- Significant built-in automation
- Basis of the Internet and Enterprise Networking
- Supports a large scope of applications/services
- Statistical multiplexing
IP Routing (Simplified)
Networks are defined by two fundamental characteristics
- How they choose what path is taken (routing)
- The forwarding treatment at every node (per hop behaviors – PHB)
Both can influence the performance of IP networks/customer experience.
Control Plane / Routing Protocols
- Routers exchange information about networks connected to them/they know about.
- Routes from other routers, plus own/local & configured routes, are stored in a routing table.
More information on IP Routing Protocols:
- Information is extracted from routing table(s) to the forwarding table
- Forwarding table has information on how to forward different destination addresses
- Router moves a received packet, one router closer to the destination
For more on forwarding:
IP routing strengths
- Routing automatically understands path changes without human intervention.
- Routing automatically understands new destinations without human intervention.
- Routing supports a large scope of concurrent applications/services.
- Statistical multiplexing combined with load balancing lead to better link capacity utilization.
IP routing weaknesses
- Automated path learning and forwarding table creation adds complexity
- Packet looping can occur temporarily as a consistent view of the network is reestablished following a topology change
Beyond Best Effort IP
While IP routing started as a single approach to hop-by-hop, connectionless, best effort packet switching, it is evolved to be a toolset of approaches to networking. Saying “how” IP routing works, is no longer a simple affair.
- IP can forward all packets without discrimination
- IP can forward based on priority
- IP can forward based on bandwidth allocation
- IP can forward along a path that has the least number of routers
- IP can forward along a path that has the most bandwidth
- IP can forward along a path that has the lowest latency
- IP can spread the forwarding load over many different paths
- IP can forward along a virtual topology that is a subset of the physical topology
- IP can be partitioned into many virtual private networks
- IP can transport IP, Ethernet, & TDM
- IP supports voice, video, email, websites, collaboration, and more
|Forwarding header||IPv4 header||IPv6 header||MPLS label||MPLS label||IPv6 header|
|Routing protocols||BGP4, OSPF, IS-IS||BGP4, OSPF, IS-IS||BGP4, OSPF, IS-IS||BGP4, OSPF, IS-IS||BGP4, OSPF, IS-IS|
|Load balancing||ECMP||ECMP||ECMP, TE||ECMP, TE||ECMP, TE|
|Label mapping protocols||N/A||N/A||LDP, |
|Traffic steering||Weights||Weights||Weights, TE||Weights TE||Weights, TE|
- BGP: Border Gateway protocol
- DIFFSERV: Differentiated Services
- ECMP: Equal cost multipath, an approach to load balancing traffic over two or more routes.
- IP: Internet Protocol
- IPv4: IP Version 4
- IPv6: IP Version 6
- IS-IS: Intermediate System to Intermediate System
- MPLS: Multprotocol Label Switching
- OSPF: Open Shortest Path First
- SR MPLS: Segment routing for MPLS
- SRv6: Segment routing for IPv6
- TE: Traffic Engineering
Digestible snacks about related topics for beginners/learners.
- Forwarding / data / user plane
- Control plane
- Management plane
- IP Addressing
- IP Loopback Interface
- IP Protocol Structure
- Segment Routing
- Traffic Engineering
- IPv6 Adoption
- Network Collective (Podcast)
- Packet Pushers (Podcast)
- Network Direction
- Software gone wild
- Reply All
- BGP Instability Report
- Arista Networks
- Cisco CCNA Introduction to Networking (playlist)
- Juniper Networks
- Nokia Networks