Transcript Lecture_TCP_IP_ Routing_Part

Chapter 5 – TCP/IP: Routing – Part 2
Dr. V.T. Raja
Oregon State University
TCP/IP – Routing - Part 4b
Outline
Routing Protocols
Routing Tables
Unicast messages
Broadcast messages
Routing Protocols
Autonomous System of Networks
Each large organizational network connected to Internet
(e.g., AT&T, IBM, OSU) can be viewed as a separate
autonomous system
Computers within each autonomous system usually
exchange routing information among themselves
Routing protocols used inside an autonomous system
are called interior routing protocols
Routing protocols used between autonomous systems
are called exterior routing protocols
Routing Protocols
Internet Control Message Protocol (ICMP)
– Error advisement
• Example: Ping command – Host (Destination)
unreachable
– Flow control
• Requesting a device to reduce the rate at which it
transmits
Routing Protocols
Routing Information Protocol (RIP)
–
–
–
–
Dynamic distance vector routing protocol
Scalability: 15-hop limit
Good for smaller networks
Broadcast interruptions (entire routing table
transmitted very often)
– Slower convergence – Takes a longer time for
routing tables to be transmitted very often
Routing Protocols
Open Shortest Path First (OSPF)
– Link State Dynamic Routing Protocol
– Faster convergence
• Designated router updated on changes in route status
Border Gateway Protocol (BGP)
– Distance Vector Dynamic Routing Protocol
– Used between autonomous systems
– Changes in route status info transmitted
Comparison of Routing Protocols
RIP
OSPF
BGP
Interior/Exterior?
Interior
Interior
Exterior
Type (Distance Vector/
Link State?)
Distance Vector Link State
Routing update content
Routing Table
(Routing Table/Updates?)
Distance Vector
Updates only
Updates only
Routing update frequency Very often (e.g., Updates only
every 30
seconds)
Updates only
Convergence
(Slow/Fast/Complex?)
Slow
Fast
Complex
Scalability
Poor
Very Good
Very Good
TCP/IP and Routing
TCP/IP can use RIP, ICMP,
OSPF, BGP
It is compatible with distance
vector and link state
protocols
Can operate either as
connectionless or connection
oriented routing
Can support QoS routing (a
new version of OSPF called
QOSPF)
Routing Tables
Routing Table for B
Destination
A
C
D
E
F
G
Default
Route
A
C
A
E
E
C
A
Routing Table (Continued)
Network
Destination
Netmask
Gateway
Interface
Metric
(Cost)
Default route: 0.0.0.0
0.0.0.0
128.193.76.1
128.193.77.65
20
Loop back (Self)
127.0.0.0
255.0.0.0
127.0.0.1
127.0.0.1
1
Network Route
128.193.76.0
255.255.254.0
128.193.77.65
128.193.77.65
20
Local Host
128.193.77.65
255.255.255.255
127.0.0.1
127.0.0.1
20
Subnet broadcast
128.193.255.255
255.255.255.255
128.193.77.65
128.193.77.65
20
240.0.0.0
128.193.77.65
128.193.77.65
20
255.255.255.255
128.193.77.65
128.193.77.65
1
Multicast: 224.0.0.0
Broadcast
255.255.255.255
Introduction
Router Forwarding Table
Destination Address Prefix (Mask)
Metric (Cost)
Interface Next-Hop Router
172.19.
16 (255.255.0.0) 47
2
G
172.19.17
24
55
3
H
172.229.
16
34
1
F
172.229.
16
20
3
H
172.15.122
24
3
3
Local
0.0.0.0
0
5
3
H
Unicast/Broadcast
Unicast
– Most common type of
message transmitted (from one
sender to one final destination)
– Example:
Broadcast
– Subnet broadcast
• Example
– LAN broadcast
• Example
Multicast