ch 21. other ip-related protocols
DESCRIPTION
Ch 21. Other IP-related Protocols. 21.1 Address Mapping. IP packets use logical address , and need to be encapsulated in a frame at data link layer, which requires physical address Address Resolution Protocol (ARP) ARP request – broadcast ARP reply – unicast - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Ch 21. Other IP-related Protocols](https://reader030.vdocument.in/reader030/viewer/2022032709/56813196550346895d980815/html5/thumbnails/1.jpg)
Ch 21. Other IP-related Protocols
![Page 2: Ch 21. Other IP-related Protocols](https://reader030.vdocument.in/reader030/viewer/2022032709/56813196550346895d980815/html5/thumbnails/2.jpg)
21.1 Address Mapping
• IP packets use logical address, and need to be encapsulated in a frame at data link layer, which requires physical address
• Address Resolution Protocol (ARP)– ARP request
– broadcast– ARP reply
– unicast– Information is cached
at the sender
![Page 3: Ch 21. Other IP-related Protocols](https://reader030.vdocument.in/reader030/viewer/2022032709/56813196550346895d980815/html5/thumbnails/3.jpg)
ARP Packet Format
Length of the physical address
Length of the logical address
![Page 4: Ch 21. Other IP-related Protocols](https://reader030.vdocument.in/reader030/viewer/2022032709/56813196550346895d980815/html5/thumbnails/4.jpg)
Example1. The sender A and the receiver B are hosts (local network). IP is
mapped to a physical address.2. The sender A is a host and the receiver B is a router. (packet is sent to
another network)3. The sender A and receiver B are routers (sent to another network). 4. The sender A is a router and the receiver B is a host.
![Page 5: Ch 21. Other IP-related Protocols](https://reader030.vdocument.in/reader030/viewer/2022032709/56813196550346895d980815/html5/thumbnails/5.jpg)
Proxy ARP
• When a local network consists of multiple subnetworks
![Page 6: Ch 21. Other IP-related Protocols](https://reader030.vdocument.in/reader030/viewer/2022032709/56813196550346895d980815/html5/thumbnails/6.jpg)
Other Address Mapping
• Reverse Address Resolution Protocol (RARP)– Find a logical address corresponding to a physical address
• Bootstrap Protocol (BOOTP)– Application level protocol to provide mapping from physical address
to logical address– Set source IP address to all 0’s, and set destination IP address to all 1’s
• Dynamic Host Configuration Protocol (DHCP)– Provides static and dynamic address allocation that can be manual or
automatic– A host may move from one network to another– DHCP provides temporary IP addresses
![Page 7: Ch 21. Other IP-related Protocols](https://reader030.vdocument.in/reader030/viewer/2022032709/56813196550346895d980815/html5/thumbnails/7.jpg)
21.2 ICMP• IP provides unreliable and connectionless datagram delivery. It lacks of error
control and assistance mechanisms.• What happens if
– a router must discard a datagram because it cannot fined a router;– or time to live field has a zero value– The final destination host must discard all fragments of a datagram because it is not
received all fragments, with a predetermined time limit.• Internet Control Message Protocol
– Error-reporting (about a router or a host) or query message
![Page 8: Ch 21. Other IP-related Protocols](https://reader030.vdocument.in/reader030/viewer/2022032709/56813196550346895d980815/html5/thumbnails/8.jpg)
Error Reporting
• Encapsulation of error reporting message– Copy (IP headers + 8 bytes data) of the received pkt
![Page 9: Ch 21. Other IP-related Protocols](https://reader030.vdocument.in/reader030/viewer/2022032709/56813196550346895d980815/html5/thumbnails/9.jpg)
Query Message
• Encapsulation of query message
![Page 10: Ch 21. Other IP-related Protocols](https://reader030.vdocument.in/reader030/viewer/2022032709/56813196550346895d980815/html5/thumbnails/10.jpg)
ICMP Application
• “ping”– To find if a host is alive– ICMP echo-request and echo-reply message
![Page 11: Ch 21. Other IP-related Protocols](https://reader030.vdocument.in/reader030/viewer/2022032709/56813196550346895d980815/html5/thumbnails/11.jpg)
ICMP Application
• “traceroute” (in Unix; “tracert” in Windows)– To find the route of a packet– ICMP time-exceeded message
Nowadays, many hosts and routers do not respond (or a gateway blocks the packets) due to security reason
![Page 12: Ch 21. Other IP-related Protocols](https://reader030.vdocument.in/reader030/viewer/2022032709/56813196550346895d980815/html5/thumbnails/12.jpg)
21.3 IGMP
• Multicasting: one-to-many communication• Internet Group Management Protocol (IGMP)
– One of protocols necessary for multicasting– Manage group membership
• Operations– Join a group– Leave a group– Monitor membership – Server periodically sends a query to
ensure membership. Hosts use a delayed response to reduce traffic
![Page 13: Ch 21. Other IP-related Protocols](https://reader030.vdocument.in/reader030/viewer/2022032709/56813196550346895d980815/html5/thumbnails/13.jpg)
Encapsulation
• Encapsulation into IP datagram and frame
• IP packet with an ICMP message has a value of “1” in its TTL field IGMP works locally
• IP destinationaddress
![Page 14: Ch 21. Other IP-related Protocols](https://reader030.vdocument.in/reader030/viewer/2022032709/56813196550346895d980815/html5/thumbnails/14.jpg)
• Encapsulation at data link layer– Multicast support (most LANs) – map multicast IP
address to physical address (many-to-one)– No multicast support (most WANs) – use tunneling
• Application “netstat”
![Page 15: Ch 21. Other IP-related Protocols](https://reader030.vdocument.in/reader030/viewer/2022032709/56813196550346895d980815/html5/thumbnails/15.jpg)
Homework
• Exercise– 17– 19– 22– 23– 25