RE: multicast [7:47591]
In regards to the OSI specs, is it safe to say that IP multicasts exist at layers 2 and 3? -Original Message- From: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED]] Sent: Friday, June 28, 2002 1:15 AM To: [EMAIL PROTECTED] Subject: Re: multicast [7:47591] At 10:14 PM 6/27/02, Howard C. Berkowitz wrote: > >IP multicast gets used for many purposes and those purposes may be at > >different layers: > > > >Sending routing updates (EIGRP, OSPF, RIPv2) - Layer 3 > >Establishing routing protocol neighbor relationships (EIGRP, OSPF) - Layer 3 > >Sending multimedia streaming audio or video - Layer 7 with some help from > >Layer 6 (MPEG or whatever), Layer 5 (RTSP), and Layer 4 (UDP) > >Finding services (Service Location Protocol) - Layer 7 > >Joining groups (IGMP) - Layer 3 > >Determining a dynamic L3 address assignment (IPv6) - Layer 3 > > >You're not saying, are you, that IP multicast exists at layers above >3, are you? No, I said it's used by upper layers. Those layers are aware of it, though. The Service Location Protocol (SLP) RFC, for example, states which IP multicast address to use. The Realtime Streaming Protocol (RTSP) knows about IP multicast too. I don't know the details, but RTSP specifies a method for a client to find out what IP multicast address a server is sending to. There's a presentation description that includes the multicast address. If you look at the RFC for RTSP, there's lots of discussion of multicast. RTSP is nominally an application-layer protocol, at least according to the author of the RFC. Priscilla >I think it is correct to say that a higher-layer protocol >may assume that a lower-layer protocol will require use of a layer 3 >multicast service, but doesn't itself implement multicast. The upper >layer entity (in strict OSI terms) need not have direct access to the >multicast network layer service, but potentially could indirectly >request that functionality through higher-layer service interfaces. > >Without looking at the Transport Service Specification, I can't >remember if it has the semantics, with the Connectionless Transport >Service, of multicasts. My general recollection is that you use a >network service address and let the Network Service figure out the >semantics. > > > >There's probably lots of others too! > > > >Layer 2 multicasts are used for IP multicast, but for many other purposes > >too, such as BPDU, CDP, VTP, DISL, AppleTalk Name Binding Protocol (NBP) > >lookups, etc. > > > >Priscilla > > > > > >>TIA > >> > >>Robert > > > > > >Priscilla Oppenheimer > >http://www.priscilla.com Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=47650&t=47591 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: multicast [7:47591]
At 10:14 PM 6/27/02, Howard C. Berkowitz wrote: > >IP multicast gets used for many purposes and those purposes may be at > >different layers: > > > >Sending routing updates (EIGRP, OSPF, RIPv2) - Layer 3 > >Establishing routing protocol neighbor relationships (EIGRP, OSPF) - Layer 3 > >Sending multimedia streaming audio or video - Layer 7 with some help from > >Layer 6 (MPEG or whatever), Layer 5 (RTSP), and Layer 4 (UDP) > >Finding services (Service Location Protocol) - Layer 7 > >Joining groups (IGMP) - Layer 3 > >Determining a dynamic L3 address assignment (IPv6) - Layer 3 > > >You're not saying, are you, that IP multicast exists at layers above >3, are you? No, I said it's used by upper layers. Those layers are aware of it, though. The Service Location Protocol (SLP) RFC, for example, states which IP multicast address to use. The Realtime Streaming Protocol (RTSP) knows about IP multicast too. I don't know the details, but RTSP specifies a method for a client to find out what IP multicast address a server is sending to. There's a presentation description that includes the multicast address. If you look at the RFC for RTSP, there's lots of discussion of multicast. RTSP is nominally an application-layer protocol, at least according to the author of the RFC. Priscilla >I think it is correct to say that a higher-layer protocol >may assume that a lower-layer protocol will require use of a layer 3 >multicast service, but doesn't itself implement multicast. The upper >layer entity (in strict OSI terms) need not have direct access to the >multicast network layer service, but potentially could indirectly >request that functionality through higher-layer service interfaces. > >Without looking at the Transport Service Specification, I can't >remember if it has the semantics, with the Connectionless Transport >Service, of multicasts. My general recollection is that you use a >network service address and let the Network Service figure out the >semantics. > > > >There's probably lots of others too! > > > >Layer 2 multicasts are used for IP multicast, but for many other purposes > >too, such as BPDU, CDP, VTP, DISL, AppleTalk Name Binding Protocol (NBP) > >lookups, etc. > > > >Priscilla > > > > > >>TIA > >> > >>Robert > > > > > >Priscilla Oppenheimer > >http://www.priscilla.com Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=47637&t=47591 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: multicast [7:47591]
A thanks to everyone who replied to this topic... -Original Message- From: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED]] Sent: Thursday, June 27, 2002 6:36 PM To: [EMAIL PROTECTED] Subject: Re: multicast [7:47591] At 04:42 PM 6/27/02, Lopez, Robert wrote: >At what OSI layer do IP multicasts lie? Reading through CCO has made me >more doubtful in my choices. IP multicasts are sent to a layer 3 IP multicast address. That address is converted to a data-link-layer multicast address. The Internet Assigned Numbers Authority (IANA) owns a block of MAC-layer addresses that are used for group multicast addresses. The range of addresses for Ethernet is 0x01:00:5E:00:00:00 through 0x01:00:5E:7F:FF:FF. When a host sends a frame to an IP group that is identified by a Class D address, the host inserts the low-order 23 bits of the Class D address into the low-order 23 bits of the MAC-layer destination address. The top 9 bits of the Class D address are not used. The top 25 bits of the MAC address are 0x01:00:5E followed by a zero bit (0001 0100 0 in binary). IP multicast gets used for many purposes and those purposes may be at different layers: Sending routing updates (EIGRP, OSPF, RIPv2) - Layer 3 Establishing routing protocol neighbor relationships (EIGRP, OSPF) - Layer 3 Sending multimedia streaming audio or video - Layer 7 with some help from Layer 6 (MPEG or whatever), Layer 5 (RTSP), and Layer 4 (UDP) Finding services (Service Location Protocol) - Layer 7 Joining groups (IGMP) - Layer 3 Determining a dynamic L3 address assignment (IPv6) - Layer 3 There's probably lots of others too! Layer 2 multicasts are used for IP multicast, but for many other purposes too, such as BPDU, CDP, VTP, DISL, AppleTalk Name Binding Protocol (NBP) lookups, etc. Priscilla >TIA > >Robert Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=47629&t=47591 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: multicast [7:47591]
Did you copy/paste that right out of a textbook? =) Before I even saw anything indicating that you authored that post, I got about 1/2 way through the paragraph and was thinking to myself "This had to be from Priscilla". Mike W. "Priscilla Oppenheimer" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > At 04:42 PM 6/27/02, Lopez, Robert wrote: > >At what OSI layer do IP multicasts lie? Reading through CCO has made me > >more doubtful in my choices. > > IP multicasts are sent to a layer 3 IP multicast address. That address is > converted to a data-link-layer multicast address. The Internet Assigned > Numbers Authority (IANA) owns a block of MAC-layer addresses that are used > for group multicast addresses. The range of addresses for Ethernet is > 0x01:00:5E:00:00:00 through 0x01:00:5E:7F:FF:FF. When a host sends a frame > to an IP group that is identified by a Class D address, the host inserts > the low-order 23 bits of the Class D address into the low-order 23 bits of > the MAC-layer destination address. The top 9 bits of the Class D address > are not used. The top 25 bits of the MAC address are 0x01:00:5E followed by > a zero bit (0001 0100 0 in binary). > > IP multicast gets used for many purposes and those purposes may be at > different layers: > > Sending routing updates (EIGRP, OSPF, RIPv2) - Layer 3 > Establishing routing protocol neighbor relationships (EIGRP, OSPF) - Layer 3 > Sending multimedia streaming audio or video - Layer 7 with some help from > Layer 6 (MPEG or whatever), Layer 5 (RTSP), and Layer 4 (UDP) > Finding services (Service Location Protocol) - Layer 7 > Joining groups (IGMP) - Layer 3 > Determining a dynamic L3 address assignment (IPv6) - Layer 3 > > There's probably lots of others too! > > Layer 2 multicasts are used for IP multicast, but for many other purposes > too, such as BPDU, CDP, VTP, DISL, AppleTalk Name Binding Protocol (NBP) > lookups, etc. > > Priscilla > > > >TIA > > > >Robert > > > Priscilla Oppenheimer > http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=47627&t=47591 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: multicast [7:47591]
At 6:36 PM -0400 6/27/02, Priscilla Oppenheimer wrote: >At 04:42 PM 6/27/02, Lopez, Robert wrote: >>At what OSI layer do IP multicasts lie? Reading through CCO has made me >>more doubtful in my choices. > >IP multicasts are sent to a layer 3 IP multicast address. That address is >converted to a data-link-layer multicast address. The Internet Assigned >Numbers Authority (IANA) owns a block of MAC-layer addresses that are used >for group multicast addresses. The range of addresses for Ethernet is >0x01:00:5E:00:00:00 through 0x01:00:5E:7F:FF:FF. When a host sends a frame >to an IP group that is identified by a Class D address, the host inserts >the low-order 23 bits of the Class D address into the low-order 23 bits of >the MAC-layer destination address. The top 9 bits of the Class D address >are not used. The top 25 bits of the MAC address are 0x01:00:5E followed by >a zero bit (0001 0100 0 in binary). > >IP multicast gets used for many purposes and those purposes may be at >different layers: > >Sending routing updates (EIGRP, OSPF, RIPv2) - Layer 3 >Establishing routing protocol neighbor relationships (EIGRP, OSPF) - Layer 3 >Sending multimedia streaming audio or video - Layer 7 with some help from >Layer 6 (MPEG or whatever), Layer 5 (RTSP), and Layer 4 (UDP) >Finding services (Service Location Protocol) - Layer 7 >Joining groups (IGMP) - Layer 3 >Determining a dynamic L3 address assignment (IPv6) - Layer 3 You're not saying, are you, that IP multicast exists at layers above 3, are you? I think it is correct to say that a higher-layer protocol may assume that a lower-layer protocol will require use of a layer 3 multicast service, but doesn't itself implement multicast. The upper layer entity (in strict OSI terms) need not have direct access to the multicast network layer service, but potentially could indirectly request that functionality through higher-layer service interfaces. Without looking at the Transport Service Specification, I can't remember if it has the semantics, with the Connectionless Transport Service, of multicasts. My general recollection is that you use a network service address and let the Network Service figure out the semantics. > >There's probably lots of others too! > >Layer 2 multicasts are used for IP multicast, but for many other purposes >too, such as BPDU, CDP, VTP, DISL, AppleTalk Name Binding Protocol (NBP) >lookups, etc. > >Priscilla > > >>TIA >> >>Robert > > >Priscilla Oppenheimer >http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=47624&t=47591 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: multicast [7:47591]
At 04:42 PM 6/27/02, Lopez, Robert wrote: >At what OSI layer do IP multicasts lie? Reading through CCO has made me >more doubtful in my choices. IP multicasts are sent to a layer 3 IP multicast address. That address is converted to a data-link-layer multicast address. The Internet Assigned Numbers Authority (IANA) owns a block of MAC-layer addresses that are used for group multicast addresses. The range of addresses for Ethernet is 0x01:00:5E:00:00:00 through 0x01:00:5E:7F:FF:FF. When a host sends a frame to an IP group that is identified by a Class D address, the host inserts the low-order 23 bits of the Class D address into the low-order 23 bits of the MAC-layer destination address. The top 9 bits of the Class D address are not used. The top 25 bits of the MAC address are 0x01:00:5E followed by a zero bit (0001 0100 0 in binary). IP multicast gets used for many purposes and those purposes may be at different layers: Sending routing updates (EIGRP, OSPF, RIPv2) - Layer 3 Establishing routing protocol neighbor relationships (EIGRP, OSPF) - Layer 3 Sending multimedia streaming audio or video - Layer 7 with some help from Layer 6 (MPEG or whatever), Layer 5 (RTSP), and Layer 4 (UDP) Finding services (Service Location Protocol) - Layer 7 Joining groups (IGMP) - Layer 3 Determining a dynamic L3 address assignment (IPv6) - Layer 3 There's probably lots of others too! Layer 2 multicasts are used for IP multicast, but for many other purposes too, such as BPDU, CDP, VTP, DISL, AppleTalk Name Binding Protocol (NBP) lookups, etc. Priscilla >TIA > >Robert Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=47601&t=47591 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: multicast [7:47591]
Robert, Layer 3 is where multicasting takes place. Raul -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Lopez, Robert Sent: Thursday, June 27, 2002 4:42 PM To: [EMAIL PROTECTED] Subject: multicast [7:47591] At what OSI layer do IP multicasts lie? Reading through CCO has made me more doubtful in my choices. TIA Robert Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=47595&t=47591 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: multicast [7:47591]
I'm going to say the addresses are L3, udp used as transport is L4, and the apps are L7, with some of the formats such as MPeg2 L6. ""Lopez, Robert"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > At what OSI layer do IP multicasts lie? Reading through CCO has made me > more doubtful in my choices. > > TIA > > Robert Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=47593&t=47591 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
