No need to break data into packets and re-assemble
Useful for some applications (ping)
Standard set of integer numbers assigned to applications
Port 23 is telnet, 80 is http, 25 is email/smtp
Helps to identify which application sent the data
48 bits (12 hex digits)
Burnt into nic (hard coded - cant be easily changed)
Normally unique in the world
32 bits (4 decimal numbers, 0-255 each)
Software configured (easily changed)
Special ip addresses (broadcasting):
Normally unique in the world
Key Fields in Packet Headers
TTL (time to live)
Source ip address
Destination ip address
Header checksum, length
Source and Destination
Source/dest. ethernet address
Class of IP Address
Class A - Other Networks
8bits for networks/24 bits for hosts
Class B - large organizations/universities
16 bits for networks/16 bits for hosts
Class C - small companies
24 bits for networks/8 bits for hosts
256 hosts, actually 254
Example: Rutgers University
2 class B ip addresses
165.230.x.x and 128.6.x.x
Rutgers using subnetting
Ex: 22.214.171.124 – clam
165.230 => rutgers.edu
99 => subnet in BSB
70 => the system on the above subnet
32 Bit IP Addresses - Classes Class A Class B Class C Class ID Network ID Host ID Clam (Class B) – 126.96.36.199 254 hosts (8 bits) 2,097,150 networks (21 bits) 110 (3 bits) 65,534 hosts (16 bits) 16,382 networks (14 bits) 10 (2 bits) Over 16 million hosts (24 bits) 128 networks (7 bits) 0 (1 bit)
More Class Info
Special IP addresses
10.0.0.0 (private ip space) – Part of Class A
127.0.0.1 (loopback address for testing internal nic)
255.255.255.255 – broadcast
0.0.0.0 – default route address
Who gets Class A address?
Military, major ISPs and research firms (ATT, IBM, GE) and others
Does rutgers really have two class B?
165.230.x.x = 10100101.11100110.x.x
Note – first two bits are 10 thus class B!
128.6.x.x = 10000000.00000110.x.x
Note – again, first two bits are 10 thus class B!
There is also a class D and E used for multicasting and experimentation
Largest wan, and user of tcp/ip (not every WAN is part of the Internet)
Today, millions of systems, all 7 continents. companies, Edu. sites, home users. micros (pc, mac), workstations (unix), mini, mainframes and even super computers.
Beginnings with the military (DARPA) and the Arpanet - 1970s.
Bitnet, edu. network. NSF (National Science Foundation) funding (government). Heavy use by research labs and universities.
Internet was an early collection of networks, most based on Unix and Vax/DEC systems.
Biggest WAN? Biggest use of TCP/IP? INTERNET!!
At rutgers: 3 connections to internet backbone in N.B., (via commodity internet: AT&T (35meg), Verizon (35meg), and I2 connection: Abilene (155meg))
The internet DOES NOT EQUAL the WWW (world wide web)
The internet pre-dates www by many years.
Applications on the Internet:
use net news, telnet,
(web browsers and
email - most used)
The internet is tcp/ip based, heavy use of unix servers (for web service, dns, etc..) and NT/2000/2003 servers
Internet vs. Intranet
Web browsers (netscape, internet explorer), web servers, web sites
ISP - internet service providers
PPP (point to point protocol) - tcp/ip access for home users
IMAP and POP - email protocols for home users
Web cache servers - save money (ISP Costs), speed users web, minimize traffic on internet
Explosive growth (sluggishness)
Attribute the explosive growth to
Creation of web servers and browser software (clients). major change over gopher (just text based). www has text, colors, sounds, video, pictures, etc..
The availability of www browsers on pc and mac systems (not just unix boxes, as it was originally)
The development of SLIP/PPP allowing home users access to the web (and other tcp/ip applications) on the internet
More users and more bandwidth intensive applications
ip address space shrinking (future - IPv6)
Only 32 bits (not 48 bits like ethernet address)
2**32 hosts (4.29X10 9 )
Firewalls - filtering based on ip# and port numbers.
Stands between internet and internal company network.
Combination of hardware and software, allow and disallow services.
Controlling incoming and outgoing packets...can block packets
Based on ip# and port numbers (telnet, ftp, email, dns, etc..)
Attempts to keep the bad guys out...
Intranet Firewall Evil Internet !
Evil Internet ?????
Hackers and Viruses and Spam, oh my!
Advanced TCP/IP Info
Voice Over IP
Instead of normal phone service (POTS/PBX)
PBX vs. VoIP - circuit vs. packet switching
Phones with ethernet jacks, plug into switches
Video over IP - video conferencing, distance learning
QOS - Quality of service, important for voice/video (not as important for data). Minimize delay (latency), packet loss, jitter.
Priority on packets (field on ip layer)
Multiple queues on routers and switches based on priority
Rate limtting (data vs voice/video)..limit bandwidth can be done at router
IP Address Space Conservation (IPv4)
Problem: Running out of ip address space
ipv6 - 32bit --> 128bit ip address (2**32 vs. 2**128 hosts)
IPv4=2**32=4,290,000,000 possible hosts (over 4 billion)
IP address for hosts (pc, macs, printers, switches, telephones, etc..)
Companies typically only use 25-50% of ip address allocated to them (efficiency issues)