Department of Computer Engineering University of California at Santa Cruz Networking Systems (1) Hai Tao

Department of Computer Engineering University of California at Santa Cruz LANs, MANs, and WANs n LANs (Local area networks) Extension over a local area typically within a few kilometers Usually owned by a single organization High data rate The number of stations connect to a LAN is usually less than 100 Usually is based on broadcasting channels Some examples include Ethernet, Token Ring, Fiber Distributed Data Interface (FDDI), local ATM (asynchronous transfer mode) networks n MANs (Metropolitan Area Networks) Covers an entire city with LAN technology Shared medium and distributed access control

Department of Computer Engineering University of California at Santa Cruz LANs, MANs, and WANs n WANs (Wide Area Networks) Typically span entire countries Point-to-Point communication Example: Internet

Department of Computer Engineering University of California at Santa Cruz LANs, WANs, Layers, Protocols, and Services n Services provides a set of applications for the requesting application n Logically related services are grouped into layers Each layer is a service provider to the layer lying above n Protocol consists of rules followed by two peers during any communications Define protocol data units (PDU) in terms of format (syntax) and meaning (semantics)

Department of Computer Engineering University of California at Santa Cruz ISO-OSI Reference Model (SearchNetworking.com)

Department of Computer Engineering University of California at Santa Cruz Layers in ISO-OSI Reference Model n Physical Layer Transmission method of individual bits over the physical medium such as fiber optics, cables, phone lines, etc Concern with modulation, delay, etc n Data Link Layer Transmission of data frame (block) Access protocols to the physical medium Error and recognition correction Flow control and block synchronization

Department of Computer Engineering University of California at Santa Cruz Data Link Layer n Medium access protocol Multi-access channels -Medium access control (MAC) to determine access from competing parties +Very important in LANs +Timed Token Rotation Protocol +Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Point-to-Point connection

Department of Computer Engineering University of California at Santa Cruz Network Layers n Transports data packets from one station to another n Provide services such as addressing, internetworking, error handling, congestion control, packet sequencing n For continuous media data, resource reservation and guarantees for through put can be achieved using Quality of Service (QoS) parameters

Department of Computer Engineering University of California at Santa Cruz Transport Layers n Provides process-to-process connection n Bridge the gap between the requested transport and the provided services from network layers n Some functionalities include Divide and assemble packets Error handling between process (e.g. TCP)

Department of Computer Engineering University of California at Santa Cruz Session Layer, Presentation Layer, and Application Layer n Session layer - Guarantee the existence of connection during a session Point-to-point session Multi-cast session – a connection with many destinations Multi-drop session – a connection with many sources n Presentation layer – Definition, abstraction, and conversion of various data exchange formats Examples: HTTP, TELNET, FTP, POP n Application Layer – Various applications based on the presentation layer (See figure for an example)

Department of Computer Engineering University of California at Santa Cruz LANs - Ethernet n Bandwidth increases dramatically: 10Mbps to 100Mbps to 1GMbps to 10 Gbps n Bus-based network Three kinds of Ethernet cabling. (a) 10Base5, (b) 10Base2, (c) 10Base-T.

Department of Computer Engineering University of California at Santa Cruz LANs - Ethernet A simple example of switched Ethernet.

Department of Computer Engineering University of California at Santa Cruz LANs - Ethernet Cable topologies. (a) Linear, (b) Spine, (c) Tree, (d) Segmented.

Department of Computer Engineering University of California at Santa Cruz LANs - Ethernet (a) A two-station Ethernet. (b) A multistation Ethernet.

Department of Computer Engineering University of California at Santa Cruz LANs - Ethernet n Using CSMA/CD protocol to solve the multiple access problem Sender station checks the network state (Listen) Only send data when no other stations are transmitting data (Send) When multiple stations send data simultaneously, sending stations detect collisions by finding errors in their own data If collision detected, wait for randomly computed time and transmit again

Department of Computer Engineering University of California at Santa Cruz Ethernet and Continuous Media n Ethernet does not explicitly guarantee end-to-end delay n To transmit continuous media data on the Ethernet, several methods can be used Using fast Ethernet – end-to-end delay can be long if the network is congested, using fast Ethernet will solve this problem under most situations Dynamic adaptation – Change the data rate of the media data according to the network load Dedicated Ethernet for media data – one network for discrete date, one network for continuous data

Department of Computer Engineering University of California at Santa Cruz LANs – Token Ring n All stations are connected to a logical ring n A special bit pattern (3Bytes) called a token circulate in the ring n A sender station will capture the token and break the ring. The station sends the data in data frames. Each frame include sender address and destination address n Connect the ring once the transmission is finished n A multiple priority scheme is used to control the network access

Department of Computer Engineering University of California at Santa Cruz LANs – Local ATM Networks n Asynchronous Transfer Mode use fixed length packet (cell) n ATM allows systems to operate at higher rate because No error protection or flow control on a link-to-link basis (but can be done in higher layers) Operate in connection oriented mode with a setup phase for resource reservation Information field is small to reduce the internal buffers in the switching nodes

Department of Computer Engineering University of California at Santa Cruz WANs n Internet – DARPA experiment in 1973, see table 1 for illustration n Interconnection devices Source and destination are connected by a sequence of interconnection devices (packet switches) Packet switches cooperatively compute the path in the network. They are called routers in network layer Routing protocols -Distance vector – each router keeps tracking and informing its neighbors of its distance to each destination. Slow propagation. -Link State - Each router determines the identities of its neighbors and the associated distance and constructs link state packet (LPS). LPS is sent to all all the other routers