1. Network
Performance
Overview

2. You learned in the first grade!
Everything you need to know about Network Troubleshooting,
You learned in the first grade!

3. Hexadecimal
= Decimal

4. What is Networking?
A combination of hardware and software that provides a means for computers in an organization to communicate with one another.
No two computer networks are exactly the same
No two companies networking needs are exactly the same
Each network is continually evolving. Applications, services and technology are changing at a very rapid pace
Technology is continually being updated and older technology phased out
Users and network support personnel need to continually adapt to the technologies installed at their place of business.

5. Network Types Local Area Network Building Backbone Campus Backbone
Metropolitan Area Network (MAN)
Wide Area Network
Enterprise Network
Connects users in a department, company or work group - Token Ring, Ethernet
Connects LANs together in a building
ATM, FDDI, Fast Ethernet, Gigabit Ethernet
Connects building LANs together
Used to connect sites in a large city
FDDI, ATM, SONET
Used to connect sites across the country
ISDN, Frame Relay, T1, T3
All of the above types of networks connected together

6. MAN

7. Wide Area Networks (WAN)
Designed to connect geographically distant network sites together, although they could be in same city or state
Obtained through a service provider (SWBT, SPRINT, AT&T)
Use either a leased line or switched circuit technology
Usually connect routers together
Can use low, or medium speeds like 56 Kbps to Mbps (T-1)
Use leased lines and pay fixed fee regardless of usage
Use circuit switched services where fee is based on usage
Examples include Switched 56 Kbps circuits, ISDN, Frame Relay, T-1, X.25, DSL and ATM
Protocol Specifications
IEEE Ethernet IEEE Token Ring IEEE Logical Link Control
Texas Instruments - Token Ring Chipset
Intel - Ethernet Chipset
ANSI - FDDI
Industry Organizations
Organization Contact Information
Institute of Electrical and Electronics Engineers (IEEE) (800) 678-IEEE
Internet Society (703)
Network Professional Association (NPA) (800)
Sniffer Users Group Check with your local sales office
A reading list is provided in the appendix.

8. Enterprise Networks
Is a term used to describe the entire network of a company which has many or all of the following networks connected:
Local Area Networks (LAN)
Building Backbone
Campus Backbone
Metropolitan Area Network (MAN)
Wide Area Network (WAN)
Protocol Specifications
IEEE Ethernet IEEE Token Ring IEEE Logical Link Control
Texas Instruments - Token Ring Chipset
Intel - Ethernet Chipset
ANSI - FDDI
Industry Organizations
Organization Contact Information
Institute of Electrical and Electronics Engineers (IEEE) (800) 678-IEEE
Internet Society (703)
Network Professional Association (NPA) (800)
Sniffer Users Group Check with your local sales office
A reading list is provided in the appendix.

9. Networking
Components

10. Basic Network Components
There are three basic Network Components
The end station
The Applications that run on the end stations
The network which supports traffic flow between end stations
End Stations:
PCs, Servers, Workstations, Laptops, Printers, Scanners
Applications:
File Services, Print Services, Operating Systems, , Imaging, Fax
Networks:
Network Operating System (NOS), Ethernet, Token Ring, FDDI, ATM, Fast Ethernet, Frame Relay, ISDN, DSL, T-1, Switches, Bridges, Routers, Hubs

11. Network Bandwidth
Networks have a finite bandwidth or capacity that can be used by the particular network.
Most of the LAN topologies use a shared media access control protocol
Ethernet - CSMA/CD - Carrier Sense Multiple Access / Collision Detection
10 Mbps, 100 Mbps, 1Gbps
Token Ring - MAC - Media Access Control
4 Mpbs, 16 Mpbs
FDDI - SMT - Station Management
100 Mbps

12. The Internet Uses TCP/IP as the common transport protocol
Developed out of the US Government ARPANET
Supports access around the world to both public and private users (VPN) Virtual Private Networks
Some of the applications that run on the Internet include:
World Wide Web (WWW) - application that allows access to different types of data including text, audio and video.
File Transfer Protocol (FTP) - application that allows files to be transferred from one computer to another
Simple Mail Transfer Protocol (SMTP) - application that provides electronic mail ( ) to be sent from user to user.

13. Accessing the Internet
The Internet is a computer network that connects many networks together and is built upon a tiered architecture
Tier 1 - National Access Points (NAP) - Regional interchange facility which connects networks in an area using routers
Tier 2 - National Service Providers (NSP) - Connect National Access Points together
Tier 3 - Internet Service Providers (ISP) - Provide Internet access to commercial and private users

14. The OSI
Model

15. The OSI Reference Model
Host A
Host B
Allows users to transfer files, send mail, etc.
Only layer that users can communicate with directly
Key features are ease of use and functionality
Standardized data encoding and decoding
Data compression
Data encryption and decryption
Manages user sessions
Reports upper-layer errors
Supports Remote Procedure Call activities
Connection management
Error and flow control
Provides reliable, efficient service
Inter-network packet routing
Minimizes subnet congestion
Resolves differences between subnets
Network access control
Packet framing
Moves bits across a physical medium
Interface between network medium and interface devices
Defines electrical and mechanical characteristics of LAN 7
Application
Application
Provides
Services
Connects
processes
Moves
Data 6
Presentation
Presentation 5
Session
Session
Transport 4
Transport 3
Network
Network 2
Data Link
Data Link 1
Physical
Physical

16. Frame Headers Frames headers revolve around the OSI model.
DLC * LLC Network Transport Application
Frames headers revolve around the OSI model.
The protocol headers are used to move the data.
How many bytes is the DLC Header
How about the IP header
Good, now how about the TCP header
*The number of headers in a frame is protocol-dependent.
There are many good reference books and classes specific to protocols, a good reference site is

17. Network Communication
Each layer of the OSI model provides a specific communications function and each layer should be independent of its adjacent layers
A header, created by each layer, implements the function for that layer. The combination of header and data is called a Protocol Data Unit (PDU)
When the PDU created by the Network layer reaches the Data Link layer, both a header and trailer are added and this creates a frame
When the frame from Host A reaches Host B, each header that was added by a layer in Host A determines the action taken by the peer layer on Host B

18. Protocols
Computers on networks use protocols to communicate and these protocols define the procedures that each system involved in the communications process will use.
Protocols are a set of procedures that are agreed upon and then followed by each communicator
Protocols are combined into what is called a communication architecture or protocol stack
Each protocol in the architecture provides a function that is necessary to make data communications possible
Generally, there are two types of protocols:
Connectionless Protocols
Connection Oriented Protocols

19. Connectionless Protocols
Simply send data from a source address to a destination address
No verification is performed to determine if the destination address is available.
Connectionless protocols are generally referred to as Datagram Service
Much like sending a postcard via the US Mail
Datagram protocols usually do not support error recovery or any type of acknowledgement routine classifying them as an unreliable transmission service - (not to be confused with the USPS)
Connectionless protocols are typically used because of efficiency and because the data being sent does not justify the extra overhead necessary to perform the error recovery or acknowledgment routine.
Example: TCP/IP’s - UDP (User Datagram Protocol), SNMP (Simple Network Management Protocol)

20. Connection Oriented Protocols
A Connection Process or handshake is implemented between two stations before the transmission of data occurs
Connections are referred to as sessions, virtual circuits, or logical connections
Most connection oriented protocols require some form of acknowledgement as data is transmitted, this is the mechanism that provides reliable data transmission over the network
When data is found to be in error, the sending side is asked to re-transmit the frame, or if the sender has not received an Acknowledgement, it will re-transmit after a specific amount of time
When the connection is no longer needed, there is a defined disconnect process
Example: TCP/IP’s - TCP (Transport Control Protocol), SPX (Sequenced Packet Exchange), SDLC

21. IP
Internet
Protocol

22. What Does IP Do? Delivers packets across a network.
Delivery is based on IP address.
Route frames from one network to another.
IP does not provide flow control or error control, but can provide Type of Service (Quality of Service).
IP fragments and re-assembles frames for traversal across networks that require small frames (X.25) based on the Maximum Transmission Unit (MTU) size.

23. IP Functionality Server Client Router APP TCP IP MAC APP TCP IP MAC IP
Subnet 1 IP
Subnet 2
MAC
MAC
Frames get sent to the MAC address of the Router. The Router strips the DLC and builds new frame to put on other subnet. Router also decrements the Time to Live (TTL) field, calculates the new checksum.

24. IP Fragmentation and Reassembly

25. TCP
Transport
Control
Protocol

26. The 4 Layer Internet Model
Application
Message 3
Transport
Segments 2
Network
Packets 1
Frames
Local Network

27. Addressing in TCP/IP Application “Messages” Process I.D.
Specifies a Host Process
Transport
“Segments”
Specifies a TCP Port
Port Address
Network
Socket
“Packets &
Datagrams”
Specifies a Logical
IP Address
Network Device
Data Link
Specifies a SAP
“Frames”
LLC Address
Specifies a DLC
Mac (DLC) Address
Network Device
Physical
Bits

28. What Does TCP Offer? Reliable Packet Delivery Flow Control
Sequence Number + TCP Length = Acknowledgment or
Sequence Number + TCP Length = Next Sequence Number
Retransmission of Data (Lost Frame, Dropped Frame, CRC error in frame)
Flow Control
Using Sliding Windows
Positive Acknowledgement with Retransmission
Multiplexing of Conversations or Connections
Error Control (TCP Header Checksum)

29. When did you learn to dial a phone?
Virtual Network Circuit
Collect Call from ABC, do you accept the charges?
Yes = (3 way handshake) (SYN)
No = Reset Connection (RST)

30. What is a Port? Virtual Circuit Identifier
Workstation
Server
“Client’s” use an
“ephemeral” port
(Short Lived, for the duration of the connection). Client ports are typically above 1023.
“Servers” use the
“well-known” port or listening port. Usually these ports are defined between 0 – 1023.
See for list of ports

31. What is a Connection? The Virtual Circuit
Workstation
Server
Port 1518
Port 23
The IP address and TCP port number of one application process (sometimes called a “socket”) is associated with the “socket” of another application process, creating a pair of addresses used to refer to the connection.
All data transfers are tracked through the socket pairing, which defines the virtual circuit being used during the duration of the connection.

32. TCP Connection
SYN
SYN
SYN
RST
ACK

33. Connection Establishment
“Three-Way Handshake”
Client
Server
Send SYN (SEQ = X)
WIN = size
Max Segment Size = 1024 1
Receive SYN
Send SYN (SEQ = Y)/ACK (X + 1)
WIN = size
Max Segment Size = 1024 2
Receive SYN/ACK Segment
Send ACK (Y + 1) 3
Receive ACK Segment

34. Reliability

35. Reliability

36. Reliability Positive Acknowledgment with Retransmission (PAR)
Server
Workstation
Positive Acknowledgment with Retransmission (PAR)
Packet
“Client” must receive ACK before the retransmission timer expires. Otherwise, packet will be re-transmitted.
Acknowledgement
Sliding Window
Seq = 1 + Len=1024
Seq = Len=1024
Acknowledgement = 2049

37. Segment Size affects Performance
Small Segments
Large Segments
54B
12 K Bytes
54B
12B
Header Data
Header Data
Header Data
Header over 4x Data;
therefore, only 1/4 of
Network Bandwidth
is being used.
54B
1.5KB
54B
1.5KB
54B
1.5KB
Header Data
Header Data
Header Data
Increases response time because of fragmentation time.
Maximum Frame Size = 1518

38. Putting it all together!

39. Simple Information to Gather!
Network Statistics
Average Network Utilization
Total Frames
Total Bytes
Average Frame Size
Packet Drops
Interface Errors
Top Talkers
#1 Station % Usage
#2 Station % Usage
#3 Station % Usage
Top Protocols
Protocol #1 %
Protocol #2 %
Protocol #3 %
Response Times
NCP / SMB Create File Cmd/Resp
NCP / SMB File Read Cmd/Resp
NFS Create File Cmd/Resp
TCP Session Establishment
DNS Request/Reply
DHCP initialization time
Telnet Cmd/Echo/Ack
Gather this information from each subnet, building or geographic location.