draft-ietf-manet-dlep-da-credit-extension-04.txt   draft-ietf-manet-dlep-da-credit-extension-05.txt 
Network Working Group B. Cheng Network Working Group B. Cheng
Internet-Draft D. Wiggins Internet-Draft D. Wiggins
Intended status: Standards Track Lincoln Laboratory Intended status: Standards Track Lincoln Laboratory
Expires: September 2, 2018 L. Berger Expires: November 2, 2018 L. Berger
LabN Consulting, L.L.C. LabN Consulting, L.L.C.
March 1, 2018 May 1, 2018
DLEP DiffServ Aware Credit Window Extension DLEP DiffServ Aware Credit Window Extension
draft-ietf-manet-dlep-da-credit-extension-04 draft-ietf-manet-dlep-da-credit-extension-05
Abstract Abstract
This document defines an extension to the DLEP protocol that enables This document defines an extension to the DLEP protocol that enables
a DiffServ aware credit-window scheme for destination-specific and a DiffServ aware credit-window scheme for destination-specific and
shared flow control. The extension is logically composed of two shared flow control.
mechanisms. The first provides credit window control, the second
identifies how flows are identified and mapped to a credit window.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 2, 2018. This Internet-Draft will expire on November 2, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Key Words . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Key Words . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Extension Overview . . . . . . . . . . . . . . . . . . . . . 4 2. Extension Usage and Identification . . . . . . . . . . . . . 3
3. Extension Usage and Identification . . . . . . . . . . . . . 5 3. Management Considerations . . . . . . . . . . . . . . . . . . 3
4. Credit Window Control . . . . . . . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
4.1. Data Plane Considerations . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4.2. Extension Messages . . . . . . . . . . . . . . . . . . . 6 5.1. Extension Type Value . . . . . . . . . . . . . . . . . . 4
4.2.1. Credit Control Message . . . . . . . . . . . . . . . 6 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.2.2. Credit Control Response Message . . . . . . . . . . . 7 6.1. Normative References . . . . . . . . . . . . . . . . . . 5
4.3. Credit Window Control Data Items . . . . . . . . . . . . 7 6.2. Informative References . . . . . . . . . . . . . . . . . 5
4.3.1. Credit Window Initialization . . . . . . . . . . . . 8 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 5
4.3.2. Credit Window Associate . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
4.3.3. Credit Window Grant . . . . . . . . . . . . . . . . . 11
4.3.4. Credit Window Status . . . . . . . . . . . . . . . . 12
4.3.5. Credit Window Request . . . . . . . . . . . . . . . . 14
5. Traffic Classification . . . . . . . . . . . . . . . . . . . 15
5.1. Traffic Classification Data Item . . . . . . . . . . . . 15
5.1.1. Traffic Classification Sub Data Item . . . . . . . . 17
5.2. DiffServ Credit Window Traffic Classification Sub Data
Item . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 19
7. Management Considerations . . . . . . . . . . . . . . . . . . 19
8. Security Considerations . . . . . . . . . . . . . . . . . . . 20
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
9.1. Extension Type Value . . . . . . . . . . . . . . . . . . 20
9.2. Message Values . . . . . . . . . . . . . . . . . . . . . 20
9.3. Data Item Values . . . . . . . . . . . . . . . . . . . . 21
9.4. DLEP Sub Data Item Registry . . . . . . . . . . . . . . . 21
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
10.1. Normative References . . . . . . . . . . . . . . . . . . 22
10.2. Informative References . . . . . . . . . . . . . . . . . 22
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 23
Appendix B. Notional Support for Ethernet Priority Code Points . 23
B.1. Notional Ethernet Credit Window Traffic Classification
Sub Data Item . . . . . . . . . . . . . . . . . . . . . . 24
B.2. Other Considerations . . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
1. Introduction 1. Introduction
The Dynamic Link Exchange Protocol (DLEP) is defined in [RFC8175]. The Dynamic Link Exchange Protocol (DLEP) is defined in [RFC8175].
It provides the exchange of link related control information between It provides the exchange of link related control information between
DLEP peers. DLEP peers are comprised of a modem and a router. DLEP DLEP peers. DLEP peers are comprised of a modem and a router. DLEP
defines a base set of mechanisms as well as support for possible defines a base set of mechanisms as well as support for possible
extensions. This document defines one such extension. extensions. This document defines one such extension.
The base DLEP specification does not include any flow control The base DLEP specification does not include any flow control
skipping to change at page 3, line 26 skipping to change at page 2, line 47
provided using one or more logical "Credit Windows", each of which provided using one or more logical "Credit Windows", each of which
will typically be supported by an associated virtual or physical will typically be supported by an associated virtual or physical
queue. Traffic sent by a router will use traffic flow classification queue. Traffic sent by a router will use traffic flow classification
information provided by the modem to identify which traffic is information provided by the modem to identify which traffic is
associated with each credit window. (For general background on associated with each credit window. (For general background on
traffic classification see [RFC2475] Section 2.3.) Credit windows traffic classification see [RFC2475] Section 2.3.) Credit windows
may be shared or dedicated on a per flow basis. The extension is may be shared or dedicated on a per flow basis. The extension is
structured to allow for reuse of the defined credit window based flow structured to allow for reuse of the defined credit window based flow
control with different traffic classification techniques. control with different traffic classification techniques.
This document defines traffic classification based on DLEP This document uses the traffic classification and credit window
control mechanisms defined in [I-D.ietf-manet-credit-flow-control] to
provided credit window based flow control based on on DLEP
destination and DiffServ [RFC2475] DSCPs (differentiated services destination and DiffServ [RFC2475] DSCPs (differentiated services
codepoints). The defined mechanism allows for credit windows to be codepoints). The defined mechanism allows for credit windows to be
shared across traffic sent to multiple DLEP destinations and DSCPs, shared across traffic sent to multiple DLEP destinations and DSCPs,
or used exclusively for traffic sent to a particular destination and/ or used exclusively for traffic sent to a particular destination and/
or DSCP. The extension also supports the "wildcard" matching of any or DSCP. The extension also supports the "wildcard" matching of any
DSCP. Traffic classification information is provided such that it DSCP.
can be readily extended to support non-DSCP related traffic
classification techniques, or be used by non-credit window related
extensions, such as [I-D.ietf-manet-dlep-pause-extension].
The extension defined in this document is referred to as "DiffServ The extension defined in this document is referred to as "DiffServ
Aware Credit Window" or, more simply, the "DA Credit" extension. Aware Credit Window" or, more simply, the "DA Credit" extension. The
Future extensions are expected to define traffic classification reader should be familiar with both the traffic classification and
techniques other than DiffServ, e.g., IEEE 802.1 Q priority code credit window control mechanisms defined in
points or even 5-tuple IP flows. [I-D.ietf-manet-credit-flow-control].
This document defines a new DLEP Extension Type Value in Section 3 This document defines a new DLEP Extension Type Value in Section 2
which is used to indicate support for the extension. Two new which is used to indicate support for the extension.
messages are defined in Section 4.2 and five new DLEP data items in
Section 4.3 are defined to support credit window control. A single
data item is defined in Section 5.1 to support traffic classification
in general, as well as identification of flows based on DSCPs.
1.1. Key Words 1.1. Key Words
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Extension Overview 2. Extension Usage and Identification
The DA Credit extension can be used to support credit based flow
control of traffic sent from a router to a modem. The extension can
be used to support DiffServ and per DLEP destination based flow
control. Both types of DLEP endpoints, i.e., a router and a modem,
negotiate the use of extension during session initialization, see
Section 5.2 [RFC8175]. When using this extension, data traffic is
allowed to be sent by the router to the modem only when there are
credits available.
Credits are managed on a per logical "Credit Windows" basis. Each
credit window can be thought of as corresponding to a queue within a
modem. Modems pass to the router information on their credit windows
and identify each via a "Credit Window Identifier", or "CID". In
addition to the CID, credit window information includes an initial
credit window size, as well as the maximum size of the logical queue
associated with each CID. The maximum size is included for
informative and potential future uses.
Modems provide an initial credit window size at the time of "Credit
Window Initialization". Such initialization can take place during
session initiation or any point thereafter. It can also take place
when rate information changes. Additional "Credit Grants", i.e.,
increments to Credit Window size, are provided using a Destination Up
or the new "Credit Control" Message. A router provides its view of
the Credit Window, which is known as "Status", in Destination Up
Response and the new "Credit Control Response" Messages. Routers can
also request credits using the new "Credit Control" Message.
When modems provide credits to a router, they will need to take into
account any overhead of their attached transmission technology and
map it into the credit semantics defined in this document. In
particular, the credit window is defined below to include per frame
(packet) MAC headers and this may not match the actual overhead of
the modem attached transmission technology. In that case a direct
mapping or an approximation will need to be made by the modem to
provide appropriate credit values.
As mentioned above, traffic classification supported by this document
is performed on a per {destination, DSCP} tuple basis. (Per
destination traffic classification is also supported.) This means
that, routers need the combination of the DLEP identified destination
and one or more DSCPs associated with a CID in order to match traffic
they send to specific credit windows. Modems provide the mapping of
DSCPs to CIDs in sets, each of which is identified via a "Traffic
Classification Identifier" or "TID". When a destination becomes
reachable, a modem "Associates" (identifies) the TID to be used for
traffic sent by the router to that destination. This use of CIDs,
TIDs and association of a TID to a DLEP destination enables a modem
to share or dedicate resources as needed to match the specifics of
its implementation and its attached transmission technology.
3. Extension Usage and Identification
The extension defined in this document is composed of the mechanisms The extension defined in this document is composed of the mechanisms
and processing defined in Section 4 and Section 5. To indicate that and processing defined in [I-D.ietf-manet-credit-flow-control]. To
the DiffServ Aware Credit Window Extension is to be used, an indicate that the DiffServ Aware Credit Window Extension is to be
implementation MUST include the DiffServ Aware Credit Window Type used, an implementation MUST include the DiffServ Aware Credit Window
Value in the Extensions Supported Data Item. The Extensions Type Value in the Extensions Supported Data Item. The Extensions
Supported Data Item is sent and processed according to [RFC8175]. Supported Data Item is sent and processed according to [RFC8175].
Any implementation that indicates use of the DiffServ Aware Credit
Window Extension MUST support all Messages, Data Items, the DiffServ
Traffic Classification Sub Data Item, and all related processing
defined in [I-D.ietf-manet-credit-flow-control].
The DiffServ Aware Credit Window Extension Type Value is TBA1, see The DiffServ Aware Credit Window Extension Type Value is TBA1, see
Section 9. Section 5.
4. Credit Window Control
This section defines additions to DLEP for the control of credit
based flow control. As mentioned above, the definition is made in
the context of credit windows which can be thought of as representing
different logical queues. Two new messages and five data items are
defined to support credit window control. Credit window control also
impacts the data plane.
4.1. Data Plane Considerations
When the use of the extension defined in this document is agreed upon
per standard DLEP processing, see Section 3, a router MUST NOT send
data traffic to a modem for forwarding when there are no credits
available in the associated Credit Window. This document defines
credit windows in octets. A credit window value MUST be larger than
the number of octets contained in a packet, including any MAC headers
used between the router and the modem, in order for the router to
send the packet to a modem for forwarding. The credit window is
decremented by the number of sent octets.
A router MUST identify the credit window associated with traffic sent
to a modem based on the traffic classification information provided
in the data items defined in this document. Note that routers will
typically view a DLEP destination as the next hop MAC address.
4.2. Extension Messages
Two new messages are defined by this extension: the Credit Control
and the Credit Control Response Message. Sending and receiving both
message types MUST be supported by any implementation that advertises
use of this extension per Section 3.
4.2.1. Credit Control Message
Credit Control Messages are sent by modems and routers. Each sender
is only permitted to have one message outstanding at one time. That
is, a sender (modem or router) MUST NOT send a second (or any
subsequent) Credit Control Message until a Credit Control Response
Message is received from its peer (router or modem).
Credit Control Messages are sent by modems to provide credit window
increases. Modems send credit increases when there is transmission
or local queue availability that exceeds the credit window value
previous provided to the router. Modems will need to balance the
load generated by sending and processing frequent credit window
increases against a router having data traffic available to send, but
no credits available.
Credit Control Messages MAY be sent by routers to request credits and
provide window status. Routers will need to balance the load
generated by sending and processing frequent credit window requests
against a having data traffic available to send, but no credits
available.
The Message Type value in the DLEP Message Header is set to TBA2.
A message sent by a modem, MUST contain one or more Credit Window
Grant Data Items as defined below in Section 4.3.3. A router
receiving this message MUST respond with a Credit Control Response
Message.
A message sent by a router, MUST contain one or more Credit Window
Request Data Items defined below in Section 4.3.5 and SHOULD contain
a Credit Window Status Data Item, defined in Section 4.3.4,
corresponding to each credit window request. A modem receiving this
message MUST respond with a Credit Control Response Message based on
the received message and data item and the processing defined below,
which will typically result in credit window increments being
provided.
Specific processing associated with each Credit Data Item is provided
below.
4.2.2. Credit Control Response Message
Credit Control Response Messages are sent by routers to report the
current Credit Window for a destination. A message sent by a router,
MUST contain one or more Credit Window Status Data Items as defined
below in Section 4.3.4. Specific receive processing associated with
the Credit Window Status Data Item is provided below.
Credit Control Response Messages sent by modems MUST contain one or
more Credit Window Grant Data Items. A data item for every Credit
Window Request data item contained in the corresponding Credit
Control Response Message received by the modem MUST be included.
Each Credit Grant Data Item MAY provide zero or more additional
credits based on the modem's transmission or local queue
availability. Specific receive processing associated with each Grant
Data Item is provided below.
The Message Type value in the DLEP Message Header is set to TBA3.
4.3. Credit Window Control Data Items
Five new data items are defined to support credit window control.
The Credit Window Initialization Data Item is used by a modem to
identify a credit window and set its size. The Credit Window
Association Data Item is used by a modem to identify which traffic
classification identifiers (flows) should be used when sending
traffic to a particular DLEP identified destination. The Credit
Window Grant is used by a modem to provide additional credits to a
router. The Credit Request is used by a router to request additional
credits. The Credit Window Status is used to advertise the sender's
view of number of available credits for state synchronization
purposes.
Any errors or inconsistencies encountered in parsing data items are
handled in the same fashion as any other data dtem parsing error
encountered in DLEP, see [RFC8175]. In particular, the node parsing
the data item MUST terminate the session with a Status Data Item
indicating Invalid Data.
The defined data items and operations have similar objectives as
those found in [I-D.ietf-manet-credit-window]. One notable
difference from this extension is that in this document credits are
never provided by the router to the modem.
4.3.1. Credit Window Initialization
The Credit Window Initialization Data Item is used by a modem to
identify a credit window and set its size. This Data Item SHOULD be
included in any Session Initialization Response Message that also
contains the DiffServ Aware Credit Window Extension Type Value in the
Extensions Supported Data Item. Updates to previously identified
credit windows or new credit windows MAY be sent by a modem by
including the data item in Session Update Messages. More than one
data item MAY be included in a message to provide information on
multiple credit windows.
The Credit Window Initialization Data Item identifies a credit window
using a Credit Window Identifier, or CID. It also provides the size
of the identified credit window. Finally, a queue size (in bytes) is
provided for informational purposes. Note that to be used, a CID
must be associated with in a Traffic Classification Identifier via a
Credit Window Association Data Item.
The format of the Credit Window Initialization Data Item is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length (16) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Credit Window Identifier (CID)| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Credit Value :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: Credit Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scale | Credit Window Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBA4
Length: 16
Per [RFC8175] Length is the number of octets in the data item. It
MUST be equal to sixteen (16).
Credit Window Identifier (CID):
A 16-bit unsigned integer identifying a credit window. The value
of 0xFFFF is reserved and MUST not be used in this data item.
There is no other restriction on values used by a modem, and there
is no requirement for sequential or ordered values.
Reserved:
MUST be set to zero by the sender (a modem) and ignored by the
receiver (a router).
Credit Value:
A 64-bit unsigned integer representing the credits, in octets, to
be applied to the Credit Window. This value includes MAC headers
as seen on the link between the modem and router.
Scale:
An 8-bit unsigned integer indicating the scale used in the Credit
Window Size fields. The valid values are:
Value Scale
------------
0 B - Bytes (Octets)
1 KB - Kilobytes (B/1024)
2 MB - Megabytes (KB/1024)
3 GB - Gigabytes (MB/1024)
Credit Window Size:
A 24-bit unsigned integer representing the maximum size, in the
octet scale indicated by the Scale field, of the associated credit
window.
A router that receives a Credit Window Initialization Data Item MUST
locate the credit window that is associated with the CID indicated in
each received data item. If no associated credit window is found,
the router MUST initialize a new credit window using the values
carried in the data item. When an associated credit window is found,
the router MUST update the credit window using the values carried in
the Data Item. It is worth noting, that such updates can result in a
credit window size being reduced, for example, due to a transmission
rate change on the modem.
4.3.2. Credit Window Associate
The Credit Window Associate Data Item is used by a modem to associate
traffic classification information with a destination. The traffic
classification information is identified using a TID value that has
previously been sent by the modem or is listed in a Traffic
Classification Data Item carried in the same message as the data
item.
A single Credit Window Associate Data Item MUST be included in all
Destination Up and Destination Update Messages sent by a modem when
the use of the extension defined in this document is agreed upon, see
Section 3. Note that a TID will not be used unless it is listed in a
Credit Window Associate Data Item.
The format of the Credit Window Associate Data Item is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length (2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Traffic Class. Identifier (TID)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBA5
Length: 2
Per [RFC8175] Length is the number of octets in the data item. It
MUST be equal to two (2).
Traffic Classification Identifier (TID):
A 16-bit unsigned integer identifying a traffic classification set
that has been identified in a Credit Window Traffic Classification
Data Item, see Section 5.1. Unknown TID values SHOULD be reported
and result in associated traffic being dropped.
A router that receives the Credit Window Associate Data Item MUST
locate the traffic classification information indicated by the
received TID. If no corresponding information can be located, the
data item MUST be treated as an error as described above. Once the
traffic classification information is located, it MUST be associated
with the destination and the router MUST ensure that any data plane
state, see Section 4.1, that is associated with the TID is updated as
needed.
4.3.3. Credit Window Grant
The Credit Window Grant data item is used by a modem to provide
credits to a router. One or more Credit Window Grant Data Items MAY
be carried in the DLEP Destination Up, Destination Announce Response,
Destination Update, Credit Control Messages, and Credit Control
Response Messages. Multiple Credit Window Grant Data Items in a
single message are used to indicate different credit values for
different credit windows. In all message types, this data item
provides an additional number of octets to be added to the indicated
credit window. Credit window are identified via using CID values
that have been previously been sent by the modem or are listed in a
Credit Window Initialization Data Item carried in the same messages
as the data item.
The format of the Credit Window Grant Data Item is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length (12) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Credit Window Identifier (CID)| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Additional Credits :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: Additional Credits |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBA6
Length: 12
Per [RFC8175], Length is the number of octets in the data item.
It MUST be equal to twelve (12).
Credit Window Identifier (CID):
A 16-bit unsigned integer identifying a credit window that has
been identified in a Credit Window Initialization Data Item, see
Section 4.3.1. Unknown CID values SHOULD be reported and ignored.
Additional Credit:
A 64-bit unsigned integer representing the credits, in octets, to
be added to the Credit Window. This value includes MAC headers as
seen on the link between the modem and router. A value of zero
indicates that no additional credits are being provided.
When receiving this data item, a router MUST identify the credit
window indicated by the CID. If the CID is not known to the router,
it SHOULD report or log this information and discard the Data Item.
It is important to note that while this data item can be received in
a destination specific message, credit windows are managed
independently from the destination identified in the message carrying
this Data Item, and the indicated CID MAY even be disjoint from the
identified destination.
Once the credit window is identified, the credit window size MUST be
increased by the value contained in the Additional Credits field. If
the increase results in a window overflow, i.e., the size of the
credit window after the increase is smaller than the original credit
window size, the Credit Window must be set to its maximum
(0xFFFFFFFFFFFFFFFF).
No response is sent by the router to a modem after processing a
Credit Window Grant Data Item received in a Credit Control Response
Message. In other cases, the receiving router MUST send a Credit
Window Status data item or items reflecting the resulting Credit
Window value of the updated credit window. When the Credit Grant
data item is received in a Destination Up Message, the Credit Window
Status data item(s) MUST be sent in the corresponding Destination Up
Response Message. Otherwise, a Credit Control Message MUST be sent.
4.3.4. Credit Window Status
The Credit Window Status data item is used by a router to report the
current credit window size to its peer modem. One or more Credit
Window Status data items MAY be carried in a Destination Up Response
Message or a Credit Control Response Message. As discussed above,
the Destination Up Response Message is used when the data item is
sent in response to a Destination Up Message, and the Credit Control
Response Message is sent in response to a Credit Control Message.
Multiple Credit Window Status data items in a single message are used
to indicate different sizes of different credit windows. Similar to
the Credit Window Grant, credit windows are identified using CID
values that have been previously been sent by the modem.
The format of the Credit Window Status Data Item is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length (12) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Credit Window Identifier (CID)| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Credit Window Size :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: Credit Window Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBA7
Length: 12
Per [RFC8175] Length is the number of octets in the data item. It
MUST be equal to twelve (12).
Credit Window Identifier (CID):
A 16-bit unsigned integer identifying a credit window that has
been identified in a Credit Window Initialization Data Item, see
Section 4.3.1.
Credit Window Size:
A 64-bit unsigned integer, indicating the current number of
credits, in octets, available for the router to send to the modem.
This is referred to as the Modem Receive Window in
[I-D.ietf-manet-credit-window].
When receiving this data item, a modem MUST identify the credit
window indicated by the CID. If the CID is not known to the modem,
it SHOULD report or log this information and discard the data item.
As with the Credit Window Grant Data Item, the CID MAY be unrelated
to the Destination indicated in the message carrying the data item.
Once the credit window is identified, the modem SHOULD check the
received Credit Window Size field value against the outstanding
credit window's available credits at the time the most Credit Window
Initialization or Grant data item associated with the indicated CID
was sent. If the values significantly differ, i.e., greater than can
be accounted for based on observed data frames, then the modem SHOULD
send a Credit Window Initialization Data Item to reset the associated
credit window size to the modem's current view of the available
credits. As defined above, Credit Window Initialization Data Items
are sent in Session Update Messages. When multiple data items need
to be sent, they SHOULD be combined into a single message when
possible. Alternatively, and also in cases where there are small
differences, the modem MAY adjust the values sent in Credit Window
Grant data items to account for the reported Credit Window.
4.3.5. Credit Window Request
The Credit Window Request Data Item is used by a router to request
additional credits for particular credit windows. Credit Window
Request Data Items are carried in Credit Control Messages, and one or
more Credit Window Request Data Items MAY be present in a message.
Credit windows identified using a CID as defined above in
Section 4.3.1. Multiple CIDs MAY be present to allow for the case
where the router identifies that credits are needed in multiple
credit windows. The special CID value of 0xFFFF is used to indicate
that a credit request is being made across all queues.
The format of the Credit Window Request Data Item is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Credit Window Identifier (CID)| ... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: ... | Credit Window Identifier (CID)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBA8
Length: Variable
Per [RFC8175] Length is the number of octets in the data item,
excluding the Type and Length fields. It will equal the number of
CID fields carried in the data item times 2 and MUST be at least
2.
Credit Window Identifier (CID):
One or more 16-bit fields used to indicate a credit window that
has been identified in a Credit Window Initialization Data Item,
see Section 4.3.1. The special value of 0xFFFFFFFF indicates that
the request applies to all CIDs.
A modem receiving this data item MUST provide a Credit Increment for
the indicated credit windows via Credit Window Grant Data Items
carried in a new Credit Control Message. Multiple values and queue
indexes SHOULD be combined into a single Credit Control Message when
possible. Unknown CID values SHOULD be reported or logged and then
ignored by the modem.
5. Traffic Classification
Traffic classification is supported by the Traffic Classification
Data Item defined below. The base data item and sub data item
structure is intended to be independent of any specific usage of the
flow identification provided within the data item. It is designed to
be extensible for future traffic classification types. While the
structure of the data items is extensible, actual flow information is
expected to be used in an extension dependent manner.
In the context of the DiffServ Aware Credit Window Extension, the
Traffic Classification Data Item is used by a modem to identify
groups of DSCPs which are to be mapped to a credit window. A DLEP
destination address is also needed to complete the traffic
classification information. This address is provided by a modem when
it identifies the traffic classification set in a Destination Up
Message using the Credit Window Associate Data Item defined above.
5.1. Traffic Classification Data Item
This sections defines the Traffic Classification Data Item. This
data item is used by a modem to provide a router with traffic
classification information. When an extension requires use of this
data item the Traffic Classification Data Item SHOULD be included by
a modem in any Session Initialization Response Message that also
contains the corresponding Extension Type Value in the Extensions
Supported Data Item. Updates to previously provided traffic
classifications or new traffic classifications MAY be sent by a modem
by including the data item in Session Update Messages. More than one
data item MAY be included in a message to provide information on
multiple traffic classifiers.
The set of traffic classification information provided in the data
item is identified using a Traffic Classification Identifier, or TID.
Addition information, e.g., the list DSCPs associated with a credit
window, is provided in a variable series of Queue Parameter sub-data
items.
The format of the Traffic Classification Data Item is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Traffic Class. Identifier (TID)| Num SDIs | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic Classification Sub Data Item 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: ... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic Classification Sub Data Item n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBA9
Length: Variable
Per [RFC8175] Length is the number of octets in the data item,
excluding the Type and Length fields.
Traffic Classification Identifier (TID):
A 16-bit unsigned integer identifying a traffic classification
set. There is no restriction on values used by a modem, and there
is no requirement for sequential or ordered values.
Num SDIs:
An 8-bit unsigned integer indicating the number of Traffic
Classification Sub Data Items included in the data item. A value
of zero (0) is allowed and indicates that no traffic should be
matched against this TID.
Reserved:
MUST be set to zero by the sender (a modem) and ignored by the
receiver (a router).
Traffic Classification Sub Data Item:
Zero or more Traffic Classification Sub Data Items of the format
defined below MAY be included. The number MUST match the value
carried in the Num SDIs field.
A router receiving the Traffic Classification Data Item MUST locate
the traffic classification information that is associated with the
TID indicated in each received data item. If no associated traffic
classification information is found, the router MUST initialize a new
information set using the values carried in the data item. When
associated traffic classification information is found, the router
MUST update the information using the values carried in the Data
Item. In both cases, a router MUST also ensure that any data plane
state, see Section 4.1, that is associated with the TID is updated as
needed.
5.1.1. Traffic Classification Sub Data Item
All Traffic Classification Sub Data Items share a common format that
is patterned after the standard DLEP data item format, see [RFC8175]
Section 11.3. There is no requirement on, or meaning to sub data
item ordering. Any errors or inconsistencies encountered in parsing
sub data items are handled in the same fashion as any other data item
parsing error encountered in DLEP.
The format of the Traffic Classification Sub Data Item is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Sub Data Item Type:
A 16-bit unsigned integer that indicates the type and
corresponding format of the data item's Value field. Sub Data
Item Types are managed according to the IANA registry described in
Section 9.4.
Length: Variable
Copying [RFC8175], Length a 16-bit unsigned integer that is the
number of octets in the sub data item, excluding the Type and
Length fields.
5.2. DiffServ Credit Window Traffic Classification Sub Data Item
The DiffServ Credit Window Traffic Classification Sub Data Item is
used to identify the DSCPs associated with a specific credit window.
Credit windows are identified using CID values that have been
previously been sent by the modem or are listed in a Credit Window
Initialization Data Item carried in the same messages as the sub data
item. DSCPs are identified in a list of DiffServ fields. An
implementation that does not support DSCPs, and wants to use credit
window flow control for all traffic to a destination or destinations,
would indicate with 0 DSCPs.
The format of the DiffServ Credit Window Traffic Classification Sub
Data Item is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Must be two (2) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Credit Window Identifier (CID)| Num DSCPs | DS Field 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DS Field 2 | ... | DS Field n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Length: Variable
Length is the number of octets in the sub data item. It is equal
to three (3) plus the value of the Num DSCPs field.
Credit Window Identifier (CID):
A 16-bit unsigned integer identifying a credit window that has
been identified in a Credit Window Initialization Data Item, see
Section 4.3.1. Unknown CID values SHOULD be reported and result
in associated traffic being dropped.
Num DSCPs:
An 8-bit unsigned integer indicating the number of DSCPs carried
in the sub data item. A zero (0) indicates a (wildcard) match
against any DSCP value.
DS Field:
Each DS Field is an 8-bit whose definition is the same as
[RFC2474].
0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| DSCP | CU |
+---+---+---+---+---+---+---+---+
DSCP: differentiated services codepoint
CU: currently unused, MUST be zero
A router receiving the DiffServ Traffic Classification Sub Data Item
MUST validate the information on receipt prior to the information and
data plane update described earlier in this section. The credit
window associated with the CID indicated in each data item must be
located. It is important to note that the CID value may be present
in a Credit Window Initialization Data Item carried in the same
message as the sub data item. If the CID is not located, then it
MUST be treated as an error as described above.
When there are no unknown CIDs, the receiver MUST ensure that each DS
Field value is listed only once across the whole Traffic
Classification Data Item. Note, this check is across the data item
and not the individual sub data item. If the same DS Field value is
listed more than once within the same Traffic Classification Data
Item, the data item MUST be treated as an error as described above.
In all cases, the router MUST use validated DSCPs in data plane
credit window identification as described in Section 4.1.
6. Compatibility
Sessions established with both peers identified as supporting the
DiffServ Aware Credit Window Extension Type, see Section 3, MUST NOT
use the [I-D.ietf-manet-credit-window] defined Credit data items. If
a node supporting the extension defined in this document, receives a
[I-D.ietf-manet-credit-window] defined data item, the recipient MUST
ignore the received information.
7. Management Considerations 3. Management Considerations
This section provides several network management guidelines to This section provides several network management guidelines to
implementations supporting the DiffServ Aware Credit Window implementations supporting the DiffServ Aware Credit Window
Extension. Extension.
The use of the extension defined in this document SHOULD be The use of the extension defined in this document SHOULD be
configurable on both modems and routers. configurable on both modems and routers.
Modems SHOULD support the configuration of DSCP to credit window Modems SHOULD support the configuration of DSCP to credit window
(queue) mapping. (queue) mapping.
skipping to change at page 20, line 4 skipping to change at page 4, line 13
(queue) mapping. (queue) mapping.
Modems MAY support the configuration of the number of credit windows Modems MAY support the configuration of the number of credit windows
(queues) to advertise to a router. (queues) to advertise to a router.
Routers may have limits on the number of queues that they can support Routers may have limits on the number of queues that they can support
and, perhaps, even limits in supported credit window combinations, and, perhaps, even limits in supported credit window combinations,
e.g., if per destination queues can even be supported at all. When e.g., if per destination queues can even be supported at all. When
modem-provided credit window information exceeds the capabilities of modem-provided credit window information exceeds the capabilities of
a router, the router MAY use a subset of the provided credit windows. a router, the router MAY use a subset of the provided credit windows.
Alternatively, a router MAY reset the session and indicate that the Alternatively, a router MAY reset the session and indicate that the
extension is not supported. In either case, the mismatch of extension is not supported. In either case, the mismatch of
capabilities SHOULD be reported to the user via normal network capabilities SHOULD be reported to the user via normal network
management mechanisms, e.g., user interface or error logging. management mechanisms, e.g., user interface or error logging.
8. Security Considerations 4. Security Considerations
The extension introduces a DiffServ awareness to the mechanisms This document defines a DLEP extension that uses base DLEP mechanisms
defined in [I-D.ietf-manet-credit-window]. The extension does not and the credit window control and flow mechanisms defined in
inherently introduce any additional threats above those documented in [I-D.ietf-manet-credit-flow-control]. The use of those mechanisms,
[RFC8175]. The approach taken to Security in that document and and the introduction of a new extension, do not inherently introduce
[I-D.ietf-manet-credit-window] apply equally when running the any additional threats above those documented in [RFC8175]. The
extension defined in this document. approach taken to Security in that document applies equally to the
mechanism defined in this document.
9. IANA Considerations 5. IANA Considerations
This document requests the assignment of 5 values by IANA. All This document requests one assignment by IANA. All assignments are
assignments are to registries defined by [RFC8175]. to registries defined by [RFC8175].
9.1. Extension Type Value 5.1. Extension Type Value
This document requests 1 new assignment to the DLEP Extensions This document requests 1 new assignment to the DLEP Extensions
Registry named "Extension Type Values" in the range with the Registry named "Extension Type Values" in the range with the
"Specification Required" policy. The requested value is as follows: "Specification Required" policy. The requested value is as follows:
+------+------------------------------+ +------+------------------------------+
| Code | Description | | Code | Description |
+------+------------------------------+ +------+------------------------------+
| TBA1 | DiffServ Aware Credit Window | | TBA1 | DiffServ Aware Credit Window |
+------+------------------------------+ +------+------------------------------+
Table 1: Requested Extension Type Value Table 1: Requested Extension Type Value
9.2. Message Values 6. References
6.1. Normative References
This document requests 2 new assignments to the DLEP Message Registry
named "Message Values" in the range with the "Specification Required"
policy. The requested values are as follows:
+-----------+-------------------------+
| Type Code | Description |
+-----------+-------------------------+
| TBA2 | Credit Control |
| | |
| TBA3 | Credit Control Response |
+-----------+-------------------------+
Table 2: Requested Message Values
9.3. Data Item Values
This document requests the following new assignments to the DLEP Data
Item Registry named "Data Item Type Values" in the range with the
"Specification Required" policy. The requested values are as
follows:
+-----------+------------------------------+
| Type Code | Description |
+-----------+------------------------------+
| TBA4 | Credit Window Initialization |
| | |
| TBA5 | Credit Window Association |
| | |
| TBA6 | Credit Window Grant |
| | |
| TBA7 | Credit Window Status |
| | |
| TBA8 | Credit Window Request |
| | |
| TBA9 | Traffic Classification |
+-----------+------------------------------+
Table 3: Requested Data Item Values
9.4. DLEP Sub Data Item Registry
Upon approval of this document, IANA is requested to create a new
DLEP registry, named "Sub Data Item Type Values". The registry shall
identify the type code value, the Data Item which may use the value,
and a description of the value. While the same value may be reused
in different data items, this is not recommended at this time.
The following table provides initial registry values and the
[RFC8126] defined policies that should apply to the registry:
+-------------+------------------------------+----------------------+
| Type Code | Valid Data Items | Description |
+-------------+------------------------------+----------------------+
| 0 | N/A | Reserved |
| | | |
| 1 | N/A | Reserved (for pause |
| | | sub-DI) |
| | | |
| 2 | DiffServ Credit Window | DiffServ Traffic |
| | Traffic Classification | Classification |
| | | |
| 2-65407 | | Specification |
| | | Required |
| | | |
| 65408-65534 | | Private Use |
| | | |
| 65535 | | Reserved |
+-------------+------------------------------+----------------------+
Table 4: Initial Registry Values
10. References
10.1. Normative References [I-D.ietf-manet-credit-flow-control]
IETF, "DLEP Credit-Based Flow Control Messages and Data
Items", April 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8175] Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B. [RFC8175] Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B.
Berry, "Dynamic Link Exchange Protocol (DLEP)", RFC 8175, Berry, "Dynamic Link Exchange Protocol (DLEP)", RFC 8175,
DOI 10.17487/RFC8175, June 2017, DOI 10.17487/RFC8175, June 2017,
<https://www.rfc-editor.org/info/rfc8175>. <https://www.rfc-editor.org/info/rfc8175>.
10.2. Informative References 6.2. Informative References
[I-D.ietf-manet-credit-window] [I-D.ietf-manet-credit-window]
Ratliff, S., "Credit Windowing extension for DLEP", draft- Ratliff, S., "Credit Windowing extension for DLEP", draft-
ietf-manet-credit-window-07 (work in progress), November ietf-manet-credit-window-07 (work in progress), November
2016. 2016.
[I-D.ietf-manet-dlep-pause-extension]
Cheng, B., Wiggins, D., and L. Berger, "DLEP Control Plane
Based Pause Extension", draft-ietf-manet-dlep-pause-
extension-02 (work in progress), October 2017.
[IEEE.802.1Q_2014]
IEEE, "IEEE Standard for Local and metropolitan area
networks--Bridges and Bridged Networks", IEEE 802.1Q-2014,
DOI 10.1109/ieeestd.2014.6991462, December 2014,
<http://ieeexplore.ieee.org/servlet/
opac?punumber=6991460>.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474,
DOI 10.17487/RFC2474, December 1998,
<https://www.rfc-editor.org/info/rfc2474>.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, DOI 10.17487/RFC2475, December 1998, Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
<https://www.rfc-editor.org/info/rfc2475>. <https://www.rfc-editor.org/info/rfc2475>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
Appendix A. Acknowledgments Appendix A. Acknowledgments
The sub data item format was inspired by Rick Taylor's "Data Item The sub data item format was inspired by Rick Taylor's "Data Item
Containers". He also proposed the separation of credit windows from Containers". He also proposed the separation of credit windows from
traffic classification at IETF98. Many useful comments were received traffic classification at IETF98. Many useful comments were received
from contributors to the MANET working group. from contributors to the MANET working group.
Appendix B. Notional Support for Ethernet Priority Code Points
This document is intended to allow for use of the credit control
mechanisms defined in Section 4 with different flow identification
techniques. This section explores the viability of this through the
notional definition of credit control with Ethernet Priority Code
Points. Ethernet Priority Code Point support is defined as part of
the IEEE 802.1Q [IEEE.802.1Q_2014] tag format and includes a 3 bit
"PCP" field. The tag format also includes a 12 bit VLAN identifier
(VID) field.
In theory only one new Traffic Classification Sub Data Item is
required to enable support for the traffic classification of a new
flow type. This section defines such a sub data item. This
definition is not a full Extension definition, but may serve as the
foundation for such in the future; in a new document.
B.1. Notional Ethernet Credit Window Traffic Classification Sub Data
Item
The Ethernet Credit Window Traffic Classification Sub Data Item is
used to identify the VLAN and PCPs associated with a specific credit
window. Credit windows are identified using CID values that have
been previously been sent by the modem or are listed in a Credit
Window Initialization Data Item carried in the same messages as the
sub data item. PCPs are identified in a list of priority fields. An
implementation that does not support PCPs, and wants to use credit
window flow control for all traffic to a destination or destinations,
would indicate with 0 PCPs. Such an implementation could identify a
VLAN to use per destination.
The format of the Ethernet Credit Window Traffic Classification Sub
Data Item is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD | Length (8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Credit Window Identifier (CID)|NumPCPs| VLAN Identifier (VID) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pri. 1| Pri. 2| Pri. 3| Pri. 4| Pri. 5| Pri. 6| Pri. 7| Pri. 8|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Length: Variable
Length is the number of octets in the sub data item. It is equal
to eight (8).
Credit Window Identifier (CID):
A 16-bit unsigned integer identifying a credit window that has
been identified in a Credit Window Initialization Data Item, see
Section 4.3.1. Unknown CID values SHOULD be reported and result
in associated traffic being dropped.
Num PCPs:
A 4-bit unsigned integer indicating the number of PCPs carried in
the sub data item. A zero (0) indicates a (wildcard) match
against any PCP value.
VLAN identifier (VID):
A 12-bit unsigned integer field indicating the VLAN to be used in
traffic classification. A value of all ones (0xFFF) indicates a
wild card and any VID is to be accepted during traffic
classification. Zero (0) and any other value are valid values.
Priority:
Each Priority Field is an 4-bit whose definition includes the PCP
field defined in [IEEE.802.1Q_2014]
0 1 2 3
+---+---+---+---+
| PCP |DEI|
+---+---+---+---+
PCP: Priority code point
DEI: currently unused, MUST be zero
A router receiving the Ethernet Traffic Classification Sub Data Item
MUST validate the information on receipt prior to the information and
data plane update described earlier in this section. The credit
window associated with the CID indicated in each data item must be
located. It is important to note that the CID value may be present
in a Credit Window Initialization Data Item carried in the same
message as the sub data item. If the CID is not located, the it MUST
be treated as an error as described above.
When there are no unknown CIDs, the receiver MUST ensure that each
Priority Field value is listed only once across the whole Traffic
Classification Data Item. Note, this check is across the data item
and not the individual sub data item. If the same Priority Field
value is listed more than once within the same Traffic Classification
Data Item, the data item MUST be treated as an error as described
above.
In all cases, the router MUST use validated PCPs in data plane credit
window identification as described in Section 4.1.
B.2. Other Considerations
A full definition for the support of an Ethernet Credit Window
Extensions would need to assign a new Extension Type Value as well as
the Ethernet Credit Window Traffic Classification Sub Data Item
Value. It would also need to fully document the implications of
multiple VLAN support, including configuration implications, e.g.,
limiting value to 0 to indicate PCP-only usage.
Authors' Addresses Authors' Addresses
Bow-Nan Cheng Bow-Nan Cheng
Lincoln Laboratory Lincoln Laboratory
Massachusetts Institute of Technology Massachusetts Institute of Technology
244 Wood Street 244 Wood Street
Lexington, MA 02421-6426 Lexington, MA 02421-6426
Email: bcheng@ll.mit.edu Email: bcheng@ll.mit.edu
David Wiggins David Wiggins
Lincoln Laboratory Lincoln Laboratory
Massachusetts Institute of Technology Massachusetts Institute of Technology
244 Wood Street 244 Wood Street
Lexington, MA 02421-6426 Lexington, MA 02421-6426
Email: David.Wiggins@ll.mit.edu Email: David.Wiggins@ll.mit.edu
Lou Berger Lou Berger
LabN Consulting, L.L.C. LabN Consulting, L.L.C.
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