.
  • The DNS server asks the authoritative server for the IP address.
  • The DNS server returns the IP address to the resolver.
types of dns queries
Types of DNS Queries
  • Recursive
    • Resolver is given an IP address of a server that might know the requested address and the resolver must then make another query
  • Iterative
    • Resolver expects to get the final IP address meeting their request
  • Both types of queries are common.
ip internet protocol
IP (Internet Protocol)
  • Network layer protocol that provides source and destination addressing and routing
  • Connectionless datagram protocol (fast, unreliable)
  • Assumes that other protocols used by the computer ensure reliable delivery of data.
ip services
IP services
  • Six services
    • Addressing
      • Logical IP address
    • Routing
      • Select path through the network using IP and subnet mask
    • Fragmentation—
      • MTU
    • Options–
      • source routing, additional security
    • Packet timeouts
      • TTL
    • Type of service
  • Bootstrap Protocol used to boot diskless workstations
  • NIC has a bootprom
  • BIOS bootstrap loader program points to boot prom
  • Boot request is issued to on port 67
    • Boot reply on port 68
    • Router forwards request if configured with relay agent
  • Places available IP addresses into a pool and leases to clients
  • 50% maturity client request renewal from leasing server
  • 75% maturity client requests reassignment from any server
  • Can hand out most TCP/IP configuration parameters
icmp internet control message protocol
ICMP (Internet Control Message Protocol)
  • RFC 792
  • TCP/IP best troubleshooting aid
  • Network layer protocol used to send control messages (errors and confirmations)
    • Out of band messages separate from the data
out of band messages
Out of Band Messages
  • Announce network errors
    • host not reachable
  • Announce Network Congestion
    • Source Quench messages
  • Assist Troublshooting
    • Ping utility - used to request a response from a host
      • Echo request/reply request message
      • timed out
      • Round trip time and percentage loss
  • Announce timeouts
    • Trace Route
arp address resolution protocol
ARP Address Resolution Protocol
  • Network layer protocol used to resolve a logical (IP) address to a physical (MAC) address
  • When a system begins a conversation with a host that it does not have a physical address for, it sends and ARP broadcast packet requesting the physical address that corresponds to the logical address. Then, the Data Link layer can correctly send the packet through the network.
  • RARP- assign IP address to MAC address
address resolution
Address Resolution











Requires WINS server

WINS database is dynamic–

system broadcasts when it boots to the network

Server extracts information

hosts and lmhosts
Hosts and LMHosts

Statically resolve IP addresses





tcp ip protocol suite2


TCP/IP Protocol Suite

RIP (Routing Information Protocol)

Network layer protocol

Distance-vector routing protocol used for route discovery (hops)

OSPF (Open Shortest Path First)

Network layer protocol

Link-state routing protocol used by routers running TCP/IP to determine the best path through a network.

tcp ip1



Figure 6-8

transmission control protocol tcp ip
Transmission Control Protocol (TCP/IP)

Three-Way Handshake:

  • Requestor sends a packet specifying the port number and its initial sequence number (ISN) to server
  • Server acknowledges with its ISN, which consists of the requestor’s ISN, plus 1
  • The requester replies with the server’s ISN, plus 1


tcp ip2



Figure 6-8