1. Chapter 5: Network and Transport Layers
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2. Outlines Network Protocols and TCP/IP Networking Addressing Routing
Network flow control and QoS
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3. Network Protocols and TCP/IP
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4. Transmission Control Protocol/ Internet Protocol (TCP/IP)
The Transmission Control Protocol/ Internet Protocol (TCP/IP) was developed for the U.S. Dept of Defense’s Advanced Research Project Agency Network (ARPANET) in 1974.
TCP/IP allows reasonable efficient and error-free transmission.
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5. TCP/IP TCP/IP has two parts:
TCP - performs packetizing: TCP is only active at the sender and receiver.
IP - performs routing and addressing.
A typical TCP packet has 192-bit (24-byte) header of control information.
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6. TCP/IP Two forms of IP are currently in use:
IPv4 also has a 192-bit (24-byte) header.
IPv6 has a 320-bit (40-byte) header.
The primary reason for the increase in packet size is an increase in the address size from 32 bits to 128 bits, due to the dramatic growth in the usage of the Internet.
The size of the message field depends on the data link layer protocol used. TCP/IP is commonly combined with Ethernet.
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7. TCP Packet 1 2 3 4 5 6 7 8 9 10 11 User Data 1 Source ID 16 bits
2 Destination ID 16 bits
3 Sequence number 32 bits
4 ACK number 32 bits
5 Header length 4 bits
6 Unused 6 bits
7 Flags 6 bits
8 Flow control 16 bits
9 CRC bits
10 Urgent pointer 16 bits
11 Options 16 bits
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8. IP Packet version
IP4 1 2 3 4 5 6 7 8 9 10 11 12 13 14
1 Version number 4 bits
2 Header length 4 bits
3 Type of Service 8 bits
4 Total length 16 bits
5 Identifiers 16 bits
6 Flags 3 bits
7 Packet offset 13 bits
8 Hop limit 8 bits
9 Protocol 8 bits
10 CRC bits
11 Source address 32 bits
12 Destination Address 32 bits
13 Options varies
14 User data varies
15 Flow name 24 bits
16 Next header 8 bits
IP6 1 15 4 16 8
11 (128 bits)
12 (128 bits) 14
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9. *History of IPng Effort
By the Winter of 1992 the Internet community had developed four separate proposals for IPng. These were "CNAT", "IP Encaps", "Nimrod", and "Simple CLNP". By December 1992 three more proposals followed; "The P Internet Protocol" (PIP), "The Simple Internet Protocol" (SIP) and "TP/IX". In the Spring of 1992 the "Simple CLNP" evolved into "TCP and UDP with Bigger Addresses" (TUBA) and "IP Encaps" evolved into "IP Address Encapsulation" (IPAE).
By the fall of 1993, IPAE merged with SIP while still maintaining the name SIP. This group later merged with PIP and the resulting working group called themselves "Simple Internet Protocol Plus" (SIPP). At about the same time the TP/IX Working Group changed its name to "Common Architecture for the Internet" (CATNIP).
The IPng area directors made a recommendation for an IPng in July of [RFC 1752].
The formal name of IPng is IPv6
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10. Why Need IPv6? Internet Growth Quality of Services (QoS)
Network numbers and size
Traffic management
Quality of Services (QoS)
Internet Transition
Routing
Addressing
No question that an IPv6 is needed, but when
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11. Other Protocols
Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX)
Developed by Xerox in the 1970s. It is primary network protocol used by Novell NetWare. Novell has replaced IPX/SPX with TCP/IP.
X.25
ITU-T’s standard for WAN. Mature standard. Seldom used in north America.
System Network Architecture (SNA)
IBM developed SNA in It is used on IBM’s mainframes. It is hard to integrate SNA with other networks.
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12. The Message Field Size Maximum Ethernet packet size = 1492
TCP message field
(TCP header) - 24 (IPv4 header) = 1444
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13. Addressing
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14. Types of addresses Address Example Software Example Address
Application Layer Web browser ike.ba.ttu.edu
(also called domain name)
Network Layer TCP/IP
Data Link Layer Ethernet 00-A0-C9-96-1D-90
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15. Addressing
The network layer determines the best route through the network to the final destination.
Based on this routing, the network layer identifies the data link layer address of the next computer to which the message should be sent.
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16. Assigning Addresses
In general, the data link layer address is permanently encoded in each network card, and as part of the hardware that cannot be changed.
Network layer addresses are generally assigned by software. Every network layer software package usually has a configuration file that specifies the network layer address for that computer.
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17. Assigning Addresses
Application layer addresses (or server addresses) are also assigned by a software configuration file. Virtually all servers have an application layer address, but most client computers do not.
Network layer addresses and application layer addresses go hand in hand. ike.ba.ttu.edu - means at the network layer.)
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18. How IP Addresses Distributed
Internet Corporation for Assigned Names and Numbers (ICANN) oversees the Internet Assigned Numbers Authority (IANA) and controls how the Net's 4.29 billion IP addresses are used.
IANA distributes address space to three geographically diverse Regional Internet Registries (RIRs) and encourage three RIRs to operate so that addresses remain unique, are mapped efficiently, and are treated as a precious resource.
Three RIRs dole out available pools of IP based on a shared criteria. All deploy numerical address space to ISPs, local registries, and in some cases small users.
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19. IP Address Allocation IANA InterNIC America RIPE Europe APNIC Asia
National
Regional
Consumer
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20. Three RIRs American Registry for Internet Numbers (ARIN)
Reseaux IP Europeen (RIPE)
Asia Pacific Network Information Centre (APNIC)
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21. Internet Addresses
InterNIC is responsible for network layer addresses (IP addresses) and application layer addresses or domain names (
There are five classes of Internet addresses.
Classes A, B, and C are available to organizations
Class D and E are reserved for special purposes and are not assigned to organizations.
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22. Internet Address Classes
Class A (/8 address)
The first digit is fixed, ranging (01-7E), 16 million addresses
127.x.x.x is reserved for loopback
Class B (/16 address)
First two bytes are fixed with the first digit ranging (80-BF), 65,000 addresses.
Class C (/24 address)
First 3 bytes are fixed, with the first digit ranging (C0-DF), 254 addresses.
Class D & E
The first digit is (E0-EF) and (F0-FF) respectively.
Reserved for special purposes and not available to organizations.
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23. Internet Address Classes
Ranges of the first byte for different classes: 1
126
128
191
1/2
1/4
1/8
1/16
1/16
Class A
Class B
Class C
Class D Class E
Class A: 0xxxxxxx
Class B: 10xxxxxx.xxxxxxxx
Class C: 110xxxxx.xxxxxxxx.xxxxxxxx
Class D: 1110xxxx.xxxxxxxx.xxxxxxxx
Class E: 1111xxxx.xxxxxxxx.xxxxxxxx
Note:
The IP addresses with the first
byte as 0 and 127 are reserved
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24. Internet Address Classes
# of Addresses
Class Available Addr-Structure Example Available #
Class A million First byte fixed 50.x.x.x 127
Organization assigns
last three bytes
Class B 65k First two bytes fixed x.x 16k
last two bytes
Class C First three bytes fixed x 2 millions
last byte
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25. Internet Addresses
The Internet is quickly running out of addresses. Although there are more than 1 billion possible addresses, the fact that they are assigned in sets (or groups) significantly restricts the number of usable addresses.
The IP address shortage was one of the reasons behind the IPv6, providing in theory, 3.2 x 1038 possible addresses.
How to apply for IP address?
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26. Subnets
Assign IP addresses to specific computers so that all computers on the same local area network have a similar address.
Each LAN that is logically grouped together by IP number is called a TCP/IP subnet.
Benefit:
allows it to be connected to the Internet with a single shared network address
an necessary use of the limited number of network numbers
Overload Internet routing tables on gateways outside the organization
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27. Gateway
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28. Subnet Mask
Subnet mask enables a computer to determine which computers are on the same subnet. This is very important for message routing.
E.g.
IP address:
Subnet mask:
IP address: x is for the computers in the same subnet
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29. Subnet Subnet with partial bytes addresses.
E.g to
Subnet mask:
Subnet address:
Subnet broadcast address:
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30. Subnet
IP address:
Subnet mask:
The IP prefix
Destination IP:
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31. Subnet Mask Template 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Broadcast Address
255
255
Host Address
150 1
128
192
224
240
248
252
254
255
192
224
240
248
252
Network ID–Class B
128
Mask Numbers
Possible Subnet Address
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32. Dynamic Addressing An address assignment problem:
Each time the computer is moved, or its network is assigned a new address, the software on each individual computer must be updated.
Solution: dynamic addressing
With this approach, a server is designated to supply a network layer address to a computer each time the computer connects to the network.
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33. Dynamic Addressing
Two standards for dynamic addressing are commonly used in TCP/IP networks:
Bootstrap Protocol (bootp) for dial-up networks (1985)
Dynamic Host Control Protocol (DHCP) for non-dial-up networks (1993)
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34. Dynamic Addressing
The Bootp or DHCP server can be configured to assign the same network layer address to the computer each time it requests an address or it can lease the address to the computer by picking the “next available” network layer address from a list of authorized addresses.
Dynamic addressing greatly simplifies network management in non-dial-up networks too.
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35. Address Resolution Address resolution:
The sender translates the application layer address (or server name) of the destination into a network layer address; and in turn translates that into a data link layer address.
Two approaches used in TCP/IP:
Server address resolution
Data link layer address resolution.
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36. Server Name Resolution
Domain Name Service (DNS)
Used for translating application layer addresses into network layer addresses.
InterNIC
Keeps the name and IP addresses of the name server that will provide DNS information for your address classes.
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37. Domain Name System 32-bit IP addresses have two drawbacks
Routers can’t keep track of every network path
Users can’t remember dotted decimals easily
Domain names address these problems by providing a name for each network domain (hosts under the control of a given entity)
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38. *DNS Database
Hierarchical database containing name, IP address, and related information for hosts
Provides name-to-address directory services
Key features:
Variable-depth hierarchy. Unlimited levels
Distributed database. Scattered throughout the Internet and private intranet.
Distribution controlled by the database. Thousands of separately managed zones managed by separate administrators
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39. Server Name Resolution
Server address resolution process:
TCP/IP sends a special TCP-level packet to the nearest DNS server asking for the requesting computer the IP address that matches the Internet address provided.
If the DNS does not have the answer for the request, it will forward the request to another DNS.
This is why it sometimes takes a long time to access certain sites.
IP addresses are then temporarily stored in a server address table.
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40. Data Link Layer Address Resolution
In order to actually send a message, the network layer software must know the data link layer of the destination computer.
In the case of a distant computer, the network layer would route the message by selecting a path through the network that would ultimately lead to the destination.
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41. Data Link Layer Address Resolution
The process:
TCP/IP software sends a broadcast message (using Address-Resolution-Protocol or ARP) to all computers in its subnet requesting the data link layer address.
The computer with the right IP address responds with its data link layer address
The message is sent to the destination computer
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42. Routing
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43. 9/16/2018 9:57:42 PM9/16/2018 9:57:42 PM

44. Routing
There are many possible routes or paths a message can take to get from one computer to another.
Routing
The process of determining the route or path through the network that a message will travel from the sender to the receiver.
Routing table
The routing information on each router, which specifies how message will travel through the network.
Types of routing:
Centralized routing
Decentralized routing: Static routing, Dynamic routing
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45. Routing
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46. Routing Table for Computer B
Destination Route
A A
C C
D A
E E
F E
G C
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47. Static Routing Static Routing
The routing table is developed by the network manager, and changes are made only when computers are added or removed from network.
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48. Dynamic Routing Dynamic Routing (adaptive routing)
An initial routing table is developed by the network manager, but is continuously updated by the computers themselves to reflect changing network conditions, such as network traffic.
Used when there are multiple routes through a network and it is important to select the best (or fastest) route, in order to route messages away from traffic on busy circuits.
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49. Dynamic Routing Commonly used dynamic routing protocols
Routing Information Protocol (RIP) - used by the network manager to develop the routing table.
Border Gateway Protocol (BGP). A dynamic exterior routing protocol for the Internet.
Internet Control Message Protocol (ICMP) - used on the internet with TCP/IP.
Open Shortest Path First (OSPF) uses the number of computers in a route as well as network traffic and error rates to select the best route.
Enhanced Interior Gateway Routing Protocol (EIGRP) – a dynamic link state interior routing protocol and commonly used inside an organization.
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50. Dynamic Routing Routing Information Protocol (RIP)
When new computers are added, it counts the number of computers in the possible routes to the destination and selects the rout with the least number.
Computers using RIP send broadcast messages every minute or so to announce routing state.
It is used by TCP/IP and IPX/SPX.
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51. Dynamic routing Border Gateway Protocol (BGP)
A dynamic routing protocol used on the Internet to exchange routing information between autonomous systems – the large sections of the Internet. It is seldom used inside companies
Large, complex and hard to administer
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52. Dynamic Routing Internet Control Message Protocol (ICMP)
Uses both broadcast messages and the messages to specific computers to exchange routing information
Only used by TPC/IP
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53. Dynamic Routing Open Shortest Path First (OSPF)
More efficient than RIP because it normally doesn’t use broadcast messages. Instead it selectively sends status update messages directly to selected computers
Used by TCP/IP
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54. Dynamic routing Enhanced Interior Gateway Routing Protocol (EIGRP)
A dynamic link state interior routing protocol developed by CISCO
Commonly used inside an organization
Computers/routers store their own routing table and their neighbors’ routing tables
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55. Dynamic Routing Two drawbacks to Dynamic Routing.
It requires more processing by each computer in the network than centralized or static routing.
The transmission of status information “wastes” network capacity.
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56. Connectionless vs. Connection-Oriented Routing
Two ways a group of packets can be routed:
Connectionless routing
Each packet is treated separately and makes its own way through the network.
Connection-Oriented routing
Sets up a virtual circuit between the sender and receiver. Appears to use point-to-point circuit-switching, but actually uses store-and-forward.
Has greater overhead than connectionless, due to the routing information.
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57. Connectionless vs. Connection-Oriented Routing
Virtual Circuit
Appears to the application software to use a point-to-point circuit
The network layer makes one routing decision and all packets follow the same route
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58. Connectionless vs. Connection-Oriented Routing
TCP/IP vs. UPD/IP
TCP/IP is used for connection-oriented routing
TCP establishes the virtual circuit and IP routes the messages.
UDP/IP is used for connectionless routing
The TCP packet is replaced with a User Datagram Protocol (UDP) packet.
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59. Multicast Unicasting The usual transmission between two computers.
Broadcasting
Sending messages to all computers on a LAN or subnet.
Multicasting
Sending the same message to a group of computers temporarily in a class D IP address.
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60. Broadcast Individual transfers Clients Host
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61. Multicast Data replicated by the network Clients Host One transfer
Could be one packet that all receive or
replicated by routers in the network
Data replicated
by the network
Clients
Host
Multicast
Infrastructure
One transfer
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62. Multicast
Computers wishing to participate in a multicast send a message to the sending computer or some other computer performing routing along the way using a special type of TCP-level packet called Internet Group Management Protocol (IGMP).
Each multicast group is temporarily assigned a special Class D IP address to identify the group, thus allowing a restricted broadcast of messages to this specific group.
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63. *TCP/IP Application Presentation Session TELNET FTP SMTP DNS SNMP DHCP
RIP
Transport
RTP
RTCP
Transmission
Control Protocol
User Datagram
Protocol
OSPF
IGMP
ICMP
Network
Internet Protocol
ARP
Data link
Physical
Ethernet
Token Bus
Token Ring
FDDI
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64. Flow control and QoS
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65. Quality of Service Quality of Service (QoS): QoS routing:
The idea that transmission quality (rates, error rates, bandwidth and jitter) can be measured, improved, and, to some extent, guaranteed in advance.
QoS routing:
A special type of connection-oriented dynamic routing in which different messages or packets are assigned different priorities.
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66. Categories of Traffic Elastic traffic, such as FTP, email, etc
Allow fluctuating bandwidth, the total transmission time is important
The data must correctly transmitted
Service quality concerns mainly in transmission delay and error control.
Real-time traffic, such as videoconferencing.
Demands certain bandwidth with isochronous features
Tolerates some level of errors.
Service quality criteria include: Throughput, Delay, Delay variation (jitter), and Packet loss.
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67. Routing at Routers Bandwidth schedule Queue management
First in first out
Round robin
Prioritization
Queue management
Packet discard policy
Congestion control
Packet arrival
Packet forward
Packet Drop
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68. Network Congestion What is traffic congestion?
The buffer in a forwarding device overflows. This results packet losses and incur retransmission. The transmission will worsen the situation.
Network congestion control is very important in flow management
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69. Internet Flow Control Internet flow control algorithm
Slow start, congestion avoidance
Router queue management
Random early detection (RED) for packet dropping
Data flow scheduling
FIFO, round robin, priority queueing, weighted fair queueing
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70. Internet Flow Control
Slow Start algorithm (RFC2001). To avoid router running out of space
Two windows: advertised window by receiver and congestion window by sender. The congestion window is flow control imposed by the sender, while the advertised window is flow control imposed by the receiver.
The congestion window is initialized to one segment. Each time an ACK is received, the congestion window is increased by one segment. The sender can transmit up to the minimum of the congestion window and the advertised window.
The sender starts by transmitting one segment and waiting for its ACK. When that ACK is received, the congestion window is incremented from one to two, and two segments can be sent.
When each of those two segments is acknowledged, the congestion window is increased to four. This provides an exponential growth.
At some point the capacity of the internet can be reached, and an intermediate router will start discarding packets. This tells the sender that its congestion window has gotten too large.
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71. Internet Flow Control Congestion Avoidance (RFC2001)
Sets congestion window to one segment.
When congestion occurs (indicated by a timeout or the reception of duplicate ACKs), one-half of the current window size (the minimum of congestion window and the receiver's advertised window, but at least two segments) is saved as X.
When new data is acknowledged by the other end, increase congestion window, but the way it increases depends on whether TCP is performing slow start or congestion avoidance. If congestion window is less than or equal to X, TCP is in slow start; otherwise TCP is performing congestion avoidance.
Slow start continues until TCP is halfway to where it was when congestion occurred (since it recorded half of the window size that caused the problem in step 2), and then congestion avoidance takes over.
Congestion avoidance dictates that congestion window be incremented a linear growth of congestion window, compared to slow start's exponential growth.
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72. Internet transmission services
Best-effort services
The Internet treats all packet equally.
Integrated services (IntServ)
IntServ refers to mechanisms that enable users to request a particular QoS for a flow of data.
Differentiated Services (DiffServ)
DiffServ Use type-of-service in IPv4 header to indicate the required service quality.
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73. Integrated Services
Routers require additional functionality to handle QoS-based service
IETF is developing suite of standards to support this
Two standards have received widespread support
Integrated Services Architecture (ISA): To enable the provision of QoS support over IP-based Internet.
Resource ReSerVation Protocol (RSVP)
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74. Integrated Services Architecture
Enables provision of QoS over IP-networks
Features include
Admission Control: A new flow needs a reservation for QoS
Routing Algorithm: more parameters are considered other than just delay
Queuing Discipline: Queuing policy takes into account of different requirements
Discard Policy: Particularly for congestion management
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75. *Resource Reservation Protocol (RSVP)
A tool for prevention of congestion through reservation of network resources
Can be used in unicast or multicast transmissions
Receivers (not senders) initiate resource reservations
Operation:
Complexity is in multicast transmission
RSVP uses two basic messages: Resv and Path. In multicast, Resv messages generated by one of the multicast group receivers propagate upstream through distribution tree and create soft state in routers. Once it reaches the sender, hosts are enabled to set parameters for the first hop. Path is used to provide upstream routing information and sent from senders via the down stream tree to all receivers
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76. Differentiated Services (DiffServ)
Provides QoS based on user group needs rather than traffic flows
Can use current IPv4 octets
Service-Level Agreements (SLA) govern DiffServ, eliminating need for application-based assignment
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77. IPv4 Type of Service Field
Allows user to provide guidance on individual datagrams
3-bit precedence subfield
Indicates degree of urgency or priority
Queue Service & Congestion Control
4-bit TOS subfield
Provides guidance on selecting next hop
Route selection, Network Service, & Queuing Discipline 1 2 3 4 5 6 7
Precedence
TOS
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78. DiffServ Domains Border component Host Host Interior component
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79. DiffServ Operation Routers are either boundary nodes or interior nodes
Interior nodes use per-hop behavior (PHB) rules
Boundary nodes have PHB & traffic conditioning
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80. Token Bucket Scheme Max Burstiness: RT + B R: Token replenishment rate
B: Bucket size
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81. TCP/IP Configuration Information
At least four pieces of information needed for a client computer TCP/IP configuration
IP address
Subnet mask
Gateway IP address
Domain name Server IP address
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82. A TCP/IP Example
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83. A TCP/IP Example
How a client access a web server in the same subnet with a known address?
How a client access a web server in a different subnet with a known address?
How a client access a web server in the same subnet with an unknown address?
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84. Sender Receiver Application Layer Application Layer Transport Layer
HTTP
Request
HTTP
Request
Transport
Layer
Transport
Layer
TCP
HTTP
Request
TCP
HTTP
Request
Network
Layer
Network
Layer IP
TCP
HTTP
Request IP
TCP
HTTP
Request
Data Link
Layer
Data Link
Layer
Ethernet IP
TCP
HTTP
Request
Ethernet IP
TCP
HTTP
Request
Physical
Layer
Physical
Layer
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85. Data transmission using TCP/IP and Ethernet
packet header IP
packet
TCP
packet
HTTP
packet
User Data
Ethernet
packet trailer
IP address
Data link layer address
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