![SRH
- Routing Type: 4
- Segments Left(SL): The next active segment
- Last Entry: Zero based,
- Segment List[0..n]
- Segment List[0]: Last Segment
- Segment List[1]: Penultimate segment of the SR Policy
- Segment List[n]: First Segment
- The active segment is indicated by the Destination Address (DA) of the packet.
- SRH TLVs: Only process when the Active Segment is a local SID
- HMAC TLV: Hashed Message Authentication Code
- Access Control List (ACL) that considers HMAC Key ID, or other packet fields.
- SID List Verification
- Reduced SRH: Not contain the first segment of the related SR Policy](https://image.slidesharecdn.com/srv6-240312150709-82216548/85/SRv6-note-from-book-and-some-drawing-for-different-srv6-packet-format-7-320.jpg)
![Endpoints Behavior Instruction
End Decrement Segments Left by 1
Update IPv6 DA with Segment List[Segments Left]
Submit the packet to the egress IPv6 FIB lookup
X Forwards packets through one or a group of Layer 3 outbound interfaces.
T Searches a specifed routing table and forwards packets.
D Decapsulates packets by removing the IPv6 header and related extension
headers.
V Searches a specifed table for packet forwarding based on Virtual Local Area
Network (VLAN) information.
U Searches a specifed table for packet forwarding based on unicast MAC
address information.
M Searches a Layer 2 forwarding table for multicast forwarding.
B6 Biding to SRv6 Policy
BM Biding to SR-MPLS policy](https://image.slidesharecdn.com/srv6-240312150709-82216548/85/SRv6-note-from-book-and-some-drawing-for-different-srv6-packet-format-12-320.jpg)
![END
When N receives a packet whose IPv6 DA is S and S is a local End SID,
N does the following:
S01. When an SRH is processed {
S02. If (Segments Left == 0) {
S03. Stop processing the SRH, and proceed to process the next
header in the packet, whose type is identified by
the Next Header field in the routing header.
S04. }
S05. If (IPv6 Hop Limit <= 1) {
S06. Send an ICMP Time Exceeded message to the Source Address
with Code 0 (Hop limit exceeded in transit),
interrupt packet processing, and discard the packet.
S07. }
S08. max_LE = (Hdr Ext Len / 2) - 1
S09. If ((Last Entry > max_LE) or (Segments Left > Last Entry+1)) {
S10. Send an ICMP Parameter Problem to the Source Address
with Code 0 (Erroneous header field encountered)
and Pointer set to the Segments Left field,
interrupt packet processing, and discard the packet.
S11. }
S12. Decrement IPv6 Hop Limit by 1
S13. Decrement Segments Left by 1
S14. Update IPv6 DA with Segment List[Segments Left]
S15. Submit the packet to the egress IPv6 FIB lookup for
transmission to the new destination
S16. }](https://image.slidesharecdn.com/srv6-240312150709-82216548/85/SRv6-note-from-book-and-some-drawing-for-different-srv6-packet-format-13-320.jpg)
![Generalized SRv6
When N receives a packet whose IPv6 DA is S and S is a local SID with
COC Flavor, N does:
1. If (DA.SI != 0) { //ref1
2. Decrement DA.SI by 1.
3. } Else {
4. Decrement Segments Left by 1.
5. Set DA.SI to 3 in the IPv6 Destination Address
6. }
7. Copy Segment List[Segments Left][DA.SI] into the bits //ref2
[B..B+31] of the IPv6 Destination Address.](https://image.slidesharecdn.com/srv6-240312150709-82216548/85/SRv6-note-from-book-and-some-drawing-for-different-srv6-packet-format-31-320.jpg)
SRv6 note from book and some drawing for different srv6 packet format
- 2. IPv4 limitations & work-arounds
- 3. IPv4 limitations & work-arounds
- 4. SID Format - Locator: routeable address - Function: forwarding behavior - END, END.X, END.T - Argument: - Such as END.DT2M: ESI (Ethernet Segment Identifier) filterling
- 7. SRH - Routing Type: 4 - Segments Left(SL): The next active segment - Last Entry: Zero based, - Segment List[0..n] - Segment List[0]: Last Segment - Segment List[1]: Penultimate segment of the SR Policy - Segment List[n]: First Segment - The active segment is indicated by the Destination Address (DA) of the packet. - SRH TLVs: Only process when the Active Segment is a local SID - HMAC TLV: Hashed Message Authentication Code - Access Control List (ACL) that considers HMAC Key ID, or other packet fields. - SID List Verification - Reduced SRH: Not contain the first segment of the related SR Policy
- 8. Network Nodes: SRv6 Nodes - Source Node - Transit Node - SRv6 Segment Endpoint Node
- 9. Source Node Behavior Instruction H.Encaps SR Headend with Encapsulation in an SR Policy H.Encaps.Red H.Encaps with Reduced Encapsulation H.Encaps.L2 H.Encaps Applied to Received L2 Frames H.Encaps.L2.Red H.Encaps.Red Applied to Received L2 Frames H.Insert SR Headend with insertion of an SRv6 Policy H.Insert.Red H.Insert with reduced insertion - SR Policy: an ordered list of segments. - BSID: The headend of an SR Policy binds a SID (called a Binding segment or BSID) to its policy.
- 10. Source Node Behavior The Next Header field of the SRH MUST be set to 143.
- 12. Endpoints Behavior Instruction End Decrement Segments Left by 1 Update IPv6 DA with Segment List[Segments Left] Submit the packet to the egress IPv6 FIB lookup X Forwards packets through one or a group of Layer 3 outbound interfaces. T Searches a specifed routing table and forwards packets. D Decapsulates packets by removing the IPv6 header and related extension headers. V Searches a specifed table for packet forwarding based on Virtual Local Area Network (VLAN) information. U Searches a specifed table for packet forwarding based on unicast MAC address information. M Searches a Layer 2 forwarding table for multicast forwarding. B6 Biding to SRv6 Policy BM Biding to SR-MPLS policy
- 13. END When N receives a packet whose IPv6 DA is S and S is a local End SID, N does the following: S01. When an SRH is processed { S02. If (Segments Left == 0) { S03. Stop processing the SRH, and proceed to process the next header in the packet, whose type is identified by the Next Header field in the routing header. S04. } S05. If (IPv6 Hop Limit <= 1) { S06. Send an ICMP Time Exceeded message to the Source Address with Code 0 (Hop limit exceeded in transit), interrupt packet processing, and discard the packet. S07. } S08. max_LE = (Hdr Ext Len / 2) - 1 S09. If ((Last Entry > max_LE) or (Segments Left > Last Entry+1)) { S10. Send an ICMP Parameter Problem to the Source Address with Code 0 (Erroneous header field encountered) and Pointer set to the Segments Left field, interrupt packet processing, and discard the packet. S11. } S12. Decrement IPv6 Hop Limit by 1 S13. Decrement Segments Left by 1 S14. Update IPv6 DA with Segment List[Segments Left] S15. Submit the packet to the egress IPv6 FIB lookup for transmission to the new destination S16. }
- 15. End.DT
- 16. End with layer 2
- 18. Flavors - PSP: Penultimate Segment Pop (PSP) of the SRH - After END behavior performed, if SL==0: remove SRH - USP: Ultimate Segment Pop (USP) of the SRH - Before END behavior, if SL==0: remove SRH - USD: Ultimate Segment Decapsulation (USD) - Before END behavior, if SL==0: remove Outer ipv6 header, process upper laye header. - SR Endpoint new 3 Flavors - NEXT-C-SID: uSID - REPLACE-C-SID => COC flavors => G-SRv6 - NEXT-and-REPLACE-C-SID
- 19. SRv6 Locator TLV and Prefix Reachablility TLV
- 20. Local SID Table
- 21. Packet Forwarding Process: Source Node
- 22. Packet Forwarding Process: End.X
- 23. Packet Forwarding Process: End.X PSP flavor
- 24. Transit Node E => End.DT4 SID in Node F
- 25. Header Compression Compare C-SID and complete SID
- 26. Header Compression REPLACE-C-SID Flavor: COC(Continue of Compression), C-SID 32bits NEXT-C-SID Flavor: uSID, C-SID 16bit/32bit
- 27. Micro SID ⇒ Only Update the IPv6 DA uN: End with NEXT-CSID, PSP and USD flavors uA: End.x with NEXT-CSID, PSP and USD flavors uDT: End.DT4/End.DT6/End.DT2* uDX:End.DX4/End.DX6/End.DX2
- 29. Generalized SRv6 - G-SID: 32bit SID, 128 bits Srv6 SID - G-SID Container: Always 128 bits - Contain single Srv6 SID - Contain uSID - Contain 4 C-SIDs - Use SL to index a 128 bit G-SID, use SI(CL) to index C-SID inside this G-SID! SI is a location argument of the G-SID, which is the least bits in the argument part. When G-SID is a 32 bits value, the SI is the least 2 bits in Argument. 0 Variable Length 32 bits 128 bits +--------------------------------------------------------------+ | Common Prefix | G-SID |SI| Padding |
- 31. Generalized SRv6 When N receives a packet whose IPv6 DA is S and S is a local SID with COC Flavor, N does: 1. If (DA.SI != 0) { //ref1 2. Decrement DA.SI by 1. 3. } Else { 4. Decrement Segments Left by 1. 5. Set DA.SI to 3 in the IPv6 Destination Address 6. } 7. Copy Segment List[Segments Left][DA.SI] into the bits //ref2 [B..B+31] of the IPv6 Destination Address.