Wireless Mobile & Multimedia Networking Lecture 2 PDF

Wireless Mobile & Multimedia Networking 7COM1076 Dr Myasar Tabany [email protected] Senior Lecturer School of Physics Engineering and Computer Science (SPECS)  7COM1030 –...

Wireless Mobile & Multimedia Networking 7COM1076 Dr Myasar Tabany [email protected] Senior Lecturer School of Physics Engineering and Computer Science (SPECS)  7COM1030 – Multicast and Multimedia Networking } Multicast Addresses } IGMP Protocol Multicast Lecture 2 – IGMP  7COM1030 – Multicast and Multimedia Networking All Class D addresses are multicast addresses: Class D 1 1 1 0 multicast group id 28 bits Class From To D 224.0.0.0 239.255.255.255 Multicast addresses are dynamically assigned. If an application is terminated, the multicast address is (implicitly) released. Multicast Lecture 2 – IGMP  7COM1030 – Multicast and Multimedia Networking } The range of addresses between 224.0.0.0 and 224.0.0.255, inclusive, is reserved for the use of routing protocols and other low-level topology discovery or maintenance protocols } Multicast routers should not forward any multicast datagram with destination addresses in this range. } Important permanent multicast groups: 224.0.0.1 All hosts and all routers on a network 224.0.0.2 All routers on a network 224.0.0.22 IGMPv3 } Permanent multicast groups reserved by protocols: 224.0.0.9 All RIP2 routers on a network 224.0.0.4 All DVMRP routers on a network 224.0.0.13 All PIM routers on a network Multicast Lecture 2 – IGMP  7COM1030 – Multicast and Multimedia Networking AS: Autonomous System 233 X X X AS Number Multicast Addresses } For example, the AS with the number of 0x8080 will own the multicast address range of: 233.128.128.0 ~ 233.128.128.255 Multicast Lecture 2 – IGMP  7COM1030 – Multicast and Multimedia Networking } The MAC address consists of 12 hex digits (48 bits). } There are 3 different types of Ethernet addresses: § Unicast: A unicast frame contains the unique MAC address of the destination receiver. The first six digits are assigned by the IEEE which identifies the manufacturer. The last six are assigned by the manufacturer and represent a unique hardware ID number for the NIC. § Broadcast: A broadcast frame contains all binary 1’s as the destination address (FF:FF:FF:FF:FF:FF). § Multicast: A multicast frame contains the unique multicast MAC address of an application, protocol, or data stream. Multicast Lecture 2 – IGMP  7COM1030 – Multicast and Multimedia Networking Identifes Ignored 23-bit Class D address Class D Ethernet Addresses 1110xxxx x------- -------- -------- IP Address with 01:00:5e in the first 3 bytes are reserved for IP multicast Ethernet 00000001 00000000 01011110 0------- -------- -------- Address Range 01:00:5e:80:00:00 ~ 01:00:5e:7f:ff:ff Multicast Lecture 2 – IGMP  7COM1030 – Multicast and Multimedia Networking netstat can be used with three options, -n, -r, and -a. The -n option gives the numeric versions of IP addresses, the -r option gives the routing table, and the -a option gives all addresses (unicast and multicast). This example only shows the fields relative to our discussion. $ netstat -nra Kernel IP routing table Destination Gateway Mask Flags Iface 153.18.16.0 0.0.0.0 255.255.240.0 U eth0 169.254.0.0 0.0.0.0 255.255.0.0 U eth0 127.0.0.0 0.0.0.0 255.0.0.0 U lo 224.0.0.0 0.0.0.0 224.0.0.0 U eth0 0.0.0.0 153.18.31.254 0.0.0.0 UG eth0 Any packet with a multicast address from 224.0.0.0 to 239.255.255.255 is masked and delivered to the Ethernet interface. Multicast Lecture 2 – IGMP  7COM1030 – Multicast and Multimedia Networking } This command will display all multicast group memberships for all interfaces in the current host. Multicast Lecture 2 – IGMP  7COM1030 – Multicast and Multimedia Networking } Multicast Addresses } IGMP Protocol Multicast Lecture 2 – IGMP  7COM1030 – Multicast and Multimedia Networking } The Internet Group Management Protocol (IGMP) is a simple protocol for the support of IP multicast. } IGMP operates on a physical network (e.g., single Ethernet Segment). } IGMP is used by multicast routers to keep track of membership in a multicast group. Multicast router keeps a table on the multicast groups that have joined hosts. The router only forwards a packet, if there is a host still joined. Router does not keep track which host is joined. } Support for: Joining a multicast group Leaving a multicast group (v2 and v3 only) Query membership Send membership reports Multicast Lecture 2 – IGMP  7COM1030 – Multicast and Multimedia Networking } IGMPv1 § No way to explicitly leave a multicast group. Router will timeout a group membership } IGMPv2 § Includes a “leave processing” mechanism § Routers can make group-specific query § Currently as the default for many systems } IGMPv3 § Support source-filtering, enabling receivers to signal a router about a traffic source Multicast Lecture 2 – IGMP  7COM1030 – Multicast and Multimedia Networking } IGMP query § General query: Used by routers to learn which groups have members on an attached network (group address is set to zero). “Anyone still there?” § Group-specific query. Used by routers to learn if a particular group has any members on an attached network.“Anyone still in group xx?” (N/A in IGMPv1) } IGMP report § Membership report. A host responds to an IGMP query:“Yes, I’m still in group xx.” § Join report. A host sends an IGMP report when it joins a multicast group (Note: multiple processes on a host can join. A report is sent only for the first process).“I want to join group xx.” } IGMP leave § “I want to leave group xx” § No report is sent when a process leaves a group in IGMPv1. Multicast Lecture 2 – IGMP  7COM1030 – Multicast and Multimedia Networking H1 H2 R1 Ethernet IGMP group join IGMP general query IGMP group address = group address IGMP group address = 0 Destination IP address = 224.0.0.2 Destination IP address = 224.0.0.1 Source IP address = host’s IP address Source IP address = router's IP address IGMP group leave (N/A in IGMPv1) IGMP group address = group address IGMP group-specific query Destination IP address = 224.0.0.2 IGMP group address = group address (224.0.0.22 for IGMPv3) Destination IP address = group address Source IP address = host’s IP address Source IP address = router's IP address IGMP membership report IGMP group address = group address Destination IP address= group address Source IP address = host's IP address Destination address is 224.0.0.22 for IGMPv3 Multicast Lecture 2 – IGMP  7COM1030 – Multicast and Multimedia Networking } IGMP messages are only 8 bytes long 14 bytes 20 bytes 8 bytes IGMP Ethernet Header IP header Message The first octet: 0x11 query Version Type (unused) Checksum 0x12 report (= 0) (=1-2) 32-bit Class D address Type: 1 = sent by router, 2 = sent by host Multicast Lecture 2 – IGMP  7COM1030 – Multicast and Multimedia Networking The first octet: Query 00010001 0x11 Report v1 00010010 0x12 Report v2 00010110 0x16 Report v3 00100010 0x22 Leave 00010111 0x17 Multicast Lecture 2 – IGMP  7COM1030 – Multicast and Multimedia Networking } Query Interval: When a host receives a query, rather than sending reports immediately, it starts a report delay timer with a randomly- chosen value between zero and D. When a timer expires, a Report is generated for the corresponding host group. Thus, Reports are spread out over a D second interval instead of all occurring at once. } Maximum Response Time (D): The maximum time a host can wait before responding a query. } Report Suppression: If the host receives another host's Report (version 1 or 2) while it has a timer running, it stops its timer for the specified group and does not send a Report, in order to suppress duplicate Reports. Multicast Lecture 2 – IGMP  7COM1030 – Multicast and Multimedia Networking } Scope-limiting parameter for IP Multicast datagrams } Controls the number of hops that a IP Multicast packet is allowed to propagate } TTL = 1: local network multicast § IGMP messages are sent with TTL = 1; therefore IGMP messages are never forwarded by routers § The addresses of 224.0.0.0 ~ 224.0.0.255 are always sent with TTL = 1 to limit the corresponding groups to the local network. } TTL > 1: Multicast router(s) attached to the local network forward IP Multicast datagrams Multicast Lecture 2 – IGMP  7COM1030 – Multicast and Multimedia Networking Multicast Lecture 2 – IGMP  7COM1030 – Multicast and Multimedia Networking Multicast Lecture 2 – IGMP