switching.md 1.8 KB
title: Switching Theory breadcrumbs:
- title: IT
- title: Network --- {% include header.md %}
Switching Modes (Ethernet)
- Store and forward switching:
- Receive the whole packet befoe forwarding it.
- Checks integrity.
- Adds delay.
- Cut-through switching:
- Start forwarding as soon as the destination address has been inspected.
- Forwards bad packets.
- Recuces delay.
- Fragment-free switching:
- Like cut-through switching, but reads at least 64 bytes before forwarding.
- Prevent forwarding runt frames, which are less than 64 bytes (the minimum frame length).
Virtual LAN (VLAN)
Q-in-Q
- IEEE 802.1ad/802.1Q.
- For tunneling VLANs using multiple layers of 802.1Q headers.
Virtual Extensible LAN (VXLAN)
- RFC 7348.
- For tunneling VLANs using a UDP overlay network (defauylt port 4789).
- VXLAN network identifiers (VNIs) (24-bit) identify bridge domains.
- VXLAN tunnel endpoints (VTEPs) encapsulate/decapsulate the traffic.
- VTEPs may be either on hosts or on switches/routers as gateways.
- BUM handling using multicast:
- Requires multicast-enabled infrastructure.
- VNI are mapped to multicast groups (N:1).
- VTEPs joins the groups for its VNIs using IGMP.
- BUM traffic is only sent to the relevant groups.
- BUM handlign using head end replication:
- Requires BGP EVPN.
- Doesn't scale as well as when using multicast.
- BUM traffic is replicated and sent as unicast to each VTEP that supports the VNI.
- Consider using jumbo frames to avoid fragmentation.
Miscellaneous
- Broadcast, unknown-unicast and multicast traffic (BUM traffic):
- Generally flooded.
- Doesn't scale well, which is the primary element of how well L2 domains scale.
- Throttling and port security helps prevent traffic storms.
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