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9.ppt 9.ppt Presentation Transcript

  • Networking and Telecommunications 9. TCP/IP
  • TCP/IP
    • Transmission Control Protocol/Internet Protocol
    • Developed 1978-1983 U. Cal at Berkeley
    • A family of protocols
    • #1 protocol used in Lans and Wans
    • De-facto standard
    • Non proprietary
    • Layered set of protocols (4 layers)
    • OSI is a 7 layer model (similar)
    • Each layer talks to layer above and below
    • Can replace any layer with another layer/protocol
    • Uses encapsulation/de-encapsulation
    View slide
  • Encapsulation / De-encapsulation View slide
  • 4 Layers
    • Application Data
      • applications: ftp, telnet, ssh, email(smtp), web browsing, x-windows, ping, finger, NOS, DNS, NFS
    • Transport
      • TCP layer (or UDP)
      • Break data into packets
      • Add port number and seq number
      • Reassemble at other end
    • Network
      • IP layer
      • Includes protocols like ICMP (ping), ARP, RARP
      • Add ip address (source/destination)
    • Data Link/Physical
      • Add source/destination ethernet address
      • IEEE 802.3, IEEE 802.5, X.25, ATM
  • 4 Layers of TCP / IP
  •  
  • UDP
    • User Datagram Protocol
    • Sends only 1 packet of data, smaller header
    • More efficient than TCP.
    • No need to break data into packets and re-assemble
    • Useful for some applications (ping)
  • Port Numbers
    • 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
  • Ethernet Address
    • 48 bits (12 hex digits)
    • Ex: 1A:00:05:BC:C2:5F
    • Burnt into nic (hard coded - cant be easily changed)
    • Normally unique in the world
  • IP Address
    • 32 bits (4 decimal numbers, 0-255 each)
    • Ex: 165.230.99.70
    • Software configured (easily changed)
    • Special ip addresses (broadcasting):
      • 0.0.0.0
      • 255.255.255.255
    • Normally unique in the world
  • Key Fields in Packet Headers
    • IP Packet
      • TTL (time to live)
      • Source ip address
      • Destination ip address
      • Header checksum, length
      • Data
    • TCP Packet
      • Source and Destination
      • Port number
      • Sequence Number
      • Checksum
      • Data
    • Ethernet Packet
      • Source/dest. ethernet address
      • Frame check
      • Data
  • Ethernet Packet
  • IP Packet
  • TCP Packet
  • Class of IP Address
    • Assigned central/local
    • Class A - Other Networks
      • 8bits for networks/24 bits for hosts
    • Class B - large organizations/universities
      • 16 bits for networks/16 bits for hosts
        • (65k 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: 165.230.99.70 – 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) – 165.230.99.70 254 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
  • And more….
    • 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
    • Internet
  • General Info
    • 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:
    • web browsers,
    • email (smtp),
    • use net news, telnet,
    • ftp, gopher,etc...
    • (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
  • Key Terms
    • 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
  • Problems
    • 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
  • Problems
    • ip address space shrinking (future - IPv6)
      • Only 32 bits (not 48 bits like ethernet address)
      • 2**32 hosts (4.29X10 9 )
        • 4,290,000,000 hosts
  • Security
    • 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 !
  •  
  • Hardware Firewall
  • Software Firewall
  • 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
    • Solutions:
      • 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)
        • Over 6 billion people in the world
        • IPv6=2**128=300,000,000,000,000,000,000,000,000,000,000,000,000 hosts!
        • Future...work in progress...
  • IP Address Space Conservation (IPv4)
      • Private Address Space (internal)
        • RFC 1918
          • 10.0.0.0/8 - 16,772,216 hosts
          • 172.16.0.0/12 - 1,048,576 hosts (rutgers dorms for example)
          • 192.168.0.0/16 - 65,536 hosts
        • Internal, not routed on internet
        • Unique within internal company (not unique in the world)
        • Often Needs a NAT server (firewall/router)
    • NAT - network address translator
      • Special “black box” to be a NAT device, or some hardware firewalls and routers can NAT
      • used to route private address space on the internet when needed
      • Uses table to map private address space to a small pool of normal ip addresses (which are routable).
      • Drawbacks: not all apps work well with NAT (peer to peer apps, like net meeting or napster, may have problems). Also slower access.
      • Positives: More secure (private), save ip address space
    • Thus private address space:
      • Extends life of IPv4
      • Gives companies lots of internal ip addresses
        • (if you’re a small Class C company, you can still use the 10.0.0.0 private ip address space and have over 16 million hosts!)
      • Better security, these ip address not seen directly on the internet..harder for hackers to attack
      • Drawbacks: Need NAT device to work, shouldn’t be used with servers (email, web, etc.)
  • At Rutgers….
    • Public IP address space
      • 165.230 or 128.6
      • Routable inside and outside the university
      • Unique system per ip number
      • Can be registered in DNS (normally done)
    • Coordinated Private IP address space
      • 172.16
      • Routable inside the university. Nat’d to 165 space when leaving the university
      • Unique system per ip number
      • Can be registered via internal DNS
    • Uncoordinated Private Ip address space
      • 192.168
      • not routable inside or outside the university. Nat’d before router (usually at firewall)
      • Many systems on different subnets may use same IP
      • Cannot be registered in dns
  • Vlan
    • Virtual Lan
      • 1 switch, multiple lans (subnets) multiple broadcast zones
      • Used often with switches
      • Allows to segregate common clients/servers (similar to a bridge) to cut down on traffic and broadcasts, better security, less traffic
      • Flexible network segregation
  •  
  • VPN-Virtual Private Network
    • Connect offsite to your companies internal network, appears you are on the companies internal network
    • Your offsite location is given an internal company ip number
    • Good for home access, traveling employees
    • Need a VPN box at your company site
    • Uses encryption and tunneling
    • Broadcast Address and Subnet Masks
  • Broadcast Address:
    • 128.6.100.xx (100 is the lan/subnet in a class B ip address)
      • 128.6.100.255 is the broadcast address for that lan/subnet
      • 255.255.255.255 generic broadcast address
  • Subnet Mask:
    • 128.6.100.xx (100 is the lan/subnet in a class B ip address)
    • If 255.255.255.0 is the subnet mask for the above class B address
      • Which means 24 bits used for network and 8 bits for host (16 bits assigned centrally for network, 8 bits assigned locally for network/subnet = 24 bits)
      • Thus 2**8 -2 hosts = 256-2 = 254 hosts per subnet/lan
      • If class B, then 8 bits also for subnet (lans) = 254
  • Example:
    • But what if you wanted more then 254 subnets ?
    • Assume Class B network:
    • If 255.255.255.192 is the subnet mask
    • (11111111.11111111.11111111.11000000)
      • 26 bits for network (10 bits for subnet) and 6 bits for hosts
      • # of hosts = 2**6 -2 = 64 -2 = 62 hosts per subnet/lan
      • # of subnets = 2**10 -2 = 1022 subnets/lans
    • Subnet mask is needed for routing, to determine network portion of ip address (and number of lans/subnets and hosts on each lan/subnet)
  • Another Example:
    • But what if you wanted more then 254 hosts ?
    • Assume Class B network:
    • If 255.255.254.0 is the subnet mask
    • (11111111.11111111.11111110.00000000)
      • 23 bits for network (7 bits for subnet) and 9 bits for hosts
      • # of hosts = 2**9 -2 = 512 -2 = 510 hosts per subnet
      • # of subnets = 2**7 -2 = 126 subnets/lans
    • Subnet mask is needed for routing, to determine network portion of ip address (and number of lans/subnets and hosts on each lan/subnet)
  • THE END !