Chapter 1 Introduction Networking Architecture Overview

Networking Architecture Overview A Generic Network: node: switch/router end-host: telephone/computer/server More intelligent at the edge nodes Higher speed at the core nodes : edge node : core node : end-host

Networking Architecture Overview It is all about how to send information/packets between end-hosts: Routing Protocol Build the network topology/map Find one or multiple routes/paths from any node to any other nodes Build a routing/forwarding table Two forwarding paradigms Connection-oriented: set up a virtual path and forward packets along the path Connectionless: forward packets and let each node downstream figure out how to forward the packets further downstream, known as hop-by-hop forwarding

Networking Architecture Overview More on forwarding paradigms : Connection-oriented Build the network topology through a routing protocol: each node tells its neighbors about its connectivity by flooding Based on the destination end-host’s global address, the routing protocol in the first-hop node finds a route/path to the last-hop node, e.g., a shortest path The first-hop node uses a signaling protocol to install state information along the path. The state information include incoming and out-going labels with local significance (known as label swapping table) and resources reserved for the path. The information is sent in the form of labeled packets. At each intermediate node, the incoming label in the packet is matched against the label swapping table to find the outgoing label and output interface to the downstream node. The incoming label is replaced by the outgoing label before the packet is sent to the output interface downstream, known as label swapping.

Networking Architecture Overview More on forwarding paradigms : Connectionless Build the network topology through a routing protocol: each node tells its neighbors about its connectivity by flooding; every node finds a path to every other node and for each destination node, record only the next-hop node along the path to the destination node, resulting in a destination-node-to-next-hop-node mapping table, known as routing/forwarding/longest prefix match (LPM) table. More on LPM later The information is sent in the form of packets with destination host’s global address attached At each intermediate node, the destination host’s global address is matched against the LPM table to find the next-hop node and the packet is sent to the next-hop node

Networking Architecture Overview IP internetworking basics: Networks Shared medium: broadcast domain e.g., Ethernet and token ring Use MAC (multiple access control) address to forward frames, known as layer 2 forwarding Point-to-Point e.g., packet over SONET (POS)

Networking Architecture Overview IP Internetworking is connectionless To go from one IP network to another, hop-by-hop forwarding based on the destination IP address is performed, known as layer 3 forwarding one hop

Networking Architecture Overview Layering concept and addressing schemes: Internet protocols are designed in layers; the lower layer provides service to its immediate upper layer: Application L5 Transport L4 Internetworking L3 Data link/MAC L2 PHY L1

Networking Architecture Overview Addressing schemes: Local address: VPI/VCI MPLS labels Layer 2/MAC address: A global 48-bit flat address Cannot scale to large networks Layer 3/IP address: A global 32-bit two layer hierarchical address: network part and host part Network address host address

Networking Architecture Overview Two level routing hierarchies Intradomain: OSPF, IS-IS, and RIP Interdomain: BGP LPM: select the one with the largest number of matched bits interdomain intradomain 2.2.3.* 2.2.2.2 2.2.2.*