Architecture EECS 122. Network Architecture. Layer: Example. Internet Layers - Intro

Transcription

1 rchitecture S rchitecture Introduction Layering xample Internet Layers First Look Layering Step by Step ownside of Layering Interconnecting s The Internet Introduction Issues: Inter-operability xtensibility s & Technologies Scalability Internet Solution: Layered rchitecture nd-to-nd Principle Hierachical ddressing & Naming TO rchitecture TO rchitecture Introduction Layer: xample Layer: xample Prof. Prof. Prof. Prof. Please fax letter to Prof., Urgent of paper. I believe its main Here is a Here is a letter from Prof. Please fax letter to Prof., Urgent INTF of paper. I believe its main Here is a Here is a letter from Prof. STY John OV of paper. To: Prof. I believe its main Fr: Prof. Here is a Urgent STY Mary STY FUNTIONS John SVI - SY OV of paper. To: Prof. I believe its main Fr: Prof. Here is a Urgent H STY Mary FX SYSTM SVI - FX FX SYSTM TO rchitecture Layer xample TO rchitecture Layer xample Layer: xample Internet Layers - Intro Prof. STY John of paper. I believe its main Here is a OV of paper. To: Prof. I believe its main Fr: Prof. Here is a Urgent Prof. STY Mary Secretaries implement functions that transform a simple service into a more complex one (.g., add MULTIPLXING) They follow rules of communication: POTOOL They use the header as control information Note: ncapsulation (adding header) and ecapsulation (removing header) rowsing Services Names xamples Specifications ncapsulation Functions FX SYSTM TO rchitecture Layer xample TO rchitecture Internet Layers: Intro

2 rchitecture S rowsing Name IP ddress onnect; Get; lose Supervise onnection Forward Packets cross Many Links Transmit Packets on ach Link Transmit its on ach Medium H SN Servers nd hosts nd hosts outers Link/LN Transceivers H Services Packets its Signals onnection Packets: nd to nd TO rchitecture Internet Layers: Intro rowsing TO rchitecture Internet Layers: Intro Services Names xamples onnection Packets: nd to nd onnection Packets: nd to nd NS; HTTP; TFTP; TP TP; UP; Packets Packets IP; TM; its Link its Link thernet; SL; Signals Signals Fiber-Gbps; at-00mbps; Wireless; SONT TO rchitecture Internet Layers: Intro Names TO rchitecture Internet Layers: Intro xamples Specifications ncapsulation N N + N - N + N Unit that N elivers Header: Info of N s: Formats, Functions: Service Provided Typically: State Machine N - H xamples of H: ddresses rror odes Framing elimiters TO rchitecture Internet Layers: Intro Specification TO rchitecture Internet Layers: Intro ncapsulation

3 rchitecture S Functions PP TN NT LINK PHY Set Up onnections; Presentation; Multiplexing; Flow ; ongestion Global ddressing; outing; Forwarding Framing; rror oding; Local ddressing; Switching Modulation; emodulation Layers Step y Step NS TO rchitecture Internet Layers: Intro Functions TO rchitecture Layers Step y Step In the beginning were two computers xample: Manchester ncoding S- Medium Virtual it Pipe Modem Modem 0 0 S- wires Medium wires TO rchitecture Layers Step y Step TO rchitecture Layers Step y Step Layer! " # $ %& ' & # ( it Stream Link Protocol % ' # ( TO rchitecture Layers Step y Step Link )* +%, " ) Layer What about a broadcast system? xample: Satellite, ethernet, 80. Individual transmissions can interfere and destroy many frames multiaccess protocol is required to try and avoid these collisions or the link will be too unreliable xample: TM, SM Makes the bit-pipe provided by the physical layer look intermittent to the L Protocol must interface with and L layers y convention the Multiaccess Layer (M) is considered a sub-layer of the L TO rchitecture Layers Step y Step Link

4 rchitecture S Layer What about a broadcast system? L Need ddresses urned into NIs Layer: outing L M L M Multiaccess Medium M " -#. / outing information must be contained in a message unless it is part of a circuit addressing and protocol required to accomplish delivery over multiple hops TO rchitecture Layers Step y Step Link TO rchitecture Layers Step y Step Layer: omplexity Layer: outers/switches Topology discovery Link State monitoring Forwarding uffer management S -. # * # # # & % 0, 0 % # ( TO rchitecture Layers Step y Step TO rchitecture Layers Step y Step Layer Layer PP synchronous path synchronous path PH PH a b c Link )* + Link x y z PP -. TO rchitecture Layers Step y Step TO rchitecture Layers Step y Step

5 rchitecture S Layer synchronous routed path synchronous routed path PH PH TH Link Link nd Node Subnet Node nd Node Layer synchronous routed path synchronous routed path PH PH TH Link Link nd Node Subnet Node nd Node )* + )* +6 7# TO rchitecture Layers Step y Step TO rchitecture Layers Step y Step irectory Servers ncapsulation X TH S synchronous routed path synchronous routed path PH TH PH TH PH TH PH TH 8 # " % Link Link nd Node Subnet Node nd Node ) 9 TO rchitecture Layers Step y Step NS TO rchitecture Layers Step y Step ncapsulation The downside of layering fficiency Suboptimal network behavior TP and wireless links edundant Implementation Fragmentation and reassembly Multiple address spaces onfusion in actual networks Layer, Layer and Layer -7 switches What layer does the function security belong to? devices (such as routers) may run application protocols TO rchitecture ownside Inter-onnecting s Global ddress IP IP IP - ddresses PKT TO rchitecture Interconnecting = PKT IP IP estination Next Hop IP outer sees network as a direct link - ddresses IP PKT

6 rchitecture S The Internet Overview Minimal outer State Layering nd-to-nd rgument Success aveats Overview Interconnect networks with different Speeds, eliability, ost Go across multiple networks Internet Service = est ffort datagram service: Try hard to deliver each packet nything more, e.g. voice grade service, would Preclude many networks from joining the internet equire great amounts of co-ordination and compliance monitoring reate an endless clamoring for even other kinds of guarantees such as video grade service TO rchitecture - Internet TO rchitecture - Internet Overview ase for minimal router state Layering dding connection state to routers creates problems in the presence of failures How to clean up the bad state? Scaling router state with number of transport connections would be very expensive dding connection state in only some routers might not be good enough What if many congested routers did not implement state So: The internet provides datagram service. Under this constraint, the internet is designed to support as many different types of applications as possible. TP UP IP GP HTTP TP TFTP TP UP IP thernet FI Token tc. lmost ny kind of application can write directly on IP Including new transport protocols IP cannot be avoided s long as the routers speak IP, any application that can make do with datagram service can be written and implemented on the end devices. No co-ordination, standards activity etc. is required!! TO rchitecture - Internet Minimal State TO rchitecture - Internet Layering nd-to-nd rgument (Saltzer, eed and lark 98) Success Implement a network function at the end hosts unless it cannot be implemented correctly in this manner. O on t implement a function at the lower levels of the system unless it can be completely implemented at this level (Peterson and avie) TO rchitecture - Internet rgument TO rchitecture - Internet - Success 6

7 rchitecture S Success aveats /-/6 00,,7 IP addresses,,09,9 IP links, 9,000 destinations, 70% of globally routable network prefixes; 0,999 Ses (8% of Ses),,09 peering sessions Internet is actually a lot more complicated and messy than today s lecture would suggest The end-to-end argument is being subverted and under attack The internet does a poor job of supporting high performance traffic such as voice and video The phone network is hardly going away We will deal with these issues in much more detail towards the end of the course TO rchitecture - Internet Success TO rchitecture Internet - aveats 7