1. 1 “Vision for Trustworthy Computing”, Bill Gates, 15 Jan 2002 “…now, when we face a choice between adding features and resolving security issues, we need to choose security.”

2. 2 Internet Technologies An example of how the system works* Assume: FTP is our application example. Ethernet is the underlying technology at the data link layer. * Two slides of revision for some of you.

3. 3 Application(say FTP) TCP IP Ethernet Driver Physical Layer Ethernet

4. 4 Ethernet IP TCP App. User Ethernet Header Header Header Header Data Trailer SS 46 to 1500 bytes for Ethernet IP TCP App. User Header Header Header Data TCP App. User Header Header Data App. User Header Data User Data SS

5. 5 Original Internet Principles End-to-End Design: Based on the assumption that end-points can trust one another. To move the functionality away from the network, and, towards the edges of the system. Reduces the complexity of the network. Reduces the cost of future upgrades New applications can be added without modifying the network.

6. 6 Original Internet Principles Packet Switched Communication facility Different Networks connected through Routers (used essentially for routing only). Internet communication to continue despite loss of networks or routers. Cater to distributed management of resources.

7. 7 Original Internet Principles (continued) Addresses that are simple, hierarchical and that can be overloaded for both naming a node and for routing to it. Higher level functionality at the edges and dumb network A single data delivery service (IP) to cater to both connectionless, unreliable datagram service (UDP) as well as to a reliable stream service (TCP).

8. 8 New Environment Untrustworthy end-points Denial of service attacks Spam e-mails More demanding applications Requirement for high throughput Requirement for guaranteed delivery (e.g. audio or streaming video) ISPs view wide BW and/or guaranteed data transport services as a competitive differentiator.

9. 9 New Environment Islands of wide BW and/or guaranteed service along with content servers, designed for technologists. Responses to the new environment: Modify the end-nodes Add functions to the core of the network Firewalls NATs Traffic Filters

10. 10 The Internet Internet Characteristics & Architecture as it exists today

11. 11 Table1:Internet Traffic Characteristics Flow Type% of Flows % of Bytes Ave. No. of Units Ave. No. of Bytes Web S to C20.034.016.58270 Web C to S23.33.312.5710 MBONE0.0120.010,0886,344,202 DNS32.03.2__ Others25.735.4__ C: client;DNS: Domain Name System;S: Server;MBONE:Multicast Backbone Source: Antonio Rodriquez-Moral, “LIBRA.” Bell Labs Technical Journal, 2(2): 42-67, Spring 1997.

12. 12 Table2: Routing Persistence Time% of TotalComments SecondsNAUsed in load balancing MinutesNAIn tightly coupled routers 10s of minutes9Changes usually through different cities or Autonomous Systems Hours4Usually intra network changes 6+hours19Usually intra network changes Days68 (a) 50% of these routes persist for < 7 days (b) Other 50% persist for > 7 days Source: Vern Paxson, “End-to-End Routing Behaviour in the Internet”, IEEE/ACM Transactions on communications, 5(5), October 1997.

13. 13 Table3: Internet Traffic Characteristics Round Trip Delay (RTT) Most RTTs are within 70-160 ms ITU-T G.114: limit RTT to 300 ms or less However… Surveys show some people tolerate large RTTs of 800 ms Packet Loss Very bursty Affects contiguous packets Order of Packet Arrival Studies underway, but…Paxson study shows out-of sequence arrival not unusual Source: Ulyees Black, “Advanced Internet Technologies”, pages 70-71, 1999.

14. 14 Packet Loss Data transmission: masked by TCP Audio/Video: ears and eyes catch it Audio System: G.T23.1 masks a loss of up to 10% if the loss is random and independent. It uses the previous packet to simulate the lost packet. But the packet loss in Internet is bursty.

15. 15 Packet Loss Forward Error Correction system: uses the technology used in mobile wireless system --by sending many copies of the coded voice. If even one copy arrives safely, the operation is effective. Since UDP is used for audio/video, the out-of-sequence arrival is also a problem.

16. 16 Internet: Example of a small part HAHBHX H1R4R3 R2 R1 HNH2 Internet Ethernet 155 Mbps SONET T1 Line Ethernet 45 Mbps SONET T1 Line For point-to-point (relay-type) connections through T1/SONET lines, PPP (Point to Point Protocol) is used. * SLIP (Serial Line IP) is now rarely used.

17. 17 T Lines Frame: carries 24 channels of 8 bits + 1 bit for sync.=193 bits T1: 8000 frames per second 1.544 Mbps => DS1 T2: 4 DS1’s 6.312 Mbps => DS2 T3: 7 DS2’s 44.376  45 Mbps => DS3 T4: 6 DS3’s 274.176 Mbps

18. 18 T Lines ANSI – Synchronous Optical Network SONET ITU-T – Synchronous Digital Hierarchy SDH SONET rates: OC1 51.84 Mbps OC3 155.520 Mbps OC12 622.080 Mbps OC-24 1.244 Gbps OC-48 2.488 Gbps OC-192 9.953 Gbps

19. 19 RARP IP ICMP ARP UDPTCP BGP RIP OSPF FTPSMTPTELNETDNS Physical Layer PPPETHERNET

20. 20 Ethernet Type ARP 080616 RARP 803516 IP 080016 IP Protocol OSPF 89 UDP 17 TCP 6 ICMP 1 UDP Ports RIP 520 DNS 53 TCP Ports BGP 179 DNS 53 SMTP 25 TELNET 23 FTP 21 HTTP 80 Lotus Notes 1352 HTTP PROXY 8080