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An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks

Martin Herrmann

Chair for Network Architectures and Services Department for Computer Science Technische Universit¨ at M¨ unchen

May 15, 2013

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 1

Outline

1

Motivation a.k.a. ”The Old Header”

2

IEEE 802.11

3

The new Header Structure

4

Evaluation

5

Conclusion

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 2

Motivation a.k.a. ”The Old Header”

What is a Wireless (Coded) Mesh-Network? Nodes in the network are connected wirelessly Many different possible routes = ⇒ reliability Combining packets using finite field arithmetic

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 3

Motivation a.k.a. ”The Old Header”

What is a Wireless (Coded) Mesh-Network? Nodes in the network are connected wirelessly Many different possible routes = ⇒ reliability Combining packets using finite field arithmetic

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 3

Motivation a.k.a. ”The Old Header”

What is a Wireless (Coded) Mesh-Network? Nodes in the network are connected wirelessly Many different possible routes = ⇒ reliability Combining packets using finite field arithmetic

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 3

Motivation a.k.a. ”The Old Header”

The old moep80211 Header

Frame Control Duration / ID MAC 1 (SA) MAC 2 (DA) MAC 3 (TA) SEQ MAC 4 (RA) Frame Disc. Frame Info Generation SEQ Rank Info Coefficients Ethertype Payload Length Frame Body FCS

≀≀ ≀≀ ≀≀ ≀≀ Octets 2 2 6 6 6 2 6 Octets 2 2 2 4 2 – 128 2 2 Octets 0 - 2162 4

Very large (36 – 172 Bytes), not all information is always of interest Different versions for different purposes, no efficient way for assembling the header

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 4

Motivation a.k.a. ”The Old Header”

The old moep80211 Header

Frame Control Duration / ID MAC 1 (SA) MAC 2 (DA) MAC 3 (TA) SEQ MAC 4 (RA) Frame Disc. Frame Info Generation SEQ Rank Info Coefficients Ethertype Payload Length Frame Body FCS

≀≀ ≀≀ ≀≀ ≀≀ Octets 2 2 6 6 6 2 6 Octets 2 2 2 4 2 – 128 2 2 Octets 0 - 2162 4

Very large (36 – 172 Bytes), not all information is always of interest Different versions for different purposes, no efficient way for assembling the header

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 4

Motivation a.k.a. ”The Old Header”

The old moep80211 Header

Frame Control Duration / ID MAC 1 (SA) MAC 2 (DA) MAC 3 (TA) SEQ MAC 4 (RA) Frame Disc. Frame Info Generation SEQ Rank Info Coefficients Ethertype Payload Length Frame Body FCS

≀≀ ≀≀ ≀≀ ≀≀ Octets 2 2 6 6 6 2 6 Octets 2 2 2 4 2 – 128 2 2 Octets 0 - 2162 4

Very large (36 – 172 Bytes), not all information is always of interest Different versions for different purposes, no efficient way for assembling the header

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 4

Outline

1

Motivation a.k.a. ”The Old Header”

2

IEEE 802.11

3

The new Header Structure

4

Evaluation

5

Conclusion

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 5

IEEE 802.11

Why use IEEE 802.11? moep80211 is based on IEEE 802.11 and cannot access the physical medium by itself Advantage: can be used with existing wireless hardware Disadvantage: having to ”deal” with the IEEE 802.11 header

Frame Control Duration / ID MAC 1 (RA) MAC 2 (TA) MAC 3 (SA) SEQ MAC 4 (DA) QoS Control HT Control Payload FCS

Octets 2 2 6 6 6 2 Octets 6 2 4 0 – 7951 4

Figure: Generic IEEE 802.11 header

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 6

IEEE 802.11

Why use IEEE 802.11? moep80211 is based on IEEE 802.11 and cannot access the physical medium by itself Advantage: can be used with existing wireless hardware Disadvantage: having to ”deal” with the IEEE 802.11 header

Frame Control Duration / ID MAC 1 (RA) MAC 2 (TA) MAC 3 (SA) SEQ MAC 4 (DA) QoS Control HT Control Payload FCS

Octets 2 2 6 6 6 2 Octets 6 2 4 0 – 7951 4

Figure: Generic IEEE 802.11 header

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 6

IEEE 802.11

Why use IEEE 802.11? moep80211 is based on IEEE 802.11 and cannot access the physical medium by itself Advantage: can be used with existing wireless hardware Disadvantage: having to ”deal” with the IEEE 802.11 header

Frame Control Duration / ID MAC 1 (RA) MAC 2 (TA) MAC 3 (SA) SEQ MAC 4 (DA) QoS Control HT Control Payload FCS

Octets 2 2 6 6 6 2 Octets 6 2 4 0 – 7951 4

Figure: Generic IEEE 802.11 header

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 6

IEEE 802.11

Why use IEEE 802.11? moep80211 is based on IEEE 802.11 and cannot access the physical medium by itself Advantage: can be used with existing wireless hardware Disadvantage: having to ”deal” with the IEEE 802.11 header

Frame Control Duration / ID MAC 1 (RA) MAC 2 (TA) MAC 3 (SA) SEQ MAC 4 (DA) QoS Control HT Control Payload FCS

Octets 2 2 6 6 6 2 Octets 6 2 4 0 – 7951 4

Figure: Generic IEEE 802.11 header

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 6

IEEE 802.11

Problems due to the IEEE 802.11 header Frame format must adhere to the basic IEEE 802.11 structure A receiver must still be able to differentiate between moep80211 and regular frames Changing of some fields is not possible or causes problems elsewhere = ⇒ presence of unnecessary information

Frame Control Duration / ID MAC 1 (RA) MAC 2 (TA) MAC 3 (SA) SEQ MAC 4 (DA) QoS Control HT Control Payload FCS

Octets 2 2 6 6 6 2 Octets 6 2 4 0 – 7951 4

Figure: Generic IEEE 802.11 header

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 7

IEEE 802.11

Problems due to the IEEE 802.11 header Frame format must adhere to the basic IEEE 802.11 structure A receiver must still be able to differentiate between moep80211 and regular frames Changing of some fields is not possible or causes problems elsewhere = ⇒ presence of unnecessary information

Frame Control Duration / ID MAC 1 (RA) MAC 2 (TA) MAC 3 (SA) SEQ MAC 4 (DA) QoS Control HT Control Payload FCS

Octets 2 2 6 6 6 2 Octets 6 2 4 0 – 7951 4

Figure: Generic IEEE 802.11 header

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 7

IEEE 802.11

Problems due to the IEEE 802.11 header Frame format must adhere to the basic IEEE 802.11 structure A receiver must still be able to differentiate between moep80211 and regular frames Changing of some fields is not possible or causes problems elsewhere = ⇒ presence of unnecessary information

Frame Control Duration / ID MAC 1 (RA) MAC 2 (TA) MAC 3 (SA) SEQ MAC 4 (DA) QoS Control HT Control Payload FCS

Octets 2 2 6 6 6 2 Octets 6 2 4 0 – 7951 4

Figure: Generic IEEE 802.11 header

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 7

Outline

1

Motivation a.k.a. ”The Old Header”

2

IEEE 802.11

3

The new Header Structure

4

Evaluation

5

Conclusion

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 8

The new Header Structure

Basic idea The old structure was complicated and not very efficient. Performance and expandability are improved by using following concepts: Use of a generic header that contains the basic information Adding of extension headers where special information is necessary Moving the frame discriminator into the third address field of the IEEE 802.11 header

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 9

The new Header Structure

Basic idea The old structure was complicated and not very efficient. Performance and expandability are improved by using following concepts: Use of a generic header that contains the basic information Adding of extension headers where special information is necessary Moving the frame discriminator into the third address field of the IEEE 802.11 header

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 9

The new Header Structure

Basic idea The old structure was complicated and not very efficient. Performance and expandability are improved by using following concepts: Use of a generic header that contains the basic information Adding of extension headers where special information is necessary Moving the frame discriminator into the third address field of the IEEE 802.11 header

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 9

The new Header Structure

Basic idea The old structure was complicated and not very efficient. Performance and expandability are improved by using following concepts: Use of a generic header that contains the basic information Adding of extension headers where special information is necessary Moving the frame discriminator into the third address field of the IEEE 802.11 header

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 9

The new Header Structure

The new generic frame header

Frame Control Duration / ID MAC 1 MAC 2 Frame Disc SEQ MAC 4 QoS Control HT Control Next Header Seq Number Further data

Octets 2 2 6 6 6 2 Octets 6 2 4 1 2

Frame discriminator Third address field set to value of fe:ff:ff:12:34:56 Locally administered unicast MAC address Should not be in regular use

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 10

The new Header Structure

The new generic frame header

Frame Control Duration / ID MAC 1 MAC 2 Frame Disc SEQ MAC 4 QoS Control HT Control Next Header Seq Number Further data

Octets 2 2 6 6 6 2 Octets 6 2 4 1 2

Frame discriminator Third address field set to value of fe:ff:ff:12:34:56 Locally administered unicast MAC address Should not be in regular use

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 10

The new Header Structure

The new generic frame header

Frame Control Duration / ID MAC 1 MAC 2 Frame Disc SEQ MAC 4 QoS Control HT Control Next Header Seq Number Further data

Octets 2 2 6 6 6 2 Octets 6 2 4 1 2

Frame discriminator Third address field set to value of fe:ff:ff:12:34:56 Locally administered unicast MAC address Should not be in regular use

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 10

The new Header Structure

The new generic frame header

Frame Control Duration / ID MAC 1 MAC 2 Frame Disc SEQ MAC 4 QoS Control HT Control Next Header Seq Number Further data

Octets 2 2 6 6 6 2 Octets 6 2 4 1 2

Frame discriminator Third address field set to value of fe:ff:ff:12:34:56 Locally administered unicast MAC address Should not be in regular use

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 10

The new Header Structure

Extension headers Contain specific additional information Are identified by their extension header ID (EID) in the previous header Usually start with a next header field May affect the data following after the extension

Next Header Extension-specific information

Octets 1

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 11

The new Header Structure

Extension headers Contain specific additional information Are identified by their extension header ID (EID) in the previous header Usually start with a next header field May affect the data following after the extension

Next Header Extension-specific information

Octets 1

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 11

The new Header Structure

Extension headers Contain specific additional information Are identified by their extension header ID (EID) in the previous header Usually start with a next header field May affect the data following after the extension

Next Header Extension-specific information

Octets 1

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 11

The new Header Structure

Extension headers Contain specific additional information Are identified by their extension header ID (EID) in the previous header Usually start with a next header field May affect the data following after the extension

Next Header Extension-specific information

Octets 1

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 11

The new Header Structure

Extension headers Contain specific additional information Are identified by their extension header ID (EID) in the previous header Usually start with a next header field May affect the data following after the extension

Next Header Extension-specific information

Octets 1

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 11

The new Header Structure

Existing extensions

Ethertype Payload length

Octets 2 2

(a) EthertypeLength header

Padding (reserved) Overall length

Octets 2 2

(b) Multipacket header

Coding param. Generation SEQ Feedback Coeff. Type MA Coeff SL Coeff MA gen RX rank TX rank SL gen RX rank TX rank

Octets 2 2 8 2 – 128 Bits 2 7 7 16 8 8 16 8 8

(c) Coding header

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 12

The new Header Structure

Multipacket frame format

Multipacket header EthtypeLen header 1 Payload 1 . . . EthtypeLen header k Payload k

k packets Octets 4 4 n1 Octets 4 nk

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 13

Outline

1

Motivation a.k.a. ”The Old Header”

2

IEEE 802.11

3

The new Header Structure

4

Evaluation

5

Conclusion

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 14

Evaluation

Comparison of header sizes

IEEE 802.11 header Generic header Ethertype Length IEEE 802.11 header Generic header Ethertype Length

Octets Old 30 4 4 = 38 Octets New 24 3 4 = 31

(a) Comparison of uncoded PTM headers

IEEE 802.11 header Generic header Coding header IEEE 802.11 header Generic header Coding header

Octets Old 30 4 16 = 50 Octets New 24 3 17 = 44

(b) Comparison of coded NCM headers

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 15

Evaluation

Efficiency of header generation

• ld

new 35 40 45 50 Implementation Translation time [ns]

(a) PTM translation times for moep80211 to IEEE 802.11

• ld

new 100 150 200 Implementation Translation time [ns]

(b) PTM translation times for IEEE 802.11 to moep80211

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 16

Evaluation

Efficiency of header generation

802.11 Generic EthertypeLength 32 34 36 38 40 42 Header building function Translation time [ns]

Figure: Evaluation of the functions generating the different header

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 17

Outline

1

Motivation a.k.a. ”The Old Header”

2

IEEE 802.11

3

The new Header Structure

4

Evaluation

5

Conclusion

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 18

Conclusion

Have the goals been reached? Unified structure: all frames use the same format and add extensions where needed Smaller headers: the new structure is in many cases significantly smaller Efficency: conversion is not significantly slower Extendability: support of additional coding fields and new features

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 19

Conclusion

Have the goals been reached? Unified structure: all frames use the same format and add extensions where needed Smaller headers: the new structure is in many cases significantly smaller Efficency: conversion is not significantly slower Extendability: support of additional coding fields and new features

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 19

Conclusion

Have the goals been reached? Unified structure: all frames use the same format and add extensions where needed Smaller headers: the new structure is in many cases significantly smaller Efficency: conversion is not significantly slower Extendability: support of additional coding fields and new features

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 19

Conclusion

Have the goals been reached? Unified structure: all frames use the same format and add extensions where needed Smaller headers: the new structure is in many cases significantly smaller Efficency: conversion is not significantly slower Extendability: support of additional coding fields and new features

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 19

Conclusion

Have the goals been reached? Unified structure: all frames use the same format and add extensions where needed Smaller headers: the new structure is in many cases significantly smaller Efficency: conversion is not significantly slower Extendability: support of additional coding fields and new features

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 19

Conclusion

Future developments moep80211 cannot be considered finished Message encryption and authentication will become necessary in the future but are not supported yet Addition is being developed by Julius Michaelis

Next Header Info field Data Padding HMAC AES Encrypted

Octets 1 1 1 – 16 20

Figure: Encrypted session data format (by Julius Michaelis)

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 20

Conclusion

Future developments moep80211 cannot be considered finished Message encryption and authentication will become necessary in the future but are not supported yet Addition is being developed by Julius Michaelis

Next Header Info field Data Padding HMAC AES Encrypted

Octets 1 1 1 – 16 20

Figure: Encrypted session data format (by Julius Michaelis)

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 20

Conclusion

Future developments moep80211 cannot be considered finished Message encryption and authentication will become necessary in the future but are not supported yet Addition is being developed by Julius Michaelis

Next Header Info field Data Padding HMAC AES Encrypted

Octets 1 1 1 – 16 20

Figure: Encrypted session data format (by Julius Michaelis)

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 20

Conclusion

Future developments moep80211 cannot be considered finished Message encryption and authentication will become necessary in the future but are not supported yet Addition is being developed by Julius Michaelis

Next Header Info field Data Padding HMAC AES Encrypted

Octets 1 1 1 – 16 20

Figure: Encrypted session data format (by Julius Michaelis)

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 20

Bibliography

D.D. Coleman and D.A. Westcott, Cwna certified wireless network administrator official study guide: Exam pw0-104, Serious skills, Wiley, 2009. Jerome Henry and Marcus Burton, 802.11s Mesh Networking, Tech. report, Certified Wireless Network Professional, 2011. IEEE Standard for Information technology–Telecommunications and information exchange between systems Local and metropolitan area networks–Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, IEEE Std 802.11-2012 (Revision of IEEE Std 802.11-2007) (2012). Stephan M. G¨ unther, moep80211 - Towards a Coded Wireless Mesh Network based on IEEE 802.11 Consumer Hardware, 2012. D.A. Westcott, D.D. Coleman, B. Miller, and P . Mackenzie, Cwap certified wireless analysis professional official study guide: Exam pw0-270, Serious skills, Wiley, 2011.

Martin Herrmann: An Extendable Link Layer Frame Format for Wireless Coded Mesh Networks 21