Introduction Chapter 1 Introduction Computer Networking: A Top Down Approach Featuring the Internet, 3 rd edition. Jim Kurose, Keith Ross Addison-Wesley, July A note on the use of these ppt slides: We’re making these slides freely available to all (faculty, students, readers). They’re in PowerPoint form so you can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following:  If you use these slides (e.g., in a class) in substantially unaltered form, that you mention their source (after all, we’d like people to use our book!)  If you post any slides in substantially unaltered form on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this material. Thanks and enjoy! JFK/KWR All material copyright J.F Kurose and K.W. Ross, All Rights Reserved

Introduction A few comments about the Internet  Network Edge  End machines to routers  Network Core  Mesh of connected routers  ~ hierarchical Internet  Two Internet services  Connection-oriented (TCP)  Connectionless (UDP)  End to end data transfer  Uses Internet services which  Use IP for data delivery to a destination local ISP company network regional ISP router workstation server mobile

Introduction Circuit versus packet switching  Circuit switching  Resources reserved for the entire duration of call  Classical example: POTS  Waste of resources  Packet Switching  Uses chunks of data that traverse the network while sharing it with other chunks  Statistical Multiplexing  For bursty data (Internet)  PKT switching is the way to go  What about voice over IP and similar applications???

Introduction Choices for Packet switching?  IP provides service to TCP and to UDP  A datagram approach – one of the two possible ways of transferring data end to end  The other possibility is virtual circuit More suitable for VoIP and the likes?  Present day Internet has emerged as:  Datagram (IP) in the edges  IP over virtual circuits in the core  Idea: End users originate “bursty” traffic while traffic from large networks is semi-bursty  X.25  Frame Relay  ATM  MPLS

Introduction Network Taxonomy Telecommunication networks Circuit-switched networks FDM TDM Packet-switched networks Networks with VCs Datagram Networks Note: X.25 is a VC network and so is MPLS but these two were designed with totally different philosophies in mind! 1) X.25: reliability provided in the network itself 2) MPLS: easy integration with IP while providing virtual circuits

Introduction Internet structure: network of networks  roughly hierarchical  at center: “tier-1” ISPs (e.g., MCI, Sprint, AT&T, Cable and Wireless), national/international coverage  treat each other as equals Tier 1 ISP Tier-1 providers interconnect (peer) privately NAP Tier-1 providers also interconnect at public network access points (NAPs)

Introduction Internet structure: network of networks  “Tier-2” ISPs: smaller (often regional) ISPs  Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs Tier 1 ISP NAP Tier-2 ISP Tier-2 ISP pays tier-1 ISP for connectivity to rest of Internet  tier-2 ISP is customer of tier-1 provider Tier-2 ISPs also peer privately with each other, interconnect at NAP

Introduction Internet structure: network of networks  “Tier-3” ISPs and local ISPs  last hop (“access”) network (closest to end systems) Tier 1 ISP NAP Tier-2 ISP local ISP local ISP local ISP local ISP local ISP Tier 3 ISP local ISP local ISP local ISP Local and tier- 3 ISPs are customers of higher tier ISPs connecting them to rest of Internet

Introduction Internet structure: network of networks  a packet passes through many networks!  Where is MPLS??????? Tier 1 ISP NAP Tier-2 ISP local ISP local ISP local ISP local ISP local ISP Tier 3 ISP local ISP local ISP local ISP

Introduction IP routing versus MPLS  Discussion limited to core network – there is no MPLS to end systems  Even if we use MPLS in core  The “payload” it carries today is still IP  What differentiates IP from MPLS?  The routing and forwarding paradigm!