Routing

A world without networks and routing  No connection between offices, people and applications  Worldwide chaos because of the lack of centralized configurations and support  Limited possibilities of communications on vocal and visual levels  No further technical progress achievements

Hardware requirements Network hardware:  Cables  Lan cards  Routers  Switches  Hubs  Repeaters

Broadcast & Collision domains  Broadcast Domain A broadcast domain is a logical division of a computer network, in which all nodes can reach each other by broadcast at the data link layer. A broadcast domain can be within the same LAN or it can be routed towards other LAN segments.  Collision Domain A collision domain is a physical network segment where data packets can "collide" with one another for being sent on a shared medium, in particular in the Ethernet.

The routing table The routing table consists of at least three information fields:-  the network id: i.e. the destination network id  cost: i.e. the cost or metric of the path through which the packet is to be sent  next hop: The next hop, or gateway, is the address of the next station to which the packet is to be sent on the way to its final destination Depending on the application and implementation, it can also contain additional values that refine path selection:  quality of service associated with the route. For example, the U flag indicates that an IP route is up.  links to filtering criteria/access lists associated with the route  interface: such as eth0 for the first Ethernet card, eth1 for the second Ethernet card, etc.

Routing protocols - RIP  Defined in RFC 1058  Two versions 1 and 2  Uses hops as metric  Maximum 15 hops allowed  No VLSM support in V1  Slow convergence  Advantage: Easy to configure  Disadvantage: Limited scalability

Routing protocols - EIGRP  CISCO proprietary  Based on DUAL (Diffusing Update Algorithm)  Crates three tables – neighbor, topology and routing  Relies on triggered updates  Uses five different metrics: bandwidth load delay reliability MTU  Advantage: Load balancing possibility  Disadvantage: Extremely complicated metric for calculating

Routing protocols – OSPF  Defined in RFC 2328  Single/Multi area OSPF  Uses SPF (shortest path first algorithm)  Several router types – ABR, ASBR, IR (internal router), BR (backbone router)  Works with subnet masks, but uses wildcard bits for configuration  Advantage: Once properly configured, the network is very stable and well- scalable, just adding the new routers (members) to an existing area.  Disadvantage: Redistributing OSPF processes can be painful, due to the large number of requirements – type, metric, metric-type, matching external types and internal type routes  Very fast convergence, thanks to the fast hello packets

Routing protocols – IS-IS  NOT an interned standard  Published in RFC 1142  Uses Dijkstra’s algorithm  Uses levels instead of pure areas (compared to OSPF)  More suitable for ISP infrastructure than enterprise networking

Routing protocols - BGP  The CORE protocol for the internet  Can withstand heavy load and enormous traffic  Defined in RFC 4271  Uses simple FSM (Finite state machine) that uses six states – idle, connect, active, OpenSent, OpenConfirm, established  Advantage – supports almost limitless number of addresses in the routing table and can shift between them very fast  Disadvantage – these big, heavily-loaded routes require powerful hardware and this makes the routers doing the BGP routing a bit more expensive

The future of networks  NGN (Next generation networks) plan for unifying all kinds of services via single carrier  Installing fiber-optic cables and replacing the existing LAN cables  Implementing IPv6 due to the limited availability of IPv4 addresses  Thanks to a faster network, implementation of QoS will be easier  Centralization of the network will ensure buying less amount of network hardware, reducing the price of the total packet (internet, TV, radio, telephony)