1. Copyright 2002, S.D. Personick. All Rights Reserved.1 Telecommunications Networking II Topic 24 Internet Wrap-up Dr. Stewart D. Personick Drexel University

2. Copyright 2002, S.D. Personick. All Rights Reserved.2 Ref: the New Yorker magazine

3. Copyright 2002, S.D. Personick. All Rights Reserved.3 On the Internet … Arfie wants to send a copy of this New Yorker cartoon to his friend Fuzzball Arfie works at the Laboratory for Canine Sciences (LCS) at MIT Arfie’s Internet address is Arfie@lcs.mit.edu Arfie has Fuzzball’s business card:

4. Copyright 2002, S.D. Personick. All Rights Reserved.4 Fuzzball fb@eecs.berkeley.edu

5. Copyright 2002, S.D. Personick. All Rights Reserved.5 On the Internet... Arfie uses his scanner to “capture” the cartoon as a bit-mapped image: 3 inches x 4 inches using 600 x 600 dpi scanning; 1 byte per dot (pixel) => 3 x 4 x 600 x 600 x 1 byte = 4.32 MB

6. Copyright 2002, S.D. Personick. All Rights Reserved.6 On the Internet... Arfie will be sending this file to Fuzzball Arfie “brings up” his mail application; enters Fuzzball’s domain and user name: fb@eecs.berkeley.edu; attaches the 4.32 MB file; enters a subject line and a brief plain text note; and pushes the “send button”

7. Copyright 2002, S.D. Personick. All Rights Reserved.7 On the Internet... Arfie’s host computer needs to translate fb@eecs.berkeley.edu into a 4-byte IP a address It sends a query to Arfie’s domain name server asking for this translation. This query is sent using UDP (transport layer protocol) inside of an IP datagram…inside (initially) an Ethernet frame

8. Copyright 2002, S.D. Personick. All Rights Reserved.8 DNS Query DNS query UDP Header IP Header Ethernet Frame

9. Copyright 2002, S.D. Personick. All Rights Reserved.9 Arfie’s local DNS server at MIT doesn’t have a cached translation for fb@eecs.berkeley.edu….so Arfie’s host computer sends a query to.edu to find out where the eecs.berkeley.edu DNS server is It then sends a query to the eecs.berkeley.edu DNS server, at it’s IP address, to find out what the IP address of fb@eecs.berkeley.edu’s mail server is On the Internet...

10. Copyright 2002, S.D. Personick. All Rights Reserved.10 Arfie’s host then opens up a TCP connection to Fuzzball’s mail server; and proceeds to send a sequence of TCP segments Each TCP segment contains a piece of the ~13MB message. Arfie’s connection into the Internet, at layer 1-2 consists of an wireless 802.11b link terminating on a 10Mbps Ethernet, leading into a 155 Mbps access line to MIT’s Internet service provider On the Internet...

11. Copyright 2002, S.D. Personick. All Rights Reserved.11 Arfie 10 Mbps Ethernet Router 155 Mbps Router eecs.berkeley.edu mail server Backbone of the Internet 155 Mbps 100 Mbps Ethernet MIT Cambridge MA Berkeley CA The propagation delay between MIT and Berkeley averages.03 seconds (~ 2.5 speed of light delay) Wireless Port 802.11b

12. Copyright 2002, S.D. Personick. All Rights Reserved.12 On the Internet Limitations on the speed with which this message can be sent are: -The data rate on Arfie’s 802.11b wireless connection -Congestion on Arfie’s 10Mbps Ethernet -Congestion elsewhere in the path between Arfie’s computer and Fuzzball’s mail server -TCP window size (flow control) limitations