IGP Extensions for DetNet Deterministic LinksZTE CorporationChinaxiong.quan@zte.com.cnZTE CorporationChinaqian.xiaocong@zte.com.cn
Routing
LSRThis document proposes the deterministic links to provide a one-dimensional
deterministic metric to guarantee the deterministic forwarding capabilities
at different levels and proposes the deterministic links distribution
by IGP extensions.IntroductionAccording to , Deterministic Networking (DetNet) operates
at the IP layer and delivers service which provides extremely low data
loss rates and bounded latency within a network domain. The bounded
latency indicates the minimum and maximum end-to-end latency from source
to destination and bounded jitter (packet delay variation).
has described the
enhanced requirements for DetNet enhanced data plane including the deterministic
latency guarantees. has proposed the
packet treatment which should support new functions such as
queuing mechanisms to ensure the deterministic latency.
As per ,
network nodes collects topology information and DetNet capabilities
through IGP. The computing method of end-to-end delay bounds is defined in .
It is the sum of the six delays in DetNet bounded latency model. It is
the sum of non-queuing delay bound and queuing delay bound in DetNet
bounded latency model. The upper bounds of queuing delay depends on
the queuing mechanisms deployed along the path. For example, a link
with a queuing mechanism that does not guarantee a bounded delay a
non-determinisitc link and a link with a queuing mechanism that can
provide deterministic delay is called a deterministic link. The
delay of a a deterministic link is consist of the propagation delay
of the packet on the link and the queuing delay of the packet at the
node. A deterministic link can be a sub-network that provides
deterministic transmission or a Point-to-Point (P2P) link. This document proposes the deterministic links to provide a one-dimensional
deterministic metric to guarantee the deterministic forwarding capabilities
at different levels and proposes the deterministic links distribution
by IGP extensions.Requirements LanguageThe 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.TerminologyThe terminology is defined as and
.Deterministic LinksThis document proposes the deterministic links to provide a one-dimensional
deterministic metric to guarantee the deterministic forwarding capabilities
at different levels. The deterministic links can shield the differences from
underlying forwarding and queuing mechanisms.Deterministic Links ModelAs per , six types of
delays are defined in timing Model of DetNet. And the DetNet domain can also
be modeling as deterministic links and nodes as shown in Figure 1. The
deterministic node delay is constant while the deterministic link delay is
variable within bounded latency. The end-to-end bounded latency depends on
the sum of the deterministic link delay.
Deterministic Link Delay = Regulation delay + Queuing subsystem delay +
Output delay + Link delay + Frame preemption delay
Deterministic Node Delay = Processing delay
DetNet transit node A DetNet transit node B
+-------------------------+ +------------------------+
| Queuing | | Queuing |
| Regulator subsystem | | Regulator subsystem |
| +-+-+-+-+ +-+-+-+-+ | | +-+-+-+-+ +-+-+-+-+ |
-->+ | | | | | | | | | + +------------>+ | | | | | | | | | + +--->
| +-+-+-+-+ +-+-+-+-+ | | +-+-+-+-+ +-+-+-+-+ |
| | | |
+-------------------------+ +------------------------+
|-->|------->|------->|-->|------------>|-->|------->|------>|-->|-->|
2,3 4 5 6 1 2,3 4 5 6 1 2,3
|---- Deterministic Link Delay ---->|
Deterministic Links Deterministic Node
| A |---------------------------------->| B |----------------------->|
Classfication of deterministic LinksThere are a number of deterministic links between deterministic nodes.
And each deterministic link provides different level of deterministic
forwarding capabilities indicated by Deterministic Class-Type (DT).Deterministic Class-Type (DT): indicate the set of Traffic Trunks
crossing a deterministic link that is governed by a specific set of
bounded latency constraints. DT is used for the purposes of deterministic
link resource planning, reservation and allocation, deterministic link
resource constraint-based routing and admission control. A given Traffic
Trunk belongs to the same DT on all links.For example, three deterministic links with guaranteed jitter
are supported between the Node A and Node B as following shown.
deterministic link 1, DT=1 (Jitter Guarantee, queuing type=CSQF), bandwidth=20Mbit/s, jitter=10us.
deterministic link 2, DT=2 (Jitter Guarantee, queuing type=TCQF), bandwidth=30Mbit/s, jitter=20us.
deterministic link 3, DT=3 (Jitter Guarantee, queuing type=TQF), bandwidth=40Mbit/s, jitter=30us.
Deterministic Links ResourcesThe traditional resource reservation method only considers
the bandwidth availability of the BE (Best Effort) flow,
which means that the reserved bandwidth meets the peak
information rate (PIR) of the business flow at the macro level.
As per ,
the enhanced DetNet need to support multiple queuing mechanisms
to provide deterministic latency. For such scheduling mechanisms,
even the bandwidth resources meet the transmission requirements
at the macro level, there may not be enough resources in a
specific timeslot, cycle or authorization time zone, so bounded
delay and jitter cannot be guaranteed. So it is required to provide
provisioning of fine-grained reservation for time-based resources.Time-based Resources Container (TRC): the entity which is used
for deterministic link to provide the time-based resources
with deterministic capabilities by resolving resource conflicts
between different levels. The container indicates the maximum
transmitting bits per scheduling timeslot and it contains the
corresponding scheduling resources reserved to guarantee the
capability of deterministic link such as queuing, buffer and
bandwidth. ISIS Extensions of Deterministic LinksThis document defines new IS-IS TE sub-TLVs to distribute the
deterministic links attributes at TE link and it can be announced
in TLVs 22, 23, 141, 222, and 223" registry. Deterministic Link Sub-TLVA new IS-IS Deterministic Link Sub-TLV is defined and the format
is as shown in the following figure.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DT | Link Scheduling Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Sub-sub-TLV ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Type: Set to TBD1.
Length: Contains the total length of the subobject in octets.
The Length MUST be at least 8 and MUST be a multiple of 4.
DT: the value of DT to indicates the set of Traffic Trunks
crossing the deterministic linke that is governed by a specific
set of bounded latency constraints.
Link Scheduling Type: indicates the type of the queuing or
scheduling mechanisms on this deterministic link.
Sub-sub-TLV: indicates the optional sub-sub-TLV carried in
this sub-TLV.
Deterministic Link Maximum Reservble Bandwidth Sub-sub-TLVA new IS-IS Deterministic Link Maximum Reservble Bandwidth Sub-sub-TLV
is defined and the format is as shown in the following figure.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Reserved Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Type: Set to TBD2.
Length: Contains the total length of the subobject in octets.
The Length MUST be at least 8 and MUST be a multiple of 4.
Maximum Reserved Bandwidth: indicates the maximum reservble
bandwidth for this deterministic link.
Deterministic Link Available Bandwidth Sub-sub-TLVA new IS-IS Deterministic Link Available Bandwidth Sub-sub-TLV
is defined and the format is as shown in the following figure.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Available Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Type: Set to TBD3.
Length: Contains the total length of the subobject in octets.
The Length MUST be at least 8 and MUST be a multiple of 4.
Available Bandwidth: indicates the available bandwidth of
this deterministic link.
Deterministic Link Delay Sub-sub-TLVA new IS-IS Deterministic Link Delay Sub-sub-TLV is defined and the format
is as shown in the following figure.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A| Reserved | Maximum Deterministic Link Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Minimum Deterministic Link Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Maximum Deterministic Link Delay Variation |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Type: Set to TBD4.
Length: Contains the total length of the subobject in octets.
The Length MUST be at least 8 and MUST be a multiple of 4.
A: The A bit represents the Anomalous (A) bit. The A bit is set
when the measured value of this parameter exceeds its configured
maximum threshold.
Maximum Deterministic Link Delay: indicates the maximum
deterministic link delay value (in microseconds) over a
configurable interval, encoded as an integer value.
Minimum Deterministic Link Delay: indicates the minimum
deterministic link delay value (in microseconds) over a
configurable interval, encoded as an integer value.
Maximum Deterministic Link Delay Variation: indicates the
maximum deterministic link delay variation value over a
configurable interval in microseconds, encoded as an
integer value.
OSPF Extensions of Deterministic LinksTBASecurity ConsiderationsTBAIANA ConsiderationsIANA is requested to register the following sub-TLVs
in the "Sub-TLVs for TLVs 22, 23, 141, 222,and 223" registry:AcknowledgementsTBAReferencesNormative References