As per Relevance of the word security, we have this rfc below:
Network Working Group A.
Request for Comments: 2615 Ascend Communications, Inc
Obsoletes: 1619 W.
Category: Standards Track
June 1999
PPP over SONET/
Status of this
This document specifies an Internet standards track protocol for
Internet community, and requests discussion and suggestions
improvements. Please refer to the current edition of the "
Official Protocol Standards" (STD 1) for the standardization
and status of this protocol. Distribution of this memo is unlimited
Copyright
Copyright (C) The Internet Society (1999). All Rights Reserved
The Point-to-Point Protocol (PPP) [1] provides a standard method
transporting multi-protocol datagrams over point-to-point links
This document describes the use of PPP over Synchronous
Network (SONET) and Synchronous Digital Hierarchy (SDH) circuits
This document replaces and obsoletes RFC 1619. See section 7 for
summary of the changes from RFC 1619.
Table of
1. Introduction .......................................... 2
2. Physical Layer Requirements ........................... 3
3. Framing ............................................... 4
4. X**43 + 1 Scrambler Description ....................... 4
5. Configuration Details ................................. 6
6. Security Considerations ............................... 6
7. Changes from RFC 1619 ................................. 7
8. Intellectual Property ................................. 7
9. Acknowledgments ....................................... 8
10. References ............................................ 8
11. Authors' Addresses .................................... 9
12. Full Copyright Statement .............................. 10
Malis & Simpson Standards Track [Page 1]
RFC 2615 PPP over SONET/SDH June 1999
1.
PPP was designed as a standard method of communicating
point-to-point links. Initial deployment has been over short
lines, leased lines, and plain-old-telephone-service (POTS)
modems. As new packet services and higher speed lines are introduced
PPP is easily deployed in these environments as well
This specification is primarily concerned with the use of the
encapsulation over SONET/SDH links. Since SONET/SDH is by
a point-to-point circuit, PPP is well suited to use over these links
Real differences between SONET and SDH (other than terminology)
minor; for the purposes of encapsulation of PPP over SONET/SDH,
are inconsequential or irrelevant
For the convenience of the reader, we list the equivalent terms below
SONET
---------------------------------------------
SPE
STS-SPE Higher Order VC (VC-3/4/4-Nc
STS-1 frame STM-0 frame (rarely used
STS-1-SPE VC-3
STS-1 payload C-3
STS-3c frame STM-1 frame, AU-4
STS-3c-SPE VC-4
STS-3c payload C-4
STS-12c/48c/192c frame STM-4/16/64 frame, AU-4-4c/16c/64
STS-12c/48c/192c-SPE VC-4-4c/16c/64
STS-12c/48c/192c payload C-4-4c/16c/64
The only currently supported SONET/SDH SPE/VCs are the following
SONET
----------------------------------------
STS-3c-SPE VC-4
STS-12c-SPE VC-4-4
STS-48c-SPE VC-4-16
STS-192c-SPE VC-4-64
The keywords MUST, MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED
SHALL, SHALL NOT, SHOULD, and SHOULD NOT are to be interpreted
defined in [6].
Malis & Simpson Standards Track [Page 2]
RFC 2615 PPP over SONET/SDH June 1999
2. Physical Layer
PPP treats SONET/SDH transport as octet oriented synchronous links
SONET/SDH links are full-duplex by definition
Interface
PPP in HDLC-like framing presents an octet interface to
physical layer. There is no provision for sub-octets to
supplied or accepted [3][5].
The octet stream is mapped into the SONET STS-SPE/SDH Higher
VC, with the octet boundaries aligned with the SONET STS-SPE/
Higher Order VC octet boundaries
Scrambling is performed during insertion into the SONET STS
SPE/SDH Higher Order VC to provide adequate transparency
protect against potential security threats (see Section 6).
backwards compatibility with RFC 1619 (STS-3c-SPE/VC-4 only),
scrambler MAY have an on/off capability where the scrambler
bypassed entirely when it is in the off mode. If this
is provided, the default MUST be set to scrambling enabled
For PPP over SONET/SDH, the entire SONET/SDH payload (SONET STS
SPE/SDH Higher Order VC minus the path overhead and any
stuff) is scrambled using a self-synchronous scrambler
polynomial X**43 + 1. See Section 4 for the description of
scrambler
The proper order of operation is
When transmitting
IP -> PPP -> FCS generation -> Byte stuffing -> Scrambling ->
SONET/SDH
When receiving
SONET/SDH framing -> Descrambling -> Byte destuffing ->
detection -> PPP ->
The Path Signal Label (C2) indicates the contents of the SONET STS
SPE/SDH Higher Order VC. The value of 22 (16 hex) is used
indicate PPP with X^43 + 1 scrambling [4].
For compatibility with RFC 1619 (STS-3c-SPE/VC-4 only), if
has been configured to be off, then the value 207 (CF hex) is
for the Path Signal Label to indicate PPP without scrambling
Malis & Simpson Standards Track [Page 3]
RFC 2615 PPP over SONET/SDH June 1999
The Multiframe Indicator (H4) is unused, and MUST be zero
Control
PPP does not require the use of control signals. When available
using such signals can allow greater functionality
performance. Implications are discussed in [2].
3.
The framing for octet-synchronous links is described in "PPP
HDLC-like Framing" [2].
The PPP frames are located by row within the SONET STS-SPE/SDH
Order VC payload. Because frames are variable in length, the
are allowed to cross SONET STS-SPE/SDH Higher Order VC boundaries
4. X**43 + 1 Scrambler
The X**43 + 1 scrambler transmitter and receiver operation are
follows
Transmitter schematic
Unscrambled
|
+-------------------------------------+ +---+
+->| --> 43 bit shift register --> |--->|xor
| +-------------------------------------+ +---+
| |
+-----------------------------------------------+
|
Scrambled
Malis & Simpson Standards Track [Page 4]
RFC 2615 PPP over SONET/SDH June 1999
Receiver schematic
Scrambled
|
+-----------------------------------------------+
| |
|
| +-------------------------------------+ +---+
+->| --> 43 bit shift register --> |--->|xor
+-------------------------------------+ +---+
|
Unscrambled
Note: While the HDLC FCS is calculated least significant bit first
shown
<- <- <- <-
A B C
(that is, the FCS calculator is fed as follows: A[0], A[1], ... A[7],
B[0], B[1], etc...), scrambling is done in the opposite manner,
significant bit first, as shown
-> -> -> ->
A B C D
That is, the scrambler is fed as follows: A[7], A[6], ... A[0], B[7],
B[6], etc...
The scrambler operates continuously through the bytes of the
STS-SPE/SDH Higher Order VC, bypassing bytes of SONET Path
and any fixed stuff (see Figure 20 of ANSI T1.105 [3] or Figure 10-17
of ITU G.707 [5]). The scrambling state at the beginning of a
STS-SPE/SDH Higher Order VC is the state at the end of the
SONET STS-SPE/SDH Higher Order VC. Thus, the scrambler
continuously and is not reset per frame. The initial seed is
chosen by transmitter to improve operational security (see
6). Consequently, the first 43 transmitted bits following startup
reframe operation will not be descrambled correctly
Malis & Simpson Standards Track [Page 5]
RFC 2615 PPP over SONET/SDH June 1999
5. Configuration
Other than the FCS length (see below), the standard LCP
configuration defaults apply to SONET/SDH links
The following Configuration Options are RECOMMENDED for STS-3c
SPE/VC-4:
Magic
No Address and Control Field
No Protocol Field
For operation at STS-12c-SPE/VC-4-4c and above, Address and
Field Compression and Protocol Field Compression are NOT RECOMMENDED
The Magic Number option remains RECOMMENDED
Regarding the FCS length, with one exception, the 32-bit FCS MUST
used for all SONET/SDH rates. For STS-3c-SPE/VC-4 only, the 16-
FCS MAY be used, although the 32-bit FCS is RECOMMENDED. The
length is set by provisioning and is not negotiated
6. Security
The major change from RFC 1619 is the addition of payload
when inserting the HDLC-like framed PPP packets into the SONET STS
SPE/SDH Higher Order VC. RFC 1619 was operationally found to
malicious users to generate packets with bit patterns that
create SONET/SDH-layer low-transition-density
problems, emulation of the SDH set-reset scrambler pattern,
replication of the STM-N frame alignment word
The use of the x^43 + 1 self-synchronous scrambler was introduced
alleviate these potential security problems. Predicting the
of the scrambler requires knowledge of the 43-bit state of
transmitter as the scrambling of a known input is begun.
requires knowledge of both the initial 43-bit state of the
when it started and every byte of data scrambled by the device
it was started. The odds of guessing correctly are 1/2**43, with
additional probability of 1/127 that a correct guess will leave
frame properly aligned in the SONET/SDH payload, which results in
probability of 9e-16 against being able to deliberately
SONET/SDH-layer problems. This seems reasonably secure for
application
This scrambler is also used when transmitting ATM over SONET/SDH,
public network carriers have considerable experience with its use
Malis & Simpson Standards Track [Page 6]
RFC 2615 PPP over SONET/SDH June 1999
A known security issue is bandwidth reduction by
transmission of characters or sequences requiring
processing by including flag and/or escape characters in user data.
user may cause up to a 100% increase in the bandwidth required
transmitting his or her packets by filling the packet with
and/or escape characters
7. Changes from RFC 1619
As mentioned in the previous section, the major change from RFC 1619
was the addition of payload scrambling when inserting the HDLC-
framed PPP packets into the SONET STS-SPE/SDH Higher Order VC.
changes were
The terminology was updated to better match that used by ANSI
ITU-T
The specification's applicability is now specifically restricted to
SONET
----------------------------------------
STS-3c-SPE VC-4
STS-12c-SPE VC-4-4
STS-48c-SPE VC-4-16
STS-192c-SPE VC-4-64
The Path Signal Label (C2) is set to 22 (16 hex) when using X^43 + 1
scrambling
The 32-bit FCS is required except for operation with STS-3c-SPE/VC-4,
in which case the 16-bit FCS is allowed (but the 32-bit FCS is
recommended).
The Security Considerations section was added
8. Intellectual
The IETF takes no position regarding the validity or scope of
intellectual property or other rights that might be claimed
pertain to the implementation or use of the technology described
this document or the extent to which any license under such
might or might not be available; neither does it represent that
has made any effort to identify any such rights. Information on
IETF's procedures with respect to rights in standards-track
standards-related documentation can be found in BCP-11. Copies
claims of rights made available for publication and any assurances
licenses to be made available, or the result of an attempt made
obtain a general license or permission for the use of
Malis & Simpson Standards Track [Page 7]
RFC 2615 PPP over SONET/SDH June 1999
proprietary rights by implementors or users of this specification
be obtained from the IETF Secretariat
The IETF invites any interested party to bring to its attention
copyrights, patents or patent applications, or other
rights which may cover technology that may be required to
this standard. Please address the information to the IETF
Director
9.
The scrambler description was provided by J. Manchester, S. Davida
B. Doshi, and J. Anderson of Lucent Technologies, R. Broberg of
Systems, and Peter Lothberg of Sprint Corporation. The
analysis was provided by Iain Verigin of PMC-Sierra and Larry
of Cisco Systems. The authors would also like to thank the
of the IETF's Point-to-Point Protocol Extensions Working Group
their many suggestions and improvements to the text
10.
[1] Simpson, W., Editor, "The Point-to-Point Protocol (PPP)",
51, RFC 1661, Daydreamer, July 1994.
[2] Simpson, W., Editor, "PPP in HDLC-like Framing", STD 51,
1662, Daydreamer, July 1994.
[3] American National Standards Institute, "Synchronous
Network (SONET) - Basic Description including
Structure, Rates and Formats," ANSI T1.105-1995.
[4] American National Standards Institute, "Synchronous
Network (SONET)--Payload Mappings," T1.105.02-1998.
[5] ITU Recommendation G.707, "Network Node Interface For
Synchronous Digital Hierarchy", 1996.
[6] Bradner, S., "Key words for use in RFCs to indicate
Levels", BCP 14, RFC 2119, March 1997.
Malis & Simpson Standards Track [Page 8]
RFC 2615 PPP over SONET/SDH June 1999
11. Authors'
Andrew G.
Ascend Communications, Inc
1 Robbins
Westford, MA 01810
Phone: +1 978 952 7414
EMail: malis@ascend.
William Allen
Computer Systems Consulting
1384
Madison Heights, Michigan 48071
EMail: wsimpson@GreenDragon.
Malis & Simpson Standards Track [Page 9]
RFC 2615 PPP over SONET/SDH June 1999
12. Full Copyright
Copyright (C) The Internet Society (1999). All Rights Reserved
This document and translations of it may be copied and furnished
others, and derivative works that comment on or otherwise explain
or assist in its implementation may be prepared, copied,
and distributed, in whole or in part, without restriction of
kind, provided that the above copyright notice and this paragraph
included on all such copies and derivative works. However,
document itself may not be modified in any way, such as by
the copyright notice or references to the Internet Society or
Internet organizations, except as needed for the purpose
developing Internet standards in which case the procedures
copyrights defined in the Internet Standards process must
followed, or as required to translate it into languages other
English
The limited permissions granted above are perpetual and will not
revoked by the Internet Society or its successors or assigns
This document and the information contained herein is provided on
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE
Funding for the RFC Editor function is currently provided by
Internet Society
Malis & Simpson Standards Track [Page 10]
if you see any problems within the linking, don't worry be happy,
this is version 0.1 of the Relevance System and you gotta expect some crappy subroutines sometimes,
just be content we did not write this in Java, which would have made this "bigger and better" HAHAHHA.
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