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