Module 4 Notes
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Hierarchal Internetworking Model: divides enterprise networks into three or four layers.
- Border (not always): Connect to the Internet (Routing/Layer 3)
- Core: Dumb and fast (Switching/Layer 2)
- Distribution: Smart! (Routing/Layer 3)
- Access (or Edge) layer: Wireless AP's and Switches, Access VLANS (Layer 2)
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Access (Edge) Layer
- End-stations and servers connect to enterprise at this level.
- Access layer devices are usually commodity switching platforms (aka switches and wireless access points)
- Also called the desktop layer
- Layer 2 Tech like VLANS
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Distribution Layer
- Smart Layer
- Routing, filtering (internal firewalling), and QoS policies are managed at the distribution layer.
- Typically multilayer switches
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Core Layer - Network Backbone
- he core network provides high-speed, highly-redundant forwarding services to move packets between distribution-layer devices in different regions of the network.
- Core switches and routers are usually the most powerful, in terms of raw forwarding power, in the enterprise;
- However, they are typically pretty dumb - just switching (layer 2)
- Often don’t need much configuration - just links the distribution layers to each other - and to the Border
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Border Layer
- Connect the enterprise network to the internet
- Routers, border firewall, border load balancers, border IPS and other security devices
- Layer 3 and up
- DNS
- Application Layer Protocol - RFC 1034 and 1035
- Thirteen organizations manage the Root Name Servers, located in multiple sites worldwide
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- Two Types of queries
- Recursive: If a host requests a specific IP address, the request is handles by local DNS server and traverses the path that goes through local, root, TLD and authoritative DNS server and back, the IP address is provided to host by local DNS.
- Iterative