Transcript ppt

ECEN5553 Telecom Systems
Dr. George Scheets
Week 6
Readings:
[12a] "The Real Story of Stuxnet"
[12b] "Everything You Know About Cyberwar is Wrong"
[12c] "How do the FBI and Secret Service Know Your Network is
Breeched Before You Do?"
[13a] "Can You Trust Your Fridge?"
[13b] "Disaster as CryptoWall encrypts US firm's entire
server installation"
[13c] "ARIN Finally Runs Out of IPv4 Addresses"
Exam #1 No later than 28 September (Remote DL)
Results to date (90 points)
Hi = 81.4, Low = 46.4, Ave = 68.98, σ = 10.63
A > 78, B > 66, C > 57, D > 48 (Tentative)
utline 7 October 2015, Lecture 22 (Live)
No later than 14 October (Remote DL)
Exam #1

Grading
 Lost points? No comments? → Insufficient info provided

Rule of Thumb: "X" point question needs > "X" facts
 Lost

points? Comments? Your score ≈ % correct
Not happy with your score? Did you…
 Start studying at the last minute?
 Read assigned articles?
 Answer the question asked?
 Use the space provided?


Leave the instructor with impression you could've said more
There is plenty of time to Recover

365 points remain to be claimed
Outlines
Received
due 7 October (local)
14 October (remote)
18 %
WAN Design (Link Reduction)
Start with Traffic Matrix
 Examine Full Mesh
 Consider eliminating lightly used links

 Reroute

affected traffic
Compare costs at each iteration
WAN Connectivity Options

Internet
 Routers
are packet aware
 Datagrams are assigned trunk BW via StatMux
 BW
 Each
required based more so on average input rates
packet individually routed
 MPLS
 Pricing
&
enabled networks can use Virtual Circuits
a function of connection size
Possibly QoS if MPLS and/or DiffServe used
Ex) Commodity Internet
Corporate Connectivity
Detroit
ISP Network
OKC
Router
Local Carriers dedicate bandwidth
to our use. ISP provides random Packet Switched
StatMux connectivity via datagrams.
NYC
Ex) Commodity Internet
Corporate & Internet Connectivity
Detroit
576 Kbps
OKC
From/To OKC
640 Kbps
DETRouter
NYC ISP
ISP Network
448 Kbps
NYC
OKC
-
144
76
60
DET
88
-
28
50 310/280 I/O @ OKC → 640 Kbps
NYC
112
34
-
40 194/186 I/O @ NYC → 448 Kbps
ISP
110
100
90
278/166 I/O @ DET → 576 Kbps
-
Ex) IP with QoS
Corporate & Commodity Internet
Connectivity
OKC
Detroit
576 Kbps
Internet Service
Provider Network
768 Kbps
448 Kbps
From/To OKC
DET
NYC ISP
OKC
-
144
76
60
DET
88
-
28
50
NYC
112
34
-
40
ISP
110
100
90
-
NYC
Detroit & NYC: No change.
OKC: Port Speed must be bumped to
relay Detroit ↔ NYC corporate traffic.
Leased Line at OKC ↔ ISP

Outbound
 OKC→Det 144
 OKC→NYC 76
 OKC→ISP 60
 Det →NYC 28
 NYC → Det 34
From/To OKC
DET

Inbound
 Det→OKC 88
 Det→NYC 28
 NYC→OKC 112
 NYC→Det 34
 ISP → OKC 110
NYC ISP
OKC
-
144
76
60
DET
88
-
28
50
NYC
112
34
-
40
ISP
110
100
90
-
Total Outbound = 342 Kbps
Total Inbound = 372 Kbps
Leased Line Size > 744 Kbps
Leased Line = 768 Kbps minimum.
Carrier Leased Line Network
Byte
Aware
Cross-Connect
Carrier reserves BW from pool for our use.
Ex) For a 384 Kbps connection, Cross-Connects assign 6 byte
sized TDM time slots 8000 times/second = 6*8*8000 = 384 Kbps.
Internet Service Provider Backbone
Packet
Aware
Router
ISP Routers assign BW for our use on Random,
as needed basis via StatMux & Packet Switching.
Internet Service Provider Network
LAN
PC
Router
LAN
Corporate customers might attach
via Edge Router & Leased Lines.
WS
Internet (Inside the Cloud)

Infinite Buffers
 "OK"
so long as Average Offered Input Rate
< Output Line Speed
Internet
Router
?? 1.54 Mbps Connections
P(Access Line is Active) = 10%
100 Mbps
Trunk
How many access lines can this switch support?
100 Mbps/154 Kbps = 649 (theoretically)
Internet (Inside the Cloud)

Negligible Buffers
 OK
so long as Instantaneous Offered Input Rate
< Output Line Speed
Internet
Router
?? 1.54 Mbps Connections
P(Access Line is Active) = 10%
100 Mbps
Trunk
How many access lines can this switch support?
With 404 users, 99.99% sure Input Rate < Line Speed
Instantaneous
Input < Line
Speed
Bounds on Packet Switch Carrying Capacity
100 Mbps Trunk, 1.54 Mbps Inputs
with 154 Kbps average loads
Lower
90%
553
99%
485
99.9% 439
99.99% 404
Where switch
probably operates
Upper
649
649
649
649
Where switch
could operate
Queue Size: Correlated vs Uncorrelated
Identical Loads (traffic carried/line speed)
mean(queue)=135.6
The negligible
buffer analysis
does not
account for long
term bursts.
Correlated: Long Term Bursts
mean(queue)=32.80
Real world switches
have finite buffers.
Required size to
prevent dropped
packets depends on
length of burst.
Uncorrelated: Random Input
Carrier Leased Line Network
LAN
PC
Byte
Aware
Cross-Connect
Corporate customers might attach
via Edge Router & Leased Lines.
LAN
WS
Leased Lines (TDM)
3 3 2 2 1 1
Leased
Line
Cross-Connect



TDM time slots are moved from input to output
TDM switch is not "packet aware"
Time slots are allocated whether or not there is any
traffic on them
Circuit Switched connections waste
bandwidth for bursty traffic.
traffic
NYC
to OKC
1.54 Mbps Line Speed
146 Kbps Average
time
Idle Time >> Active Time
Leased Lines (Inside the Cloud)

Example
Leased
Line
Cross-Connect
?? 1.54 Mbps Connections
P(Access Line is Active) = 10%
100 Mbps
Trunk
How many access lines can this switch support?
64 (100% input bps < trunk bps)
Given 100 Mbps of Bandwidth...
1.54 Mbps Circuit Switched
TDM Customers with
64 x 154 Kbps =
154 Kbps average load &
9.856 Mbps
100% availability
 404 - 649
1.54 Mbps Packet Switched
StatMux Customers with
404 x 154 Kbps =
154 Kbps average load &
62.22 Mbps
99.99% availability
More Bursty Data Traffic can be moved
with the Packet Switched StatMux network.

64
Switched Network Carrying Capacities
Packet Switch
StatMux
Circuit Switch
TDM
0% Bursty
100% Bursty
Offered Load
100% Fixed Rate
0% Fixed Rate
Network Cost...
Can be spread over 64 Leased Line customers
 Can be spread over 404 Internet customers
 The Internet
Is a Packet Switched StatMux network
Largely hauling bursty data traffic
Effectively hauling bursty data traffic
Inexpensive (compared to a Leased Line)

Internet Performance
This type of plot valid for all
real world full duplex
statistically multiplexed switches:
Ethernet, Internet, Frame Relay
Number of
dropped packets
Average Delay for
delivered packets
0%
Trunk Offered Load
100%
Internet Performance
Effect of priorities
Average Delay for
low priority packets
Average Delay for all
delivered packets
Average Delay for
high priority packets
0%
Trunk Offered Load
100%
Internet Performance
Effect of priorities
Number of
low priority drops
Number
of dropped packets
Number of
high priority drops
0%
Trunk Offered Load
100%
Internet Backbone Engineering
 Option
A)
Deploy ‘best effort’ Routers
Rapidly Deploy Trunk Bandwidth
Keep Trunks Lightly Loaded
 Delays
will be small
 Dropped packets will be few
 Quality fine for all traffic
Backbone Engineering: Option A
Number of
dropped packets
Average Delay for
delivered packets
0%
100%
Keep Trunks Lightly Loaded
Internet Backbone Engineering

Option B)
Deploy more complex QoS enabled
Routers
Deploy fewer, more heavily loaded
Trunks
Give preferential treatment to
interactive Voice/Video

Option A seems to be preferred today
Backbone Engineering: Option B
High Priority delay at 50% Load =
Delay for all traffic at 20% Load
Average Delay for
low priority packets
Average Delay for all
delivered packets
Average Delay for
high priority packets
0%
Heavier Trunk Load
70%
Frame Relay
ANSI Standard covering OSI Layer 2
 Accessed by Routers
 Derived from X.25 Protocol
Dumps almost all error checking
 Requires fiber on the long haul
 Uses Virtual Circuits (VC’s)
VC differs from Datagram
Path thru network set up in advance
Requires Carrier intervention

Frame Relay

1st Commercial Deployment 1990
 WilTel
→ Worldcom→ bankrupt → Verizon
Cheaper alternative to Leased Lines
 Faster alternative to X.25
 Internet a small network in 1990

 Academia
 Military
 Some
 See
commercial traffic
CUCKOO'S EGG to get a flavor
Frame Relay
7 Application
 6 Presentation
 5 Session
 4 Transport
 3 Network
 2 Data Link
 1 Physical

TCP
TCP
IP
Frame Relay
Frame Relay
Committed Information Rate (CIR)
Is a Quality of Service Guarantee
"Guaranteed" minimum Bandwidth
Should be set > average traffic during
appropriate peak period
 Port Connection Speed
a.k.a. Port Speed or Burst Speed
Bandwidth you can burst to provided
network capacity exists.
Set = Bit Rate of Access Line

Frame Relay Packet Format
3
20
20
up to 8,146
3
FR
Header
IP
TCP
Data + Padding
FR
Trailer
Header includes 10 bit Data Link Connection
Identifier (DLCI) - Locally Unique (FR ports)
Trailer includes 2 byte CRC Sequence that only
checks Header
I/O decisions based on FR address & look-up table.