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Update: The Internet is a homogeneous accumulation of systems, all utilizing TCP/IP and related conventions. ... Publication: If you permit the Internet on your website, you have just ...
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PC Networks Chapter 5 Network Layer 2 Prof. Jerry Breecher CSCI 280 Spring 2002

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The Weeks Ahead Mar 11 Chapter 5.1: Network Layer Mar 13 Chapter 5.1 Mar 18 EXAM 2 Mar 20 Chapter 5.1: Mar 21 LAB – You ought to have a few tests running. Deface 25 Chapter 5.2: More Network Layer Mar 27 Chapter 5.2: Apr 1 Chapter 5.2 Apr 3 Chapter 6.1: Transport Layer Apr 8 Chapter 6.1: Apr 10 EXAM 3 Apr 15 Chapter 6.1: Apr 17 Chapter 6.1: Apr 22 Chapter 6.1: Apr 24 Chapter 6.1: Apr 25 LAB – Drop Dead Date!! May 3 Final Exam – 8:00 – 10:00 Chap. 5-Net2

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Chapter Overview The Network Layer is worried about getting parcels from source to destination, regardless of what number of jumps it might take. It\'s about directing. 5.1 Network Layer Design Issues What do we have to think about in this layer? 5.2 Routing Algorithms Strategies for getting from source to destination. 5.3 Congestion Control Algorithms How would we keep from bottlenecking from excessively numerous bundles? 5.4 Internetworking Working with various systems and conventions keeping in mind the end goal to convey parcels. 5.5 The Network Layer in the Internet Gluing together an accumulation of subnets. Chap. 5-Net2

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Overview Internetworking Getting different systems to all play together. Issues happen in light of the fact that: Companies don\'t have strong strategies for systems administration. New innovation replaces a portion of the old innovation. 5.1 Network Layer Design Issues 5.2 Routing Algorithms 5.3 Congestion Control Algorithms 5.4 Internetworking 5.5 The Network Layer in the Internet Chap. 5-Net2

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Overview Internetworking Reminder: The I nternet is a homogeneous accumulation of systems, all utilizing TCP/IP and related conventions. The i nternet, the more bland term, is comprised of a mishmash of various equipment and conventions. Different systems and various system sorts are an unavoidable truth: There are various purposes behind this: Growth: Individual offices in a college purchase LANs for their own machines and in the end need to interconnect with different grounds LANs. Issue confinement, topography, and security: Even when achievable to utilize one system, an association can get selective control over a solitary nearby system. Control: Some associations need to have the capacity to say what happens on their system. Modernization: As new innovation shows up, a few associations supplant their systems while other\'s don\'t. Chap. 5-Net2

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Overview Internetworking A case of combining numerous sorts of systems. Chap. 5-Net2

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Overview Internetworking manages the issues of interconnecting different systems. Physical systems can be associated at a few levels: Repeaters work at the physical (layer 1), replicating signals starting with one LAN then onto the next. They work at the bit level, and have no idea of what the bits (or even casings!) mean. Spans work at the information join (layer 2), replicating outlines starting with one LAN then onto the next. They perform store-and-forward bundle exchanging, however utilize just level-2 (e.g. outline fields) data. We\'ve discussed these before concerning the MAC layer, where we took a gander at spreading over tree and source steering techniques. Switches work at the system layer (level 3). Like scaffolds in idea. At the system layer, they are completely mindful of various system innovations, and can issues as interconnect distinctive between them. Transport entryways interface two systems at the vehicle layer (level 4). Application entryways work at more elevated amounts (level "7"). Application passages can interpret between OSI mail and SMTP (Internet) mail positions, for occurrence. Chap. 5-Net2

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Overview Internetworking Router Ownership One issue that emerges with Routers is who possesses them. Regularly, connects associate LANs of one association, thus possession is not an issue. The proprietorship inquiry is imperative for switches in light of the fact that somebody must be in charge of the switch\'s operation and double possession much of the time prompts blame dealing when something turns out badly. One arrangement is to utilize half passages. In the event that two nations are included, for occurrence, every nation claims its half of the switch, with a wire isolating the two. A unique convention works over the wire, and every 50% of the switch is in charge of executing the convention. For instance, the CCITT X.75 standard is utilized to interface half passages in association arranged systems. The truth isn\'t so essentially layered - numerous items join scaffold and switch usefulness. Chap. 5-Net2

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How Networks Differ Internetworking We\'ve taken a gander at some of these properties some time recently, yet here are a rundown of contrasts: Item Some Possibilities Service Offered Connection-arranged versus connectionless Protocols IP, IPX, CLNP, Appletalk, DecNet, . . . . Addressing Flat (802) versus various leveled (IP) Multicasting Present or missing (likewise broadcasting) Packet Size Every system has its own particular max Quality of Service May be available or truant - a wide range of kinds Error Handling Reliable, requested, and unordered delivery Flow control Sliding window, rate control, other, none Congestion Control Leaky pail, gag bundles, etc. Security Privacy rules, encryption, etc. Parameters Different timeouts, stream specs, etc. Accounting By associate time, by parcel, by byte, or none Chap. 5-Net2

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Multiprotocol Routers Internetworking Can utilize "routers" and "gateways" conversely or consider switches inside a subnet (same system) versus passages (between subnets). Content calls portals multi-convention switches. Convention Routers are bundle switches that work at the system layer (level 3). Working at the system level gives switches expanded adaptability contrasted with extensions as far as: Translating locations between unique systems. Dividing huge bundles for transmission crosswise over systems that convey just little greatest parcel lengths. Selecting a fitting way through the subnet. Implementing strategies (e.g., don\'t forward any nearby parcels off of this system). Since switches accomplish more work than extensions, they by and large run slower than scaffolds. Chap. 5-Net2

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Concatenated Virtual Circuits Internetworking in an association arranged environment works basically as in the single system case: The sending host opens a virtual circuit as some time recently, yet now a circuit experiences switch bounces. Any two neighboring switches at the internetworking level must be associated with a typical system. Customary switch based virtual circuits associate neighboring switches on the same physical system. The end-to-end virtual circuit is a link of individual virtual circuits through each of the systems along the way. So every passage/switch keeps up tables for each of the associations going through it - what switch to pass the bundle on to, and an identifier for the virtual circuit. Chap. 5-Net2

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Connectionless Internetworking Connectionless webs work pretty much as connectionless systems. A host sends a parcel to a neighboring switch, which advances it the following switch, et cetera. Pretty much as with connectionless systems, switches try endeavor at conveying the parcel. Datagrams The Network layer puts datagrams on the subnet. See Figure 5.37 Issues that must be managed: Networks with various systems conventions are difficult to interpret between. This is once in a while endeavored. (See burrowing underneath.) Addressing - when adjoining systems have contrasting location conspires, the going gets intense. Once more, issues are for the most part outlandish. Chap. 5-Net2

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Connectionless Internetworking Chap. 5-Net2

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Tunneling Internetworking Tunneling is an uncommon case between two same-sort systems crosswise over mediating remote network(s). The entire bundle is epitomized in the convention of the outside system to be crossed, and after that restored on the other side. See Figure 5.38 This maintains a strategic distance from, thoroughly, attempting to decipher the parcel. Chap. 5-Net2

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Fragmentation Internetworking How to cross systems whose greatest transmission unit (MTU) is littler than the parcel being transmitted. Association arranged online worlds stay away from this issue. By selecting a most extreme bundle size at association set up time. That most extreme is just min( MTU 1 , MTU 2 , ...) of the MTUs in the mediating system. Once the association is built up, the way never shows signs of change, so the sender can choose a bundle size and never again stress that it will be too vast. In connectionless virtual worlds, the proper parcel size relies on upon the way utilized. Along these lines, it can change whenever. In the general case, setting a base MTU for all systems is unfeasible. A base MTU would of need be little, yet sending bigger parcels ought to be supported for productivity reasons. Arrangements: Have switch drop parcels that are too substantial to send over a system and return a blunder message to the sender. The sending host could then retransmit the information in a littler bundle. Have switch section expansive bundles into a few parts, every sufficiently little to navigate the system. There are two flavors called Transparent and non-Transparent Fragmentation. Chap. 5-Net2

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Fragmentation Internetworking Transparent Fragmentation With straightforward fracture, end has (sender and recipient) are unconscious that discontinuity has occurred. A switch sections a parcel, and the following bounce switch on the same system reassembles the pieces again into the first bundle. Downsides are: All pieces must go through to the same switch. They should all be reassembled by the same next-bounce switch Routers

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