ASN.1 Compiler for text-based protocols!

1
ASN.1 Compiler for text-based protocols!

• Raman Govindan
• Software Consultant, Wipro Technologies

2
AGENDA

• What is ASN.1 Compiler?
• Components of ASN.1 Compiler
• Example of ASN.1 Specification
• Working of ASN.1 Compiler
• Case Study

3
What is ASN.1 Compiler?

• ASN.1 Compiler is a tool to convert the data
  description in ASN.1 format to programming
  language dependent data structures and associated
  routines to encode/decode the same.
• Two approaches to generate encode/decode routines
• dedicated routines per message
• generic routines (which is considered for the
  rest of the presentation)

4
ASN.1 Compiler Components
ASN.1
specification
Input Validation
and Parsing

Header
File
Table
Decoded Data
ASN.1 Encode
ASN.1 Decode
Network
Encoded bytes
5
ASN.1 Example

• typedef struct
• char b
• C c
• D d
• int e
• A
• typedef struct
• char c
• int e
• C
• typedef struct
• int e
• D

• A SEQUENCE
• b BOOLEAN
• c C
• d D
• e INTEGER
• C SEQUENCE
• c BOOLEAN
• e INTEGER
• D SEQUENCE
• e INTEGER

6
Wipro ASN.1 Compiler Front-End Working
B
BOOLEAN
A
I
INTEGER
D
C
I
B
Info B Info I Info C Info D Info
A B, I I,
B, C, D, I
7
Wipro ASN.1 Compiler Back-End Working
Driving Table

• typedef struct
• char b(1)
• C c
• D d
• int e(5)
• A
• typedef struct
• char c(0)
• int e(2)
• C
• typedef struct
• int e(3)
• D

B
I
C
D
A
ROOT
BOOLEAN
BOOLEAN
Encoded Bit stream
INTEGER
INTEGER
INTEGER
1
2
3
0
5
8
Footprint of various alternatives.
Units are in KB
160
140
120
100
80
60
40
20
0
RAS
Q.931
H.245
H.225
H.323
9
Advantages of text-based protocols and how ASN.1
Tools help achieve the same.

• easy implementation
• easy debugging
• similar parser implementation available
• high extensibility

ASN.1 Compiler eases implementation
ASN.1 Compiler trace facility for debug
ASN.1 Compiler generates code.
ASN.1 support extension elements
10
Case Study Text-based ASN.1-based

• Case study is on a comparative study of
  text-based versus ASN.1-based protocol
• extract of text-based protocol and its equivalent
  ASN.1 representation is taken as reference for
  the study.

11
Extract of Text-based protocol

• time-fields 1( "t"
  start-time space stop-time
• (CRLF
  repeat-fields) CRLF)
• 
  zone-adjustments CRLF
• repeat-fields "r"
  repeat-interval space typed-time
• 1(space
  typed-time)
• zone-adjustments time space "-"
  typed-time
• (space
  time space "-" typed-time)
• start-time time "0"
• stop-time time "0"
• time POS-DIGIT
  9(DIGIT)
• sufficient
  for 2 more centuries
• repeat-fields "r"
  repeat-interval space typed-time
• 1(space
  typed-time)
• repeat-interval typed-time
• typed-time 1(DIGIT)
  fixed-len-time-unit
• fixed-len-time-unit "d" "h" "m" "s"
• zone-adjustments time space "-"
  typed-time
• (space
  time space "-" typed-time)

12
Equivalent ASN.1 Representation

• TimeFields SEQUENCE
• timeFields SEQUENCE OF TimeField
• zoneAdjustments ZoneAdjustments OPTIONAL
• TimeField SEQUENCE
• startTime NTPTimeStamp Optional -- Optional
  means 0
• stopTime NTPTimeStamp Optional -- Optional
  means 0
• repeatFields SEQUENCE OF RepeatField OPTIONAL
• NTPTimeStamp INTEGER(1000000000..4294967295)
  
• positiveNegativeNTPTimeStamp
  INTEGER(1000000000..4294967295)
• repeatFields SEQUENCE
• repeatInterval typedTime
• duration typedTime
• offset SEQUENCE OF typedTime

13
Equivalent ASN.1 Representation . . .

• zoneAdjustements SEQUENCE
• time NTPTimeStamp
• adjust positiveNegativetypedTime
• typedTime CHOICE
• ntpTimeStamp NTPTimeStamp
• days INTEGER (1..73050)
  -- Two centuries
• hours INTEGER (1..8784)
  -- One year
• minutes INTEGER (1..527040)
  -- One year
• seconds INTEGER (1..31622400) --
  One year
• positiveNegativetypedTime CHOICE
• ntpTimeStamp positiveNegativeNTPTimeStam
  p
• days INTEGER(-73050..730
  50)
• hours INTEGER(-8784..8784
  )
• minutes INTEGER(-527040..5270
  40)
• seconds INTEGER(-31622400..316
  22400)

14
Benchmark Results Text-based ASN.1-based

• 2800 Encoding - 1micro-seconds
• 280 Decoding - 1micro- seconds
• Is there a tool to optimize parser-generated
  code?
• Footprint is 100KB for entire grammar which
  includes the one in this case study.
• Text compression can be used for efficient
  bandwidth at the expense of performance

• 23000 Encoding - 1micro-seconds
• 22000 Decoding - 1micro-seconds
• Optimized ASN.1 Compiler leads to easier
  development
• Footprint is 45KB
• PER can be used for efficient bandwidth

15
Hurdles to ASN.1-based protocol

• Availability of limited free ASN.1 tools

Contribute more and more tools in public domain.
Tool to convert BNF to ASN.1 representation will
promote text-based evangelists to consider
ASN.1-based protocols.
16
One Application of ASN.1
VoiceEngine for RG
VoiceEngine for RG
ASN.1 is used here
Wipro
VoiceEngine
H323-NCS GW
HFC out
C
Settop Box,
Home Gateway,
M
HFC OUT
LAN Access Point
visit us at http//www.wipro.com/homenet
VoiceEngine Software provides the Voice Over
Cable Capability to the device
17
Thank You
visit us at http//www.wipro.com/homenet