19531 - Telematics · IETF Important standardization related documents: Bradner The Internet Standards Process – Revision 3 RFC 2026, 1996 Alvestrand The IESG and RFC Editor Documents:

19531 - Telematics2nd Tutorial - IETF, Reference Models, Terms, . . .

Bastian Blywis

Department of Mathematics and Computer ScienceInstitute of Computer Science04. November, 2010

Institute of Computer Science – Telematics Tutorial – 04. November, 2010 1

Outline

1. IETF

2. Reference Models

3. Classification of Computer Networks

4. Multilevel Signals

5. Transmission medium

6. Units

7. Noise and Attenuation

8. Important Terms


IETF

– Read RFC 2026 and discuss the InternetEngineering Task Force (IETF) standardizationprocess.

– What types of documents are published by theIETF?

– What are important differences to otherstandardization bodies, e.g., the IEEE?

?? ?Institute of Computer Science – Telematics Tutorial – 04. November, 2010 3

IETF

Internet Engineering Task Force– International community of network designers,

operators, vendors, and researchers– Concerned with evolution of the Internet

architecture and the smooth operation of theInternet

– Technical work done in working groups, organizedby topics

– Mailing lists as important communication channel,meetings three times a year

– Examples: TCP and IP (and thus the TCP/IPInternet model)


IETF

Important standardization related documents:

Bradner The Internet Standards Process – Revision 3RFC 2026, 1996

Alvestrand The IESG and RFC Editor Documents: ProceduresRFC 3932, 2004

Bradner Intellectual Property Rights in IETF TechnologyRFC 3979, 2005

Bradner Rights Contributors Provide to the IETF TrustRFC 5378, 2008


IETF

Internet Engineering Steering Group (IESG)– IESG responsible for technical management of IETF activities and Internet

standards process– Administers the process according to rules and procedures ratified by the Internet

Society (ISOC) trustees (see RFC 2026/BCP 9)– Directly responsible for actions associated with entry into and movement along the

Internet ”standards track”, including final approval of specifications as InternetStandards.

– Consists of the Area Directors (ADs) selected by Nominations Committee(NomCom); appointed for two years (see RFC 2727/BCP 10)


IETF

The goals of the Internet Standards Process are:– Technical excellence– Prior implementation and testing– Clear, concise, and easily understood

documentation– Openness and fairness– Timeliness


IETF

Request for Comment (RFC)– Internet standards-related specification– Series of documents on networking– Started as part of the ARPANET project in 1969– Available in ASCII text; additional versions may

contain more “material”– ASCII text version is definitive reference (complete

and accurate)– Informal submission process

– Draft version of document (Internet-Draft)– Drafts removed when not modified for 6 months and

not recommended for publication as an RFC– Drafts have no formal status; subject to change or

removal at any time

– RFCs are never modified after publication!– RFC can be updated and obsoleted by other RFCs– Newest RFC has number 5910 (but less than 5910

RFCs in total)


IETF

Some oddities

Waitzman A Standard for the Transmission of IP Datagrams on Avian CarriersRFC 1149, 1990

Hancock The 12-Days of Technology Before ChristmasRFC 1882, 1995

Masinter Hyper Text Coffee Pot Control Protocol (HTCPCP/1.0)RFC 2324, 1998

Christey The Infinite Monkey Protocol Suite (IMPS)RFC 2795, 2000

Bellovin The Security Flag in the IPv4 HeaderRFC 3514, 2003

Published on 1st of April, because of holidays, or other reasons.


IETF

Internet Standard– Some RFC’s are Internet Standards– STD subseries of RFCs– Successful operational experience required– Standards track required to get RFC to standard status


IETF

1. Evolution through a set of maturity levels(”standards track”)

2. Further evolution based on experience and newrequirements

Proposal

Proposed Standard

Draft Standard

Full Standard

Experimental

Informal

Proposed Std.: Generally stable, has resolved design choises, well understood,significant amount of reviews, has community support

Draft Std.: Two independent and interoperable implementations from differentcode bases developed, sufficient successful operational experience

Standard: Significant implementation and successful operational experience


IETF

Best Current Practice (BCP)– Numbered document series by IETF– All BCPs are also RFCs

– RFC number refers to specific version of a document– BCP number refers to the most recent revision

– BCPs used to document items not suitable forstandardization

– Guidelines– Processes– Methods

– Internet standards process is defined in a series ofBCPs

– List of FYIs: http://www.rfc-editor.org/bcp-index.html

Example BCP

Klensin Terminology for Describing Internet ConnectivityRFC 4084, BCP 104, 2005


http://www.rfc-editor.org/bcp-index.html

IETF

For Your Information (FYI)– FYI series of notes by IETF– All FYIs are also RFCs– Provide Internet users with repository about topics

which relate to the Internet– ”Why it was was done this way”– Answers to commonly asked operational questions

– General information or discussion of advancedtopics

– List of FYIs: http://www.rfc-editor.org/fyi-index.html

Example FYI

Libes Choosing a Name for Your ComputerRFC 1178, FYI 5, 1990


http://www.rfc-editor.org/fyi-index.html

IETF

Figure: Publication Rate per Year, source http://arkko.com/tools/rfcstats


IETF

Figure: Number of Pages in Documents, source http://arkko.com/tools/rfcstats

min = 1 pagemax = 581 pagesInstitute of Computer Science – Telematics Tutorial – 04. November, 2010 15

IETF

Figure: Comparison of Countries over the Years (normalized), source http://arkko.com/tools/rfcstats


IETF

Figure: Distribution of RFCs according to the continents of their authors, sourcehttp://arkko.com/tools/rfcstats


IETF

Figure: Distribution of authors from companies, source http://arkko.com/tools/rfcstats


IETF

Differences of the IETF to other standardization bodies:– Mailing list centric discussion– No fees for participation in working groups– Much less industry driven than, e.g., IEEE– Focus on layer 3-7 of the ISO/OSI reference model– Attendance at IETF meetings not required– All documents are freely available

Further standardization bodies:– Institute of Electrical and Electronics Engineers (IEEE)– International Telecommunication Union (ITU)– International Organization for Standardization (ISO)– Deutsche Institut fur Normung (DIN)– European Committee for Standardization (CEN)– Organization for the Advancement of Structured Information

Standards (OASIS)


Reference Models

– Repeat and discuss the differences in the ISO/OSIand TCP/IP models.

– Take a look at the session and presentation layerfunctions of the ISO/OSI model.

– Where are they implemented in the TCP/IP model?– Discuss if this is a good design decision.


Reference ModelsApplicationPresentationSessionTransportNetworkData LinkPhysical Logical Link ControlMedium Access ControlFigure: ISO/OSI Model

ApplicationTransportNetworkHost to NetworkFigure: TCP/IP Model


Reference Models

TCP/IP Reference Model– Services, interfaces, and protocols were originally not distinguished– Model was created as description after protocols were specified– Host-To-Network layer

– Not specified– Some network technology able transport of IP datagrams– Routers must be able to handle 576 byte sized datagrams → common MTU of 576 byte– Very often IEEE specific standards, e.g., IEEE 802.3 Ethernet or

IEEE 802.11 Wireless LAN– Alternative names: network interface, data link, network access

– Network layer is always connection-less– Application layer

– Implemented by some specific software component– Usually in user space application– Sometimes in kernel space

– Generally includes session and presentation layer because they are often highlyapplication dependent

– May be split up in several sub-layers


Classification of Computer Networks

– List and explain the different classes of computernetworks.

– Additionally, explain what body area, vehicular,wireless sensor, and wireless mesh networks are.

– Name example application scenarios for theseclasses and who is usually managing the networks.


Classification of Computer Networks

Traditional networks (usually wired, last hop maybe wireless):– Local Area Network (LAN)– Metropolitan Area Network (MAN)– Wide Area Network (WAN)

New network types (wireless and/or mobile):– Body Area Network (BAN)– Vehicular Network (VANET)– Wireless Sensor Network (WSN)– Wireless Mesh Network (WMN)


Multilevel Signals

– Represent the following sequence of bits as aquaternary signal with a baud rate of 5/s in atime-voltage-diagram:

00011011001110011010

– Determine the bitrate. ?? ?Institute of Computer Science – Telematics Tutorial – 04. November, 2010 25

Multilevel Signals

t

10

11

01

00

1s 2s

– Quarternary signal: four discrete levels, 4 symbols– 10 symbols with 2 bit: 00 01 10 11 00 11 10 01 10 10

– 5 baud = 5 symbols per second⇒ 10 bps


Transmission medium

– What is a transmission medium?– Give examples!– Is a transmission medium always required for

communication? ?? ?Institute of Computer Science – Telematics Tutorial – 04. November, 2010 27

Transmission medium

Transmission medium– Material substance (liquid, gas, solid)– Propagates waves (sound, electro-magnetic, light)– Guided (wired) or unguided (wireless)– Frequency specific properties per medium (attenuation, reflection, refraction)– Transmission medium not required: electro-magnetic waves in vacuum


Units

– What is the difference between 1 kb, 1 kB, and1 KiB? ?? ?


Units

1 kb = 1 kbit (1)

1 kB = 1 kByte = 8 kbit = 1000 Byte (2)

1 KiB = 1 kibibyte = 210 Byte = 1024 Byte (3)

– International System of Units (SI) prefix kilo refers to base 10– Binary prefix kibi established by International Electrotechnical Commission (IEC)

in 1999– 1 kByte are often considered 1024 bytes in literature– General rule: Be aware that different people have different understandings of unit

prefixes. Ask if you are not sure.– Sometimes it does matter if base 2 or 10 is used, e.g., analytical evaluation of

networks and protocols


Noise and Attenuation

– Every signal is subjected to noise.– Can you specify what noise is and how it affects the

signal?– Name sources of noise.– What is attenuation and how does it influence a

signal??? ?



Noise– Unwanted energy from other sources– Example types of noise:

– White noise: random signal/process with flat power spectral density– Brown noise: power density decreases 6 dB per octave with increasing frequency– Blue noise: power density increases 3 dB per octave with increasing frequency

– Complicates detection of a signal or renders it impossible– Received signal is a mixture of original signal and noise⇒ bit errors possible– Sources:

– WLAN access points and clients– Mobile phones– Microwave oven– Cables– Electronic circuits of any kind

– Transmission range and interference range have a different sizeDefinition of interference

“Disturbance of the transmission or reception of signals by the intrusion ofextraneous signals; hence, signals collectively or radiation which causes suchdisturbance, or the effects by which it is perceived (e.g. unwanted sounds inradio reception).”

Source: Oxford English Dictionary



0 2 4 6 8 10 12 14 1621012

Sig

nal (i

dealiz

ed)

0 2 4 6 8 10 12 14 1621012

Sig

nal (r

eal)

0 2 4 6 8 10 12 14 161.00.50.00.51.0

Nois

e

0 2 4 6 8 10 12 14 16time [ms]

21012

Sig

nal+

Nois

e



Attenuation– Loss of energy as the signal propagates– Attenuation due to absorption or scattering– Energy loss depends on medium and frequency (signal often consists of multiple

Fourier components!)– Attenuation is defined as

Attenuation [dB] = −10 log10

(Pout

Pin

)– Decibel := “relation of power measured at two points”– Attenuation of a medium expressed in [dB/km]



Example:

Pin = 5mW → Medium, 40 km → Pout = 250µW

Attenuation [dB] = −10 log10

(250µW5mW

)Attenuation [dB] = −10 log10

(250× 10−6W5× 10−3W

)Attenuation [dB] = 13.01 dB

= 0.325 dB/km


Important Terms

– What do the terms overhearing, eavesdropping,and crosstalk mean in the context of Telematics?

– Give examples. ?? ?Institute of Computer Science – Telematics Tutorial – 04. November, 2010 36

Important Terms

Overhearing: to hear contrary to the intention or without the knowledge of thespeaker

Eavesdropping: to listen secretly to private conversation

Crosstalk: transmission creates an undesired effect in another circuit or channel


The Last SlideTM

Thank you for your attention.Questions?
