Semantic Address Based Instructive Routing for Satellite Network
draft-lhan-satellite-instructive-routing-02
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| Authors | Lin Han , Alvaro Retana , Richard Li | ||
| Last updated | 2023-03-03 | ||
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draft-lhan-satellite-instructive-routing-02
Network Working Group L. Han, Ed.
Internet-Draft A. Retana
Intended status: Informational R. Li
Expires: 4 September 2023 Futurewei Technologies, Inc.
3 March 2023
Semantic Address Based Instructive Routing for Satellite Network
draft-lhan-satellite-instructive-routing-02
Abstract
This document presents a method to do IP routing over satellite
network that consists of LEO (Low Earth Orbit) satellites and ground-
stations. The method uses the source routing mechanism. The whole
routing info is obtained by path calculation. The routing path
information is converted to be a list of instructions and embedded
into user packet's IPv6 extension header. At each hop or each
satellite, the routing process engine will forward the packet based
on the specified instruction for the satellite. Until the packet
reaches the edge of satellite network, or the last satellite, the
packet will be sent to a ground station.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
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This Internet-Draft will expire on 4 September 2023.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
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Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Review of LEO satellite constellation for future Internet . . 5
4. Basics of Instructive Routing . . . . . . . . . . . . . . . . 6
4.1. Forwarding Directions . . . . . . . . . . . . . . . . . . 7
4.2. Forwarding Segments . . . . . . . . . . . . . . . . . . . 8
4.3. Forwarding Instructions . . . . . . . . . . . . . . . . . 9
4.4. Example . . . . . . . . . . . . . . . . . . . . . . . . . 9
5. IPv6 Routing Header for Instructive Routing . . . . . . . . . 11
6. Instruction List for Instructive Routing . . . . . . . . . . 12
7. Instructive Routing Behaviors . . . . . . . . . . . . . . . . 13
7.1. Fwd.Inc.Sat_ID . . . . . . . . . . . . . . . . . . . . . 14
7.2. Fwd.Dec.Sat_ID . . . . . . . . . . . . . . . . . . . . . 15
7.3. Fwd.Inc.Opb_ID . . . . . . . . . . . . . . . . . . . . . 16
7.4. Fwd.Dec.Opb_ID . . . . . . . . . . . . . . . . . . . . . 17
7.5. Fwd.Inc.Shl_ID . . . . . . . . . . . . . . . . . . . . . 18
7.6. Fwd.Dec.Shl_ID . . . . . . . . . . . . . . . . . . . . . 19
7.7. End.Intf_ID . . . . . . . . . . . . . . . . . . . . . . . 20
7.8. End.Punt . . . . . . . . . . . . . . . . . . . . . . . . 20
7.9. End.Lookup . . . . . . . . . . . . . . . . . . . . . . . 21
7.10. End.Lookup.IPv4 . . . . . . . . . . . . . . . . . . . . . 21
7.11. End.Lookup.IPv6 . . . . . . . . . . . . . . . . . . . . . 22
7.12. Fwd.Sat_Addr . . . . . . . . . . . . . . . . . . . . . . 22
7.13. Fwd.Sat_MacAddr . . . . . . . . . . . . . . . . . . . . . 23
7.14.
Forwarding_API(Packet,Input_Satellite,Input_Direction) . 24
7.15. Forwarding_API_SAT(Packet,Input_Satellite,Sat_Addr) . . 24
7.16.
Forwarding_API_MAC(Packet,Input_Satellite,Sat_MacAddr) . 24
7.17. Forwarding_GS_API(Packet,Input_Interface) . . . . . . . . 25
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
9. Security Considerations . . . . . . . . . . . . . . . . . . . 25
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 26
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 26
12.1. Normative References . . . . . . . . . . . . . . . . . . 26
12.2. Informative References . . . . . . . . . . . . . . . . . 26
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
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1. Introduction
Massive LEO constellation is expected to be used for future Internet.
It has raised challenges to the current IP networking technologies to
support such super-fast-moving network.
[I-D.lhan-problems-requirements-satellite-net] has analyzed the
problems when using the regular routing protocols in such network.
Since all satellites in a LEO constellation are well organized and
form a kind of multi-layered grid network, each satellite's relative
position in the satellite network will be steady during its life
time. [I-D.lhan-satellite-semantic-addressing] has proposed to use
couple of indexes to identify each satellite in the network. The
combination of the indexes is called the satellite semantic address.
The semantic address can be embedded into the field of the interface
identifier (i.e., the rightmost 64 bits) of the IPv6 address, if IPv6
is used in the satellite network.
This memo proposes a method for routing for LEO satellite network, it
is based on the satellite semantic address. It is a source routing
mechanism and conceptually similar to SRv6 (IPv6 Segment Routing)
[RFC8754] with loose-hop, but with many differences in the
architecture and details. The routing information is embedded into
the IPv6 packet as routing extension header defined in [RFC8200].
Unlike the SRv6 [RFC8754] and programming [RFC8986], The new method
will not use IPv6 SID (Segment Identifier) to represent the segments
on the routing path. Instead, it will convert the segments on the
path to be a list of instructions since each satellite could be
represented by the semantic address. Each instruction can tell each
satellite how to forward the packet to an adjacent satellite and when
to stop, either on the same orbit, or on the adjacent orbit.
Compared with the traditional IP forwarding, the new method will not
use TCAM (Ternary Content-addressable Memory) lookup for IP prefix.
Each satellite only needs to store a simple adjacency table.
Therefore, the new method can save significant TCAM and the
processing time for routing/forwarding tables.
It must be noted this memo just describes one aspect of the whole
solution for satellite constellation used for Internet access and NTN
(Non-Terrestrial Network) integration with 5G, following areas are
not covered in this memo and will be addressed in other documents
separately:
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1. IP forwarding path determination for a LEO constellation. There
are different strategies and algorithms to determine the IP path.
One example using modified OSPF and Dijkstra algorithm
[I-D.retana-lsr-ospf-monitor-node] to get the shortest geographic
path can be found in [Large-Scale-LEO-Network-Routing].
2. Data planes for different scenarios, such as Internet access and
NTN integration.
3. Other protocols for control plane.
2. Terminology
LEO Low Earth Orbit with the altitude from 180 km to
2000 km.
LEO constellation LEO constellation consists of certain number of
LEOs. Each LEO has pre-assigned orbit element.
ISL Inter Satellite Link
GS Ground Station, a device on ground connecting
satellite. In the document, GS will hypothetically
provide L2 and/or L3 functionality in addition to
process/transmit/receive radio wave. It might be
different as the reality that the device to
process/transmit/receive radio wave and the device
to provide L2 and/or L3 functionality could be
separated.
L2 Layer 2, or Data Link Layer in OSI model
[OSI-Model]
L3 Layer 3, or Network Layer in OSI model [OSI-Model],
it is also called IP layer in TCP/IP model
OS Operating System
NTN Non-Terrestrial Network
SID Segment Identifier
Sat-GS Links Wireless links between satellites and ground-
stations, it consists of uplink (from ground to
satellite) and downlink (from satellite to ground.
Link Metrics The cost of the outgoing interface for routing,
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typically, it may indicate the bandwidth, delay or
other costs for the interface.
Sat_ID Satellite Index, the Index for the satellite in a
orbit plane, see
[I-D.lhan-satellite-semantic-addressing]
Obp_ID Orbit Plane Index, the Index for the orbit plane in
a shell group of satellite, see
[I-D.lhan-satellite-semantic-addressing]
Shl_ID Shell Index, the Index for the shell group of
satellite in a satellite constellation, see
[I-D.lhan-satellite-semantic-addressing]
Intf_ID Interface Index
Sat_Addr Satellite Semantic Address, it consists of indexes
Shl_ID, Obp_ID and Sat_ID. It is 32-bit long and
is defined in Section 5.4 in
[I-D.lhan-satellite-semantic-addressing]
Sat_MacAddr The MAC (Media Access Control) Address for a
satellite
3. Review of LEO satellite constellation for future Internet
LEO satellite constellation is expected to be integrated with
terrestrial network in future Internet. StarLink project [StarLink]
has launched its satellites and provided the beta service in some
areas. 3GPP [ThreeGPP] has studied the issues when NTN is integrated
with Internet and 5G. 3GPP [TR38-821] has also proposed the
Satellite-based NG-RAN architectures for NTN integration. In the
3GPP new Release 18 (in-progress), there is a working item "Study on
5G System with Satellite Backhaul" [TR23-700]. In which, LEO
satellite network will provide the transport functionality for 5G RAN
access network. As a summary, the targets of LEO constellation for
future Internet and NTN integration are as follows:
1. Global coverage: The Satellite network should cover all places on
earth and any flying objects as long as the place or objects are
below LEO attitude and within the coverage footprint of satellite
constellation, the satellite network should be the complementary
to terrestrial network.
2. Internet access: The Satellite network can provide the Internet
access service for covered areas.
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3. NTN integration: The Satellite network is fully integrated with
Internet including Wireless such as 4G or 5G.
4. Competitive service: The Satellite network can provide the
services that are competitive to terrestrial network in terms of
service stability, Quality of Service, especially the latency for
Satellite network is shorter.
As a new form of network, LEO constellation has lots of difference
with the steady terrestrial network especially in the mobility.
[I-D.lhan-problems-requirements-satellite-net] has analyzed the
movement and coverage of satellite. For a massive LEO constellation,
all satellites are moving on the allocated orbits, and form one or
multiple layers of network. Finally, the massive LEO constellation
will have the following unprecedented mobility:
1. Each LEO moves at the speed of 7.x km/s.
2. Ground Stations move at the speed of 463 m/s due to earth
rotation.
3. Half of LEOs move on the direction that is different with another
half of LEOs.
4. Huge number of links between satellites and ground-stations, and
all of them are constantly flipping within short period of time.
All Link Metrics of Sat-GS Links are also constantly changing.
5. All Link Metrics of ISL on the Longitude direction are constantly
changing.
6. All Links of ISL on the Longitude direction may be interrupted at
two polar areas.
7. All Link Metrics of ISL on the radius direction (for satellites
with different altitude) are constantly changing.
8. All Links of ISL on the radius direction can only last for a
limited time.
4. Basics of Instructive Routing
In IP routing or forwarding, the IP path consists of a list of IP
nodes (hops). In LEO satellite network, the IP forwarding path is a
list of satellites. Instructive routing essentially is a mechanism
that converts satellites on the path to a list of segment and then to
a list of instructions. It will utilize the special characters of
LEO satellite network to achieve the minimized packet overhead while
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the forwarding functions can be executed quickly.
A typical LEO satellite network is an interleaved and meshed network
moving constantly. Each satellite only has limited adjacent
satellites, thus the limited packet forwarding directions (see
Section 4.1).
The satellites on a forwarding path can be converted to a list of
segments. The number of segments is normally much smaller than the
number of satellites on the path.
The number of segment type will determine the number of instruction
type. Since the segment type is also limited (see Section 4.2), so
the instruction type is limited.
Finally, combining the above characters and with the use of semantic
address, the Instructive Routing will only introduce limited overhead
that is much smaller than SRv6 and SRv6 with compressed SID.
4.1. Forwarding Directions
When using ISL for satellites in a LEO constellation, each layer of
network will have satellite nodes connected by limited ISLs. A
typical satellite will have about six ISL to connected to its
adjacent satellites in 3D space. Additionally, there might have very
few numbers of ISL working as un-steady link to connect to other
satellites. Un-stead links are those between satellites moving to
different directions, see
[I-D.lhan-problems-requirements-satellite-net] for the detailed
explanation. After using the semantic address for each satellite,
the satellite relationship will be static. Figure 1 illustrates one
satellite and its six direct connected adjacent satellites, it is
easy to determine some indexes of its adjacent satellites:
1. S0, S1 and S2 have the same Shl_ID, the difference of Obp_ID
between S0 and S1, S0 and S2 are both equal to one.
2. S0, S3 and S4 have the same Shl_ID and Obp_ID, the difference of
Sat_ID between S0 and S3, S0 and S4 are both equal to one.
3. S0, S5 and S6 have different Shl_ID, and the difference of Shl_ID
between S0 and S5, S0 and S6 are both equal to one.
Another benefit to use the semantic address is that the packet
forwarding for routing and switching will be simplified
significantly. There will be only six major forwarding directions to
the directly connected adjacent satellites described above, plus one
or few specified directions probably. The specified direction is to
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forward packet to a specified adjacent satellite through an un-steady
link. The un-steady link can connect to any satellite but only last
for a short time. The usages of un-steady links are expected to be
limited and are not major scenarios in a LEO constellation.
Following are all directions for forwarding:
1. Forward to the Sat_ID Incremental or Decremental directions.
2. Forward to the Obp_ID Incremental or Decremental directions.
3. Forward to the Shl_ID Incremental or Decremental directions.
4. Forward to a specified satellite through an un-steady link.
^ Shl_ID Incremental direction
|
/
/
S5 ^ Sat_ID Increment direction
/| /
/ | S3
/ / | / /
/ / | / /
/ |/ /
S2------S0------S1 -> Obp_ID Increment direction
/ /| / /
/ / | / /
/ / | / /
S4 |/
S6
/
/
/
Figure 1: The LEO Satellite Relationship in 3D Space
4.2. Forwarding Segments
A forwarding segment is defined as a list of satellites, and four
type segments are defined for LEO satellite network where semantic
address is used:
1. Segment with adjacent Shl_ID: For any direct adjacent satellites
on the segment, their Shl_ID are also adjacent (differ by one).
2. Segment with adjacent Obp_ID: For any direct adjacent satellites
on the segment, their Obp_ID are also adjacent (differ by one),
the Shl_ID are the same.
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3. Segment with adjacent Sat_ID: For any direct adjacent satellites
on the segment, their Sat_ID are also adjacent (differ by one),
the Obp_ID and Shl_ID are identical.
4. Segment with non-adjacent index: this segment only has two
satellites and two satellites do not belong to the above three
categories.
4.3. Forwarding Instructions
Each forwarding instruction consists of Functional Code and Argument
(see Section 6). For the most often used instructions, the Argument
represents one specified index (Sat_ID or Obp_ID or Shl_ID) of a
satellite semantic address and only has the size of one octet.
Each segment maps to a forwarding instruction that can guides the
packet forwarded at each satellite from the start to the end of the
segment. For the segment types (1) to (3) described in Section 4.2,
there are two directions to forward packet, each direction can be
defined as either an increment or a decrement of a specified index.
For type (4), there is one direction to forward packet. In total we
have seven directions to forward packets among all satellites: to the
satellite ahead or behind; to either sides; above or below; or to
another non-adjacent satellite.
When an IP packet is forwarded on a segment by an instruction, at
each satellite, the forwarding logic needs to check if the packet
reaches the end of the segment. In the regular segment routing, the
long size of SID is used to do such indication. But for satellite
network, since 32-bit satellite's semantic address is embedded into
the IPv6 address, it is not needed to include the long SID into the
packet header. Instead, we only need to compare one octet index of
the current satellite's semantic address, instead of whole IPv6
address, with the Argument in the instruction.
4.4. Example
Figure 2 illustrates a 2D example. It shows how a packet is
forwarded in a grid satellite network. Intuitively, we can obtain
the list of instructions to guide the packet and get the forwarding
behaviors at different satellites. Following is an example:
1. At S1 to S2, forward packet to the Sat_ID Incremental direction,
until the packet reaches S2
2. At S2 to S3, forward packet to the Obp_ID Incremental direction,
until the packet reaches the orbit plane of S3
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3. At S3 to S4, forward packet to the Sat_ID Incremental direction,
until the packet reaches S4
4. At S4 to S5, forward packet to the Obp_ID Decremental direction,
until the packet reaches the orbit plane of S5
5. At S5 to S6, forward packet to the Sat_ID Decremental direction,
until the packet reaches S6
By using a specified index of semantic address as the argument as
described in Section 4.3, we can further simplify the above
instructions as:
1. At S1 to S2, forward packet to the Sat_ID Incremental direction,
until the packet reaches a satellite and the satellite's Sad_ID
is equal to the given instruction argument (S2's Satellite Index)
2. At S2 to S3, forward packet to the Obp_ID Incremental direction,
until the packet reaches a satellite and the satellite's Obp_ID
is equal to the given instruction argument (S3's Orbit Plane
Index)
3. At S3 to S4, forward packet to the Sat_ID Incremental direction,
until the packet reaches a satellite and the satellite's Sat_ID
is equal to the given instruction argument (S4's Satellite Index)
4. At S4 to S5, forward packet to the Obp_ID Decremental direction,
until the packet reaches a satellite and the satellite's Obp_ID
is equal to the given instruction argument (S5's Orbit Plane
Index)
5. At S5 to S6, forward packet to the Sat_ID Decremental direction,
until the packet reaches a satellite and the satellite's Sat_ID
is equal to the given instruction argument (S6's Satellite Index)
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^ Sat_ID Incremental Direction
|
|
+----> Obp_ID Incremental Direction
x: The ISL is down
Obp_ID Obp_ID+1 Obp_ID+2 Obp_ID+3 Obp_ID+4
| | | | |
----+-------S5<<<<<<S<<<<<<<S4------+----
| V x ^ |
| V | ^ |
----+-------S6------+---x---S-------+----
| | | ^ |
x x x ^ |
----S2>>>>>>S>>>>>>>S>>>>>>>S3------+----
^ | | | |
^ | | | |
----S---x---+-------+-------+-------+----
^ | | | |
^ | | | |
----S1--x---+-------+-------+-------+----
| | | | |
| | | | |
Figure 2: Packet Forwarding in 2D LEO satellite constellation network
5. IPv6 Routing Header for Instructive Routing
For instructive routing, IPv6 routing header is used with a new
routing type "Instructive Routing Type". The format of the new
routing header is illustrated in Figure 3.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | Routing Type | Inst. Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Remained Inst. | ST | Rsvd |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Inst. List ~
| +-+-+-+-+-+-+-+-+
| ~ paddings |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: The IPv6 Routing Hdr for Instructive Routing
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Routing Type Instructive Routing Type
Inst. Offset The offset in the number of octets from the start of
Instruction List. The initial value is set to 0 and
it points to the 1st instruction to be executed. The
value is incremented by the number of octets of the
total size of an instruction after the instruction is
executed.
Remained Inst. Remained Number of Instructions. The initial value
is set to the total number of instructions. The
value will be decremented by one after one
instruction is executed. The minimum number is one,
and it indicates that the end of instruction stack is
reached.
ST The satellite address type, default is 0.
Inst. List A list of instructions, the size is variable.
Paddings Pad1 or PadN options to make the packet extension
header alignment, see [RFC8200]
6. Instruction List for Instructive Routing
For instructive routing, the instruction list is used to instruct
each satellite how to do routing job. The format of the instruction
list is illustrated in Figure 4. Each instruction consists of
Function Code and Arguments.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Func. Code | Arguments | Func. Code | Arguments ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\--------------\/--------------/ \--------------\/--------------/
instruction[0] instruction[1]...
Figure 4: The Instruction List for Instructive Routing
Func. Code Function Code, size is 1 octet
Arguments Arguments for the function, Variable length
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7. Instructive Routing Behaviors
The behavior for each satellite for instructive routing is described
here. Table 1 is the summary of the name, Hex values of all
functions, arguments and size. New functions can be defined if
needed.
The subsections below are the detailed explanation for each function.
+======================+=======================+==============+
| Func Name/Hex Value | Arguments/Size(Octet) | Reference |
+======================+=======================+==============+
| Fwd.Inc.Sat_ID/0X01 | Sat_ID/1 | Section 7.1 |
+----------------------+-----------------------+--------------+
| Fwd.Dec.Sat_ID/0X02 | Sat_ID/1 | Section 7.2 |
+----------------------+-----------------------+--------------+
| Fwd.Inc.Obp_ID/0X03 | Obp_ID/1 | Section 7.3 |
+----------------------+-----------------------+--------------+
| Fwd.Dec.Obp_ID/0X04 | Obp_ID/1 | Section 7.4 |
+----------------------+-----------------------+--------------+
| Fwd.Inc.Shl_ID/0X05 | Shl_ID/1 | Section 7.5 |
+----------------------+-----------------------+--------------+
| Fwd.Dec.Shl_ID/0X06 | Shl_ID/1 | Section 7.6 |
+----------------------+-----------------------+--------------+
| End.Intf_ID/0X07 | Intf_ID/1 | Section 7.7 |
+----------------------+-----------------------+--------------+
| End.Punt/0X08 | 0X0/1 | Section 7.8 |
+----------------------+-----------------------+--------------+
| End.Lookup/0X09 | 0X0/1 | Section 7.9 |
+----------------------+-----------------------+--------------+
| End.Lookup.IPv4/0X0A | IPv4_Addr/4 | Section 7.10 |
+----------------------+-----------------------+--------------+
| End.Lookup.IPv6/0X0B | IPv6_Addr/16 | Section 7.11 |
+----------------------+-----------------------+--------------+
| Fwd.Sat_Addr/0X0C | Sat_Addr/4 | Section 7.12 |
+----------------------+-----------------------+--------------+
| Fwd.Sat_MacAddr/0X0D | Sat_MacAddr/6 | Section 7.13 |
+----------------------+-----------------------+--------------+
Table 1: Functions, Arguments and Reference
The functions in Section 7.1 to Section 7.6 are used for the
instructions to forward packet to one of the six major directions
discussed in Section 4. They will call API in Section 7.14 to
forward the packet to the specified direction.
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The functions in Section 7.12 and Section 7.13 are used for the
instructions to forward packet to a specified adjacent satellite
discussed in Section 4. They will call APIs in Section 7.15 and
Section 7.16 respectively to forward the packet to the specified
adjacent satellite.
In order to forward packet, each satellite should have an adjacency
table stored locally; the table should contain the information about
all adjacent satellites, it should at least store:
1. Each adjacent satellite's semantic address.
2. The ID of local interface connecting to each adjacent satellite.
3. The MAC address for the remote interface of each adjacent
satellite.
7.1. Fwd.Inc.Sat_ID
The definition of this function is "Forward the packet on the
Satellite Index Incremental Direction until the packet reaches a
Satellite whose Satellite Index is equal to the value specified in
the argument"
This function is used for the instruction to forward packet to one of
the six major directions discussed in Section 4.
When a satellite receives a packet with new routing header, assume
the satellite indexes in the address are Shl_index, Obp_index,
Sat_index respectively, the satellite does the following. During the
forwarding, the Forwarding_API in Section 7.14 is called to forward
the packet to the specified direction.
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S01. When an IRH is processed {
S02. If ((RI > 1) and (Argument != Sat_index)) {
S03. Input_Satellite = Current Satellite;
S04. Input_Direction = Satellite Index Incremental direction;
S05. Forwarding_API(Packet,Input_Satellite,Input_Direction);
S06. } else {
S07. IOF += 2;
S08. RI --;
S09. if (RI <= 0)
Send an ICMP Parameter Problem to the Source Address
with Code 0 (Erroneous header field encountered)
and Pointer set to the RI field,
interrupt packet processing, and discard the packet;
S10. Proceed to execute the next Instruction;
S11. }
S12.}
7.2. Fwd.Dec.Sat_ID
The definition of this function is "Forward the packet on the
Satellite Index Decremental Direction until the packet reaches a
Satellite whose Satellite Index is equal to the value specified in
the argument"
This function is used for the instruction to forward packet to one of
the six major directions discussed in Section 4.
When a satellite receives a packet with new routing header, assume
the satellite indexes in the address are Shl_index, Obp_index,
Sat_index respectively, the satellite does the following. During the
forwarding, the Forwarding_API in Section 7.14 is called to forward
the packet to the specified direction.
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S01. When an IRH is processed {
S02. If ((RI > 1) and (Argument != Sat_index)) {
S03. Input_Satellite = Current Satellite;
S04. Input_Direction = Satellite Index Decremental direction;
S05. Forwarding_API(Packet,Input_Satellite,Input_Direction);
S06. } else {
S07. IOF += 2;
S08. RI --;
S09. if (RI <= 0)
Send an ICMP Parameter Problem to the Source Address
with Code 0 (Erroneous header field encountered)
and Pointer set to the RI field,
interrupt packet processing, and discard the packet;
S10. Proceed to execute the next Instruction;
S11. }
S12.}
7.3. Fwd.Inc.Opb_ID
The definition of this function is "Forward the packet on the Orbit
Plane Index Incremental Direction until the packet reaches a
Satellite whose Orbit Plane Index is equal to the value specified in
the argument"
This function is used for the instruction to forward packet to one of
the six major directions discussed in Section 4.
When a satellite receives a packet with new routing header, assume
the satellite indexes in the address are Shl_index, Obp_index,
Sat_index respectively, the satellite does the following. During the
forwarding, the Forwarding_API in Section 7.14 is called to forward
the packet to the specified direction.
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S01. When an IRH is processed {
S02. If ((RI > 1) and (Argument != Obp_index)) {
S03. Input_Satellite = Current Satellite;
S04. Input_Direction = Orbit Plane Index Incremental direction;
S05. Forwarding_API(Packet,Input_Satellite,Input_Direction);
S06. } else {
S07. IOF += 2;
S08. RI --;
S09. if (RI <= 0)
Send an ICMP Parameter Problem to the Source Address
with Code 0 (Erroneous header field encountered)
and Pointer set to the RI field,
interrupt packet processing, and discard the packet;
S10. Proceed to execute the next Instruction;
S11. }
S12.}
7.4. Fwd.Dec.Opb_ID
The definition of this function is "Forward the packet on the Orbit
Plane Index Decremental Direction until the packet reaches a
Satellite whose Orbit Plane Index is equal to the value specified in
the argument"
This function is used for the instruction to forward packet to one of
the six major directions discussed in Section 4.
When a satellite receives a packet with new routing header, assume
the satellite indexes in the address are Shl_index, Obp_index,
Sat_index respectively, the satellite does the following. During the
forwarding, the Forwarding_API in Section 7.14 is called to forward
the packet to the specified direction.
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S01. When an IRH is processed {
S02. If ((RI > 1) and (Argument != Obp_index)) {
S03. Input_Satellite = Current Satellite;
S04. Input_Direction = Orbit Plane Index Decremental direction;
S05. Forwarding_API(Packet,Input_Satellite,Input_Direction);
S06. } else {
S07. IOF += 2;
S08. RI --;
S09. if (RI <= 0)
Send an ICMP Parameter Problem to the Source Address
with Code 0 (Erroneous header field encountered)
and Pointer set to the RI field,
interrupt packet processing, and discard the packet;
S10. Proceed to execute the next Instruction;
S11. }
S12.}
7.5. Fwd.Inc.Shl_ID
The definition of this function is "Forward the packet on the Orbit
Shell Index Incremental Direction until the packet reaches a
Satellite whose Orbit Shell Index is equal to the value specified in
the argument"
This function is used for the instruction to forward packet to one of
the six major directions discussed in Section 4.
When a satellite receives a packet with new routing header, assume
the satellite indexes in the address are Shl_index, Obp_index,
Sat_index respectively, the satellite does the following. During the
forwarding, the Forwarding_API in Section 7.14 is called to forward
the packet to the specified direction.
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S01. When an IRH is processed {
S02. If ((RI > 1) and (Argument != Shl_index)) {
S03. Input_Satellite = Current Satellite;
S04. Input_Direction = Orbit Shell Index Incremental direction;
S05. Forwarding_API(Packet,Input_Satellite,Input_Direction);
S06. } else {
S07. IOF += 2;
S08. RI --;
S09. if (RI <= 0)
Send an ICMP Parameter Problem to the Source Address
with Code 0 (Erroneous header field encountered)
and Pointer set to the RI field,
interrupt packet processing, and discard the packet;
S10. Proceed to execute the next Instruction;
S11. }
S12.}
7.6. Fwd.Dec.Shl_ID
The definition of this function is "Forward the packet on the Orbit
Shell Index Decremental Direction until the packet reaches a
Satellite whose Orbit Shell Index is equal to the value specified in
the argument"
This function is used for the instruction to forward packet to one of
the six major directions discussed in Section 4.
When a satellite receives a packet with new routing header, assume
the satellite indexes in the address are Shl_index, Obp_index,
Sat_index respectively, the satellite does the following. During the
forwarding, the Forwarding_API in Section 7.14 is called to forward
the packet to the specified direction.
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S01. When an IRH is processed {
S02. If ((RI > 1) and (Argument != Shl_index)) {
S03. Input_Satellite = Current Satellite;
S04. Input_Direction = Orbit Shell Index Decremental direction;
S05. Forwarding_API(Packet,Input_Satellite,Input_Direction);
S06. } else {
S07. IOF += 2;
S08. RI --;
S09. if (RI <= 0)
Send an ICMP Parameter Problem to the Source Address
with Code 0 (Erroneous header field encountered)
and Pointer set to the RI field,
interrupt packet processing, and discard the packet;
S10. Proceed to execute the next Instruction;
S11. }
S12.}
7.7. End.Intf_ID
The definition of this function is "End of processing for the
Instructive routing, remove the Instructive Routing Header, Forward
the packet to the interface specified in the argument"
This function is normally used on the Dst_Sat to forward packet to
Dst_GS.
When a satellite receives a packet with new routing header, the
satellite does the following, Forwarding_GS_API in Section 7.17 is
called to forward the packet to the specified interface.
S01. When an IRH is processed {
S02. Change the Next header in the packet header to be
the Next Header field in the Instructive Routing header;
S03. Remove the Instructive Routing Header;
S04. Forwarding_GS_API(Packet, Argument);
S05.}
7.8. End.Punt
The definition of this function is "End of processing for the
Instructive routing, remove the Instructive Routing Header, Punt the
packet to the OS for process"
This function is normally used send packet to a satellite. At the
destination satellite, the packet is punted to the OS to be processed
further.
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When a satellite receives a packet with new routing header, the
satellite does the following:
S01. When an IRH is processed {
S02. Change the Next header in the packet header to be
the Next Header field in the Instructive Routing header;
S03. Remove the Instructive Routing Header;
S04. Punt packet to the local CPU for process;
S05.}
7.9. End.Lookup
The definition of this function is "End of processing for the
Instructive routing, remove the Instructive Routing Header, Lookup
the destination address in packet header and forward the packet
accordingly"
This function is normally used to send packet to Dst_GS. After the
packet reaches the Dst_Sat, the packet is forwarded to Dst_GS by
looking up the destination address in the IPv6 packet header.
When a satellite receives a packet with new routing header, the
satellite does the following:
S01. When an IRH is processed {
S02. Change the Next header in the packet header to be
the Next Header field in the Instructive Routing header;
S03. Remove the Instructive Routing Header;
S04. Lookup the destination address in packet hdr and forward
the packet;
S05.}
7.10. End.Lookup.IPv4
The definition of this function is "End of processing for the
Instructive routing, remove the Instructive Routing Header, Lookup
the IPv4 address specified in the argument and forward the packet
accordingly"
This function is normally used to send packet to Dst_GS. After the
packet reaches the Dst_Sat, the packet is forwarded to Dst_GS by
looking up the IPv4 destination address specified in the Function
Argument.
When a satellite receives a packet with new routing header, the
satellite does the following:
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S01. When an IRH is processed {
S02. Fetch the IPv4 addr in the argument;
S03. Change the Next header in the packet header to be
the Next Header field in the Instructive Routing header;
S04. Remove the Instructive Routing Header;
S05. Lookup the fetched IPv4 address and forward the packet;
S06.}
7.11. End.Lookup.IPv6
The definition of this function is "End of processing for the
Instructive routing, remove the Instructive Routing Header, Lookup
the IPv6 address specified in the argument and forward the packet
accordingly"
This function is normally used to send packet to Dst_GS. After the
packet reaches the Dst_Sat, the packet is forwarded to Dst_GS by
looking up the IPv6 destination address specified in the Function
Argument.
When a satellite receives a packet with new routing header, the
satellite does the following:
S01. When an IRH is processed {
S02. Fetch the IPv6 addr in the argument;
S03. Change the Next header in the packet header to be
the Next Header field in the Instructive Routing header;
S04. Remove the Instructive Routing Header;
S05. Lookup the fetched IPv6 address and forward the packet;
S06.}
7.12. Fwd.Sat_Addr
The definition of this function is "Forward the packet to the
adjacent satellite with the address specified in the argument"
This function is normally used for the instruction to forward packet
to an adjacent satellite specified by its Satellite Semantic Address.
The Satellite Semantic Address is 32-bit long and is defined in
Section 5.4 in [I-D.lhan-satellite-semantic-addressing]
When a satellite receives a packet with new routing header, assume
the satellite semantic address is Sat_Addr, the satellite does the
following:
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S01. When an IRH is processed {
S02. If ((RI > 1) and (Argument != Sat_Addr)) {
S03. Input_Satellite = Current Satellite;
S04. SatAddr = Argument;
S05. Forwarding_API_SAT(Packet,Input_Satellite,SatAddr);
S06. } else {
S07. IOF += 4;
S08. RI --;
S09. if (RI <= 0)
Send an ICMP Parameter Problem to the Source Address
with Code 0 (Erroneous header field encountered)
and Pointer set to the RI field,
interrupt packet processing, and discard the packet.
S10. Proceed to execute the next Instruction;
S11. }
S12.}
7.13. Fwd.Sat_MacAddr
The definition of this function is "Forward the packet to the
adjacent satellite with the MAC address specified as the argument"
This function is normally used for the instruction to forward packet
to an adjacent satellite specified by its MAC address.
When a satellite receives a packet with new routing header, assume
the satellite Mac address is Sat_MacAddr, the satellite does the
following:
S01. When an IRH is processed {
S02. If ((RI > 1) and (Argument != Sat_MacAddr)) {
S03. Input_Satellite = Current Satellite;
S04. SatMacAddr = Argument;
S05. Forwarding_API_Mac(Packet,Input_Satellite,SatMacAddr);
S06. } else {
S07. IOF += 6;
S08. RI --;
S09. if (RI <= 0)
Send an ICMP Parameter Problem to the Source Address
with Code 0 (Erroneous header field encountered)
and Pointer set to the RI field,
interrupt packet processing, and discard the packet.
S10. Proceed to execute the next Instruction;
S11. }
S12.}
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7.14. Forwarding_API(Packet,Input_Satellite,Input_Direction)
This API will forward a packet to the specified direction. When a
satellite executes the API, it will do following:
S01. Forwarding_API(Packet,Input_Satellite,Input_Direction) {
S02. Lookup the local adjacency table to find out
1) The adjacent satellite of "Input_Satellite" on the
direction equal to "Input_Direction" (The adjacent
satellite's semantic address can be inferred by
the "Input_Satellite" and "Input_Direction").
2) The L2 address for the adjacent satellite;
3) The local interface connecting to the adjacent
satellite;
S03. Rewrite the L2 header of the Packet by the L2 address;
S04. Send the Packet to the local interface;
S05.}
7.15. Forwarding_API_SAT(Packet,Input_Satellite,Sat_Addr)
This API will forward a packet to the specified adjacent satellite
with the semantic address as the argument. When a satellite executes
the API, it will do following:
S01. Forwarding_API_SAT(Packet,Input_Satellite,SatAddr) {
S02. Lookup the local adjacency table to find out
1) The adjacent satellite of "Input_Satellite"
(The adjacent satellite address is SatAddr);
2) The L2 address for the adjacent satellite;
3) The local interface connecting to the adjacent
satellite;
S03. Rewrite the L2 header of the Packet by the L2 address;
S04. Send the Packet to the local interface;
S05.}
7.16. Forwarding_API_MAC(Packet,Input_Satellite,Sat_MacAddr)
This API will forward a packet to the specified adjacent satellite
with the MAC address as the argument. When a satellite executes the
API, it will do following:
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S01. Forwarding_API_MAC(Packet,Input_Satellite,SatMacAddr) {
S02. Lookup the local adjacency table to find out
1) The adjacent satellite of "Input_Satellite"
(The adjacent satellite MAC address is SatMacAddr);
2) The L2 address for the adjacent satellite;
3) The local interface connecting to the adjacent
satellite;
S03. Rewrite the L2 header of the Packet by the L2 address;
S04. Send the Packet to the local interface;
S05.}
7.17. Forwarding_GS_API(Packet,Input_Interface)
This API will forward a packet to ground station the connected to the
specified interface. When a satellite executes the API, it will do
following:
S01. Forwarding_API(Packet,Input_Interface) {
S02. Lookup the local adjacency table to find out
1) The connected GS to the interface
equal to "Input_Interface";
2) The L2 address for the GS;
S03. Rewrite the L2 header of the Packet by the L2 address;
S04. Send the Packet to the "Input_Interface";
S05.}
8. IANA Considerations
This document defines a new IPv6 Routing Type: the "Instructive
Routing Header". It needs to be assigned a number by IANA.
This document also defines an 8-bit Function Name, for which IANA
will create and will maintain a new sub-registry entitled
"Instructive Routing Function Name" under the "Internet Protocol
Version 6 (IPv6) Parameters" [IPv6_Parameters] registry. Initial
values for the subtype registries are given in Table 1.
9. Security Considerations
The instructive routing is only applicable to a satellite network
that is using the satellite semantic address. It will add
instructive routing header at a GS and the header will be removed
before reaching another GS. Normally, a satellite network including
all GS is trusted domain. Traffic will be filtered at the domain
boundaries. Non-authorized users cannot access the satellite
network.
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10. Contributors
11. Acknowledgements
12. References
12.1. Normative References
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>.
12.2. Informative References
[I-D.lhan-problems-requirements-satellite-net]
Han, L., Li, R., Retana, A., chenmeiling, Su, L., Jiang,
T., and N. Wang, "Problems and Requirements of Satellite
Constellation for Internet", Work in Progress, Internet-
Draft, draft-lhan-problems-requirements-satellite-net-04,
4 January 2023, <https://datatracker.ietf.org/doc/html/
draft-lhan-problems-requirements-satellite-net-04>.
[I-D.lhan-satellite-semantic-addressing]
Han, L., Li, R., Retana, A., chenmeiling, and N. Wang,
"Satellite Semantic Addressing for Satellite
Constellation", Work in Progress, Internet-Draft, draft-
lhan-satellite-semantic-addressing-02, 4 September 2022,
<https://datatracker.ietf.org/doc/html/draft-lhan-
satellite-semantic-addressing-02>.
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[I-D.retana-lsr-ospf-monitor-node]
Retana, A. and L. Han, "OSPF Monitor Node", Work in
Progress, Internet-Draft, draft-retana-lsr-ospf-monitor-
node-00, 7 March 2022,
<https://datatracker.ietf.org/doc/html/draft-retana-lsr-
ospf-monitor-node-00>.
[StarLink] "Star Link", <https://en.wikipedia.org/wiki/Starlink>.
[ThreeGPP] "3GPP", <https://www.3gpp.org/>.
[OSI-Model]
"OSI Model", <https://en.wikipedia.org/wiki/OSI_model>.
[TR38-821] "Solutions for NR to support Non-Terrestrial Networks
(NTN)",
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3525>.
[TR23-700] "Study on support of satellite backhauling in 5GS",
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=4000>.
[IPv6_Parameters]
IANA, "Internet Protocol Version 6 (IPv6) Parameters",
<https://www.iana.org/assignments/ipv6-parameters/
ipv6-parameters.xhtml#ipv6-parameters-3>.
[Large-Scale-LEO-Network-Routing]
"Large Scale LEO Satellite Networks for the Future
Internet: Challenges and Solutions to Addressing and
Routing," Computer Networks and Communications, 1(1),
31-58", <https://ojs.wiserpub.com/index.php/CNC/article/
view/2105>.
Appendix A. Change Log
* Initial version, 02/28/2022
* Revision 1, 09/02/2022
* Revision 2, 03/03/2023
Authors' Addresses
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Lin Han (editor)
Futurewei Technologies, Inc.
2330 Central Express Way
Santa Clara, CA 95050,
United States of America
Email: lhan@futurewei.com
Alvaro Retana
Futurewei Technologies, Inc.
2330 Central Express Way
Santa Clara, CA 95050,
United States of America
Email: alvaro.retana@futurewei.com
Richard Li
Futurewei Technologies, Inc.
2330 Central Express Way
Santa Clara, CA 95050,
United States of America
Email: rli@futurewei.com
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