Isis srv6 review

[SuryyaKrJana]

Feature Overview

• Related Issue: (e.g., Fixes #<issue_number>)
• Brief Description:
  This time, highlighting only SRv6 Traffic part

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Feature Details

• Redocly docs for this feature/branch

• New Locations/Nomenclature:
  Flow / traffic schemas (flow/packet-headers/)

• ipv6_routing.yaml — new SRH (Segment Routing Header) packet-header schema; fields: routing_type (fixed 4), segments_left, last_entry, flags, tag, and segment_list (array of IPv6 SID addresses) — resolves P0 gap G-T1b

• ipv6.yaml — updated to allow SRH as a next-header option so flow stacks can include an SRv6 routing extension header

• uSID container encoding — segment_list items accept packed uSID values (e.g. fc00:0:1:1:2:1::) directly; no decomposition helper needed — resolves G-T3/G-UN1

• Reduced-SRH (no-SRH) / USD inner-payload — modeled by omitting the SRH layer from the flow stack; inner IPv4/IPv6 payload stacked after outer IPv6 DA set to the active uSID — resolves G-T5/G-UN2

• [Dev-Snappi branch reference] (Isis srv6 review 2 snappi#282)

• Example command to fetch the dev-snappi branch:

  go get github.com/open-traffic-generator/snappi/gosnappi@<isis-srv6-review-2>
  

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Code snippets

Example - 1: Multiple uSIDs with NO SRH: 3-hop path packed into one F3216 uSID container,
placed directly in the IPv6 destination via ipv6.dst_usids - no routing extension
header required.
OTG model used:
Flow.Ipv6 (dst = uSID container, NH auto-set to 17 by next header)
F3216 uSID container layout (128 bits):
fc00:0:1:2:3::
Locator-Block = fc00:0000 (32 bits, shared domain prefix)
uSID-1 = 0001 (16 bits, hop 1 - egress of node 1)
uSID-2 = 0002 (16 bits, hop 2 - egress of node 2)
uSID-3 = 0003 (16 bits, hop 3 - egress of node 3)
Remaining = 0:: (48 bits, zeros = end of uSID list)

 #  USID creation without helper API
    .......................
     .........................
    f.tx_rx.port.tx_name = p1.name
    f.tx_rx.port.rx_name = p2.name
   
    eth = f.packet.add().ethernet
    eth.src.value = "00:11:22:33:44:55"
    eth.dst.value = "00:aa:bb:cc:dd:ee"

    ip6 = f.packet.add().ipv6
    ip6.src.value = "2001:db8::1"
    du = ip6.dst_usids
    du.locator.value = "fc00::"
    du.locator_length.value = 32
    du.usids.add().usid = "0001"
    du.usids.add().usid = "0002"
    du.usids.add().usid = "0003"
    # next_header auto-computed by IxNetwork from the following UDP header

 # USID creation by helper API: set_usid_dst()
    f.tx_rx.port.tx_name = p1.name
    f.tx_rx.port.rx_name = p2.name
   

    eth = f.packet.add().ethernet
    eth.src.value = "00:11:22:33:44:55"
    eth.dst.value = "00:aa:bb:cc:dd:ee"

    ip6 = f.packet.add().ipv6
    ip6.src.value = "2001:db8::1"
    set_usid_dst(ip6.dst_usids, "fc00::", 32, ["0001", "0002"])
 

Example - 2: Multiple uSIDs with 1 uSID SRH container: 3-hop path packed in one F3216 uSID
container, carried inside a uSID SRH extension header with a single segment entry.

OTG model used:
Flow.Ipv6 (NH=43, dst = uSID container)
Flow.Ipv6ExtHeader.routing.segment_routing_usid (Flow.Ipv6SegmentRoutingUsid)
segment_list: 1 entry (last_entry=0, segments_left=0)

F3216 uSID container layout (128 bits):
fc00:0:1:2:3::
Locator-Block = fc00:0000 (32 bits, shared domain prefix)
uSID-1 = 0001 (16 bits, hop 1)
uSID-2 = 0002 (16 bits, hop 2)
uSID-3 = 0003 (16 bits, hop 3)
Remaining = 0:: (48 bits, zeros = end of uSID list)

    usid_container = "fc00:0:1:2:3::"   # F3216: block=fc00:0:, hops=0001,0002,0003
    f.tx_rx.port.tx_name = p1.name
    f.tx_rx.port.rx_name = p2.name
   

    eth = f.packet.add().ethernet
    eth.src.value = "00:11:22:33:44:55"
    eth.dst.value = "00:aa:bb:cc:dd:ee"

    ip6 = f.packet.add().ipv6
    ip6.src.value = "2001:db8::1"
    ip6.dst.value = usid_container
    ip6.next_header.value = 43

    usid = f.packet.add().ipv6_extension_header.routing.segment_routing_usid
    usid.segments_left.value = segments_left
    usid.last_entry.value    = last_entry
    usid.tag.value           = 0
    _add_usid_container(usid.segment_list, usid_container)

Example - 1: Multiple uSIDs with more than 1 uSID SRH container: 4-hop path spread across
2 F3216 uSID containers, carried in a uSID SRH with 2 segment list entries.

OTG model used:
Flow.Ipv6 (NH=43, dst = first/active uSID container)
Flow.Ipv6ExtHeader.routing.segment_routing_usid (Flow.Ipv6SegmentRoutingUsid)
segment_list: 2 entries (last_entry=1, segments_left=1)

F3216 uSID containers (128 bits each):
container-1: fc00:0:1:2::
Locator-Block = fc00:0000 (32 bits)
uSID-1 = 0001 (16 bits, hop 1)
uSID-2 = 0002 (16 bits, hop 2)
Remaining = 0:: (64 bits, zeros)

container-2: fc00:0:3:4::
Locator-Block = fc00:0000 (32 bits)
uSID-3 = 0003 (16 bits, hop 3)
uSID-4 = 0004 (16 bits, hop 4)
Remaining = 0:: (64 bits, zeros)

     usid_containers = ["fc00:0:1:2::", "fc00:0:3:4::"]   # 2 hops each
    segments_left = 1
    last_entry = 1

    f = b2b_raw_config.flows.add()
    
    f.tx_rx.port.tx_name = p1.name
    f.tx_rx.port.rx_name = p2.name

    eth = f.packet.add().ethernet
    eth.src.value = "00:11:22:33:44:55"
    eth.dst.value = "00:aa:bb:cc:dd:ee"

    ip6 = f.packet.add().ipv6
    ip6.src.value = "2001:db8::1"
    ip6.dst.value = usid_containers[0]
    ip6.next_header.value = 43

    usid = f.packet.add().ipv6_extension_header.routing.segment_routing_usid
    usid.segments_left.value = segments_left
    usid.last_entry.value = last_entry
    usid.tag.value = 0
    for usid_container in usid_containers:
        _add_usid_container(usid.segment_list, usid_container)

[apratimmukherjee]

This line must be removed.

[apratimmukherjee]

What happens on repeated invocation across start/stop ; does it retain old values or only values from last start ?
Is this also part of set_config ?

[apratimmukherjee]

Also, if it is part of set_config then should modify_config not be the right path ?

[apratimmukherjee]

This needs to be made generic

[apratimmukherjee]

Needs to be made generic

[apratimmukherjee]

Generic

[apratimmukherjee]

Why are there two entries with same value. Looks suspicious.

[apratimmukherjee]

This means there is NO extension header. How can this option be within extension header ?

[apratimmukherjee]

3 encodings needed :

1. Eth
   IPv6 outer -> dest has compressed usid info upto 3 hops. [ in ipv6.dst ] -> How can user give this into within Extension Header if that is completely missing. [ Difficult with current but a helper in code maybe ; nothing needed in model extra ?]
   IPv6 / IPv4 inner [ Might not be present ]
   TCP/UDP

2. Eth
   IPv6
   Extension Hdr
   Routing
   SRH
   [ Many SIDs ] -> Already supported.
   Inner IPv4/v6 header (??)

3. Et h
   IPv6
   Extension Hdr
   Routing
   SRH ( above = current )
   SRH_Usid
   List of usids [ max pack = 3 per IPv6 ] -> why usid1 , usid2 ?

[apratimmukherjee]

Not needed. Duplicate of existing choice field.