e hogie ccsds hdlc concept

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June 2004 SIW-4 - HDLC for CCSDS 1

Inc lud ing HDLC Fram ing in

CCSDS Recommendat ions

James Rash

- NASA/GSFC

Keith Hogie, Ed Criscuolo,

Ron Parise

- Computer Sciences

Corp

R/S Codeblock

Packets, Bits, etc.VC Packets, Bits, etc.DLCI

SyncMark

Data R/Ssymbols

HDLC FrameCRC

FLG

Space Data LinkProtocols

Sync and ChannelCoding

CRC

Transfer Frame Frame Relay Frame

Bits or BytesTransfer Frames

FLG




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 nationaland international carriers Frame Relay and IP networks

• It supports encapsulation of IP and many other network protocols




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

• Currently no definition for IP on CCSDS uplinks




HDLC Frame

Link Layer Header

FR Hdr

(2B)

Encap Hdr

(2B) Frame Data

Link FramingFlag

(1B)

Flag

(1B)Data CRC-16

(2B)

Flag

(1B)

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




RFC 2427 Frame Headers

• First 2 bytes of Frame Relay

information

Upper DLCI(6 bits)

C/R EA=0

Lower DLCI(4 bits)

DE EA=1

BECN

FECN

RFC 2427 Encapsulation Header

Control (UI) 0x03

(8 bits)

NLPID

(8 bits)

List of Commonly Used NLPIDs

0x00 Null Network Layer or Inactive Set

(not used with Frame Relay)

0x08 Q.933 [2]0x80 SNAP

0x81 ISO CLNP

0x82 ISO ESIS

0x83 ISO ISIS

0x8E IPv6

0xB0 FRF.9 Data Compression [14]

0xB1 FRF.12 Fragmentation [18]

0xCC IPv4

0xCF PPP in Frame Relay [17]

Address extension (EA) : Used to determine the size of

the header.

Data link c onn ection identif ier (DLCI) :

A logicalidentifier used to distinguish between multiple Frame

Relay connections over a link.

Comm and/response (C/R) : This bit indicates whether

the current frame is a command frame or a response

frame.

Forward and backward expl ic i t congest ion

notif ic at ion (FECN, BECN) : The network uses these

notifications for congestion avoidance. The network sends

these notifications to the users in advance of congestion

problems.

Discard eligibi l i ty (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.

• Next 2 bytes of protocol

encapsulation information


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Downconvert

Receiver

Demod

Bit sync

Derandomize

Conv. Decode

Upconvert

Transmitter

Modulator

Randomize

Conv. Encode

CCSDS

Downconvert

Receiver

Demod

Bit sync

Derandomize

Conv. Decode

FEC Decode

Upconvert

Transmitter

Modulator

Randomize

Conv. Encode

FEC Encode

Antenna

HDLC FramingHDLC Framing

IPIP

101010

(bits)

Frame

Net PDU

Commercial Router/Frame Relay Switch

Packet Insert

VCDU Framing

FEC Encode

Packet Extract

VCDU Framing

FEC Decode

NP or IP NP or IP

CCSDS and HDLC Ground Support Comparison

• Very similar except the HDLC commercial world separates FEC

and framing at a bitstream level interface



ASM R/S SymCoding

HDLC Frame Data

••• ASM

Fixed Length FEC Codeblock

Variable Bit Length HDLC Frames

Codeblock Size number of Bits

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



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

R/S Codeblock

Packets, Bits, etc.VC Packets, Bits, etc.DLCI

SyncMark

Data R/Ssymbols

HDLC FrameCRC

FLG

Space Data Link

Protocols

Sync and ChannelCoding

CRC

Transfer Frame Frame Relay Frame

Bits or BytesTransfer Frames

FLG



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)

• Routers used by SSTL DMC stations in UK, Turkey, Algeria, andNigeria

• Linux router used by CHIPSat ground stations

• Full operational support for IP services being developed for

TDRSS under Space Network IP Services (SNIS) project



Current HDLC in Space Status

• Used for over 20 years in small educational and experimental

spacecraft.

• Over 80 past, present, or planned missions used or will use HDLC

• 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



HDLC Spacecraft

Spacecraft Launch Year Owner Organization Owner Country Status

UoSat-1 1981 University of Surrey UK decayedUoSat-2 1984 University of Surrey UK operational

AO-13 1988 AMSAT USA non-operational

SAREX 1990 AMSAT USA multiple shuttle missions

UoSat-3 1990 University of Surrey UK operational

UoSat-4 1990 University of Surrey/ESA UK non-operational

HealthSat-I 1990 SateLife USA operational

Dove 1990 AMSAT-Brazil Brazil non-operational

WeberSat 1990 Weber State University USA non-operational

LUSAT 1990 AMSAT-LU Argentina operational

PACSAT 1990 AMSAT USA semi-operational

JAS-1b 1990 JAMSAT Japan operational

UO-14 1990 University of Surrey UK operationalSARA 1991 Amateur Radio Astronomy France non-operational

S80/T 1992 Matra Espace/CNES France operational

KITSat-1 1992 Korean Advanced Institute of Science Korea operational

Arsene 1993 ENSAE/CNES France non-operational

PoSAT 1993 Portugal Portugal operational

HealthSat-II 1993 SateLife USA operational

KITSat-2 1993 Korean Advanced Institute of Science Korea operational

ITAMSAT 1993 AMSAT-I Italy semi-operational

AO-27 1993 AMRAD USA operational

Cerise 1995 Alcatel Espace/DME France operational

Fasat-A 1995 Chile Chile non-commissioned

UNAMSAT-1 1995 University Program of Space Research Mexico failed launchUNAMSAT-2 1996 University Program of Space Research Mexico non-operational

JAS-2 1996 JAMSAT Japan operational

Fasat-B 1998 Chilean Air Force (FACH) Chile operational

TechSat-1b 1998 IARC Israel unknow n

SEDSAT 1998 University of Alabama, Huntsville USA semi-operational

TMSAT-1 1998 TMSC and MUT Thailand operational

PanSat 1998 Naval Post-Graduate School USA operational

Clementine 1999 Alcatel Espace(France) France operational

SunSat 1999 Stellenbosch University South Africa non-operational



HDLC Spacecraft (cont)

UoSat-12 1999 Surrey Satellite Technology LTD UK operational

JAWSAT 1999 USAFA/Weber State Univ. USA unknow n

SNAP-1 2000 SSTL development satellite UK operationalTsinghua-1 2000 Tsinghua University, Beijing China operational

Opal 2000 Stanford University USA operational

ASUsat-1 2000 Arizona State University USA non-operational

SaudiSat-1A 2000 King Abdulaziz City for Science & Tech Saudi Arabia unknow n

SaudiSat-1B 2000 King Abdulaziz City for Science & Tech Saudi Arabia unknow n

TIUNGSAT-1 2000 Astronautic Technology Maylasia operational

AO-40 2000 AMSAT-DL Germany operational

ARISS 2000 AMSAT USA in use on ISS

PicoSat 2000 USAF USA unknow n

FalconSat I 2000 Air Force Academy USA operational

Sapphire 2001 Stanford University USA operational

PCSat 2001 US Naval Academy USA operationalStarshine 3 2001 Project Starshine (NASA/USN/USAF) USA operational

Emerald 2002 Stanford University USA in development

ChipSat 2002 UC Berkeley USA in development

CUTE 2002 Tokyo Institute of Technology Japan in development

XI-IV 2002 University of Tokyo Japan in development

3 Corner Sat 2002 USAF/ASU USA in development

HokieSat 2002 VA Tech (University Nanosat) USA in development

AlSat (DMC) 2002 Algeria Algeria operational

TopSat 2003 UK MoD and BNSC UK in development

StenSat 2003 StenSat Group USA in development

MOST 2003 University of British Columbia Canada in development

Starshine 4 2003 Project Starshine (NASA/USN/USAF) USA in developmentStarshine 5 2003 Project Starshine (NASA/USN/USAF) USA in development

NigeriaSat (DMC) 2003 Nigeria Nigeria operational

BILSAT (DMC) 2003 Turkey Turkey operational

UK-DMC (DMC) 2003 UK UK operational

DTUsat TBD Technical University of Denmark Denmark in development

AAU Cubesat TBD Aalborg University Denmark in development

BiltenSat TBD Turkey Turkey in development

RapidEye TBD RapidEye A.G. Germany in development

PolySat TBD California Polytechnic University USA in development

Citizen-Explorer TBD University of Colorado USA in development

CESAR-1 TBD AMSAT-Chile Chile in development

e hogie ccsds hdlc concept

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