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FYI on Questions and Answers: Answers to commonly asked "new internet user" questions
RFC 1177

Document	Type	RFC - Informational (August 1990) Obsoleted by RFC 1206
	Authors	Joyce K. Reynolds , Gary S. Malkin , April Marine
	Last updated	2013-03-02
	RFC stream	Legacy stream
	Formats	txt html pdf htmlized bibtex
IESG	Responsible AD	(None)
	Send notices to	(None)

IPR References Referenced by Search Lists

RFC 1177

Network Working Group G. Malkin
Request for Comments: 1177 FTP Software, Inc.
FYI: 4 A. Marine
SRI
J. Reynolds
ISI
August 1990

FYI on Questions and Answers
Answers to Commonly asked "New Internet User" Questions

Status of this Memo

This FYI RFC is one of three FYI's called, "Questions and Answers"
(Q/A), produced by the User Services Working Group (USWG) of the
Internet Engineering Task Force (IETF). The goal is to document the
most commonly asked questions and answers in the Internet.

This memo provides information for the Internet community. It does
not specify any standard. Distribution of this memo is unlimited.

Table of Contents

1. Introduction.................................................... 1
2. Acknowledgements................................................ 2
3. Questions About the Internet.................................... 2
4. Questions About TCP/IP.......................................... 3
5. Questions About Internet Documentation.......................... 4
6. Questions about Internet Organizations and Contacts............. 6
7. Questions About Services........................................ 9
8. Mailing Lists................................................... 11
9. References...................................................... 11
10. Suggested Reading.............................................. 12
11. Condensed Glossary............................................. 12
12. Security Considerations........................................ 23
13. Authors' Addresses............................................. 24

1. Introduction

New users joining the Internet community for the first time have had
the same questions as did everyone else who has ever joined. Our
quest is to provide the Internet community with up to date, basic
Internet knowledge and experience, while moving the redundancies away
from the electronic mailing lists so that the lists' subscribers do
not have to read the same queries and answers over and over again.

Future updates of this memo will be produced as USWG members become

User Services Working Group [Page 1]
RFC 1177 FYI Q/A - for New Internet Users August 1990

aware of additional questions that should be included, and of
deficiencies or inaccuracies that should be amended in this document.
Additional FYI Q/A's will be published which will deal with
intermediate and advanced Q/A topics.

The Q/A mailing lists are maintained by Gary Malkin at FTP.COM. They
are used by a subgroup of the USWG to discuss the Q/A FYIs. They
include:

quail@ftp.com This is a discussion mailing list. Its
primary use is for pre-release (to the
USWG) review of the Q/A FYIs.

quail-request@ftp.com This is how you join the quail mailing list.

quail-box@ftp.com This is where the questions and answers
will be forwarded-and-stored. It is
not necessary to be on the quail mailing
list to forward to the quail-box.

2. Acknowledgements

The following people deserve thanks for their help and contributions
to the FYI Q/As: Berlin Moore (PREPNet), Craig Partridge (BBN),
Jon Postel (ISI), Karen Roubicek (BBNST), James Van Bokkelen (FTP
Software, Inc.), John Wobus (Syracuse University), and David Paul
Zimmerman (Rutgers).

3. Questions About the Internet

I just got on the Internet. What can I do now?

You now have access to all the resources you are authorized to use
on your own Internet host, on any other Internet host on which you
have an account, and on any other Internet host that offers
publicly accessible information. The Internet gives you the
ability to move information between these hosts via file
transfers. Once you are logged into one host, you can use the
Internet to open a connection to another, log in, and use its
services interactively. In addition, you can send electronic mail
to users at any Internet site and to users on many non-Internet
sites that are accessible via electronic mail.

There are various other services you can use. For example, some
hosts provide access to specialized databases or to archives of
information. The Internet Resource Guide provides information
regarding some of these sites. The Internet Resource Guide lists
facilities on the Internet that are available to users. Such

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bandwidth transmissions, and increased latencies. IEEE 802.15.4
admits a maximum physical layer packet size of 127 octets. The
maximum frame header size is 25 octets, which leaves 102 octets for
the payload. IEEE 802.15.4 security features further reduce this
payload length by up to 21 octets, yielding a net of 81 octets for
CCNx or NDN packet headers, signatures and content.

6LoWPAN [RFC4944], [RFC6282] is a convergence layer that provides
frame formats, header compression and link fragmentation for IPv6
packets in IEEE 802.15.4 networks. The 6LoWPAN adaptation introduces
a dispatching framework that prepends further information to 6LoWPAN
packets, including a protocol identifier for IEEE 802.15.4 payload
and meta information about link fragmentation.

Prevalent Type-Length-Value (TLV) based packet formats such as in
CCNx and NDN are designed to be generic and extensible. This leads
to header verbosity which is inappropriate in constrained
environments of IEEE 802.15.4 links. This document presents ICN
LoWPAN, a convergence layer for IEEE 802.15.4 motivated by 6LoWPAN.
ICN LoWPAN compresses packet headers of CCNx as well as NDN and
allows for an increased effective payload size per packet.
Additionally, reusing the dispatching framework defined by 6LoWPAN
enables compatibility between coexisting wireless networks of
competing technologies. This also allows to reuse the link
fragmentation scheme specified by 6LoWPAN for ICN LoWPAN.

ICN LoWPAN defines a more space efficient representation of CCNx and
NDN packet formats. This syntactic change is described for CCNx and
NDN separately, as the header formats and TLV encodings differ
notably. For further reductions, default header values suitable for
constrained IoT networks are selected in order to elide corresponding
TLVs. Experimental evaluations of the ICN LoWPAN header compression
schemes in [ICNLOWPAN] illustrate a reduced message overhead, a
shortened message airtime, and an overall decline in power
consumption for typical Class 2 devices compared to uncompressed ICN
messages.

In a typical IoT scenario (see (Figure 1)), embedded devices are
interconnected via a quasi-stationary infrastructure using a border
router (BR) that uplinks the constrained LoWPAN network by some
Gateway with the public Internet. In ICN based IoT networks, non-
local Interest and Data messages transparently travel through the BR
up and down between a Gateway and the embedded devices situated in
the constrained LoWPAN.

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|Gateway Services|
-------------------------
|
,--------,
| |
| BR |
| |
'--------'
LoWPAN
O O
O
O O embedded
O O O devices
O O

Figure 1: IoT Stub Network

The draft has received fruitful reviews by members of the ICN
community and the research group (see Acknowledgments) for a period
of two years. It is the consensus of ICNRG that this document should
be published in the IRTF Stream of the RFC series. This document
does not constitute an IETF standard.

2. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
The use of the term, "silently ignore" is not defined in RFC 2119.
However, the term is used in this document and can be similarly
construed.

This document uses the terminology of [RFC7476], [RFC7927], and
[RFC7945] for ICN entities.

The following terms are used in the document and defined as follows:

ICN LoWPAN: Information-Centric Networking over Low-power Wireless
Personal Area Network

LLN Low-Power and Lossy Network

CCNx: Content-Centric Networking Architecture

NDN: Named Data Networking Architecture

time-value: a time value measured in seconds

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time-code: an 8-bit encoded time-value

3. Overview of ICN LoWPAN

3.1. Link-Layer Convergence

ICN LoWPAN provides a convergence layer that maps ICN packets onto
constrained link-layer technologies. This includes features such as
link-layer fragmentation, protocol separation on the link-layer
level, and link-layer address mappings. The stack traversal is
visualized in Figure 2.

Device 1 Device 2
,------------------, Router ,------------------,
| Application . | __________________ | ,-> Application |
|----------------|-| | NDN / CCNx | |-|----------------|
| NDN / CCNx | | | ,--------------, | | | NDN / CCNx |
|----------------|-| |-|--------------|-| |-|----------------|
| ICN LoWPAN | | | | ICN LoWPAN | | | | ICN LoWPAN |
|----------------|-| |-|--------------|-| |-|----------------|
| Link-Layer | | | | Link-Layer | | | | Link-Layer |
'----------------|-' '-|--------------|-' '-|----------------'
'--------' '---------'

Figure 2: ICN LoWPAN convergence layer for IEEE 802.15.4

Section 4 of this document defines the convergence layer for IEEE
802.15.4.

3.2. Stateless Header Compression

ICN LoWPAN also defines a stateless header compression scheme with
the main purpose of reducing header overhead of ICN packets. This is
of particular importance for link-layers with small MTUs. The
stateless compression does not require pre-configuration of global
state.

The CCNx and NDN header formats are composed of Type-Length-Value
(TLV) fields to encode header data. The advantage of TLVs is its
native support of variably structured data. The main disadvantage of
TLVs is the verbosity that results from storing the type and length
of the encoded data.

The stateless header compression scheme makes use of compact bit
fields to indicate the presence of optional TLVs in the uncompressed
packet. The order of set bits in the bit fields corresponds to the
order of each TLV in the packet. Further compression is achieved by

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specifying default values and reducing the codomain of certain header
fields.

Figure 3 demonstrates the stateless header compression idea. In this
example, the first type of the first TLV is removed and the
corresponding bit in the bit field is set. The second TLV represents
a fixed-length TLV (e.g., the Nonce TLV in NDN), so that the type and
the length fields are removed. The third TLV represents a boolean
TLV (e.g., the MustBeFresh selector in NDN) for which the type,
length and the value fields are elided.

Uncompressed:

Variable-length TLV Fixed-length TLV Boolean TLV
,-----------------------,-----------------------,-------------,
+-------+-------+-------+-------+-------+-------+------+------+
| TYP | LEN | VAL | TYP | LEN | VAL | TYP | LEN |
+-------+-------+-------+-------+-------+-------+------+------+

Compressed:

+---+---+---+---+---+---+---+---+
| 1 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | Bit field
+---+---+---+---+---+---+---+---+
| | |
,--' '----, '- Boolean Value
| |
+-------+-------+-------+
| LEN | VAL | VAL |
+-------+-------+-------+
'---------------'-------'
Var-len Value Fixed-len Value

Figure 3: Compression using a compact bit field - bits encode the
inclusion of TLVs.

Stateless TLV compression for NDN is defined in Section 5. Section 6
defines the stateless TLV compression for CCNx.

The extensibility of this compression is described in Section 4.1.1
and allows future documents to update the compression rules outlined
in this manuscript.

3.3. Stateful Header Compression

ICN LoWPAN further employs two orthogonal stateful compression
schemes for packet size reductions which are defined in Section 8.
These mechanisms rely on shared contexts that are either distributed

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and maintained in the entire LoWPAN, or are generated on-demand hop-
wise on a particular Interest-data path.

The shared context identification is defined in Section 8.1. The
hop-wise name compression "en-route" is specified in Section 8.2.

4. IEEE 802.15.4 Adaptation

4.1. LoWPAN Encapsulation

The IEEE 802.15.4 frame header does not provide a protocol identifier
for its payload. This causes problems of misinterpreting frames when
several network layers coexist on the same link. To mitigate errors,
6LoWPAN defines dispatches as encapsulation headers for IEEE 802.15.4
frames (see Section 5 of [RFC4944]). Multiple LoWPAN encapsulation
headers can prepend the actual payload and each encapsulation header
is identified by a dispatch type.

[RFC8025] further specifies dispatch pages to switch between
different contexts. When a LoWPAN parser encounters a "Page switch"
LoWPAN encapsulation header, then all following encapsulation headers
are interpreted by using a dispatch table as specified by the "Page
switch" header. Page 0 and page 1 are reserved for 6LoWPAN. This
document uses page TBD1 ("1111 TBD1 (0xFTBD1)") for NDN and page TBD2
("1111 TBD2 (0xFTBD2)") for CCNx.

The base dispatch format (Figure 4) is used and extended by CCNx and
NDN in Section 5 and Section 6.

0 1 2 ...
+---+---+-----------
| C | M |
+---+---+-----------

Figure 4: Base dispatch format for ICN LoWPAN

C: Compression

0: The message is uncompressed.

1: The message is compressed.

M: Message Type

0: The payload contains an Interest message.

1: The payload contains a Data message.

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ICN LoWPAN frames with compressed CCNx and NDN messages (C=1) use the
extended dispatch format in Figure 5.

0 1 2 3 ...
+---+---+---+---+---
| 1 | M |CID|EXT|
+---+---+---+---+---

Figure 5: Extended dispatch format for compressed ICN LoWPAN

CID: Context Identifier

0: No context identifiers are present.

1: Context identifier(s) are present (see Section 8.1).

EXT: Extension

0: No extension octets are present.

1: Extension octet(s) are present (see Section 4.1.1).

The encapsulation format for ICN LoWPAN is displayed in Figure 6.

Figure 6: LoWPAN Encapsulation with ICN-LoWPAN

IEEE 802.15.4: The IEEE 802.15.4 header.

RFC4944 Disp.: Optional additional dispatches defined in Section 5.1
of [RFC4944]

Page: Page Switch. TBD1 for NDN and TBD2 for CCNx.

ICN LoWPAN: Dispatches as defined in Section 5 and Section 6.

Payload: The actual (un-)compressed CCNx or NDN message.

4.1.1. Dispatch Extensions

Extension octets allow for the extensibility of the initial
compression rule set. The base format for an extension octet is
depicted in Figure 7.

User Services Working Group [Page 2]
RFC 1177 FYI Q/A - for New Internet Users August 1990

facilities include supercomputer centers, library catalogs and
specialized data collections. The guide is published by the NSF
Network Service Center (NNSC) and is continuously being updated.
The Resource Guide is distributed free via e-mail (send a note to
resource-guide-request@nnsc.nsf.net to join the e-mail
distribution) and via anonymous FTP (in nnsc.nsf.net:resource-
guide/*). Hardcopy is available at a nominal fee (to cover
reproduction costs) from the NNSC. Call the NNSC at 617-873-3400
for more information.

How do I find out if a site has a computer on the Internet?

Three good sources to consult are "!%@:: A Directory of Electronic
Mail Addressing and Networks" by Donnalyn Frey and Rick Adams;
"The User's Directory to Computer Networks", by Tracy LaQuey; and
"The Matrix: Computer Networks and Conferencing Systems
Worldwide", by John Quarterman.

In addition, it is possible to find some information about
Internet sites in the WHOIS database maintained at the DDN NIC at
SRI International. The DDN NIC provides an information retrieval
interface to the database that is also called WHOIS. To use this
interface, Telnet to NIC.DDN.MIL and type "whois" (carriage
return). No login is necessary. Type "help" at the whois prompt
for more information on using the facility. WHOIS will show many
sites, but may not show every site registered with the DDN NIC
(simply for reasons having to do with how the program is set up to
search the database).

4. Questions About TCP/IP

What is TCP/IP?

TCP/IP (Transmission Control Protocol/Internet Protocol) [4,5,6]
is the common name for a family of data-communications protocols
used to tie computers and data-communications equipment into
computer networks. TCP/IP originated for use on a network called
ARPANET, but it is currently used on a large international network
of universities, other research institutions, government
facilities, and some corporations called the Internet. TCP/IP is
also sometimes used for other networks, particularly local area
networks that tie together numerous different kinds of computers
or tie together engineering workstations.

What are the other standard protocols in the TCP/IP family?

Other than TCP and IP, the three main protocols in the TCP/IP
suite are the Simple Mail Transfer Protocol (SMTP), the File

User Services Working Group [Page 3]
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Transfer Protocol (FTP), and the Telnet Protocol. There are many
other protocols in use on the Internet. The Internet Activities
Board (IAB) regularly publishes an RFC [2] that describes the
state of standardization of the various Internet protocols. This
document is the best guide to the current status of Internet
protocols and their recommended usage.

5. Questions About Internet Documentation

What is an RFC?

The Request for Comments documents (RFCs) are working notes of the
Internet research and development community. A document in this
series may be on essentially any topic related to computer
communication, and may be anything from a meeting report to the
specification of a standard. Submissions for Requests for
Comments may be sent to the RFC Editor, Jon Postel
(POSTEL@ISI.EDU).

Most RFCs are the descriptions of network protocols or services,
often giving detailed procedures and formats providing the
information necessary for creating implementations. Other RFCs
report on the results of policy studies or summarize the work of
technical committees or workshops.

While RFCs are not refereed publications, they do receive
technical review from either the task forces, individual technical
experts, or the RFC Editor, as appropriate. Currently, most
standards are published as RFCs, but not all RFCs specify
standards.

Anyone can submit a document for publication as an RFC.
Submissions must be made via electronic mail to the RFC Editor.
RFCs are distributed online by being stored as public access
files, and a short message is sent to the distribution list
indicating the availability of the memo. Requests to be added to
this distribution list should be sent to RFC-REQUEST@NIC.DDN.MIL.

The online files are copied by interested people and printed or
displayed at their sites on their equipment. (An RFC may also be
returned via electronic mail in response to an electronic mail
query.) This means that the format of the online files must meet
the constraints of a wide variety of printing and display
equipment.

Once a document is assigned an RFC number and published, that RFC
is never revised or re-issued with the same number. There is
never a question of having the most recent version of a particular

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RFC 1177 FYI Q/A - for New Internet Users August 1990

RFC. However, a protocol (such as File Transfer Protocol (FTP))
may be improved and re-documented many times in several different
RFCs. It is important to verify that you have the most recent RFC
on a particular protocol. The "IAB Official Protocol Standards"
[2] memo is the reference for determining the correct RFC to refer
to for the current specification of each protocol.

How do I obtain RFCs?

RFCs can be obtained via FTP from NIC.DDN.MIL, with the pathname
RFC:RFCnnnn.TXT or RFC:RFCnnnn.PS (where "nnnn" refers to the
number of the RFC). Login with FTP, username "anonymous" and
password "guest". The NIC also provides an automatic mail service
for those sites which cannot use FTP. Address the request to
SERVICE@NIC.DDN.MIL and in the subject field of the message
indicate the RFC number, as in "Subject: RFC nnnn" (or "Subject:
RFC nnnn.PS" for PostScript RFCs).

RFCs can also be obtained via FTP from NIS.NSF.NET. Using FTP,
login with username "anonymous" and password "guest"; then connect
to the RFC directory ("cd RFC"). The file name is of the form
RFCnnnn.TXT-1 (where "nnnn" refers to the number of the RFC). The
NIS also provides an automatic mail service for those sites which
cannot use FTP. Address the request to NIS-INFO@NIS.NSF.NET and
leave the subject field of the message blank. The first line of
the text of the message must be "SEND RFCnnnn.TXT-1", where nnnn
is replaced by the RFC number.

Requests for special distribution should be addressed to either
the author of the RFC in question, or to NIC@NIC.DDN.MIL. Unless
specifically noted otherwise on the RFC itself, all RFCs are for
unlimited distribution.

Which RFCs are Standards?

See "IAB Official Protocol Standards" (currently, RFC 1140) [2].

How do I obtain OSI Standards documents from the Internet?

OSI Standards documents are NOT available from the Internet via
anonymous FTP due to copyright restrictions. These are available
from:

Omnicom Information Service
501 Church Street NE
Suite 304
Vienna, VA 22180 USA
Telephone: (800) 666-4266 or (703) 281-1135 Fax: (703) 281-1505

User Services Working Group [Page 5]
RFC 1177 FYI Q/A - for New Internet Users August 1990

6. Questions about Internet Organizations and Contacts

What is the IAB?

The Internet Activities Board (IAB) is the coordinating committee
for Internet design, engineering and management [7]. IAB members
are deeply committed to making the Internet function effectively
and evolve to meet a large scale, high speed future. The chairman
serves a term of two years and is elected by the members of the
IAB. The current Chair of the IAB is Vint Cerf. The IAB focuses
on the TCP/IP protocol suite, and extensions to the Internet
system to support multiple protocol suites.

The IAB performs the following functions:

1) Sets Internet Standards,

2) Manages the RFC publication process,

3) Reviews the operation of the IETF and IRTF,

4) Performs strategic planning for the Internet, identifying
long-range problems and opportunities,

5) Acts as an international technical policy liaison and
representative for the Internet community, and

6) Resolves technical issues which cannot be treated within
the IETF or IRTF frameworks.

The IAB has two principal subsidiary task forces:

1) Internet Engineering Task Force (IETF)

2) Internet Research Task Force (IRTF)

Each of these Task Forces is led by a chairman and guided by a
Steering Group which reports to the IAB through its chairman. For
the most part, a collection of Research or Working Groups carries
out the work program of each Task Force.

All decisions of the IAB are made public. The principal vehicle
by which IAB decisions are propagated to the parties interested in
the Internet and its TCP/IP protocol suite is the Request for
Comments (RFC) note series and the Internet Monthly Report.

User Services Working Group [Page 6]
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What is the IANA?

The task of coordinating the use of the parameters of protocols is
delegated by the Internet Activities Board (IAB) to the Internet
Assigned Numbers Authority (IANA). These protocol parameters are
op-codes, type fields, terminal types, system names, object
identifiers, and so on. The "Assigned Numbers&Gundogan, et al. Expires September 10, 2020 [Page 9]
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0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| - | - | - | - | - | - | - |EXT|
+---+---+---+---+---+---+---+---+

Figure 7: Base format for dispatch extensions.

EXT: Extension

0: No other extension octet follows.

1: A further extension octet follows.

Extension octets are numbered according to their order. Future
documents MUST follow the naming scheme "EXT_0, EXT_1, ...", when
updating or referring to a specific dispatch extension octet.
Amendments that require an exchange of configurational parameters
between devices SHOULD use manifests to encode structured data in a
well-defined format, as, e.g., outlined in [I-D.irtf-icnrg-flic].

4.2. Link Fragmentation

Small payload sizes in the LoWPAN require fragmentation for various
network layers. Therefore, Section 5.3 of [RFC4944] defines a
protocol-independent fragmentation dispatch type, a fragmentation
header for the first fragment, and a separate fragmentation header
for subsequent fragments. ICN LoWPAN adopts this fragmentation
handling of [RFC4944].

The Fragmentation LoWPAN header can encapsulate other dispatch
headers. The order of dispatch types is defined in Section 5 of
[RFC4944]. Figure 8 shows the fragmentation scheme. The reassembled
ICN LoWPAN frame does not contain any fragmentation headers and is
depicted in Figure 9.

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+------...------+----...----+--------...
| IEEE 802.15.4 | Frag. 2nd | Payload /
+------...------+----...----+--------...

.
.
.

+------...------+----...----+--------...
| IEEE 802.15.4 | Frag. Nth | Payload /
+------...------+----...----+--------...

Figure 8: Fragmentation scheme

+------...------+--------+------...-------+--------...
| IEEE 802.15.4 | Page | ICN LoWPAN | Payload /
+------...------+--------+------...-------+--------...

Figure 9: Reassembled ICN LoWPAN frame

5. Space-efficient Message Encoding for NDN

5.1. TLV Encoding

The NDN packet format consists of TLV fields using the TLV encoding
that is described in [NDN-PACKET-SPEC]. Type and length fields are
of variable size, where numbers greater than 252 are encoded using
multiple octets.

If the type or length number is less than "253", then that number is
encoded into the actual type or length field. If the number is
greater or equals "253" and fits into 2 octets, then the type or
length field is set to "253" and the number is encoded in the next
following 2 octets in network byte order, i.e., from the most
significant byte (MSB) to the least significant byte (LSB). If the
number is greater than 2 octets and fits into 4 octets, then the type
or length field is set to "254" and the number is encoded in the
subsequent 4 octets in network byte order. For larger numbers, the
type or length field is set to "255" and the number is encoded in the
subsequent 8 octets in network byte order.

In this specification, compressed NDN TLVs make use of a different
TLV encoding scheme that reduces size. Instead of using the first
octet as a marker for the number of following octets, the compressed

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NDN TLV scheme uses a method to chain a variable number of octets
together. If an octet equals "255 (0xFF)", then the following octet
will also be interpreted. The actual value of a chain equals the sum
of all constituents.

If the type or length number is less than "255", then that number is
encoded into the actual type or length field (Figure 10 a). If the
type or length number (X) fits into 2 octets, then the first octet is
set to "255" and the subsequent octet equals "X mod 255" (Figure 10
b). Following this scheme, a variable-sized number (X) is encoded
using multiple octets of "255" with a trailing octet containing "X
mod 255" (Figure 10 c).

0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
a) | < 255 (X) | = X
+-+-+-+-+-+-+-+-+

0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
b) | 255 | < 255 (X) | = 255 + X
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-.....-+-+-+-+-+-+-+-+-+-+-+
c) | 255 | 255 | < 255 (X) | = (N * 255) + X
+-+-+-+-+-+-+-+-+-+-+-.....-+-+-+-+-+-+-+-+-+-+-+
(N)

Figure 10: Compressed NDN TLV encoding scheme

5.2. Name TLV Compression

This Name TLV compression encodes length fields of two consecutive
NameComponent TLVs into one octet, using 4 bits each. This process
limits the length of a NameComponent TLV to 15 octets. A length of 0
marks the end of the compressed Name TLV. An example for this
encoding is presented in Figure 11.

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Name: /HAW/Room/481/Humid/99

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 1 1|0 1 0 0| H | A | W |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| R | o | o | m |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 1 1|0 1 0 1| 4 | 8 | 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| H | u | m | i |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| d |0 0 1 0|0 0 0 0| 9 | 9 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 11: Name TLV compression for /HAW/Room/481/Humid/99

5.3. Interest Messages

5.3.1. Uncompressed Interest Messages

An uncompressed Interest message uses the base dispatch format (see
Figure 4) and sets the C as well as the M flag to "0" (Figure 12).
"resv" MUST be set to 0. The Interest message is handed to the NDN
network stack without modifications.

0 1 ... 7
+---+---+-----------------------+
| 0 | 0 | resv |
+---+---+-----------------------+

Figure 12: Dispatch format for uncompressed NDN Interest messages

5.3.2. Compressed Interest Messages

The compressed Interest message uses the extended dispatch format
(Figure 5) and sets the C flag to "1" and the M flag to "0" Request for
Comments (RFC) [1] documents the currently assigned values from
several series of numbers used in network protocol
implementations.

Current types of assignments listed in Assigned Numbers and
maintained by the IANA are:

Address Resolution Protocol Parameters
ARPANET and MILNET X.25 Address Mappings
ARPANET and MILNET Logical Addresses
ARPANET and MILNET Link Numbers
BOOTP Parameters and BOOTP Extension Codes
Domain System Parameters
IANA Ethernet Address Blocks
Ethernet Numbers of Interest
IEEE 802 Numbers of Interest
Internet Protocol Numbers
Internet Version Numbers
IP Time to Live Parameter
IP TOS Parameters
Machine Names
Mail Encryption Types
Multicast Addresses
Network Management Parameters
PRONET 80 Type Numbers
Port Assignments
Protocol and Service Names
Protocol/Type Field Assignments
Public Data Network Numbers
Reverse Address Resolution Protocol Operation Codes
Telnet Options
Terminal Type Names
Unix Ports
X.25 Type Numbers

For more information on number assignments, contact IANA@ISI.EDU.

What is "The NIC"?

"The NIC" is the Defense Data Network, Network Information Center
(DDN NIC) at SRI International, which is a network information

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center which holds a primary repository for RFCs and Internet
drafts. The host name is NIC.DDN.MIL. Shadow copies of the RFCs
and the Internet Drafts are maintained by the NSFnet on
NNSC.NSF.NET and on MERIT.EDU.

The DDN NIC also provides various user assistance services for DDN
users; contact NIC@NIC.DDN.MIL or call 1-800-235-3155 for more
information. In addition, the DDN NIC is the Internet
registration authority for the root domain and several top and
second level domains; maintains the official DoD Internet Host
Table; is the site of the Internet Registry (IR); and maintains
the whois database of network users, hosts, domains, networks, and
Points of Contact.

What is the IR?

The Internet Registry (IR) is the organization that is responsible
for assigning identifiers, such as IP network numbers and
autonomous system numbers, to networks. The IR also gathers and
registers such assigned information. The IR may, in the future,
allocate the authority to assign network identifiers to other
organizations; however, it will continue to gather data regarding
such assignments. At present, the DDN NIC at SRI International
serves as the IR.

What is the IETF?

The Internet has grown to encompass a large number of widely
geographically dispersed networks in academic and research
communities. It now provides an infrastructure for a broad
community with various interests. Moreover, the family of
Internet protocols and system components has moved from
experimental to commercial development. To help coordinate the
operation, management and evolution of the Internet, the IAB
established the Internet Engineering Task Force (IETF).

The IETF is chaired by Phill Gross and managed by its Internet
Engineering Steering Group (IESG). The IETF is a large open
community of network designers, operators, vendors, and
researchers concerned with the Internet and the Internet protocol
suite. It is organized around a set of eight technical areas,
each managed by a technical area director. In addition to the
IETF Chairman, the area directors make up the IESG membership.

The IAB has delegated to the IESG the general responsibility for
making the Internet work and for the resolution of all short- and
mid-range protocol and architectural issues required to make the
Internet function effectively.

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What is the IRTF?

To promote research in networking and the development of new
technology, the IAB established the Internet Research Task Force
(IRTF).

In the area of network protocols, the distinction between research
and engineering is not always clear, so there will sometimes be
overlap between activities of the IETF and the IRTF. There is, in
fact, considerable overlap in membership between the two groups.
This overlap is regarded as vital for cross-fertilization and
technology transfer.

The IRTF is a community of network researchers, generally with an
Internet focus. The work of the IRTF is governed by its Internet
Research Steering Group (IRSG). The chairman of the IRTF and IRSG
is David Clark.

7. Questions About Services

How do I find someone's electronic mail address?

There are a number of directories on the Internet; however, all of
them are far from complete. The two largest directories are the
WHOIS database at the DDN NIC and the PSInet White Pages.
Generally, it is still necessary to ask the person for his or her
email address.

How do I use the WHOIS program at the DDN NIC?

To use the WHOIS program to search the WHOIS database at the DDN
NIC, telnet to the NIC host, NIC.DDN.MIL. There is no need to
login. Type "whois" to call up the information retrieval program.
Next, type the name of the person, host, domain, network, or
mailbox for which you need information. If you are only typing
part of the name, end your search string with a period. Type
"help" for a more in-depth explanation of what you can search for
and how you can search. If you have trouble, send a message to
NIC@NIC.DDN.MIL or call 1-800-235-3155. Bug reports can be sent
to BUG-WHOIS@NIC.DDN.MIL and suggestions for improvements to the
program can be sent to SUGGESTIONS@NIC.DDN.MIL.

How do I become registered in the DDN NIC's WHOIS database?

If you would like to be listed in the WHOIS database, you must
have an electronic mailbox accessible from the Internet. First
obtain the file NETINFO:USER-TEMPLATE.TXT. You can either
retrieve this file via anonymous FTP from NIC.DDN.MIL or get it

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through electronic mail. To obtain the file via electronic mail,
send a message to SERVICE@NIC.DDN.MIL and put the file name in the
subject line of the message; that is, "Subject: NETINFO USER-
TEMPLATE.TXT". The file will be returned to you overnight.

Fill out the name and address information requested in the file
and return it to REGISTRAR@NIC.DDN.MIL. Your application will be
processed and you will be added to the database. Unless you are
an official Point of Contact for a network entity registered at
the DDN NIC, the DDN NIC will not regularly poll you for updates,
so you should remember to send corrections to your information as
your contact data changes.

How do I use the White Pages at PSI?

Performance Systems International, Inc. (PSI), sponsors a White
Pages Pilot Project that collects personnel information from
member organizations into a database and provides online access to
that data. This effort is based on the OSI X.500 Directory
standard.

To access the data, telnet to WP.PSI.COM and login as "fred" (no
password is necessary). You may now look up information on
participating organizations. The program provides help on usage.
For example, typing "help" will show you a list of commands,
quot;. If an
Interest message contains TLVs that are not mentioned in the
following compression rules, then this message MUST be sent
uncompressed.

This specification assumes that a HopLimit TLV is part of the
original Interest message. If such HopLimit TLV is not present, it
will be set with a default value of DEFAULT_NDN_HOPLIMIT prior to the
compression.

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In the default use case, the Interest message is compressed with the
following minimal rule set:

1. The "Type" field of the outermost MessageType TLV is removed.

2. The Name TLV is compressed according to Section 5.2. For this,
all NameComponents are expected to be of type
GenericNameComponent with a length greater than 0. An
ImplicitSha256DigestComponent or ParametersSha256DigestComponent
MAY appear at the end of the name. In any other case, the
message MUST be sent uncompressed.

3. InterestLifetime TLV is moved to the end of the compressed
Interest and is encoded as described in Section 7. If a lifetime
is not a valid time-value, then the lifetime is rounded up to the
nearest valid time-value as specified in Section 7.

4. The Type and Length fields of Nonce TLV, HopLimit TLV and
InterestLifetime TLV are elided. The Nonce value has a length of
4 octets and the HopLimit value has a length of 1 octet. The
compressed InterestLifetime (Section 7) has a length of 1 octet.
The presence of an InterestLifetime TLV is deduced from the
remaining length to parse.

The compressed NDN LoWPAN Interest message is visualized in
Figure 13.

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T = Type, L = Length, V = Value, Vc = Compressed Value

Figure 13: Compression of NDN LoWPAN Interest Message

Further TLV compression is indicated by the ICN LoWPAN dispatch in
Figure 14.

0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| 1 | 0 |CID|EXT|PFX|FRE|FWD|APM|
+---+---+---+---+---+---+---+---+

Figure 14: Dispatch format for compressed NDN Interest messages

CID: Context Identifier See Figure 5.

EXT: Extension

0: No extension octet follows.

1: Extension octet "EXT_0" follows immediately. See
Section 5.3.3.

PFX: CanBePrefix TLV

0: The uncompressed message does not include a
CanBePrefix TLV.

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1: The uncompressed message does include a CanBePrefix
TLV and is removed from the compressed message.

FRE: MustBeFresh TLV

0: The uncompressed message does not include a
MustBeFresh TLV.

1: The uncompressed message does include a MustBeFresh
TLV and is removed from the compressed message.

FWD: ForwardingHint TLV

0: The uncompressed message does not include a
ForwardingHint TLV.

1: The uncompressed message does include a
ForwardingHint TLV. The Type field is removed from
the compressed message. Further, all link delegation
types and link preference types are removed. All
included names are compressed according to
Section 5.2. If any name is not compressible, the
message MUST be sent uncompressed.

APM: ApplicationParameters TLV

0: The uncompressed message does not include an
ApplicationParameters TLV.

1: The uncompressed message does include an
ApplicationParameters TLV. The Type field is removed
from the compressed message.

5.3.3. Dispatch Extension

The "EXT_0" octet follows the description in Section 4.1.1 and is
illustrated in Figure 15.

0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| NCS |DIG| RSV |EXT|
+---+---+---+---+---+---+---+---+

Figure 15: EXT_0 format

NCS: Name Compression Strategy

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00: Names are compressed with the default name
compression strategy (see Section 5.2).

01: Reserved.

10: Reserved.

11: Reserved.

DIG: ImplicitSha256DigestComponent TLV

0: The name does not include an
ImplicitSha256DigestComponent as the last TLV. If
"EXT_0" is absent, then DIG is treated as 0.

1: The name does include an
ImplicitSha256DigestComponent as the last TLV. The
Type and Length fields are omitted.

RSV: Reserved Must be set to 0.

EXT: Extension

0: No extension octet follows.

1: A further extension octet follows immediately.

5.4. Data Messages

5.4.1. Uncompressed Data Messages

An uncompressed Data message uses the base dispatch format and sets
the C flag to "0" and the M flag to "1" (Figure 16). "resv" MUST be
set to 0. The Data message is handed to the NDN network stack
without modifications.

0 1 ... 7
+---+---+-----------------------+
| 0 | 1 | resv |
+---+---+-----------------------+

Figure 16: Dispatch format for uncompressed NDN Data messages

5.4.2. Compressed Data Messages

The compressed Data message uses the extended dispatch format
(Figure 5) and sets the C flag as well as the M flag to "1". If a

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Data message contains TLVs that are not mentioned in the following
compression rules, then this message MUST be sent uncompressed.

By default, the Data message is compressed with the following base
rule set:

1. The "Type" field of the outermost MessageType TLV is removed.

2. The Name TLV is compressed according to Section 5.2. For this,
all NameComponents are expected to be of type
GenericNameComponent and to have a length greater than 0. In any
other case, the message MUST be sent uncompressed.

3. The MetaInfo TLV Type and Length fields are elided from the
compressed Data message.

4. The FreshnessPeriod TLV MUST be moved to the end of the
compressed Data message and the length is set to 1. Type and
Length fields are elided and the value is encoded as described in
Section 7. If the freshness period is not a valid time-value,
then the message MUST be sent uncompressed in order to preserve
the security envelope of the Data message. The presence of a
FreshnessPeriod TLV is deduced from the remaining length to
parse.

5. The Type fields of the SignatureInfo TLV, SignatureType TLV and
SignatureValue TLV are removed.

The compressed NDN LoWPAN Data message is visualized in Figure 17.

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T = Type, L = Length, V = Value, Vc = Compressed Value

For more information, send a message to INFO@PSI.COM.

What is Usenet? What is Netnews?

Usenet and Netnews are common names of a distributed computer
bulletin board system that some computers on the Internet
participate in. It is not strictly an Internet service: many
computers not on the Internet also participate.

How do I get on Usenet? How do I get Netnews on my computer?

To get on Usenet, you must acquire the software, which is
available for some computers at no cost from some anonymous ftp
sites across the Internet, and you must find an existing Usenet
site that is willing to support a connection to your computer.

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What is anonymous FTP?

Anonymous FTP is a conventional way of allowing you to sign on to
a computer on the Internet and copy specified public files from it
[3]. Some sites offer anonymous FTP to distribute software and
various kinds of information. You use it like any FTP, but the
username is "anonymous" and the password is "guest".

8. Mailing Lists

What are some good mailing lists or news groups?

The TCP-IP, IETF, and RFC Distribution lists are primary lists for
new Internet users who desire further information about current
and emerging developments in the Internet. The first two lists
are unmoderated discussion lists, and the latter is an
announcement service used by the RFC Editor.

How do I subscribe to the TCP-IP mailing list?

To be added to the TCP-IP mailing list, send a message to:

TCP-IP-REQUEST@NIC.DDN.MIL

How do I subscribe to the IETF mailing list?

To be added to the IETF mailing list, send a message to:

IETF-REQUEST@ISI.EDU

How do I subscribe to the RFC Distribution list?

To be added to the RFC Distribution list, send a message to:

RFC-REQUEST@NIC.DDN.MIL

9. References

[1] Reynolds, J., and J. Postel, "Assigned Numbers", RFC 1060,
USC/Information Sciences Institute, March 1990.

[2] Postel, J., Editor, "IAB Official Protocol Standards", RFC 1140,
Internet Activities Board, May 1990.

[3] Postel, J., and J. Reynolds, "File Transfer Protocol (FTP), RFC
959, USC/Information Sciences Institute, October 1985.

[4] Postel, J., "Internet Protocol - DARPA Internet Program Protocol

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Specification", RFC 791, DARPA, September 1981.

[5] Postel, J., "Transmission Control Protocol - DARPA Internet
Program Protocol Specification", RFC 793, DARPA, September 1981.

[6] Leiner, B., R. Cole, J. Postel, and D. Mills, "The DARPA Internet
Protocol Suite", IEEE INFOCOM85, Washington D.C., March 1985.
Also in IEEE Communications Magazine, March 1985. Also as
ISI/RS-85-153.

[7] Cerf, V., "The Internet Activities Board" RFC 1160, CNRI, May
1990.

10. Suggested Reading

For further information about the Internet and its protocols in
general, you may choose to obtain copies of the following works:

Bowers, K., T. LaQuey, J. Reynolds, K. Roubicek, M. Stahl, and A.
Yuan, "Where to Start - A Bibliography of General Internetworking
Information", RFC 1175, FYI 3, CNRI, U Texas, ISI, BBN, SRI,
Mitre, August 1990.

Comer, D., "Internetworking with TCP/IP: Principles, Protocols,
and Architecture", Prentice Hall, New Jersey, 1989.

Krol, E., "The Hitchhikers Guide to the Internet", RFC 1118,
University of Illinois Urbana, September 1989.

11. Condensed Glossary

As with any profession, computers have a particular terminology all
their own. Below is a condensed glossary to assist in making some
sense of the Internet world.

address There are two separate uses of this term in internet
networking: "electronic mail address" and "internet
address". An electronic mail address is the string
of characters that you must give an electronic mail
program to direct a message to a particular person.
See "internet address" for its definition.

AI Artificial Intelligence
The branch of computer science which deals with the
simulation of human intelligence by computer systems.

AIX Advanced Interactive Executive
IBM's version of Unix.

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ANSI American National Standards Institute
A group that defines U.S. standards for the information
processing industry. ANSI participates in defining
network protocol standards.

ARP Address Resolution Protocol
An Internet protocol which runs on Ethernets and
Token Rings which maps internet addresses to MAC addresses.

ARPA Advanced Research Projects Agency
The former name of what is now called DARPA.

ARPANET Advanced Research Projects Agency Network
A pioneering long haul network funded by ARPA. It
served as the basis for early networking research as
well as a central backbone during the development of
the Internet. The ARPANET consisted of individual
packet switching computers interconnected by leased lines.

ASCII American Standard Code for Information Interchange

B Byte
One character of information, usually eight bits wide.

b bit - binary digit
The smallest amount of information which may be stored
in a computer.

BBN Bolt, Beranek, and Newman, Inc.
The Cambridge, MA company responsible for development,
operation and monitoring of the ARPANET, and later,
the Internet core gateway system, the CSNET Coordination
and Information Center (CIC), and NSFnet Network
Service Center (NNSC).

BITNET Because It's Time Network
BITNET has about 2,500 host computers, primarily at
universities, in many countries. It is managed by
EDUCOM, which provides administrative support and
information services. There are three
main constituents of the network: BITNET in the United
States and Mexico, NETNORTH in Canada, and EARN in
Europe. There are also AsiaNet, in Japan, and
connections in South America. See CREN.

bps bits per second
A measure of data transmission speed.

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BSD Berkeley Software Distribution
Term used when describing different versions
of the Berkeley UNIX software, as in "4.3BSD
UNIX".

catenet A network in which hosts are connected to networks
with varying characteristics, and the networks
are interconnected by gateways (routers). The
Internet is an example of a catenet.

CCITT International Consultative Committee for
Telegraphy and Telephony.

core gateway
Historically, one of a set of gateways (routers)
operated by the Internet Network Operations Center
at BBN. The core gateway system forms a central part
of Internet routing in that all groups must advertise
paths to their networks from a core gateway.

CREN The Corporation for Research and Educational Networking
BITNET and CSNET have recently merged to form CREN.

CSNET Computer + Science Network
A large data communications network for institutions doing
research in computer science. It uses several different
protocols including some of its own. CSNET sites include
universities, research laboratories, and commercial
companies. See CREN.

DARPA U.S. Department of Defense Advanced Research Projects Agency
The government agency that funded the ARPANET and later
started the Internet.

datagram
The unit transmitted between a pair of internet modules.
The Internet Protocol provides for transmitting blocks of
data, called datagrams, from sources to destinations.
The Internet Protocol does not provide a reliable
communication facility. There are no acknowledgements
either end-to-end or hop-by-hop. There is no error
control for data, only a header checksum. There are
no retransmissions. There is no flow control. See IP.

DCA Defense Communications Agency
The government agency responsible for installation of

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the Defense Data Network (DDN), including the ARPANET
and MILNET lines and PSNs. Currently, DCA administers
the DDN, and supports the user assistance and network
registration services of the DDN NIC.

DDN Defense Data Network
Comprises the MILNET and several other DoD networks.

DDN NIC The network information center at SRI International.
It is the primary repository for RFCs and Internet drafts,
as well as providing other services.

DEC Digital Equipment Corporation

DECnet Digital Equipment Corporation network
A networking protocol for DEC computers and network devices.

default route
A routing table entry which is used to direct any data
addressed to any network numbers not explicitly listed
in the routing table.

DOD U.S. Department of Defense

DOE U.S. Department of Energy

DNS The Domain Name System is a mechanism used in
the Internet for translating names of host computers
into addresses. The DNS also allows host computers
not directly on the Internet to have registered
names in the same style.

EARN European Academic Research Network
One of three main constituents of BITNET.

EBCDIC Extended Binary-coded Decimal Interchange Code

EGP External Gateway Protocol
A protocol which distributes routing information to
the routers and gateways which interconnect networks.

Ethernet
A network standard for the hardware and data link levels.
There are two types of Ethernet: Digital/Intel/Xerox (DIX)
and IEEE 802.3.

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FIPS Federal Information Processing Standard

FTP File Transfer Protocol
The Internet standard high-level protocol for
transferring files from one computer to another.

gateway A special-purpose dedicated computer that attaches to
two or more networks and routes packets from one
network to the other. In particular, an Internet
gateway routes IP datagrams among the networks it
connects. Gateways route packets to other
gateways until they can be delivered to the final
destination directly across one physical network.

GB Gigabyte
A unit of data storage size which represents 2^30 (over
1 billion) characters of information.

Gb Gigabit
2^30 bits of information (usually used to express a
data transfer rate; as in, 1 gigabit/second = 1Gbps).

GNU Gnu's Not UNIX
A UNIX-compatible operating system developed by the
Free Software Foundation.

header The portion of a packet, preceding the actual data,
containing source and destination addresses and
error-checking fields.

host number
The part of an internet address that designates which
node on the (sub)network is being addressed.

HP Hewlett-Packard

HYPERchannel
High-speed communications link.

I/O Input/Output

IAB Internet Activities Board
The IAB is the coordinating committee for Internet
design, engineering and management.

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IBM International Business Machines Corporation

IEEE Institute for Electrical and Electronics Engineers

IETF Internet Engineering Task Force
The IETF is a large open community of network designers,
operators, vendors, and researchers whose purpose is to
coordinate the operation, management and evolution of
the Internet, and to resolve short- and mid-range
protocol and architectural issues. It is a major source
of proposed protocol standards which are submitted to the
Internet Activities Board for final approval. The IETF
meets three times a year and extensive minutes of the
plenary proceedings are issued.

internet
internetwork
Any connection of two or more local or wide-area networks.

Internet
The global collection of interconnected regional and
wide-area networks which use IP as the network
layer protocol.

internet address
An assigned number which identifies a host in an internet.
It has two or three parts: network number, optional subnet
number, and host number.

IP Internet Protocol
The network layer protocol for the Internet. It the
datagram protocol defined by RFC 791.

IRTF Internet Research Task Force
The IRTF is a community of network researchers,
generally with an Internet focus. The work of the IRTF
is governed by its Internet Research Steering Group (IRSG).

ISO International Standards Organization

JvNC John von Neumann National Supercomputer Center

KB Kilobyte
A unit of data storage size which represents 2^10
(1024) characters of information.

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Kb Kilobit
2^10 bits of information (usually used to express a
data transfer rate; as in, 1 kilobit/second = 1Kbps = 1Kb).

KNET Kangaroo Network
Hardware/software product (Spartacus/Fibronics) that enables
IBM mainframes to communicate over networks with the TCP/IP
protocol suite.

LAN Local Area Network
A network that takes advantage of the proximity of computers
to offer relatively efficient, higher speed communications
than long-haul or wide-area networks.

LISP List Processing Language

MAC Medium Access Control
For broadcast networks, it is the method which devices use
to determine which device has line access at any given
time.

Mac Apple Macintosh computer.

MB Megabyte
A unit of data storage size which represents over
2^20 (one million) characters of information.

Mb Megabit
2^20 bits of information (usually used to express a
data transfer rate; as in, 1 megabit/second = 1Mbps).

MILNET Military Network
A network used for unclassified military production
applications. It is part of the Internet.

MIT Massachusetts Institute of Technology

MTTF Mean Time to Failure
The average time between hardware breakdown or loss of
service. This may be an empirical measurement or a
calculation based on the MTTF of component parts.

MTTR Mean Time to Recovery
The average time it takes to restore service after a
breakdown or loss. This is usually an empirical measurement.

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MVS Multiple Virtual Storage
An IBM operating system based on OS/1.

NASA National Aeronautics and Space Administration

NBS National Bureau of Standards
Now called NIST.

network number
The part of an internet address which designates the
network to which the addressed node belongs.

NFS Network File System
A network service that lets a program running on one
computer to use data stored on a different computer on
the same internet as if it were on its own disk.

NIC Network Information Center
An organization which provides network users with
information about services provided by the network.

NOC Network Operations Center
An organization which is responsible for maintaining
a network.

NIST National Institute of Standards and Technology
Formerly NBS.

NSF National Science Foundation

NSFNET National Science Foundation Network
A high-speed internet that spans the country, and is
intended for research applications. It is made up of
the NSFnet Backbone and the NSFnet regional networks.
It is part of the Internet.

NSFNET Backbone
A network connecting 13 sites across the continental United
States. It is the central component of NSFnet.

NSFNET Regional
A network connected to the NSFnet Backbone that covers a
region of the United States. It is to the regionals that
local sites connect.

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RFC 1177 FYI Q/A - for New Internet Users August 1990

NYSERnet
New York State Educational and Research Network
An internet which serves NY educational and research
institutions. It also serves as the NSFnet regional
network for New York State.

OSI Open Systems Interconnection
A set of protocols designed to be an international standard
method for connecting unlike computers and networks. Europe
has done most of the work developing OSI and will probably
use it as soon as possible.

Figure 17: Compression of NDN LoWPAN Data Message

Further TLV compression is indicated by the ICN LoWPAN dispatch in
Figure 18.

0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| 1 | 1 |CID|EXT|FBI|CON|KLO|RSV|
+---+---+---+---+---+---+---+---+

Figure 18: Dispatch format for compressed NDN Data messages

CID: Context Identifier See Figure 5.

EXT: Extension

0: No extension octet follows.

1: Extension octet "EXT_0" follows immediately. See
Section 5.4.3.

FBI: FinalBlockId TLV

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0: The uncompressed message does not include a
FinalBlockId TLV.

1: The uncompressed message does include a FinalBlockId
and it is encoded according to Section 5.2. If the
FinalBlockId TLV is not compressible, then the
message MUST be sent uncompressed.

CON: ContentType TLV

0: The uncompressed message does not include a
ContentType TLV.

1: The uncompressed message does include a ContentType
TLV. The Type field is removed from the compressed
message.

KLO: KeyLocator TLV

0: If the included SignatureType requires a KeyLocator
TLV, then the KeyLocator represents a name and is
compressed according to Section 5.2. If the the name
is not compressible, then the message MUST be sent
uncompressed.

1: If the included SignatureType requires a KeyLocator
TLV, then the KeyLocator represents a KeyDigest. The
Type field of this KeyDigest is removed.

RSV: Reserved Must be set to 0.

5.4.3. Dispatch Extension

The "EXT_0" octet follows the description in Section 4.1.1 and is
illustrated in Figure 19.

0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| NCS | RSV |EXT|
+---+---+---+---+---+---+---+---+

Figure 19: EXT_0 format

NCS: Name Compression Strategy

00: Names are compressed with the default name
compression strategy (see Section 5.2).

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01: Reserved.

10: Reserved.

11: Reserved.

RSV: Reserved Must be set to 0.

EXT: Extension

0: No extension octet follows.

1: A further extension octet follows immediately.

6. Space-efficient Message Encoding for CCNx

6.1. TLV Encoding

The generic CCNx TLV encoding is described in [RFC8609]. Type and
Length fields attain the common fixed length of 2 octets.

The TLV encoding for CCNx LoWPAN is changed to the more space
efficient encoding described in Section 5.1. Hence NDN and CCNx use
the same compressed format for writing TLVs.

6.2. Name TLV Compression

Name TLVs are compressed using the scheme already defined in
Section 5.2 for NDN. If a Name TLV contains T_IPID, T_APP, or
organizational TLVs, then the name remains uncompressed.

6.3. Interest Messages

6.3.1. Uncompressed Interest Messages

An uncompressed Interest message uses the base dispatch format (see
Figure 4) and sets the C as well as the M flag to "0" (Figure 20).
"resv" MUST be set to 0. The Interest message is handed to the CCNx
network stack without modifications.

0 1 ... 7
+---+---+-----------------------+
| 0 | 0 | resv |
+---+---+-----------------------+

Figure 20: Dispatch format for uncompressed CCNx Interest messages

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6.3.2. Compressed Interest Messages

The compressed Interest message uses the extended dispatch format
(Figure 5) and sets the C flag to "1" and the M flag to "0". If an
Interest message contains TLVs that are not mentioned in the
following compression rules, then this message MUST be sent
uncompressed.

In the default use case, the Interest message is compressed with the
following minimal rule set:

1. The Type and Length fields of the CCNx Message TLV are elided and
are obtained from the Fixed Header on decompression.

The compressed CCNx LoWPAN Interest message is visualized in
Figure 21.

T = Type, L = Length, V = Value

Figure 21: Compression of CCNx LoWPAN Interest Message

Further TLV compression is indicated by the ICN LoWPAN dispatch in
Figure 22.

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0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| 1 | 0 |CID|EXT|VER|FLG|PTY|HPL|FRS|PAY|ILT|MGH|KIR|CHR|VAL|RSV|
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

Figure 22: Dispatch format for compressed CCNx Interest messages

CID: Context Identifier See Figure 5.

EXT: Extension

0: No extension octet follows.

1: Extension octet "EXT_0" follows immediately. See
Section 6.3.3.

VER: CCNx protocol version in the fixed header

0: The Version field equals 1 and is removed from the fixed
header.

1: The Version field is carried in-line.

FLG: Flags field in the fixed header

0: The Flags field equals 0 and is removed from the Interest
message.

1: The Flags field is carried in-line.

PTY: PacketType field in the fixed header

0: The PacketType field is elided and assumed to be
"PT_INTEREST"

1: The PacketType field is elided and assumed to be
"PT_RETURN"

HPL: HopLimit field in the fixed header

0: The HopLimit field is carried in-line

1: The HopLimit field is elided and assumed to be "1"

FRS: Reserved field in the fixed header

0: The Reserved field is carried in-line

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1: The Reserved field is elided and assumed to be "0"

PAY: Optional Payload TLV

0: The Payload TLV is absent.

1: The Payload TLV is present and the type field is elided.

ILT: Optional Hop-By-Hop InterestLifetime TLV

See Section 6.3.2.1 for further details on the ordering
of hop-by-hop TLVs.

0: No InterestLifetime TLV is present in the Interest
message.

1: An InterestLifetime TLV is present with a fixed length of
1 octet and is encoded as described in Section 7. The
type and length fields are elided. If a lifetime is not
a valid time-value, then the lifetime is rounded up to
the nearest valid time-value (see Section 7).

MGH: Optional Hop-By-Hop MessageHash TLV

See Section 6.3.2.1 for further details on the ordering
of hop-by-hop TLVs.

This TLV is expected to contain a T_SHA-256 TLV. If
another hash is contained, then the Interest MUST be sent
uncompressed.

0: The MessageHash TLV is absent.

1: A T_SHA-256 TLV is present and the type as well as the
length fields are removed. The length field is assumed
to represent 32 octets. The outer Message Hash TLV is
omitted.

KIR: Optional KeyIdRestriction TLV

This TLV is expected to contain a T_SHA-256 TLV. If
another hash is contained, then the Interest MUST be sent
uncompressed.

0: The KeyIdRestriction TLV is absent.

1: A T_SHA-256 TLV is present and the type as well as the
length fields are removed. The length field is assumed

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to represent 32 octets. The outer KeyIdRestriction TLV
is omitted.

CHR: Optional ContentObjectHashRestriction TLV

This TLV is expected to contain a T_SHA-256 TLV. If
another hash is contained, then the Interest MUST be sent
uncompressed.

0: The ContentObjectHashRestriction TLV is absent.

1: A T_SHA-256 TLV is present and the type as well as the
length fields are removed. The length field is assumed
to represent 32 octets. The outer
ContentObjectHashRestriction TLV is omitted.

VAL: Optional ValidationAlgorithm and ValidationPayload TLVs

0: No validation related TLVs are present in the Interest
message.

1: Validation related TLVs are present in the Interest
message. An additional octet follows immediately that
handles validation related TLV compressions and is
described in Section 6.3.2.2.

RSV: Reserved Must be set to 0.

6.3.2.1. Hop-By-Hop Header TLVs Compression

Hop-By-Hop Header TLVs are unordered. For an Interest message, two
optional Hop-By-Hop Header TLVs are defined in [RFC8609], but several
more can be defined in higher level specifications. For the
compression specified in the previous section, the Hop-By-Hop TLVs
are ordered as follows:

1. Interest Lifetime TLV

2. Message Hash TLV

Note: Other Hop-By-Hop Header TLVs than those two remain
uncompressed.

6.3.2.2. Validation

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0 1 2 3 4 5 6 7 8
+-------+-------+-------+-------+-------+-------+-------+-------+
| ValidationAlg | KeyID | Reserved |
+-------+-------+-------+-------+-------+-------+-------+-------+

Figure 23: Dispatch for Interset Validations

ValidationALg: Optional ValidationAlgorithm TLV

0000: An uncompressed ValidationAlgorithm TLV is included.

0001: A T_CRC32C ValidationAlgorithm TLV is assumed, but no
ValidationAlgorithm TLV is included.

0010: A T_CRC32C ValidationAlgorithm TLV is assumed, but no
ValidationAlgorithm TLV is included. Additionally, a
Sigtime TLV is inlined without a type and a length field.

0011: A T_HMAC-SHA256 ValidationAlgorithm TLV is assumed, but
no ValidationAlgorithm TLV is included.

0100: A T_HMAC-SHA256 ValidationAlgorithm TLV is assumed, but
no ValidationAlgorithm TLV is included. Additionally, a
Sigtime TLV is inlined without a type and a length field.

0101: Reserved.

0110: Reserved.

0111: Reserved.

1000: Reserved.

1001: Reserved.

1010: Reserved.

1011: Reserved.

1100: Reserved.

1101: Reserved.

1110: Reserved.

1111: Reserved.

KeyID: Optional KeyID TLV within the ValidationAlgorithm TLV

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00: The KeyId TLV is absent.

01: The KeyId TLV is present and uncompressed.

10: A T_SHA-256 TLV is present and the type field as well as
the length fields are removed. The length field is
assumed to represent 32 octets. The outer KeyId TLV is
omitted.

11: A T_SHA-512 TLV is present and the type field as well as
the length fields are removed. The length field is
assumed to represent 64 octets. The outer KeyId TLV is
omitted.

The ValidationPayload TLV is present if the ValidationAlgorithm TLV
is present. The type field is omitted.

6.3.3. Dispatch Extension

The "EXT_0" octet follows the description in Section 4.1.1 and is
illustrated in Figure 24.

0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| NCS | RSV |EXT|
+---+---+---+---+---+---+---+---+

Figure 24: EXT_0 format

NCS: Name Compression Strategy

00: Names are compressed with the default name
compression strategy (see Section 5.2).

01: Reserved.

10: Reserved.

11: Reserved.

RSV: Reserved Must be set to 0.

EXT: Extension

0: No extension octet follows.

1: A further extension octet follows immediately.

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6.4. Content Objects

6.4.1. Uncompressed Content Objects

An uncompressed Content object uses the base dispatch format (see
Figure 4) and sets the C flag to "0" and the M flag to "1"
(Figure 25). "resv" MUST be set to 0. The Content object is handed
to the CCNx network stack without modifications.

0 1 ... 7
+---+---+-----------------------+
| 0 | 1 | resv |
+---+---+-----------------------+

Figure 25: Dispatch format for uncompressed CCNx Content objects

6.4.2. Compressed Content Objects

The compressed Content object uses the extended dispatch format
(Figure 5) and sets the C flag as well as the M flag to "1". If a
Content object contains TLVs that are not mentioned in the following
compression rules, then this message MUST be sent uncompressed.

By default, the Content object is compressed with the following base
rule set:

1. The PacketType field is elided from the Fixed Header.

2. The Type and Length fields of the CCNx Message TLV are elided and
are obtained from the Fixed Header on decompression.

The compressed CCNx LoWPAN Data message is visualized in Figure 26.

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T = Type, L = Length, V = Value

Figure 26: Compression of CCNx LoWPAN Data Message

Further TLV compression is indicated by the ICN LoWPAN dispatch in
Figure 27.

0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| 1 | 1 |CID|EXT|VER|FLG|FRS|PAY|RCT|MGH| PLTYP |EXP|VAL| RSV |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

Figure 27: Dispatch format for compressed CCNx Content objects

CID: Context Identifier See Figure 5.

EXT: Extension

0: No extension octet follows.

1: Extension octet "EXT_0" follows immediately. See
Section 6.4.3.

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" of OSI which defines its seven layers and
their functions. Sometimes used to help describe other
networks.

OSPFIGP Open Shortest-Path First Internet Gateway Protocol
An experimental replacement for RIP. It addresses some
problems of RIP and is based upon principles that have
been well-tested in non-internet protocols. Often referred
to simply as OSPF.

packet The unit of data sent across a packet switching network.
The term is used loosely. While some Internet
literature uses it to refer specifically to data sent
across a physical network, other literature views
the Internet as a packet switching network
and describes IP datagrams as packets.

PC Personal Computer

PCNFS Personal Computer Network File System

POSIX Portable Operating System Interface
Operating system based on UNIX.

protocol
A formal description of message formats and the rules
two computers must follow to exchange those messages.
Protocols can describe low-level details of
machine-to-machine interfaces (e.g., the order in
which bits and bytes are sent across a wire)
or high-level exchanges between allocation
programs (e.g., the way in which two programs
transfer a file across the Internet).

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PSC Pittsburgh Supercomputing Center

PSCNET Pittsburgh Supercomputing Center Network

RFC The Internet's Request for Comments documents series
The RFCs are working notes of the Internet research and
development community. A document in this series may be on
essentially any topic related to computer communication, and
may be anything from a meeting report to the specification of
a standard.

RIP Routing Interchange Protocol
One protocol which may be used on internets simply to pass
routing information between gateways. It is used on may
LANs and on some of the NSFnet regional networks.

RJE Remote Job Entry
The general protocol for submitting batch jobs and
retrieving the results.

RLOGIN Remote Login
A service on internets very similar to TELNET. RLOGIN was
invented for use between Berkeley Unix systems on the same
LAN at a time when TELNET programs didn't provide all the
services users wanted. Berkeley plans to phase it out.

RPC Remote Procedure Call
An easy and popular paradigm for implementing the
client-server model of distributed computing.

server A computer that shares its resources, such as printers
and files, with other computers on the network. An
example of this is a Network Files System (NFS)
Server which shares its disk space with a workstations
that does not have a disk drive of its own.

SESQUINET
Sesquicentennial Network
Texas-based regional network named for their sesquicentennial
celebration

SMTP Simple Mail Transfer Protocol
The Internet standard protocol for transferring
electronic mail messages from one computer to another.
SMTP specifies how two mail systems interact and the
format of control messages they exchange to transfer mail.

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SNA System Network Architecture
IBM's data communications protocol.

subnet A portion of a network, which may be a physically independent
network, which shares a network address with other portions
of the network and is distinguished by a subnet number. A
subnet is to a network what a network is to an internet.

subnet number
A part of the internet address which designates a subnet.
It is ignored for the purposes internet routing, but is
used for intranet routing.

SURANET Southeastern Universities Research Association Network
An NSFNET regional network.

T1 A term for a digital carrier facility used to transmit a
DS-1 formatted digital signal at 1.544 megabits per second.

T3 A term for a digital carrier facility used to transmit a DS-3
formatted digital signal at 44.746 megabits per second.

TCP Transmission Control Protocol
A transport layer protocol for the Internet. It is a
connection oriented, stream protocol defined by RFC 793.

TCP/IP Transmission Control Protocol/Internet Protocol
This is a common shorthand which refers to the suite
of application and transport protocols which run over IP.
These include FTP, Telnet, SMTP, and UDP (a transport
layer protocol).

Telenet A public packet-switching network operated by US Sprint.

Telnet The Internet standard protocol for remote terminal
connection service. Telnet allows a user at one site
to interact with a remote timesharing system at
another site as if the user's terminal was connected
directly to the remote computer.

Token Ring
A type of LAN. Examples are IEEE 802.5, ProNET-10/80 and
FDDI. The term "token ring" is often used to denote 802.5

Tymnet A public packet-switching network operated by McDonnell
Douglas Network Systems Company.

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UDP User Datagram Protocol
A transport layer protocol for the Internet. It is a
datagram protocol which simply adds a level of reliability
to IP datagrams. It is defined by RFC 768.

ULTRIX UNIX-based operating system for Digital Equipment Corporation
computers.

UNIX An operating system developed by Bell Laboratories that
supports multiuser and multitasking operations.

UUCP UNIX-to-UNIX Copy Program
A protocol used for communication between consenting
UNIX systems.

VMS Virtual Memory System
A Digital Equipment Corporation operating system.

WAN Wide Area Network

WESTNET One of the National Science Foundation funded regional
TCP/IP networks that covers the states of Arizona,
Colorado, New Mexico, Utah, and Wyoming.

WHOIS An Internet program which allows users to query a database of
people and other Internet entities, such as domains, networks,
and hosts, kept at the NIC. The information for people shows
a person's company name, address, phone number and email
address.

XNS Xerox Network System
A data communications protocol developed by Xerox. It
uses Ethernet to move the data between computers.

X.25 A data communications protocol developed to describe how
data passes into and out of public data communications
networks. The public networks such as Telenet and Tymnet,
use X.25 to interface to customer computers.

12. Security Considerations

Security issues are not discussed in this memo.

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13. Authors' Addresses

Gary Scott Malkin
FTP Software, Inc.
26 Princess Street
Wakefield, MA 01880
Phone: (617) 246-0900
EMail: gmalkin@ftp.com

April N. Marine
SRI International
Network Information Systems Center
333 Ravenswood Avenue, EJ294
Menlo Park, CA 94025
Phone: (415) 859-5318
EMail: APRIL@NIC.DDN.MIL

Joyce K. Reynolds
USC/Information Sciences Institute
4676 Admiralty Way
Marina del Rey, CA 90292-6695
Phone: (213) 822-1511
EMail: jkrey@isi.edu

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FYI on Questions and Answers: Answers to commonly asked "new internet user" questions RFC 1177

FYI on Questions and Answers: Answers to commonly asked "new internet user" questions
RFC 1177