CIS 173 Networking Week #9 OBJECTIVES Chapter #6 Network Communications Protocols

The Packet Header –Source & Destination Address –Alert Signal that data is being sent –Clocking Info. To Synchronize Transmission Data –Actual data being sent Trailer –CRC for verification

7 Layers & the packet At each layer additional header information is added as it goes DOWN At each layer header info. Is removed as it goes UP

Packets Packets only sent to one computer BROADCAST Packets if for many or all

Protocols How the data actually moves through the network Two Methods of delivering the data with protocols –Connectionless –Connection-Oriented

Connectionless Place data on network and assume it will arrive Fast Require little overhead ($) Packets here are referred to as “DATAGRAMS”

Connection-Oriented More reliable Slower Connection MUST first be established Data sent orderly Receipt is acknowledged –Or packet is resent Connection is terminated

Routable vs. NonRoutable Routable –Protocols that function at the NETWORK layer Non-Routable –Those protocols that DON’T function at the NETWORK layer

PROTOCOLS (Pg ) Network Protocols (IP, IPX, NetBEUI) –Provide Addressing & Routing Information –Error Checking –Retransmit Requests –Rules for Comm. In the network environment Transport Protocols (TCP, SPX, NetBIOS/NetBEUI) –Ensure Reliable data delivery between PC’s Application Protocols –Work at upper layer of OSI model APPLICATION Layer –Application to Application services –SMTP Simple Mail Transport Protocol –FTP File Transfer Protocol

Most Common Protocols NetBIOS/NetBEUI –Small to Medium sized NETWORKS –2-200 PC’s –NOT inseparable, NOR the same –NetBIOS Works at the Session Layer to provide peer-to-peer support Broadcasts a computers name –NetBEUI Works at the Transport & Network Layer Can run on any network card Can run on any Medium

Most Common Protocols IPX/SPX –Internetwork Packet eXchange/Sequenced Packet eXchange. –NWLink=Microsoft’s implementation of Novell’s NetWare & IntranetWare –IPX Handles all addressing & routing over the network Uses MAC addresses of NIC’s to ID Connectionless –Fast –Unreliable –SPX Works with IPX to provide Connection-Oriented Services –Slower –More Reliable

Most Common Protocols TCP/IP –MOST Commonly used –Easy cross-platform comm. –Basis for Internet IP –Provides source & destination addressing –Provides routing –Connectionless ARP –Address Resolution Protocol Associate a logical IP address to physical MAC address TCP –Accepts messages of an;y length from an upper-layer protocol and provides transportation –Connection-Oriented –Responsible for message Fragmentation & Reassembly –Uses Sequencing function to ensure packets are reassembled in proper order DNS- Domain Name System –Uses PC’s logical name rather than numerical address FTP- File Transfer Protocol SMTP- Simple Mail Transfer Protocol

IP Addressing IP Addresses are logical addresses 32 bits (4 bytes=octet) long Octet –Represented by a decimal number from –Separated by a period 8 bits = 256 possible combos –0 & 255 are reserved for BROADCASTS –Networks & Hosts can only use 1-254

IP Addressing Part of address designates which network the computer is on Another part represents the host ID of that computer Assigned by INTERNIC in blocks of 255 SUBNET MASK –Used to ID which part of address is the network & which is the ID of PC

IP Addressing ###.###.###.### –First part indicates Which Network –Second Part indicates which Organization –Third part indicates which group within Org. –Fourth part indicates individual PC

DHCP Dynamic Host Configuration Protocol –Designed to keep track of which IP addresses have been assigned and to which machines –Uses a server that is configured with a block of available IP addresses and their subnet masks. –Each time a PC is turned on the server assigns a “temp” IP When booted up again it assigns another IP address until all are gone or a machine turns off

Channel Access Handled at the Media Access Control (MAC) sublayer of the DATALINK Layer 4 Types –Contention –Token-Passing –Demand Priority –Polling

Contention Any PC sends data anytime it has to Can cause LOTS of “Collisions” because only one PC can transmit at a time Okay for very small networks Two types of CONTENTION –CSMA/CD Carrier Sense Multiple Access with Collision Detection –CSMA/CA Carrier Sense Multiple Access with Collision Avoidance

Contention CSMA/CD Carrier Sense Multiple Access with Collision Detection –One of most popular –Used by Ethernet to prevent collisions by “listening” to the channel to see if another computer is using it If so it will wait If not it will send

Contention CSMA/CA –Carrier-Sense Multiple Access with Collision Avoidance –First senses the channel not in use THEN signals it’s intent to transmit data

Token Passing Token passed from 1 PC to another sequentially If no data to transmit must pass the token on Only the PC holding the token can transmit IF 2 tokens are needed must wait to get it the second time MORE EXPENSIVE

Demand Priority Recently developed Used ONLY by the 100VG-AnyLAN 100 Mbps Ethernet stantard –IEEE –HIGH speed networks Intelligent HUBs control the network PC’s signal the HUB that they have data to send HUB sends only to addressee. HIGHLY EXPENSIVE

ADD PROTOCOLS

HOMEWORK Review Questions at end of chapter #6