Networking and Telecommunications

1. Networking and Telecommunications 9. TCP/IP

2. 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

3. 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

4. Encapsulation / De-encapsulation

5. 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

6. 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

7. 4 Layers of TCP / IP

9. 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)

10. 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

11. 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

12. 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

13. Key Fields in Packet Headers

14. IP Packet • TTL (time to live) • Source ip address • Destination ip address • Header checksum, length • Data

15. TCP Packet • Source and Destination Port number • Sequence Number • Checksum • Data

16. Ethernet Packet • Source/dest. ethernet address • Frame check • Data

17. Ethernet Packet

18. IP Packet

19. TCP Packet

20. 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

21. Example: Rutgers University • Ex: 165.230.99.70 – clam • 165.230 => rutgers.edu • 99 => subnet in BSB • 70 => the system on the above subnet • 2 class B ip addresses • 165.230.x.x and 128.6.x.x • Rutgers using subnetting

22. 32 Bit IP Addresses - Classes Class ID Network ID Host ID Class A Class B Class C Clam (Class B) – 165.230.99.70

23. 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

24. 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

25. Internet

26. 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.

28. 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.

29. Biggest WAN? Biggest use of TCP/IP? INTERNET!!

30. 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.

31. 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

32. 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

33. 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

34. Problems • ip address space shrinking (future - IPv6) • Only 32 bits (not 48 bits like ethernet address) • 2**32 hosts (4.29X109) • 4,290,000,000 hosts

35. 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...

36. Firewall Evil Internet ! Intranet

38. Hardware Firewall

39. Software Firewall

40. Evil Internet ????? • Hackers and Viruses and Spam, oh my!

41. Advanced TCP/IP Info

42. 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

43. 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...

44. 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)

45. 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

46. 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.)

47. 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

48. 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

50. 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