Transcript CCSDS HDLC Concept

Including HDLC Framing in
CCSDS Recommendations
James Rash
- NASA/GSFC
Keith Hogie, Ed Criscuolo,
Trans fer Frame
VC
Frame Re lay Frame
Pack ets , Bits , e tc.
C
R
C
DL
CI
Pack ets , Bits , e tc.
Ron Parise
- Computer Sciences
Corp
F
L
G
Space Data Link
Protocols
Transfer Frames
Sync and Channel
Coding
C F
R L
CG
Bits or Bytes
R/S Code block
Sy nc
Mark
June 2004
HDLC Frame
SIW-4 - HDLC for CCSDS
Data
R/S
sy mbols
1
Basic Concept
•
Add ISO HDLC frame synchronization as an option to TM/TC/AOS
recommendations for data link frame synchronization
•
Add IETF RFC 2427 multi-protocol data link frame header as an
option to TM/TC/ AOS recommendations for data link
•
This adds an option for spacecraft to use data link formats that
are supported by all common carriers and network equipment
vendors’ synchronous serial interfaces
•
It provides an option that separates link frame sync and FEC
coding sync which allows changing FEC coding type and block
length independent of data link format
•
It allows spacecraft data to be inserted directly into all national
and international carriers Frame Relay and IP networks
•
It supports encapsulation of IP and many other network protocols
June 2004
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2
What About IP Encapsulation in CCSDS Frames
•
•
CCSDS has defined a way to encapsulate IP packets inside
CCSDS frames that uses the IP header fields for packet
identification and length like CCSDS packet header fields
This doesn’t fit with the concept of providing end-to-end IP
network connectivity using COTS routers
– Custom CCSDS/IP gateways are required to process IP packets
– These gateways need to evolve rapidly like COTS routers to incorporate
new routing, traffic management, and security options
– This is not feasible in a low-volume CCSDS gateway
•
IP packets encapsulated in CCSDS frames require more
complicated data processing that IP in Frame Relay/HDLC
– First header pointers and lengths require clean links to recover data
– Approach results in IP packets split across link frames just like it does with
CCSDS packets (with HDLC, one IP packet is in one HDLC frame)
– Losing one CCSDS frame results in the loss of many IP packets
– Tightly coupled to link coding and requires major hardware change
whenever coding changes
•
June 2004
Currently no definition for IP on CCSDS uplinks
SIW-4 - HDLC for CCSDS
3
HDLC Space Link Data Framing
•
ISO/IEC 13239:2002, “Information technology -Telecommunications and information exchange between systems
-- High-level data link control (HDLC) procedures”, International
Organization For Standardization (Adopted ISO/IEC 13239:2002,
third edition, 2002-07-15)
•
HDLC FLAG bytes (01111110) between frames
– no fill frames or packets
– continual FLAG bit pattern when no data frames being transmitted
•
Bit stuffing to ensure no FLAG patterns in data or CRC
•
CRC-16 on end of frame for error detection
•
Variable length frames up to at least 4K Bytes
Bit stuffing applied
Link Framing
Flag
(1B)
Variable Length Frame Data
CRC-16
(2B)
Flag
(1B)
Flag
(1B)
HDLC Frame
June 2004
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4
Frame Relay Space Link Data Framing
•
IETF Multi-Protocol Encapsulation over Frame Relay (RFC 2427, STD 55)
– Uses Frame Relay/HDLC - Not X.25 or LAP-B
– No windowing, optional flow control - completely independent of delay
•
•
•
Frame Relay DLCI provides 1024 virtual channels
Standard Frame Relay processing supported by all telecom vendors
Normally one user data packet per variable length frame
– No first header pointers or packet extraction processing
– Any packet segmentation or fragmentation handled in upper layer protocols
•
Supports encapsulation of IP and many other network protocols
Frame Relay/Multi-Protocol Encapsulation Header
Link Layer Header
Link Framing
Flag
(1B)
FR Hdr Encap Hdr
(2B)
(2B)
Frame Data
Data
CRC-16
(2B)
Flag
(1B)
Flag
(1B)
HDLC Frame
June 2004
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RFC 2427 Frame Headers
•
First 2 bytes of Frame Relay
information
Upper DLCI
(6 bits)
C/R EA
=0
Lower DLCI
(4 bits)
•
Next 2 bytes of protocol
encapsulation information
FE BE DE EA
CN CN
=1
RFC 2427 Encapsulation Header
Address extension (EA): Used to determine the size of
the header.
Data link connection identifier (DLCI): A logical
identifier used to distinguish between multiple Frame
Relay connections over a link.
Command/response (C/R): This bit indicates whether
the current frame is a command frame or a response
frame.
Forward and backward explicit congestion
notification (FECN, BECN): The network uses these
notifications for congestion avoidance. The network sends
these notifications to the users in advance of congestion
problems.
Discard eligibility (DE): DE is used to discard frames
when the network experiences congestion. Frames that
exceed the traffic parameters (CIR, Bc, Be) are tagged by
the network with the DE bit to indicate that they are more
likely to be discarded if the need arises.
June 2004
Control (UI) 0x0 3
(8 bits)
NLPID
(8 bits)
List of Commonly Used NLPIDs
0x00
0x08
0x80
0x81
0x82
0x83
0x8E
0xB0
0xB1
0xCC
0xCF
SIW-4 - HDLC for CCSDS
Null Network Layer or Inactive Set
(not used with Frame Relay)
Q.933 [2]
SNAP
ISO CLNP
ISO ESIS
ISO ISIS
IPv6
FRF.9 Data Compression [14]
FRF.12 Fragmentation [18]
IPv4
PPP in Frame Relay [17]
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CCSDS and HDLC Ground Support Comparison
•
Very similar except the HDLC commercial world separates FEC
and framing at a bitstream level interface
Commercial Router/
Frame Relay Switch
CCSDS
NP or IP
NP or IP
Packet Insert
VCDU Framing
FEC Encode
Packet Extract
VCDU Framing
FEC Decode
Randomize
Derandomize
Conv. Encode
Conv. Decode
Net PDU
IP
IP
Frame
HDLC Framing
HDLC Framing
FEC Encode
FEC Decode
Randomize
Derandomize
Conv. Encode
Conv. Decode
101010
(bits)
Bit sync
Bit sync
Modulator
Demod
Modulator
Demod
Transmitter
Receiver
Transmitter
Receiver
Upconvert
Downconvert
Upconvert
Downconvert
Antenna
June 2004
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Fixed Length FEC Coding Blocks and HDLC
•
•
•
•
Question - How do you put variable bit length HDLC frames in
fixed byte length code blocks (e.g. Reed-Solomon, TPC, LDPC) ?
Answer - Separate data link framing and FEC coding
Different approach from traditional CCSDS framing where transfer
frame and R-S code block use the same attached sync mark (ASM)
HDLC inserts into fixed length R/S, TPC, LDPC codeblock as a
bitstream and is extracted as a bitstream on the other end of link
– In the commercial network world R/S, TPC, LDPC and convolutional coding
are performed at the physical layer independent of HDLC data link framing
– FEC has no relation to any framing present in the bit stream
– HDLC provides its own sync independent of any optional coding sync marks
•
Separation of coding allows changing coding type and block
length with no changes to HDLC framing
Variable Bit Length HDLC Frames
HDLC
Frame Data
Codeblock Size number of Bits
Coding
R/S Sym
ASM
ASM
•••
Fixed Length FEC Codeblock
June 2004
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Adding HDLC to CCSDS Recommendations
•
IP packets similar to CCSDS packets
•
RFC 2427 encapsulation similar to CCSDS encapsulation header
•
HDLC framing appears as a bitstream service directly into CCSDS
forward-error-correction code blocks
•
HDLC framing can be radiated directly without R/S coding added
Trans fer Frame
VC
Frame Re lay Frame
Pack ets , Bits , e tc.
C
R
C
F
L
G
Space Data Link
Protocols
Transfer Frames
Sync and Channel
Coding
Pack ets , Bits , e tc.
HDLC Frame
C F
R L
CG
Bits or Bytes
R/S Code block
Sy nc
Mark
June 2004
DL
CI
Data
SIW-4 - HDLC for CCSDS
R/S
sy mbols
9
Ground Support for HDLC
•
•
HDLC is widely used by the amateur radio community
HDLC has been used by NASA’s South Pole TDRSS Relay (SPTR)
since 1997
– TDRSS relay satellites don’t see frames of CCDSDS or HDLC they just
relay RF signals
– Routers installed at White Sands in a special configuration for SPTR
•
HDLC was installed in a few months to support the STS-107
shuttle flight and the Communication and Navigation
Demonstration on Shuttle (CANDOS) experiment
– Routers and convolutional decoders at NASA Ground Network (GN) sites at
Wallops and Merritt Island
– Routers at NASA Space Network (SN) sites at White Sands Ground
Terminal (WSGT) and Second TDRSS Ground Terminal (STGT)
•
•
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June 2004
Routers used by SSTL DMC stations in UK, Turkey, Algeria, and
Nigeria
Linux router used by CHIPSat ground stations
Full operational support for IP services being developed for
TDRSS under Space Network IP Services (SNIS) project
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Current HDLC in Space Status
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Used for over 20 years in small educational and experimental
spacecraft.
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Over 80 past, present, or planned missions used or will use HDLC
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Developed and operated by 23 universities, 8 amateur groups, and
7 commercial space entities in 24 countries
•
Also represented are NASA, the US Air Force, the US Navy, and
the Chilean Air Force.
•
Earth resources satellites by Germany and Turkey, are currently in
development and will use HDLC.
•
A Disaster Monitoring Constellation (DMC) by UK, Algeria, Nigeria,
and Turkey is currently operational and uses HDLC with 8Mbps
downlinks.
•
NASA’s CHIPSat is currently operational and uses HDLC
•
Future missions (e.g. GPM, MMS, LRO) are selecting HDLC/Frame
Relay for its flexibility, simple implementation, low-cost, and wide
availability
June 2004
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HDLC Spacecraft
Spacecraf t
UoSat-1
UoSat-2
AO-13
SAREX
UoSat-3
UoSat-4
HealthSat-I
Dov e
WeberSat
LUSAT
PACSAT
JAS-1b
UO-14
SARA
S80/T
KITSat-1
Arsene
PoSAT
HealthSat-II
KITSat-2
ITAMSAT
AO-27
Cerise
Fasat-A
UNAMSAT-1
UNAMSAT-2
JAS-2
Fasat-B
TechSat-1b
SEDSAT
TMSAT-1
PanSat
Clementine
SunSat
June 2004
Launch Y ear
1981
1984
1988
1990
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1999
Owner Organization
Univ ersity of Surrey
Univ ersity of Surrey
AMSAT
AMSAT
Univ ersity of Surrey
Univ ersity of Surrey /ESA
SateLif e
AMSAT-Brazil
Weber State Univ ersity
AMSAT-LU
AMSAT
JAMSAT
Univ ersity of Surrey
Amateur Radio Astronomy
Matra Espace/CNES
Korean Adv anced Institute of Science
ENSAE/CNES
Portugal
SateLif e
Korean Adv anced Institute of Science
AMSAT-I
AMRAD
Alcatel Espace/DME
Chile
Univ ersity Program of Space Research
Univ ersity Program of Space Research
JAMSAT
Chilean Air Force (FACH)
IARC
Univ ersity of Alabama, Huntsv ille
TMSC and MUT
Nav al Post-Graduate School
Alcatel Espace(France)
Stellenbosch Univ ersity
SIW-4 - HDLC for CCSDS
Owner Country
Status
UK
UK
USA
USA
UK
UK
USA
Brazil
USA
Argentina
USA
Japan
UK
France
France
Korea
France
Portugal
USA
Korea
Italy
USA
France
Chile
Mexico
Mexico
Japan
Chile
Israel
USA
Thailand
USA
France
South Af rica
decay ed
operational
non-operational
multiple shuttle missions
operational
non-operational
operational
non-operational
non-operational
operational
semi-operational
operational
operational
non-operational
operational
operational
non-operational
operational
operational
operational
semi-operational
operational
operational
non-commissioned
f ailed launch
non-operational
operational
operational
unknown
semi-operational
operational
operational
operational
non-operational
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HDLC Spacecraft (cont)
UoSat-12
JAWSAT
SNAP-1
Tsinghua-1
Opal
ASUsat-1
SaudiSat-1A
SaudiSat-1B
TIUNGSAT-1
AO-40
ARISS
PicoSat
FalconSat I
Sapphire
PCSat
Starshine 3
Emerald
ChipSat
CUTE
XI-IV
3 Corner Sat
HokieSat
AlSat (DMC)
TopSat
StenSat
MOST
Starshine 4
Starshine 5
NigeriaSat (DMC)
BILSAT (DMC)
UK-DMC (DMC)
DTUsat
AAU Cubesat
BiltenSat
RapidEy e
Poly Sat
Citizen-Explorer
CESAR-1
June 2004
1999
1999
2000
2000
2000
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2000
2000
2000
2000
2000
2000
2001
2001
2001
2002
2002
2002
2002
2002
2002
2002
2003
2003
2003
2003
2003
2003
2003
2003
TBD
TBD
TBD
TBD
TBD
TBD
TBD
Surrey Satellite Technology LTD
USAFA/Weber State Univ .
SSTL dev elopment satellite
Tsinghua Univ ersity , Beijing
Stanf ord Univ ersity
Arizona State Univ ersity
King Abdulaziz City f or Science & Tech
King Abdulaziz City f or Science & Tech
Astronautic Technology
AMSAT-DL
AMSAT
USAF
Air Force Academy
Stanf ord Univ ersity
US Nav al Academy
Project Starshine (NASA/USN/USAF)
Stanf ord Univ ersity
UC Berkeley
Toky o Institute of Technology
Univ ersity of Toky o
USAF/ASU
VA Tech (Univ ersity Nanosat)
Algeria
UK MoD and BNSC
StenSat Group
Univ ersity of British Columbia
Project Starshine (NASA/USN/USAF)
Project Starshine (NASA/USN/USAF)
Nigeria
Turkey
UK
Technical Univ ersity of Denmark
Aalborg Univ ersity
Turkey
RapidEy e A.G.
Calif ornia Poly technic Univ ersity
Univ ersity of Colorado
AMSAT-Chile
SIW-4 - HDLC for CCSDS
UK
USA
UK
China
USA
USA
Saudi Arabia
Saudi Arabia
May lasia
Germany
USA
USA
USA
USA
USA
USA
USA
USA
Japan
Japan
USA
USA
Algeria
UK
USA
Canada
USA
USA
Nigeria
Turkey
UK
Denmark
Denmark
Turkey
Germany
USA
USA
Chile
operational
unknown
operational
operational
operational
non-operational
unknown
unknown
operational
operational
in use on ISS
unknown
operational
operational
operational
operational
in dev elopment
in dev elopment
in dev elopment
in dev elopment
in dev elopment
in dev elopment
operational
in dev elopment
in dev elopment
in dev elopment
in dev elopment
in dev elopment
operational
operational
operational
in dev elopment
in dev elopment
in dev elopment
in dev elopment
in dev elopment
in dev elopment
in dev elopment
13