Post on 28-Dec-2015
Section 8: TCP/IP Protocol Suite and Utilities
CSIS 479R Fall 1999“Network +”
George D. Hickman, CNI, CNE
Objectives Identify the components of the
TCP/IP protocol suite as they relate to the OSI and DoD models
Describe distance vector routing with IP
Describe link state routing with IP List the protocols that comprise
TCP/IP
Objectives (Con’t) Use Windows TCP/IP utilities Describe the IPX/SPX Protocol Suite
and the OSI reference model Describe routing with RIP/SAP Describe the Protocols used in a
Windows NT Network
TCP/IP TCP
Transmission Control Protocol Responsible for establishing
communication between two systems IP
Internet Protocol Responsible for the transfer of data
DoD Model Process/Application
Acts as the User Interface; Provides applications that transfer data between hosts
Host-to-Host Maintains data integrity; sets up reliable end-to-end
communication; ensures error-free delivery (proper sequence, no loss or duplication)
Internet Routing; Foundation of TCP/IP protocol suite
Network Access Defines physical interconnection between hosts
TCP/IP Suite and OSI Model See figure 8-2 on page 8-6
TCP maps to Transport layer
IP maps to Network layer
Routing IP IP is the portion of the TCP/IP Suite
that provides addressing and connectionless services for packet forwarding; packet switching
IP allows an internetwork to be divided into logical groups called autonomous systems
Autonomous Systems A group of networks administered
by a single authority IGPs: Interior gateway protocols
route information within an autonomous system
EGPs: Exterior gateway protocols (or Border gateway protocols—BGP) interconnect autonomous systems
Distance Vector Routing with IP
RIP Routing Information Protocol
Routers advertise a “metric” of how many hops they are from a network Can be advertised higher if needed
Costs of a route are 1-16 metrics A route with a cost of 16 is
considered unreachable
Drawbacks of RIP and Distance Vector Routing Convergence
The amount of time it takes all routers to synchronize their databases when a change occurs to the network
Slow convergence Also called the count-to-infinity
problem
Count-to-infinity problem Split Horizon
Destinations are not advertised at all to the interface from which they were learned
Figure 8-6 page 8-12 Poison Reverse
All routes learned from a network are advertised back to the network with a cost of 16
Enabling Poison Reverse reduces convergence time, but increases RIP traffic
RIP and RIP II RIP routers broadcast their routes
every 30 seconds RIP II routers add support for:
Authentication Subnet masks Next Hop Addresses Multicast Packets
IP multicast address for RIP II is 224.0.0.9
Link State Routing—OSPF L. S. routing minimizes size of routing
tables Open Shortest Path First Protocol
Build route tables from packets distributed by other routers
“Hello packets” contain information about a routers directly connected interfaces and their costs.
They establish/maintain neighbor relationships between routers on same segment
OSPF learning routes 1. Identify neighboring routers (“Hello”)
Announces itself (address and mask) to other routers
Determines router’s neighbors Establishes interval that routers send
hello’s Identifies DR (Designated Router)
Router with highest priority Identifies BDR (Backup Designated Router)
Router with second highest priority
OSPF learning routes (Con’t)
2. Synchronizing link state advertisement databases All routers create and synchronize their
LS advertisement databases with the DR and BDR (after DR and BDR elected, neighbor list created)
Before synchronization routers communicate in two-way state
After synchronization, routers enter the full neighbor state. Routers then have adjacency
Selecting Routes Link State Advertisement DB is OSPF
router’s view of the internetwork OSPF algorithm determines path(s)
and adds up the cost(s). Lowest cost wins, and is added to routing table.
Algorithm rebuilds table when change in LSDB occurs, after a hold-down interval
Maintaining Route Information Link State Update (LSU) packets are
sent when changes occur or every 30 minutes (default)
DR floods packet to local network Each router compares LSU to it’s
DB. Resets aging timer. Entry dropped if age=4 times router dead interval
Router sends ACK to original router
OSPF Terms Autonomous System (AS)
A group of routers that exchange routing information using a common routing protocol in a single administrative unit.
Autonomous System Border Router (ASBR) A router that exchanges routing information
with routers belonging to other AS. ASBRs distribute routing info about external destinations
OSPF Terms (Con’t) Area
Large enterprise-area networks are logically divided into smaller contiguous networks.
Areas act like an AS, so OSPF routers do not have to maintain LSDB on other areas
Reduces LS Acknowledgements (LSA) sent Reduces size of DB on each router Reduces amount of time to recompute routes
following a change to the internetwork
OSPF Terms (Con’t) Backbone
A logical area to which all other areas are connected. Address is always 0.0.0.0
Stub area An area with only one ABR
Transit area Areas with more than one ABR
See page 8-23
OSPF vs. RIP OSPF is considered superior to RIP
Support for large Internetworks RIP Metric <= 16; OSPF Metric <= 65535
Variable Length Subnetting LSA’s include subnet mask information
about networks. Different segments can have different subnets
Rapid Convergence No count-to-infinity problem
Reduced Internetwork Traffic RIP broadcasts DB every 30 seconds;
OSPF only when changes occur
Protocols in the TCP/IP Suite Internet Layer Protocols
IP ICMP
Address resolution Protocols ARP RARP BOOTP
Protocols in the TCP/IP Suite Host-to-Host layer Protocols
TCP UDP
Process/Application layer Protocols FTP / TFTP HTTP SMTP POP3 SNMP
Internet Layer Protocols
Primary purpose is to route packets between hosts, often through many routers
Internet layer performs routing and packet switching
IP
Provides specifications that allow routing, fragmentation, and reassembly to occur
Provides connectionless, non-guaranteed delivery of transport layer packets (TPDU)
IP can fragment TPDU into smaller parts for transmission and reassemble them later
ICMP Internet Control Message Protocol Works with IP to provide internetwork
error and other control info to TCP and other upper-layer protocols
ICMP messages are sent when A packet cannot reach destination A packets TTL expires IP header problem To notify internetwork of congested/failed
links Etc.
Address Resolution Protocols ARP/Reverse ARP Maps 4-byte software-based IP addresses
to 6-byte hardware-based Data Link addresses
RARP retrieves IP address from hardware address. Used by diskless workstations
BOOTP BOOTP servers keep MAC and IP addresses Newer, more commonly used than RARP
DHCP Dynamic Host Configuration Protocol
Provides configuration parameters to IP hosts
Automatic allocation Permanent address assigned to host
Dynamic allocation Address leased to host for a limited time
Manual allocation DHCP delivers manually assigned numbers
TCP Transmission Control Protocol
Transport Protocol Accepts messages of any length from
UPLs, Provides full-duplex, acknowledged,
connection-oriented, flow controlled, transport to a TCP peer
UDP User Datagram Protocol
Transport Protocol Not connection oriented No acknowledgements UDP just accepts and transports
datagrams from a ULP UDP has lower overhead, so is faster
than TCP
FTP File Transfer Protocol
Move files between hosts Allows login, directory inspection, file
manipulation, command execution Uses virtual circuits to establish a
reliable path between hosts TFTP Trivial FTP
No password, directory listings. Good for downloads
Runs on UDP—not as reliable
HTTP Hyper Text Transfer Protocol Language of the WWW portion of
Internet Establishes connection with a
server and sends a request URL: Uniform Resource Locators
SMTP Simple Mail Transfer Protocol A standard for exchanging mail
between workstations Relies primarily on TCP to route
messages between network hosts Does not provide user interface
POP3 Post Office Protocol 3 Standard Mail server Provides message store Users connect and retrieve all
pending messages and attachements at once
Uses SMTP messaging protocol
SNMP
Simple Network Management Protocol Allows management of a network from a
“SNMP manager” workstation Each host has a Management Information
Base (MIB) that holds data about itself When a threshhold is reached, a “trap”
message is sent to the management console Example: router sends SNMP trap when an
interface goes down
Windows TCP/IP Utilities ARP.EXE
Diagnostic utility for ethernet TCP/IP ARP stores a cache of host IP addresses
and physical addresses FTP .EXE IPCONFIG.EXE (WinNT) WINIPCFG
(Win9x) Shows IP settings on local machine
Windows TCP/IP Utilities NBTSTAT.EXE
Displays statistics and existing TCP/IP connections using NetBIOS over TCP/IP
NETSTAT.EXE Identifies status of TCP/IP connections
and provides statistics on them
Windows TCP/IP Utilities PING.EXE
Packet InterNet Groper Determine if a host is available; quality of
the connection TELNET.EXE
Remote Terminal Connection TRACERT.EXE
Traces a connection route to a host and its hops
IPX/SPX Novell’s protocol suite based on
Xerox Network System (XNS) protocol suite
IPX gets packets through internetwork
SPX offers connection-oriented guaranteed delivery of packets.
IPX Addressing Network Address
8 digit hexadecimal number assigned to wire Internal Network Address
8 digit hexadecimal number assigned to server MAC or Node Address
12 digit hexadecimal number assigned to NIC Socket number
Determines destination within a device (RIP, SPX)
RIP/SAP Routing RIP is IPX distance vector
Uses hop and tick counts to determine cost SAP is Service Advertising Protocol
Advertise services of all known servers on the network
Periodic SAP Information broadcasts (60 seconds)
SAP Service Inquiries SAP Service Responses
SAP traffic needs to be filtered to avoid bandwidth problems
Windows NT Protocols NetBEUI
NetBIOS Extended User Interface Not Routable
NWLink IPX/SPX Compatible Transport NDIS-compliant version of Novell IPX/SPX
Others Apple Talk DLC Protocol
IBM Mainframes and AS/400 Print to HP JetDirect