1. ECEN5553 Telecom Systems Dr. George Scheets
ECEN5553 Telecom Systems Dr. George Scheets Week #5 Homework: Read [7] "Cybercrime: Dissecting the State of Underground Enterprise" Exam #1: Lecture 14, 16 September (Live) No later than 23 September (Remote DL) 4 page test. Work pages will be off Fall 2015 Exam #1 Outline: Lecture 22, 5 October (Live) No later than 12 October (Remote DL)

2. Outlines Received due 5 October (local) 12 October (remote)
10 %

3. Exam #1 (90 points)
Friday, 16 September (Local) Remote Distant Learners, no later than 23 September
Work 3 of 4 pages
Closed Book & Notes
Calculators & phones are NOT allowed ...Set up numerical problem for full credit
Most equations are provided (on 5th page)
Approximately 40% of upcoming exam will be lifted from the Fall 2015 Exam #1
Anything in the notes, on Power Point, or in reading assignments is fair game

4. On Short Answer or Essay Questions
Answer the Question!
Memory Dump in the space provided
Knowledgeable individual can write more
To get "A" or "B", instructor needs to walk away with impression you could've said more
Got space? Anything else pertinent to add?
Rule of Thumb: "X" point question needs > "X" facts
It is NOT necessary to write small or fill up allotted space to get a good score!

5. OSU Backbone Trunks Access Line Router
Access lines attach to switches and other routers.
Highest internal trunk speeds now 40 & 100 Gbps.

6. ISO OSI Seven Layer Model
Layer Application
Layer Presentation Windows API
Layer Session Windows TCP
Layer Transport Windows TCP
Layer Network Windows IP
Layer Data Link PC NIC
Layer Physical PC NIC

7. Internet Protocal v4 (20 Bytes)
TOS
TTL
Source Address
Destination Address

8. Microsoft's Tracert

9. 802.3 Ethernet Packet Format
Bytes:
MAC
Destination
Address
MAC
Source
Address
IPv4
TCP
Data + Padding
CRC

10. IPv4 Header Contains two addresses Example address
4B Source Address
4B Destination Address
4B = 32b = G potential addresses
Example address
Dotted Decimal Format simplifies
x.x.x.x
Treat each byte as Base2 number, write in Base10
Above number simplifies to

11. IP Header Alpha-numeric name simplifies further
es302.ceat.okstate.edu
Domain Name Servers convert to numerical
All OSU Stillwater addresses are of form to
IP addresses & alpha-numeric names are effectively backwards
mapped to es302.ceat.okstate.edu

12. IP vs Ethernet Addresses
Ethernet has a flat address space
Similar to Social Security Number
Adjacent #'s nearby or on other side of globe?
Huge look up tables required to avoid flooding
Need trillion entries
IP has a hierarchical address space
Packet delivery similar to Mail delivery
Adjacent IP addresses frequently nearby
Reduces size of look up tables
Don't need billion entries

13. ISP Router Overload Fall 2011 Level3 BGP entries 375,550 IPv4
Source:
1 October 2007
Network World
Fall 2011
Level3
BGP entries
375,550 IPv4
7,210 IPv6
Peak Traffic
8.0 Tbps IPv4
500 Mbps IPv6

14. ISP Router Overload Core BGP entries as of 19 August 2014
IPv4 about 520,400
IPv6 about 18,300
2nd week of August
Caused some problems
Some routers had 512,000 entry limit
source:
bgp.potaroo.net
Network World , 13Aug2014, "Internet outages expected to abate as routers are modified, rebooted"

15. ISP BGP Table
source:

16. TCP Header 4 Bytes Source Port Destination Port Sequence Number
ACK Number
Window
Checksum

17. Wireshark Packet Capture
This interaction started with a click on a Firefox bookmark (for a distance calculator) on a computer in Engineering South at OSU Stillwater. Firefox then triggers a query to an OSU Domain Name Server asking for the IPv4 address of This is next followed by a TCP 3 way handshake to open logical connections, an HTTP request to download the distance calculator page, and the beginning of the file transfer.

18. ISO OSI Seven Layer Model
MSS = 1460 B =
Size of Layer 6 & 7 info per packet
Layer Application
Layer Presentation Windows API
Layer Session Windows TCP
Layer Transport Windows TCP
Layer Network Windows IP
Layer Data Link PC NIC
Layer Physical PC NIC
Ethernet
Payload = 1500 B

19. TCP Window Size (Layer 4) Effects End-to-End Throughput
Suppose
Window Size (set by PC) = 64 KB
Microsoft Windows XP
Maximum Segment Size = 1 KB
Server can send < 64 unACK'd packets
Server PC
3,000 Km

20. Throughput on 64 Kbps Line
Server PC
Packet #1
3,000 Km, 64 Kbps line
NPD = Prop Delay / Packet inject time
Prop Delay = distance / EM energy speed = 3,000,000 m / 200,000,000 m/sec = seconds
Packet inject time = 8,376 bits / 64 Kbits/sec = seconds (7B PPP, 20B IPv4, 20B TCP)
NPD = / =
Front end of packet arrives at far side prior to back end being transmitted.

21. Throughput on 64 Kbps Line
Server PC
Packet #2 #1
#1 ACK
3,000 Km, 64 Kbps line
At this instant in time...
2nd unACK'd packet is being transmitted
ACK for #1 enroute back to server
TCP+IP+Layer 2 → 47 bytes if PPP
When ACK#1 arrives at server, only packet #2 is unacknowledged.
Will 64 packet unACK'd limit be reached?
No. At most, 1 packet likely unACK'd.

22. Throughput on 45 Mbps Line
Server PC #3 #2 #1
3,000 Km, 45 Mbps line
NPD = Prop Delay / Packet inject time
Prop Delay = distance / EM energy speed = 3,000,000 m / 200,000,000 m/sec = seconds
Packet inject time = 8,376 bits / 45 Mbits/sec = μseconds (PPP, IPv4, TCP overhead)
NPD = / = 80.60
80.60 average sized packets will fit back-to-back on this line

23. Throughput on 45 Mbps Line
Server PC
Packets
3,000 Km, 45 Mbps line
At this instant in time, the Server...
Has transmitted 64 packets w/o ACK.
Has hit window limit. Halts.

24. Throughput on 45 Mbps Line
Server PC
Packets #1
ACK#1
3,000 Km, 45 Mbps line
At this instant in time,
The PC has processed 1st packet & sent an ACK
The Server is still halted, waiting for ACK #1.
When ACK #1 arrives, server can then transmit one additional packet.
Other ACK’s arrive fast enough to allow back-to-back transmission of next group of 64 packets

25. Can Estimate Throughput with a Time Line
to = 0 t1 t2 t3
time
to: Leading edge of 1st packet injected
t1: Trailing edge of 64th packet injected
t1 = (64*1047B)(8b/B)/(45 Mb/sec) = msec
t2: Leading edge of 1st packet hits far side
15 msec (propagation delay)
If ACK injected right away...
t3: ...ACK arrives at server at t = 30 msec
Process Repeats...

26. Can Estimate Throughput with a Time Line
to = 0
11.91
15.00
30.00
time (msec)
This system can transmit
64(1,047) = 67,008 B = 536,064 bits
Every 30 msec (one round trip time)
Estimated throughput = 536,064/0.03 = Mbps
Actual throughput a bit lower
1st ACK not transmitted until packet #1 fully received...
... and processed by PC
65th packet not transmitted until ACK #1 fully received...
... and processed by Server

27. Can Estimate Throughput with a Time Line
to = 0
11.91
15.00
30.00
time (msec)
Need to be able to fill the pipe for 1 RTT
30 msec in our example
45 Mbps * .030 sec = 1.35 M b = 168,750 B = 168,750/1,047 = packets
Window Size needs to be = segments*1,000 bytes/segment = 161,200 B
Actually would need another segment or two to cover source & sink processing

28. UDP Header (8 Bytes) 4 Bytes Source Port Destination Port Checksum
For interactive real-time traffic, usually used
with Real Time Transport Protocol (12 bytes).

29. Virtual Circuits Routing decisions made once when circuit is set up
Concerned switches have internal Look-Up tables updated
All packets part of info transfer follow the same path
Allows option of setting aside switch resources (buffer space, bandwidth) for specific traffic flows
MPLS, Frame Relay, ATM, & Carrier Ethernet use VC’s

30. Datagrams IP uses Datagrams
Routing Tables updated independently of individual traffic flows
Routers continuously talking with each other
Packets may follow different paths
Routers get no advance warning of specific packet flows.

31. IP is Connectionless
up to 1,460 IP
TCP
Data + Padding
I/O decisions based on IP address & look-up table.
Tables updated independent of traffic, hence path
thru network may suddenly change.
TCP is connection oriented.

32. TCP, UDP, and IP
30+ year old Protocols Designed for data One Utilized Priority & “Best Effort” services No QoS Guarantees Available bandwidth depends on other users
TCP (Layer 4 & 5) provides reliable transfer
UDP (Layer 4 & 5) unreliable transfer
IP at Layer 3
Arbitrary Protocols at Layers 1 & 2

33. Internet Traffic 2008 - 2009 Comparison
source:

34. Fixed Access Internet Traffic Profile
2013
Source: Sandvine_Global_Internet_Phenomena_Snapshot_2H_2012_NA_Fixed.pdf
&

35. 2016 Fixed Access

36. 2012 Mobile Access Internet Traffic Profile
Sandvine_Global_Internet_Phenomena_Snapshot_2H_2012_NA_Mobile.pdf

37. 2016 Mobile Access

38. Internet Traffic Growth
source: "The Road to 100G Deployment", IEEE Communications Magazine, March 2010

39. Internet Traffic Growth
source:

40. Combining the Figures

41. VoIP
PC to PC
Internet Phone to Internet Phone
Commodity
Internet

42. VoIP PC to Wired Phone Internet Phone to Wired Phone Gateway Commodity
System

43. VoIP (Wired Phone-to-Wired Phone)
Carrier prioritizes VoIP traffic (DiffServ)
Paths nailed down (MPLS)
Gateways control # of voice calls
Good Quality Possible with this configuration
Gateway
Gateway
Phone
System
Phone
System
"QoS Enabled"
Internet