# Software Defined Networking

Innovated to accelerate the standardization and innovation of the networking discipline.

Control requirements led to great complexity:

• isolation -> vlan, acl
• traffic engineering -> mpls, ecmp, weights
• packet processing middleboxes -> firewalls, NATs
• payload analysis -> deep packet inspection

Needed to abstract the control plane for simplicity of the discipline.

Legacy switches had hardware (ASIC) and software (JUNOS routing processes).

A Clean Slate 4D Approach - introduced problems with legacy approach

Ethane - Took 4D and put it into practice with OpenFlow

• Discovery (how does centralized controller find out about new server)

Key innovation was an abstraction over switches, Match Action Table

# Match Action Table

Key abstraction to unify different kinds of devices in networking ecosystem:

# Router

• match: longest destination IP prefix
• action: forward out a link

# Switch

• match: destination MAC address
• action: forward or flood

# Firewall

• match: IP addresses and TCP/UDP port numbers
• action: permit or deny

# NAT

• match IP address and port
• action: rewrite address and port

# Reconfigurable Match Action Table

Adds "compiler" to open flow to parse control flow and configure rules.

Read about P4 Abstract Model