Base Protocol Spec

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Base Protocol Spec

• Radia Perlman
• Radia.Perlman_at_sun.com

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A few minor things to do

• Fold in draft of Bryant, et al, about using
  4-byte, MPLS-like shim header, and distributed
  algorithm for choosing 19-bit nickname for
  RBridges
• Specify encoding of IS-IS packets 3 cases
• Layer 3 IS-IS
• RBridge IS-IS for core instance
• RBridge IS-IS per-VLAN instance

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Encapsulation Header
hop count RBridge in/out Multicast flag
SXmitting Rbridge DRcving Rbridge pttransit
original pkt (including L2 hdr)

• Shim hdr (MPLS format, 32 bits)
• label 19 bit RBridge nickname/flag
• priority (3 bits) bottom of stack flg
• TTL (8 bits)

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Shim header

• Label is either ingress or egress RBridge,
  depending on the flag
• Multicast and unknown destination ingress
• Unicast egress
• 19-bit nickname, chosen by distributed algorithm
• Priority and bottom of stack probably not
  useful for RBridges

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Question 1 Should we make those reserved field?

• Maybe wed use priority. I cant imagine using
  bottom of stack for RBridges

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Three types of IS-IS packets

• Regular router layer 3 IS-IS
• Just like normal data traffic for RBridges
• In theory we could optimize delivery only to
  links with IS-IS routers
• And we could do the same for OSPF, BGP, RIP,
• WG decided not to bother optimizing, and to
  deliver to all campus links

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RBridge IS-IS types

• Core instance (for RBridge-RBridge connectivity,
  and VLANs)
• Per-VLAN
• Endnodes
• Multicast receivers for IGMP-joined groups
• Decision Use different multicast addresses in
  outer header to differentiate these instances

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New Layer 2 Multicast addresses needed

• Address 1 For ordinary encapsulated data packets
  that will be flooded (multicast, unknown
  destination)
• Address 2 For core IS-IS RBridge instance
• Address 3 For per-VLAN IS-IS RBridge instance

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Core Instance
Dest new multicast 2 Sourcetransmitting
RBridge PTRBridge-encapsulated
outer hdr
Multicast flag Ingress RBridge
shim
inside
IS-IS packet, no layer 2 hdr
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Per VLAN Instance
Dest new multicast 3 Sourcetransmitting
RBridge PTRBridge-encapsulated
outer hdr
Multicast flag Ingress RBridge
shim
VLAN tag (12 bits 4 reserved)
inside
IS-IS packet, no layer 2 hdr
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Question 2

• Sois this all OK?

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Conclusions

• Remember Algorhyme?
• For Usenix, I asked my son to write Algorhyme 2

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Algorhyme v2

• I hope that we shall one day seeA graph more
  lovely than a tree.
• A graph to boost efficiencyWhile still
  configuration-free.
• A network where RBridges canRoute packets to
  their target LAN.
• The paths they find, to our elation,Are least
  cost paths to destination.
• With packet hop counts we now see,The network
  need not be loop-free.
• RBridges work transparently.Without a common
  spanning tree.
• Ray Perlner