Homework

1
Homework

• Read 5 "The cost of quality in
  Internet- style networks" 6 "The (un)Economic
  Internet"
• Study for Midterm on Lecture 15 7 October
  (live) Week of 13-17 October (distance
  learning)Term Paper Outline due Lecture 16 14
  October (live) Week of 20 - 24 October (distance
  learning)

2
OutlinesReceiveddue 14 October Lecture 16
5
3
MID-TERM

• Tuesday 7 October (Live)Week of 13-17 October
  (DL)
• Work 4 of 5 pages
• 2 pages of the Fall 2007 midterm will be on the
  upcoming exam
• Anything in the notes and reading assignment is
  fair game
• Equations are provided

4
Shared Ethernet EfficiencyDesigned to operate as
"Low Speed"
1.0
0.5
0.0
.01 .10 1.0
10.0 100
NPD
5
Low Speed Network?This configuration...
PC
Server
Hub
PC
PC
10BaseT Shared Hub
6
... is as good as this one...
PC
Server
Switched Hub
PC
PC
10BaseT Switched Hub

• ...IF traffic mostly going to/from same machine
• Switched Hub better if diverse traffic flow

7
Shared Ethernet EfficiencyGbps has higher NPD
1.0
0.5
0.0
.01 .10 1.0
10.0 100
NPD
10
1
.1
8
High Speed Network?This configuration has
horrible throughput.
PC
Server
Shared Hub
PC
PC
1 or 10 Gbps Shared Hub Under heavy load, too
much time spent recovering from collisions.
9
Full Duplex System
PC
PC
Switched Hub
PC
PC
All 10 Gbps, most 1 Gbps, many 100 Mbps systems
are Full Duplex, switched networks. NICs are
designed to simultaneously transmit
receive. Full duplex switched networks have
efficiency near 100. Line no longer shared. No
Collisions. No need for CSMA/CD.
10
Ethernet Efficiency

• Shared Half Duplex Network
• No Load 100
• Heavy Load Approximately 1/(15NPD)
• Shared network apply to entire network
• Switched network apply between switched hub
  end device
• Full Duplex Switched Network
• 100

11
Multiplexing

• Splitting a chunk of Bandwidth up into channels
• Channel can carry one conversation
• FDM, TDM, StatMux

12
FDM
Different channels use some of the frequency all
of the time.
frequency
1
2
3
4
5
time
13
TDM
Different channels use all of the frequency some
of the time. Fixed, predictable times.
frequency
1
2
3
time
1
etc.
14
StatMux
Different channels use all of the frequency some
of the time, at random, as needed.
frequency
1
3
1
time
2
15
StatMux vs. TDM FDM

• uses bandwidth more efficiently for bursty
  traffic
• requires more overhead
• has more variable deliveries
• requires more complex expensive hardware

16
Switching How long will a user get to use a
channel?

• For the duration of the conversation? Circuit
  Switching
• For a tiny, variable length, portion of the
  conversation? Packet Switching
• Circuit vs. Packet SwitchingCircuit has less
  end-to-end delayCircuit is less complex Packet
  is more efficient for Bursty Traffic

17
MULTIPLEXING
StatMux
TDM
FDM
Circuit
X
SWITCHING
X
Packet
Any Switching Multiplexing combo possible. Two
marked are among most common today.
18
Ethernet (Shared) Hub

• Operates at OSI Level 1
• Electric CableTraffic arriving at an input is
  immediately copied to all outputs on a bit-by bit
  basis.
• Used on LAN's. Becoming obsolete (if not already
  there).
• Repeater single input single output hub
• Not used much on Ethernet any more
• Generally now only used on WAN long haul
• Different protocol than Ethernet

19
Black Box Performance...
OSI Level 1 Hub (a.k.a. shared hub unswitched hub)
Two packets simultaneously show up at input...
20
Black Box Performance...
OSI Level 1 Hub (a.k.a. shared hub unswitched hub)
... will overwrite each other, i.e. garbage
out. Bits are output as soon as they show up on
input.
21
Black Box Performance...
OSI Level 1-2 (Switch) or 1-3 (Router)
Two packets simultaneously show up at input...
22
Black Box Performance...
OSI Level 1-2 (Switch) or 1-3 (Router)
... one will be transmitted (when allowed by
MAC), the other momentarily buffered...
23
Black Box Performance...
OSI Level 2/3 Switch or Router
... and then transmitted.
24
802.3 Ethernet Packet Format
Bytes 7 1 6
6 2
MAC Destination Address
MAC Source Address
20 20 6-1460
4
CRC
Data Padding
IP
TCP
25
Switched Hubs or Bridge

• On Power Up know nothing
• When a packet arrives at an input port...
• Look-Up Table consulted
• Source MAC address not in table?
• Table Updated MAC address Port matched
• Destination MAC address not in table?
• Packet broadcast to all outputs (a.k.a. flooding)
• Destination MAC address in table?
• Packet shipped to proper output
• Look-up Table update is dependent on packet
  arrivals

26
Router

• Operates at OSI Layers 1, 2, 3
• Capable of making complex routing decisions
• peers into packets and examines Layer 3 address
• Very useful on Large Networks with multiple
  end-to-end paths
• Routers frequently exchange connectivity info
  with neighboring Routers
• Routing Algorithms used to update Routing
  (Look-Up) Tables
• Tables updated independently of traffic

27
Bridging versus Routing

• Ethernet Bridge, Switch, or Switched Hub
• Uses Layer 2 MAC Address
• Unknown Destination? Flooded
• Look-up Table updates are packet dependent
• Router
• Uses Layer 3 Internet Protocol Address
• Unknown Destination? Default location
• Look-up Tables updated independently of traffic
• Small Network? Doesn't matter
• Big Network? Floods not a good idea.

28
ANSI FDDIFiber Distributed Data Interface

• Developed in 87 88
• Covered OSI Layers 1 2
• 1st 100 Mbps Line Speed
• Token Ring MAC
• Had Priorities.
• Originally Dual Counter-Rotating Rings

29
Designed for Metropolitan AreaCounter Rotating
Fiber Rings
Outside Active. Inside Hot Standby.
30
Designed for Metropolitan AreaCounter Rotating
Fiber Rings
1
Line Break...
Nodes 1 4 wrap. One big ring.
4
31
FDDI Status

• Funeral is over.
• Never succeeded as a LAN
• NIC's too expensive
• Dirt cheap now!
• Saw use mostly as a corporate backbone
• OSU backbone from 1989 - 1993 ish
• Was fairly common at Internet Exchanges
• Used to pass trafficfrom ISP A to ISP B
• Now too slow

32
(15) (21)
1993 OSU Stillwater Network
33
The Internet

• VAST collection of interconnected networks
• Key Building BlockRouters running IPv4 (Layer
  3)
• Router link speeds range up to 40 Gbps
• Hierarchical Alpha-Numeric Namesusername_at_machine.
  institution.domain

34
ATT 1997 Internet Backbone
35
UUNET 1998 Internet Backbone
36
Washington D.C. Area - 2000
37
OSU Internet Connectivity (simplified)...
OSU Tulsa
OSU STW
Chicago Transitrail (2 GbpsE)
OKC ONENET
Tulsa Level3
OU
Tulsa (?) Internet2
Various 100 Mbps Fast Ethernet 622 Mbps 1 Gbps
Ethernet
Dallas Quest
38
Traceroute to WWW.CISCO.COM

• 3 Internal OSU-Stillwater routers
• 4 OneNet routers (at least one in OKC)
• 1 Transitrail routers te2-1--588.tr01-chcgil01.t
  ransitrail.net
• 1 SBC (now ATT) router ex1-g1-0.eqchil.sbcglobal
  .net
• 2 Pacific Bell (now ATT) routersded4-g8-3-0.sntc
  01.pbi.netCisco-Systems-1152786.cust-rtr.pacbell.
  net
• 3 Cisco Systems routers
• Firewall
• (450 am, 4Sept08, rtt 63 msec)

39
Traceroute to WWW.TULSA.COM

• 3 Internal OSU-Stillwater routers
• 3 OneNet routers (at least one in OKC)
• 4 Quest routersdal-edge-11.inet.qwest.net
• 4 Sprint routerssl-bixby-telco-10-0.sprintlink.ne
  t
• 2 Bixby Telephone Company routersbtc-inw3.olp.net
  
• Firewall
• (400 pm, 4Sept08, rtt 166 msec)
• Bixby Telephone Company showed large delays

40
ISP Routes Not Necessarily Optimum

• Launched 5 September 2008, 2 miles from OSU
  campus
• 1 Scheets' home router
• 4 SBC routers
• adsl-70-233-191-254.dsl.okcyok.sbcglobal.net
• bb1-g1-0-2.rcfril.sbcglobal.net
• 1 Equinix router
• 1 Transitrail router
• onenet.chcgil01.transitrail.net
• 3 ONENET routers
• at least 1 in Oklahoma City
• 4 Oklahoma State routers
• rtt 55 msec

41
Internet Service Provider Backbone
Trunks
Access Line
Router
Switched Network, full duplex trunks. Access
lines attach to corporate routers routers of
other ISP's.
42
OSU Backbone
Trunks
Access Line
Router
Access lines attach to switched hubs, ISP's and
other routers.
43
Corporate WAN Connectivity
Source Network Magazine June 2005
44
ISO OSI Seven Layer Model

• Layer 7 Application
• Layer 6 Presentation Windows API
• Layer 5 Session Windows TCP
• Layer 4 Transport Windows TCP
• Layer 3 Network Windows IP
• Layer 2 Data Link PC NIC
• Layer 1 Physical PC NIC

45
Internet Protocal v4
4 Bytes
TOS
TTL
Source Address
Destination Address
46
Traceroute to www.okstate.edu from OSU Tulsa

• 2 Internal OSU-Tulsa routers
• 3 OneNet routers at least one is in OKC
• 2 OSU-Stillwater Router
• www.okstate.edu(340 pm, 5Feb03, rtt msec)
• 2 Internal OSU-Tulsa routers
• 3 OSU-Stillwater Routers
• www.okstate.edu(312 pm, 13Sept04, rtt 7
  msec)VPN exists between Tulsa StillwaterHides
  existence of routers in between.

47
Virtual Private Network
TTL 1
20 20 6-1460
Data Padding
IP
TCP

• Tulsa Router (beginning of VPN)Takes IP packet...

48
Virtual Private Network
20 20 6-1460
xxx
xx
xxx

• ... encrypts it...

49
Virtual Private Network
20 20 20 20
6-1460
xxx
xx
xxx
IP
TCP

• ... sticks on another IP TCP header...
• IP address is router at other end of VPN
• ... adds Layer 2 header (PPP)...
• ... shoots packet to far side.

50
Virtual Private Network
20 20 20 20
6-1460
xxx
xx
xxx
IP
TCP

• Tracert TTL value is in encrypted IP header

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