1. Experiential Learning Workshop on Basics of Transport/Network Layer
July 05, 2018
Dr. Ram P Rustagi
Professor, CSE Dept
KSIT, Bangalore
RPR/Experiential Learning - Transport Layer

2. Resources & Acknowledgements
Learning.html
Articles in ACCS Journal du
Slides ms
Example web pages, and programs
Acknowledgements:
Computer Networking: Kurose, Ross
RPR/Experiential Learning - Transport Layer

3. Day 1: Basics of Networking
Overview
Introduction to basic networking Tools
Handson 1: using networking tools
IP and TCP Headers
Analysis of layers in IP, TCP/UDP
Handson-2: Analyze IP and TCP headers
Fragementation and PMTU Discovery
ICMP Errors, NAT
Handson-3: ICMP errors, NAT, PMTU
ARP, DHCP, Proxy, Gratuituous ARP
Handson-4: ARP protocol
Summary
RPR/Experiential Learning - Transport Layer

4. RPR/Experiential Learning - Transport Layer
Day 2: Basics of HTTP
Overview: HTTP and Versions
Request and Response Format, Basic headers
Handson-1: Analyze HTTP headers, status codes
HTTP persistent and non-persistent connections
Apache config support for persistent connections
Handson-2: Configuring persistent connections
Web caching, HTTP headers for cache control
Handson-3: Cachecing, E-tags
HTTP cookies mechanisms
Secure cookies, sub-domains, HTTP only cookies
Handson-4: using cookies, secure cookies
Summary
RPR/Experiential Learning - Transport Layer

5. Day 3: Basics of Transport Layer
Overview: Transport layer, requirements
Connection less and connection oriented transport
Handson-1: Analyze TCP 4-tuple and UDP 2- tuple
Pseudo headers in TCP/UDP
Concurrent communications : UDP and TCP
Handson-2: Using data with same checksum
TCP and UDP Error control, TCP flags
Handson-3: Connection Mgmt, Queues, and states
TCP Streaming, Reliability misnomer,
UDP message boundaries
Handson-4: TCP Streams and UDP messages
Summary
RPR/Experiential Learning - Transport Layer

6. Day 4: Basics of Web Security
Overview: HTTPS protocol
Server certificate and server authentication
Mixed content and browser warnings
Locks icons and HTTP Status
Handson-1: HTTPS website with mixed content
MITM attack and ARP spoofing
MITM with browser and information stealing
Understanding HSTS, CSP
Handson-2: Implementing ARP Spoofing
Summary
RPR/Experiential Learning - Transport Layer

7. Day 3: Basics of Transport Layer
Overview: Transport layer, requirements
Connection less and connection oriented transport
Handson-1: Analyze TCP 4-tuple and UDP 2- tuple
Pseudo headers in TCP/UDP
Concurrent communications : UDP and TCP
Handson-2: Using data with same checksum
TCP and UDP Error control, TCP flags
Handson-3: Connection Mgmt, Queues, and states
TCP Streaming, Reliability misnomer,
UDP message boundaries
Handson-4: TCP Streams and UDP messages
Summary
RPR/Experiential Learning - Transport Layer

8. Internet transport-layer protocols
reliable, in-order delivery (TCP)
congestion control
flow control
connection setup
unreliable, unordered delivery: UDP
no-frills extension of “best- effort” IP
services not available:
delay guarantees
bandwidth guarantees
application
transport
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
logical end-end transport
network
data link
physical
network
data link
physical
network
data link
physical
application
transport
network
data link
physical
network
data link
physical
Source: Kurose, Ross: Computer Networking, A Top Down Approach
RPR/Experiential Learning - Transport Layer

9. RPR/Experiential Learning - Transport Layer
Port Numbers
IANA ranges for port numbers
Well known ports: 1 to 1023
Assigned and controlled by IANA
Reserved ports: to 49151
Only registered with IANA
Not assigned or controlled by IANA
Dynamic ports: to 65535
Can be used by any process
Also used as ephemeral ports
RPR/Experiential Learning - Transport Layer

10. Transport layer protocol
How would you design it
What would you like to achieve
At simplest level
Multiplex/de-multiplex
At advanced level
Reliable delivery i.e. Data integrity
Include error detection and retransmissions
Sequential delivery
Would need buffer
Message boundaries
Security
RPR/Experiential Learning - Transport Layer

11. Multiplexing/demultiplexing
handle data from multiple
sockets, add transport header (later used for demultiplexing)
multiplexing at sender:
use header info to deliver
received segments to correct
socket
demultiplexing at receiver:
application
application P1 P2
application
socket P3 P4
transport
process
transport
network
transport
link
network
network
physical
link
link
physical
physical
Source: Kurose, Ross: Computer Networking, A Top Down Approach
RPR/Experiential Learning - Transport Layer

12. Connectionless demux: example
clientSocket =
(9157);
clientSocket = (5775);
application
application
application P1 P3 P4
transport
transport
transport
network
network
network
link
link
link
physical
physical
physical
source port: 6428
dest port: 9157
source port: ?
dest port: ?
source port: 9157
dest port: 6428
source port: ?
dest port: ?
Source: Kurose, Ross: Computer Networking, A Top Down Approach
RPR/Experiential Learning - Transport Layer

13. Connection-oriented demux
Transport layer socket identified by 4(or 5)- tuple:
source IP address
source port number
dest IP address
dest port number
(Protocol (TCP))
demux: receiver uses all four (or five) values to direct segment to appropriate socket
server host may support many simultaneous TCP sockets:
each socket identified by its own 4-tuple
web servers have different sockets for each connecting client
non-persistent HTTP will have different socket for each request
RPR/Experiential Learning - Transport Layer

14. Connection-oriented demux: example
Source: Kurose, Ross: Computer Networking, A Top Down Approach
application
application
application P4 P5 P6 P3 P2 P3
transport
transport
transport
network
network
network
link
link
link
physical
physical
physical
server: IP address B
source IP,port: B,80
dest IP,port: A,9157
host: IP address C
host: IP address A
source IP,port: C,5775
dest IP,port: B,80
source IP,port: A,9157
dest IP, port: B,80
source IP,port: C,9157
dest IP,port: B,80
three segments, all destined to IP address: B,
dest port: 80 are demultiplexed to different sockets
RPR/Experiential Learning - Transport Layer

15. Connection-oriented demux: example
threaded server
application
application
application P4 P3 P2 P3
transport
transport
transport
network
network
network
link
link
link
physical
physical
physical
server: IP address B
source IP,port: B,80
dest IP,port: A,9157
host: IP address C
host: IP address A
source IP,port: C,5775
dest IP,port: B,80
source IP,port: A,9157
dest IP, port: B,80
source IP,port: C,9157
dest IP,port: B,80
Source: Kurose, Ross: Computer Networking, A Top Down Approach
RPR/Experiential Learning - Transport Layer
Transport Layer
3-14

16. Transport Layer Protocol Characteristics
Connection less
May arrive out of order
In order delivery requires pkts to be numbered.
No acknowledgement, Packets may be lost
No prior handshake
Connection oriented
Setup, data transfer and teardown phase
Provides reliability, ordered delivery
Handles error control in a better way *
RPR/Experiential Learning - Transport Layer

17. Transport Layer Reliability Support
Needs error and flow control, loss detection
Compels slower service
Unreliable protocol
No extra overheads
Reliability at data link layer
Provides error and flow control
Why do we need it at Transport layer when Link layer provides the same *
RPR/Experiential Learning - Transport Layer

18. UDP Design Requirement
How to design a simple transport layer ?
Just provide transport on top of IP
Multiplexing and demultiplexing
Little bit of error checking
No handshake
Rest all has to be managed by application
Application practically talks to IP
DNS uses UDP
What happens when query/response is lost? *
RPR/Experiential Learning - Transport Layer

19. RPR/Experiential Learning - Transport Layer
UDP: segment header
length, in bytes of UDP segment, including header
32 bits
source port #
dest port #
length
checksum
includes pseudo header
application
data
(payload)
UDP segment format
Source: Kurose, Ross: Computer Networking, A Top Down Approach
RPR/Experiential Learning - Transport Layer

20. Pseudo header for checksum
| source address |
| destination address |
| zero |protocol| UDP length |
Pseudo
Headers
| Source | Destination |
| Port | Port |
| | |
| Length | Checksum |
| data octets ...
Actual
Headers
Src: RFC 768
RPR/Experiential Learning - Transport Layer

21. Internet checksum: example RFC 1071
Consider 3 words
x6660
x5555
x8F0C
x14AC1
Wrapping around the overflow bit makes it
x4AC2
1’s complement will be
xB53D
RPR/Experiential Learning - Transport Layer

22. Data with Same Checksum
Adding 0xFFFF to checksum results in same value
In UDP checksum computation
length is used twice
Once in UDP header, once in psuedo headers
Consider the data addition that adds up to 0xFFFF
First thought: use 0x5555 (i.e. ‘UU’) three times
This increases length by 6, (which is counted twice)
Thus addition of 6 bytes should add to 0xFFF3
Add 0xUQUQUQ (0x )
Yields same checksum
Any other combination?
RPR/Experiential Learning - Transport Layer

23. Data with Same Checksum
Given the data text ‘ABCDEF’,
How it can be changed to use same checksum
Swapping two bytes?
e.g. CDABEF, or EFCDAB, or ABEFCD etc.
Modifying the data without swapping
BCBCEF?
AAAAIL?
RPR/Experiential Learning - Transport Layer

24. RPR/Experiential Learning - Transport Layer
TCP Characteristics
point-to-point: One sender, one receiver
reliable, in-order byte steam: No “message boundaries”
pipelined: TCP congestion and flow control set window size
full duplex data: Bi-directional data flow in same connection
MSS: maximum segment size, determined from link/frame size
connection-oriented: Handshaking (exchange of control msgs) inits sender, receiver state before data exchange
flow controlled: Sender will not overwhelm receiver *
RPR/Experiential Learning - Transport Layer

25. RPR/Experiential Learning - Transport Layer
Basis of TCP Handshake
Q: will 2-way handshake always work in network?
variable delays
retransmitted messages (e.g. req_conn(x)) due to message loss
message reordering
can’t “see” other side
2-way handshake:
Let’s talk
ESTAB OK
ESTAB
choose x
req_conn(x)
ESTAB
acc_conn(x)
ESTAB
Source: Kurose, Ross: Computer Networking, A Top Down Approach
RPR/Experiential Learning - Transport Layer

26. Basis of TCP Handshake 2-way handshake failure scenarios:
Source: Kurose, Ross: Computer Networking, A Top Down Approach
2-way handshake failure scenarios:
choose x
req_conn(x)
ESTAB
acc_conn(x)
client terminates
ESTAB
choose x
req_conn(x)
acc_conn(x)
data(x+1)
accept
connection
x completes
server
forgets x
retransmit
req_conn(x)
ESTAB
half open connection!
(no client!)
retransmit
req_conn(x)
ESTAB
data(x+1)
accept
client terminates
server
forgets x
connection
x completes
RPR/Experiential Learning - Transport Layer

27. RPR/Experiential Learning - Transport Layer
TCP 3-Way Handshake
client state
LISTEN
server state
SYNSENT
SYNbit=1, Seq=x
choose init seq num, x
send TCP SYN msg
SYN RCVD
ESTAB
SYNbit=1, Seq=y
ACKbit=1; ACKnum=x+1
choose init seq num, y
send TCP SYNACK
msg, acking SYN
ACKbit=1, ACKnum=y+1
received SYNACK(x)
indicates server is live;
send ACK for SYNACK;
this segment may contain
client-to-server data
received ACK(y)
indicates client is live
ESTAB
Source: Kurose, Ross: Computer Networking, A Top Down Approach
RPR/Experiential Learning - Transport Layer

28. RPR/Experiential Learning - Transport Layer
TCP Timeouts
On timer expiration
Retransmits the segment that is not yet acked
Sets the TimeoutInterval double of previous value
Example: First time out 0.75s
2nd/3rd/… timeout will be 1.5s,3.0s,…
On receipt of Ack, it is computed again
Provides a limited form of congestion control *
RPR/Experiential Learning - Transport Layer

29. TCP Flow Control buffered data free buffer space
to application process
buffered data
free buffer space
RcvBuffer
rwnd
TCP segment payloads
receiver-side buffering
src: Computer Networking : Kurose, Ross *
RPR/Experiential Learning - Transport Layer

30. Typical Understanding of TCP
src: ftp://
RPR/Experiential Learning - Transport Layer

31. TCP Client/Server Communication
3-way handsake
Conn Establishment {
Data Request
Data Response
Connecion Close
RPR/Experiential Learning - Transport Layer

32. RPR/Experiential Learning - Transport Layer
\ active OPEN
| CLOSED | \
< \ \ create TCB
| ^ \ \ snd SYN
passive OPEN | | CLOSE \ \
| | \ \
create TCB | | delete TCB \ \
V | \ \
CLOSE | \
| LISTEN | | |
delete TCB | |
rcv SYN | | SEND | |
| | | V
snd SYN,ACK / \ snd SYN
| |< >| |
| SYN | rcv SYN | SYN |
| RCVD |< | SENT |
| | snd ACK | |
| | | |
rcv ACK of SYN \ / rcv SYN,ACK
| | |
| x | | snd ACK
| V V
| CLOSE
| | ESTAB |
| snd FIN
TCP Connection State Diagram
TCP
State Transition Diagram
src: RFC 793
RPR/Experiential Learning - Transport Layer

33. RPR/Experiential Learning - Transport Layer
| CLOSE
| | ESTAB |
| snd FIN
| CLOSE | | rcv FIN
V | |
snd FIN / \ snd ACK
| FIN |< >| CLOSE |
| WAIT-1 | | WAIT |
rcv FIN \
| rcv ACK of FIN | CLOSE |
| snd ACK | |
V x V snd FIN V
|FINWAIT-2| | CLOSING | | LAST-ACK|
| rcv ACK of FIN | rcv ACK of FIN |
| rcv FIN | Timeout=2MSL |
| x V x V
\ snd ACK delete TCB
>|TIME WAIT| >| CLOSED |
TCP Connection State Diagram
TCP
State Transition Diagram
src: RFC 793
RPR/Experiential Learning - Transport Layer

34. RPR/Experiential Learning - Transport Layer
TCP Connection State
Use netstat -nat to know the current state
LISTEN
SYN-RECD
SYN-SENT
ESTABLISHED
CLOSED -> LAST_ACK
FIN_WAIT1
FIN_WAIT2
TIME_WAIT
Note: you may have to install net-tools
sudo apt install net-tools
RPR/Experiential Learning - Transport Layer

35. Setup Requirement: TCP/UDP
RPR/Experiential Learning - Transport Layer

36. Hands-On 1a: UDP Checksum
Between two machines communicate UDP packets using nc (-u option).
Send data content as below and compute the checksum using the IP Address and port number used and verify it with checksum value in wireshark capture.
“ABCDE” and
“ABCDEUQUQUQ”
Are the two checksum same? Why or why not?
What other characters can you attach to “ABCDE” to have the same checksum value
DrAIT/Basics of Socket Programming
RPR

37. Hands-On 1b: UDP Msg Boundary
Data Transfer
Clients sends data (100 bytes) every 2s (10 times)
AA.. (1st pkt), BB..(2nd pkt), …, JJ..(10th pkt)
Server reads 40 bytes at a time
What would server receive and display? S1 S2
DrAIT/Basics of Socket Programming
RPR

38. Hands-On 1c: UDP Packet Loss
Data Transfer
Clients sends data (100 bytes) every 2s (10 times)
AA.. (1st pkt), BB..(2nd pkt), …, JJ..(10th pkt)
Break the link between switch at 7th sec and restore after 12 sec
Server reads full 100 bytes.
What would server receive and display? S1 S2
DrAIT/Basics of Socket Programming
RPR

39. Hands-On 1d: TCP Streaming
Data Transfer
Clients sends data (100 bytes) every 2s (10 times)
AA.. (1st pkt), BB..(2nd pkt), …, JJ..(10th pkt)
Server reads 30 bytes at a time
What would server display S1 S2
DrAIT/Basics of Socket Programming
RPR

40. Hands-On 1e:TCP Recovery
Data Transfer
Clients sends data (100 bytes) every 2s (10 times)
AA.. (1st pkt), BB..(2nd pkt), …, JJ..(10th pkt)
Break the link between switch at 7th sec and restore after 12th sec
Server reads 30 bytes at a time
What would server receive: S1 S2
DrAIT/Basics of Socket Programming
RPR

41. Hands-On 1f:TCP Timeouts
TCP timeout study
T0: break the link between S1 and S2
Connect client to server
How many SYN packets are transmitted
What is the time difference between SYN pkts
When does client give up
Repeat the experiment, but with restoring the link after 1 minute. S1 S2
DrAIT/Basics of Socket Programming
RPR

42. Hands-On 1g:TCP Recovery & Streaming
Data Transfer
Clients sends data (100 bytes) every 2s (10 times)
AA.. (1st pkt), BB..(2nd pkt), …, JJ..(10th pkt)
Break the link between switch at 7th sec and restore after 12th sec
Server reads 30 bytes at a time
Study the timeouts of retransmission
Analyze the segments on retransmission
Do multiple segments combine in a single transmit
What happens if combination is more than MTU?
DrAIT/Basics of Socket Programming
RPR

43. Handson 1h: Study of TCP Queuing
Run TCP server (nc -l <port>)
Connect multiple clients to it
Look the TCP connections at both clients and server
All should show ESTABLISHED
Exchange data from all clients
When server responds, which client gets it
What happens to data of other clients
What happens to other clients when communicating client closes the connection
RPR/Experiential Learning - Transport Layer

44. RPR/Experiential Learning - Transport Layer
Session 2 : setup A ……
RPR/Experiential Learning - Transport Layer

45. RPR/Experiential Learning - Transport Layer
Session 2: Setup B 1 2
Router N1 N2
Switch 2
Ha: /24
Hc: /24
Hb: /24
RPR/Experiential Learning - Transport Layer

46. ARP - Address Resolution Protocol
Packet delivery to a host requires two addresses
Logical address - IP Address
Physical address - MAC address
Need to find mapping from logical to physical
ARP is used - RFC 826
Src: Forouzan -
Computer Networking
RPR/Experiential Learning - Network Basics

47. RPR/Experiential Learning - Network Basics
ARP - 4 cases
MAC
MAC
Src: Forouzan -
Computer Networking
RPR/Experiential Learning - Network Basics

48. RPR/Experiential Learning - Network Basics
ARP
ARP Request and Reply
ARP Request is broadcast
ARP Reply is Unicast
Other forms of ARP
Proxy ARP (RFC 1027)
Reverse ARP (RFC 903)
Gratuitous ARP
RPR/Experiential Learning - Network Basics

49. RPR/Experiential Learning - Network Basics
Proxy ARP
Router (Proxy ARP Server) replied to all requests
Used when
Splitting a network w/o changing hosts netmask
Mobile IP
Src: Forouzan -
Computer Networking
RPR/Experiential Learning - Network Basics

50. RPR/Experiential Learning - Network Basics
Reverse ARP
Reverse ARP (RARP) : RFC 903
Used for diskless stations
Organization does not have enough IP Address
Target as MAC Bcast does not cross the router
Needs one RARP server for each subnet
BOOTP
Improvement over RARP
Has a relay agent to forward across network
Static mapping of MAC to IP
Manageability issues
DHCP - replaces BOOTP
RPR/Experiential Learning - Network Basics

51. RPR/Experiential Learning - Network Basics
Gratuitous ARP
Ref:
Gratuitous ARP Request
Both src and dstn IP is set to that of m/c
Dstn MAC is broadcast i.e. ff:ff:ff:ff:ff:ff
Ordinarily, no reply will occur normally
if a m/c exists, it may respond
Gratuitous ARP Reply (for HA, LB, Spoofing)
A reply to which no request has occurred
RPR/Experiential Learning - Network Basics

52. RPR/Experiential Learning - Network Basics
Gratuitous ARP
Why Gratuitous ARP
Help detect IP conflicts
if a m/c receives G-ARP req which is its own, implies IP conflict
Helps in updating other m/cs ARP tables
Used in clustering solutions, when IP is moved
Helps inform the switch to update its port table
Each time an i/f comes up (after down), sends G- ARP
RPR/Experiential Learning - Network Basics

53. Life of Packet in Internet
DNS Record:
->
Q: User at host ‘A’ types ping -c1 What is the packet flow?
RPR/Experiential Learning - Network Basics

54. RPR/Experiential Learning - Network Basics
DHCP
Goal: allow host to dynamically obtain its IP address
Renew its lease on address in use, on lease expiry
Preferably gets the same address, not guaranteed
Support for mobile users who join network
Guarantee: only one address to only one client
Retain DHCP client address across reboots
not guaranteed
Retain DHCP client configs across server reboot
Must coexist with statically assigned addresses
Should work with DHCP server failovers
Interoperate with BOOTP relay agents
RPR/Experiential Learning - Network Basics

55. DHCP: more than IP addresses
DHCP can return more than just allocated IP address on subnet:
Address of first-hop router for client
Name and IP address of DNS sever
Network mask (indicating network versus host portion of address)
RPR/Experiential Learning - Network Basics

56. DHCP: Dynamic Host Configuration Protocol
DHCP overview:
An extension of BOOTP mechanism
Host broadcasts “DHCP Discover” msg [optional]
DHCP server responds with “DHCP Offer” msg
more than one server can make the offer
client can choose which server to send request to
Host requests IP address: “DHCP Request” msg
DHCP server sends address: “DHCP Ack” msg
Renewal happens with DHCP Request/ack
On completion, client sends DHCP Release msg
Practically not seen
RPR/Experiential Learning - Network Basics

57. RPR/Experiential Learning - Transport Layer
Handson-2a: ARP
Understand ARP working.
Know current ARP working
arp -an
ping Hx (where Hx is not in ARP table) but live
See the ARP table to have Hx entry
ping Hy (where Hy is not live)
What does ARP table shows
RPR/Experiential Learning - Transport Layer

58. RPR/Experiential Learning - Transport Layer
Handson-2b: ARP ……
Create state ARP entry for Hz not in ARP table
sudo arp -s <IP Addr> <MAC Addr>
ping Hz
No ARP Request should be transmitted.
ping -b -c5 <Broadcast address>
RPR/Experiential Learning - Transport Layer

59. Handson-2c: Gratuituos ARP……
Use arping to issue gratuituous ARP
On Ha, assign IP of Hc
sudo ip addr del /24 dev eth0
sudo ip addr add /24 dev eth0
sudo arping -A -I eth
Analyze ARP table of Hb
RPR/Experiential Learning - Transport Layer

60. Handson-2d: ICMP Redirect
Ha: 10.x.1.1/24
Hc: 10.x.1.201/24 1 2
Hb:10.x.1.101/24
Switch
lo:10.x.2.101/24
lo:10.x.3.201/24
On Ha
sudo ip route add 10.x.2.0/24 via 10.x.1.201
sudo ip route add 10.x.3.0/24 via 10.x.1.101
On Hb
sudo ip route add 10.x.3.0/24 via 10.x.1.201
On Hc
sudo ip route add 10.x.3.0/24 via 10.x.1.101
RPR/Experiential Learning - Network Basics

61. Handson-3a: Basic Routing
Hc: /24 1 2
Router
Hb-e2: /24
Hb-e1: /24
Enable routing on Hb
sudo sysctl -w net.ipv4.ip_forward=1
Define routing of /24 on Ha
Define routing of /24 on Hc
Ping Hc from Ha
Note down the ARP table of Ha and Hc.
It should show MAC addresses of Hb
RPR/Experiential Learning - Transport Layer

62. RPR/Experiential Learning - Transport Layer
Handson-3b: Proxy ARP
Ha: /22
Hc: /22 1 2
Router
Hb-e2: /24
Hb-e1: /24
Enable proxy ARP, and routing on Hb
sudo sysctl -w net.ipv4.conf.all.proxy_arp=1
sudo sysctl -w net.ipv4.ip_forward=1
Ping Hc from Ha
Note down the ARP table of Ha and Hc.
It should show MAC addresses of Hb
RPR/Experiential Learning - Transport Layer

63. Handson-3c: PMTU Discovery
Ha: 10.x.1.1/24
Hc: 10.x.3.201/24 1 2
Hb-e1:10.x.1.101/24
Router
Hb-e2:10.x.3.1/24
Router
On Hb
sudo ip link set dev eth2 mtu 1000
sudo sysctl -w net.ipv4.ip_forward=1
On Ha
ping -c 2 —s p
RPR/Experiential Learning - Network Basics

64. Handson-3d: IP Fragmentation
Ha: 10.x.1.1/24
Hc: 10.x.3.201/24 1 2
Hb-e1:10.x.1.101/24
Router
Hb-e2:10.x.3.1/24
Router
On Hb
sudo ip link set dev eth2 mtu 1000
sudo sysctl -w net.ipv4.ip_forward=1
On Ha
./udp_client -b s p c 2
RPR/Experiential Learning - Network Basics

65. Handson-4a: Longest Prefix Match
LAN:
eno1
eno1
eno1 Hb
Router
Router ……
USB
USB
Routing table of Hb
10.x.1.65/24
10.x.1.34/27
10.x.1.129/26
RPR/Experiential Learning - Transport Layer

66. RPR/Experiential Learning - Transport Layer
Summary
Transport Layer Multiplexing
UDP Message boundary
TCP Streaming
TCP Reliability: timeouts and retransmits
ICMP errors: Redirect, TTL expiry
ARP, Gratuituous ARP
IP routing, Longest prefix match
RPR/Experiential Learning - Transport Layer

67. RPR/Experiential Learning - Transport Layer
Thank You
RPR/Experiential Learning - Transport Layer