| Internet-Draft | Satellite Instructive Routing | September 2022 |
| Han, et al. | Expires 6 March 2023 | [Page] |
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.¶
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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:¶
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:¶
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:¶
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 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.¶
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:¶
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 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:¶
^ Shl_ID Incremental direction
|
/
/
S5 ^ Sat_ID Increment direction
/| /
/ | S3
/ / | / /
/ / | / /
/ |/ /
S2------S0------S1 -> Obp_ID Increment direction
/ /| / /
/ / | / /
/ / | / /
S4 |/
S6
/
/
/
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:¶
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.¶
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:¶
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:¶
^ 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---+-------+-------+-------+----
| | | | |
| | | | |
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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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]...
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 |
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.¶
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:¶
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.¶
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.}
¶
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.¶
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.}
¶
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.¶
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.}
¶
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.¶
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.}
¶
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.¶
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.}
¶
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.¶
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.}
¶
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.}
¶
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.¶
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.}
¶
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.}
¶
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:¶
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.}
¶
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.}
¶
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:¶
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.}
¶
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.}
¶
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.}
¶
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.}
¶
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:¶
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.}
¶
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.}
¶
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.¶
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.¶