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Re: I-D ACTION:draft-wan-ipdvb-rohc-00.txt
Dear Dr. Fairhurst,
Here is updated version according your previous feedback, but still
incomplete. I removed the section that carries ROHC compressed packet
directly over MPEG2-TS. So, what works for ULE should also work for GSE
except for section 4.1.4.1.1 which relies on MPEG2-TS.
In addition to 2 new ULE type, we also need to have a new EtherType for
section 3.1.2. If getting new EtherType is hard, we may need to redefine
the packet format.
As for your previous comment:
> 2) In Section 3.1.1:
>
> "In the absence of multiple receivers, a transmitter can send an
> SNDU"...
>
> I think this is only partially true, it may be safer to refer this to
> RFC4326, since this is also dependent on the way in which the ULE
> Stream is used.
I'm not sure what you meant exactly. I refer to figure 11 of RFC4326 and
the Receiver Destination NPA address field seems redundant since MAC
destination address is there. Any practical scenario where Receiver
Destination needs to be different from MAC destination address?
Diagrams has been changed to conform with the style used by RFC4326, but
style of diagram 4, 5, 6 and 7 is left untouched since it is difficult
to represent variable format imposed by medium information using the
former style.
Thank you.
Regards,
Ang Way Chuang
Gorry Fairhurst wrote:
Here is a copy of the I-D previously circulated on the list. This has
been published in the IETF I-D database. A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-wan-ipdvb-rohc-00.txt
Comments and discussion is invited on this list.
AUTHORS: Please note the name of the file. If you wish to submit an
updated revision the new version should be: draft-wan-ipdvb-rohc-01.txt
Best wishes,
Gorry Fairhurst
(ipdvb WG Chair)
---
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A New Internet-Draft is available from the on-line Internet-Drafts
directories.
Title : Robust Header Compression over Unidirectional
Lightweight Encapsulation (ULE) and MPEG2 Transport Stream (TS) frames
Author(s) : T. Wan, W. Ang, C. Teh
Filename : draft-wan-ipdvb-rohc-00.txtNPA
Pages : 26
Date : 2008-3-19
This paper introduces approach to carry ROHC packets over ULE and
MPEG2-TS frames. For completeness, ROHC Channel Parameters
Negotiation Protocol (RCPNP) is also presented.
A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-wan-ipdvb-rohc-00.txt
Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/
Below is the data which will enable a MIME compliant mail reader
implementation to automatically retrieve the ASCII version of the
Internet-Draft.
<ftp://ftp.ietf.org/internet-drafts/draft-wan-ipdvb-rohc-00.txt>
Network Working Group Tat-Chee. Wan
Internet-Draft Way-Chuang. Ang
Intended status: Standards Track Chee-Hong. Teh
Expires: September 25, 2008 Universiti Sains Malaysia
March 24, 2008
Robust Header Compression over Unidirectional Lightweight Encapsulation
(ULE) packets
draft-wan-ipdvb-rohc-01.txt
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
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This Internet-Draft will expire on September 25, 2008.
Copyright Notice
Copyright (C) The IETF Trust (2008).
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Abstract
This document introduces approach to carry ROHC packets over ULE
packets. For completeness, ROHC Channel Parameters Negotiation
Protocol (RCPNP) is also presented.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Packet Format of ROHC Packet . . . . . . . . . . . . . . . . . 7
3.1. ROHC over ULE . . . . . . . . . . . . . . . . . . . . . . 7
3.1.1. Dedicated IANA ULE Type for ROHC Compressed Packet . . 7
3.1.2. ROHC Compressed Packet as Payload of Ethernet
Packet . . . . . . . . . . . . . . . . . . . . . . . . 8
4. Establishing ROHC Channel . . . . . . . . . . . . . . . . . . 9
4.1. ROHC Channel Parameters Negotiation Protocol (RCPNP) . . . 9
4.1.1. Compressor Advertisement . . . . . . . . . . . . . . . 11
4.1.2. Compressor Solicitation . . . . . . . . . . . . . . . 11
4.1.3. Request . . . . . . . . . . . . . . . . . . . . . . . 13
4.1.4. Reply . . . . . . . . . . . . . . . . . . . . . . . . 15
4.1.4.1. Medium Information . . . . . . . . . . . . . . . . 16
4.1.4.1.1. Dedicated PID space . . . . . . . . . . . . . 16
4.1.4.1.2. ULE Medium . . . . . . . . . . . . . . . . . . 17
4.1.5. Acknowledgement/Negative Acknowledgement . . . . . . . 18
4.1.6. Compressor Shutdown . . . . . . . . . . . . . . . . . 18
4.1.7. Decompressor Shutdown . . . . . . . . . . . . . . . . 19
4.2. Interaction of RCPNP . . . . . . . . . . . . . . . . . . . 19
5. Bidirectional ROHC Channels . . . . . . . . . . . . . . . . . 21
6. IANA Consideration . . . . . . . . . . . . . . . . . . . . . . 22
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23
8. Security Considerations . . . . . . . . . . . . . . . . . . . 24
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25
9.1. Normative References . . . . . . . . . . . . . . . . . . . 25
9.2. Informative References . . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 26
Intellectual Property and Copyright Statements . . . . . . . . . . 27
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1. Introduction
This document introduces approach to carry ROHC packets over ULE
packets. For completeness, ROHC Channel Parameters Negotiation
Protocol (RCPNP) is also presented. FIXME: more details
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2. Terminologies
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 [RFC2119].
DVB
Digital Video Broadcast. A framework and set of associated
standards published by the European Telecommunications Standards
Institute (ETSI) for the transmission of video, audio, and data
using the ISO MPEG-2 Standard [ISO-MPEG2].
MAC
Medium Access Control [IEEE-802.3]. A link-layer protocol defined
by the IEEE 802.3 standard (or by Ethernet v2 [DIX]).
MPEG-2
A set of standards specified by the Motion Picture Experts Group
(MPEG) and standardized by the International Standards
Organisation (ISO/IEC 13818-1) [ISO-MPEG2], and ITU-T (in H.222
[ITU-H222]).
PDU
Protocol Data Unit. Examples of a PDU include Ethernet frames,
IPv4 or IPv6 datagrams, and other network packets.
Receiver
Equipment that processes the signal from a TS Multiplex and
performs filtering and forwarding of encapsulated PDUs to the
network-layer service (or bridging module when operating at the
link layer).
Transmitter
Router or host that sends data.
SNDU
SubNetwork Data Unit. An encapsulated PDU sent as an MPEG-2
Payload Unit.
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TS
Transport stream (TS) is a format specified in MPEG-2 Part 1,
Systems (ISO/IEC standard 13818-1). Its design goal is to allow
multiplexing of digital video and audio and to synchronize the
output. Transport stream offers features for error correction for
transportation over unreliable media, and is used in broadcast
applications such as DVB and ATSC.
ULE stream
An MPEG-2 TS Logical Channel that carries only ULE encapsulated
PDUs. ULE streams may be identified by definition of a
stream_type in SI/PSI [ISO-MPEG2].
ROHC
Robust Header Compression. A framework of compression headers of
IP packet as defined in [RFC3095].
ROHC channel
A logical unidirectional point-to-point channel carrying ROHC
packets from one compressor to one decompressor, optionally
carrying ROHC feedback information on the behalf of another
compressor-decompressor pair operating on a separate ROHC channel
in the opposite direction.
ROHC profile
A logical unidirectional point-to-point channel carrying ROHC
packets from one compressor to one decompressor, optionally
carrying ROHC feedback information on the behalf of another
compressor-decompressor pair operating on a separate ROHC channel
in the opposite direction.
MRRU
Maximum Reconstructed Reception Unit as defined in [RFC3095].
Context Identifier
[RFC3095] provides a definition for context identifiers.
MSB
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Most significant bit.
LSB
Least significant bit.
ACK
Acknowledgement.
NACk
Negative acknowledgement.
CID
Contect Identifier.
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3. Packet Format of ROHC Packet
This section briefly describes the notation used in all diagrams. ":"
in a diagram indicates that the part is optional. Likewise, "=" in a
diagram indicates the number of octets by the part is not presented
in a precise manner. This situation appears when a field or part
spans multiple or variable number of bytes.
3.1. ROHC over ULE
The packet format for ROHC compressed packet encapsulated within ULE
can be in one the following two formats:
3.1.1. Dedicated IANA ULE Type for ROHC Compressed Packet
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|D| Length (15b) | Type = ROHC ULE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Address* (6B) |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| RoHC compressed packet |
= =
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CRC-32 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: ROHC compressed packet encapsulated using dedicated ULE
type
The semantics of D-bit, Length, Type, Destination Address and CRC-32
fields are defined in section 4 of [RFC 4326]. However, the Type
fields requires a new IANA assigned ULE type value to indicate the
presence of ROHC compressed packet in PDU.
In the absence of multiple receivers, a transmitter can send an SNDU
without Destination Address Field (D bit marked). However, when
multiple receivers are listening to the same transmitter, destination
address must be included in SNDU.
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3.1.2. ROHC Compressed Packet as Payload of Ethernet Packet
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|D| Length (15b) | Type = 0x0001 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination MAC (6B) |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| Source MAC (6B) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EtherType = ROHC Ether | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| RoHC compressed packet |
= =
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CRC-32 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: ROHC compressed packet encapsulated in SNDU bridged frame
This packet format should be used when there are multiple
transmitters and receivers over a DVB link. A new EtherType value
needs to be assigned for this.
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4. Establishing ROHC Channel
This standard presents two approaches to setup a ROHC channel over a
DVB link. The first approach is to setup ROHC channel manually.
This requires that the operators at the every transmitters and
receivers to manually configure the ROHC channel parameters. When
the size of network is small, this approach is favourable.
But the former approach becomes nonviable if the network is dynamic
and is not scalable as the size of the network grows. Henceforth, we
present a negotiation protocol to create ROHC channel in the next
section.
4.1. ROHC Channel Parameters Negotiation Protocol (RCPNP)
The approach presented in this section can only work if compressor
site and decompressor site are connected through two dedicated
unidirectional DVB links, with a unidirectional link originating from
each of the sites, configured to form a bidirectional network link
between the two sites. This protocol works through ULE packets only.
It is possible to extend this protocol to work over Generic Stream
Encapsulation [GSE] in the future. While it is possible to extend
this protocol to work over asymmetrical link, this draft doesn't try
to address this issue. Since new EtherType can be allocated, this
protocol can be extended to asymmetrical link via Link-Layer
Tunneling Mechanism [RFC3077] with little modifications.
The basic format of a ULE SNDU packet for RCPNP message is as such:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|D| Length (15b) | Type = RoHC Neg |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Address* (6B) |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Version|OpCod|X| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| Source Address * (6B) |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+-+ =
| Body * |
= =
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CRC-32 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Minimal format of RCPNP message
Type
New ULE type need to be assigned for ROHC negotiation protocol.
Destination Address
Destination address field should exist for all types of message
except for Compressor Solicitation and Compressor Advertisement
messages.
Version
Version of ROHC Channel Parameters Negotiation Protocol (RCPNP).
Currently, only version 0 is supported.
OpCod
OpCod field is an abbreviation for Operation Code. The value of
Operation Code field determines the message type.
X
This bit is not used in most messages and should be ignored unless
specified otherwise.
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Source Address
Source address field should exist for all messages except for
Compressor Solicitation message and is used to indicate the
address of the sender.
Body
Body of message. This content of this field is dependent on
Operation Code. This field may not be present for certain type of
messages.
All fields marked with '*' are optional and may not be present for
certain type of messages. The following subsections will explain the
type of messages for this protocol. As mentioned, the type of
message is determined by Operation Code field.
4.1.1. Compressor Advertisement
Operation Code
The value is 0.
Destination Address
This field is not present in this message.
Body
This field is not present in this message.
This message is used by the compressor site to advertise the
availability of ROHC Compressor. Out of concern for bandwidth and
energy consumption, compressor site should limit the broadcast of
this message for a few times when it first joins the network. This
message should also be broadcasted when a Compressor Solicitation
message is received. The decompressor site will use the value
specified in the Source Address field when addressing compressor
site.
4.1.2. Compressor Solicitation
Operation Code
The value is 1.
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Destination Address
This field is not present in this message.
Source Address
This field is not present in this message.
Body
This field is not present in this message.
This message is broadcasted by decompressor to solicit for
compressor. Decompressor site should rate-limit the frequency of
solicitation to avoid flooding DVB link.
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4.1.3. Request
MSB LSB
0 1 2 3 4 5 6 7
+-----+-----+-----+-----+-----+-----+-----+-----+
| |
= MRRU (4 octets) =
| |
+-----+-----+-----+-----+-----+-----+-----+-----+
| |
+ Maximum CID +
| |
+-----+-----+-----+-----+-----+-----+-----+-----+
| Number of Media | |
=-----+-----+-----+ Medium Types =
: :
+-----+-----+-----+-----+-----+-----+-----+-----+
| |
+ Num of profiles +
| |
+-----+-----+-----+-----+-----+-----+-----+-----+
| |
+ Profile ID 1 +
| |
+-----+-----+-----+-----+-----+-----+-----+-----+
: :
+ Profile ID 2 +
: :
+-----+-----+-----+-----+-----+-----+-----+-----+
: :
+ Profile ID N +
: :
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 4: Format of Request message
The fields shown in the figure above collectively form the Body field
of a Request message. This message is sent by decompressor site to
compressor site when it wishes to establish a ROHC channel. The
meaning of each fields in the message are described below:
Operation Code
Not shown in the diagram, but this field carries the value of 2.
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MRRU
Maximum Reconstructed Reception Unit tolerated by decompressor.
Value of 0 indicates the negotiated channel doesn't allow for
segmentation of ROHC compressed packet.
Maximum CID
Maximum Context Identifier tolerated by decompressor.
Number of Media
The number of medium types carried in Medium Types field.
Medium Types
This field consists of all supported medium types by the
decompressor. Each medium type consists of 3 bits and corresponds
to Medium field described in Medium Information (Section 4.1.4.1)
section. The number of bits used by Medium Types and Number of
Media fields must be expanded to multiple of 8 if actual number of
required bits is not multiple of 8. The unused bits for such case
should be ignored by Compressor site.
Number of profiles
Number of profiles supported by decompressor.
Profile IDs
ROHC Profile IDs supported by decompressor. Each profile ID
occupies 2 octets.
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4.1.4. Reply
MSB LSB
0 1 2 3 4 5 6 7
+-----+-----+-----+-----+-----+-----+-----+-----+
| |
= MRRU (4 octets) =
| |
+-----+-----+-----+-----+-----+-----+-----+-----+
| |
+ Maximum CID +
| |
+===============================================+
| Num of profiles |
+-----+-----+-----+-----+-----+-----+-----+-----+
| |
+ Profile ID 1 +
| |
+-----+-----+-----+-----+-----+-----+-----+-----+
: :
+ Profile ID 2 +
: :
+-----+-----+-----+-----+-----+-----+-----+-----+
: :
+ Profile ID N +
: :
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 5: Format of Reply message
The fields shown in the figure above collectively form the Body field
of a Reply message. This message is sent by compressor site to
decompressor site in response to a Request message sent by
decompressor site. The meaning of each fields in the message are
described below:
Operation Code
Not shown in the diagram, but this field carries the value of 3.
MRRU
Maximum Reconstructed Reception Unit tolerated by compressor.
Decompressor site should send a NACK if it is receives higher MRRU
than what it requested.
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Maximum CID
Maximum CID tolerated by compressor. This value of this field
should be less than or equal to its counterpart in Request
message. Decompressor site should send a NACK if it receives
Maximum CID that is higher than the initial negotiated value.
Number of profile IDs
Note that this field occupies 1 octet instead of 2 because there
can be only 256 active profiles at any given ROHC channel.
Decompressor site should send a NACK if it receives more profile
IDs than it can support. FIXME: Add more notes here.
Profile IDs
Profile Identifiers of the ROHC profiles that will be used for the
negotiated ROHC channel. Decompressor site should send a NACK if
it receives any profile ID that it doesn't support.
4.1.4.1. Medium Information
The following notation depicted in the previous figure 10 indicates
the presence of medium information.
+===============================================+
Medium information conveys how compressor is to send ROHC compressed
packets to decompressor over ULE packets. The details of packet
format for ROHC over ULE are described in section 3. Medium type is
conveyed by Medium field. Other media may be supported in the future
and the support for these media will specified in other documents.
Decompressor receiving unsupported medium type should send a NACK.
When an unrecognized medium type is received, decompressor site
should send a NACK message to compressor.
4.1.4.1.1. Dedicated PID space
MSB LSB
0 1 2 3 4 5 6 7
+-----+-----+-----+-----+-----+-----+-----+-----+
| Medium=0 | |
+-----+-----+-----+ PID +
| |
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 6: Medium information for ROHC over ULE over dedicated PID
space
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PID
Packet Identifier of MPEG2-TS frames that will carry ROHC
compressed packet.
This approach should only be used when the current negotiating PID
channel of MPEG2-TS is shared by multiple senders and receivers and
the need to shave off the destination and source addresses from each
ULE packet at the cost of using additional PID is reasonable. It is
pointless to use this approach the PID channel of MPEG2-TS is only
used for Point to Point communication between a sender and a receiver
where there is no need to send source and destination addresses. For
such case, compressor site should opt the approach mentioned in the
next section.
4.1.4.1.2. ULE Medium
MSB LSB
0 1 2 3 4 5 6 7
+-----+-----+-----+-----+-----+-----+-----+-----+
| Medium=1 | Type | Reserved |
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 7: Medium information for ROHC over ULE
Type:
0
No MAC address will be sent in ULE packets. This option should
only be used if the compressor site is certain that there is only
one receiver and one transmitter over DVB link. This is similar
to what is mentioned in section Section 4.1.4.1.1, but without the
cost of additional PID channel.
1
Only destination MAC address will be sent in ULE packets that
carry ROHC compressed packet. This means that Destination Absent
bit in ULE header will be cleared. This option is used only if
there is one transmitter and many receivers listening to that
transmitter via DVB link.
2
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ROHC packets will be encapsulated in Ethernet bridged frame. This
option is used when there multiple transmitters and receivers over
a DVB link.
3
Not used. Receiver should treat it as corrupted packet, silently
discard the message and wait for a valid Reply message or until a
timeout occur at which the decompressor site will start the
negotiation afresh by sending a Request message.
Reserved field is not used and should be ignored.
4.1.5. Acknowledgement/Negative Acknowledgement
Operation Code
The value is 4.
X
If this bit is set, this message is an acknowledgement.
Otherwise, it is a negative acknowledgement.
Body
This field is not present in this message.
Decompressor site should send either an acknowledgement or negative
acknowledgement if it receives a valid Reply message. If compressor
site doesn't receive ACK nor NACK within a reasonable interval, it
should discard any information of negotiated ROHC channel parameters.
An acknowledgement must be sent to decompressor site when compressor
site receives Decompressor Shutdown message.
4.1.6. Compressor Shutdown
Operation Code
The value is 5.
Body
This field is not present in this message.
This message is sent by the compressor site to notify the
decompressor site that it is about to stop compressing IP packets.
Upon receiving this message, decompressor should release all
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resources that are being held for decompression.
Compressor must wait for an acknowledgement from decompressor site
before freeing its resource. If it doesn't receive an
acknowledgement within a reasonable interval, it should keep sending
a shutdown message for a number of times before freeing its resource.
4.1.7. Decompressor Shutdown
Operation Code
The value is 6.
Body
This field is not present in this message.
This message is sent by the decompressor site to notify the
compressor that it is about to stop decompressing IP packets. Upon
receiving this message, compressor should release all resources that
are being held and stop sending compressed IP packets.
Decompressor must wait for an acknowledgement from compressor site
before freeing its resource. If it doesn't receive an
acknowledgement within a reasonable interval, it should keep sending
a shutdown message for a number of times before freeing its resource.
4.2. Interaction of RCPNP
The following diagram depicts a possible interaction between
compressor site and decompressor site in negotiating ROHC channel
parameters.
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Compressor Site Decompressor Site
|<---------------- Solicit ---------------|
| |
|-------------- Advertise --------------->|
| |
|<-------------- Request -----------------|
| |
|---------------- Reply ----------------->|
| | Create instance
| | of decompressor
Create |<---------------- ACK -------------------|
compressor | |
| |
|= (Compression can begin at this point) =|
| |
| |
Destroy |<------- Decompressor Shutdown ----------|
compressor | |
|----------------- ACK --- -------------->| Destroy
| | decompressor
Figure 8: Packets flow of RCPNP
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5. Bidirectional ROHC Channels
While establishing bidirectional ROHC channels allows for the use of
ROHC bidirectional optimistic mode and bidirectional reliable mode,
RCPNP doesn't concern itself with the establishment of bidirectional
ROHC channels. Therefore, it is up to implementers of this protocol
to support bidirectional ROHC channels. The implementation should be
as straightforward as mapping correct pair of ROHC channels.
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6. IANA Consideration
Two ULE types should be assigned. One of it is for RCPNP and the
other is to indicate the presence of ROHC compressed packet.
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7. Acknowledgements
We would like to thank Rod Walsh (Nokia) for his valuable input and
feedback.
We also want to extend our gratitude to Dr. Gorry Fairhurst for his
guidance.
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8. Security Considerations
- None -
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9. References
9.1. Normative References
[GSE] European Telecommunication Standards Institute, "Digital
Video Broadcasting (DVB); Generic Stream Encapsulation
(GSE) Protocol", TS 102 606, 2007.
[IEEE-802.3]
IEEE 802.3, "Local and metropolitan area networks-Specific
requirements Part 3: Carrier sense multiple access with
collision detection (CSMA/CD) access method and physical
layer specifications", IEEE Computer Society, (also ISO/
IEC 8802-3), 2000.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3095] Borman, C., "RObust Header Compression (ROHC): Framework
and four profiles: RTP, UDP, ESP, and uncompressed",
RFC 3095, 2001.
9.2. Informative References
[DIX] Digital Equipment Corp, Intel Corp, Xerox Corp, "Ethernet
Local Area Network Specification Version 2.0",
November 1982.
[ISO-MPEG2]
ISO 13818-1, "Information technology -- Generic coding of
moving pictures and associated audio information -- Part
1: Systems", International Standards Organisation (ISO),
2000.
[ITU-H222]
H.222.0, "Information technology - Generic coding of
moving pictures and associated audio information: Systems,
International Telecommunication Union, (ITU-T)", 1995.
[RFC3077] Duros, E., "A Link-Layer Tunneling Mechanism for
Unidirectional Links", RFC 3077, 2001.
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Authors' Addresses
Tat-Chee Wan
Universiti Sains Malaysia
School of Computer Science
Universiti Sains Malaysia
Penang
Malaysia
Phone: +6 04 653 4633
Email: tcwan@nav6.org
URI: http://nrg.cs.usm.my/~tcwan
Way-Chuang Ang
Universiti Sains Malaysia
School of Computer Science
Universiti Sains Malaysia
Penang
Malaysia
Email: wcang@nav6.org
Chee-Hong Teh
Universiti Sains Malaysia
School of Computer Science
Universiti Sains Malaysia
Penang
Malaysia
Email: chteh@nav6.org
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