Panduan Konfigurasi Kualitas Layanan IOS, Rilis 12.2 Penghambat Kemacetan Ikhtisar Teknik penghindaran kemacetan memonitor beban lalu lintas jaringan dalam upaya mengantisipasi dan menghindari kemacetan pada kemacetan jaringan umum. Penghindaran kemacetan dicapai melalui packet dropping. Diantara mekanisme penghindaran kongesti yang umum digunakan adalah Random Early Detection (RED), yang optimal untuk jaringan transit berkecepatan tinggi. Cisco IOS QoS menyertakan implementasi RED yang, jika dikonfigurasi, dikendalikan saat router menjatuhkan paket. Jika Anda tidak mengkonfigurasi Weighted Random Early Detection (WRED), router menggunakan mekanisme drop packet default cruder yang disebut drop ekor. Untuk penjelasan tentang kemacetan jaringan, lihat bab quotQuality of Service Overview. quot Bab ini memberikan deskripsi singkat tentang jenis mekanisme penghindaran kemacetan yang disediakan oleh fitur Cisco IOS QoS. Ini membahas fitur berikut: Tail drop. Ini adalah perilaku menghindari kemacetan default saat WRED tidak dikonfigurasi. WRED. WRED dan distributed WRED (DWRED) yang keduanya merupakan implementasi Cisco dari REDcombine kemampuan algoritma RED dengan fitur IP Precedence. Di bagian WRED, fitur terkait berikut dibahas: Flow-based WRED. Flow-based WRED meluas WRED untuk memberikan keadilan yang lebih besar pada semua arus pada sebuah antarmuka sehubungan dengan bagaimana paket dijatuhkan. DiffServ Compliant WRED. DiffServ Compliant WRED meluas WRED untuk mendukung Differentiated Services (DiffServ) dan Assured Forwarding (AF) Per Hop Behavior (PHB). Fitur ini memungkinkan pelanggan menerapkan AF PHB dengan mewarnai paket sesuai dengan nilai kode layanan terdiferensiasi (DSCP) dan kemudian menetapkan probabilitas drop preferensial ke paket tersebut. Untuk informasi tentang cara mengkonfigurasi WRED, DWRED, flow-based WRED, dan DiffServ Compliant WRED, lihat bab quotConfiguring Weighted Random Early Detectionquot dalam buku ini. Tail drop memperlakukan semua lalu lintas secara merata dan tidak membedakan antara kelas layanan. Antrian mengisi selama periode kemacetan. Bila antrian output penuh dan drop ekor berlaku, paket akan jatuh sampai kemacetan dieliminasi dan antrian tidak lagi penuh. Deteksi Dini Teracak Random Bagian ini memberikan pengantar singkat tentang konsep RED dan alamat WRED, implementasi Cisco RED untuk platform Cisco IOS standar. WRED menghindari masalah globalisasi yang terjadi saat drop ekor digunakan sebagai mekanisme penghindaran kemacetan pada router. Sinkronisasi global terjadi karena gelombang puncak kemacetan hanya untuk diikuti oleh palung dimana link transmisi tidak dimanfaatkan sepenuhnya. Sinkronisasi global host TCP, misalnya, dapat terjadi karena paket dijatuhkan sekaligus. Sinkronisasi global bermanifestasi ketika beberapa host TCP mengurangi tingkat transmisi mereka sebagai respons terhadap penurunan paket, kemudian meningkatkan tingkat transmisi sekali lagi ketika kemacetan berkurang. Tentang Deteksi Dini Random Mekanisme RED diusulkan oleh Sally Floyd dan Van Jacobson pada awal tahun 1990an untuk mengatasi kemacetan jaringan secara responsif dan bukan reaktif. Mendasari mekanisme RED adalah premis bahwa kebanyakan lalu lintas berjalan pada implementasi transportasi data yang sensitif terhadap kerugian dan akan melambat sementara ketika sebagian lalu lintas mereka turun. TCP, yang merespons dengan tepat, dengan penurunan lalu lintas yang melambat dengan memperlambat transmisi lalu lintasnya, secara efektif memungkinkan perilaku penurunan lalu lintas RED berfungsi sebagai mekanisme pensinyalan penghindaran kemacetan. TCP merupakan transport jaringan yang paling banyak digunakan. Mengingat kehadiran TCP yang ada di mana-mana, RED menawarkan mekanisme penghindaran kemacetan yang luas dan efektif. Dalam mempertimbangkan kegunaan RED ketika transport yang kuat seperti TCP yang meresap, penting untuk mempertimbangkan juga implikasi negatif yang serius dalam menggunakan RED ketika persentase lalu lintas yang signifikan tidak kuat sebagai respons terhadap packet loss. Baik Novell NetWare maupun AppleTalk benar-benar tangguh dalam menanggapi packet loss, oleh karena itu sebaiknya Anda tidak menggunakan RED untuk mereka. Cara Bekerja RED bertujuan untuk mengendalikan ukuran antrian rata-rata dengan menunjukkan ke host akhir saat mereka seharusnya memperlambat pengiriman paket. RED mengambil keuntungan dari mekanisme kontrol kongesti TCP. Dengan secara acak menjatuhkan paket sebelum periode kemacetan tinggi, RED memberitahu sumber paket untuk menurunkan tingkat transmisi. Dengan mengasumsikan sumber paket menggunakan TCP, maka akan menurunkan tingkat transmisi sampai semua paket mencapai tujuan mereka, menunjukkan bahwa kemacetan akan hilang. Anda bisa menggunakan RED sebagai cara untuk menyebabkan TCP memperlambat transmisi paket. TCP tidak hanya berhenti, tapi juga restart dengan cepat dan menyesuaikan tingkat transmisi dengan kecepatan yang dapat didukung jaringan. RED mendistribusikan kerugian pada waktunya dan mempertahankan kedalaman antrian yang biasanya rendah sambil menyerap lonjakan. Saat diaktifkan pada sebuah antarmuka, RED mulai menjatuhkan paket saat kemacetan terjadi pada tingkat yang Anda pilih selama konfigurasi. Untuk penjelasan tentang bagaimana penerapan Cisco WRED menentukan parameter yang akan digunakan dalam perhitungan ukuran antrian WRED dan bagaimana menentukan nilai optimal yang akan digunakan untuk faktor bobot, lihat bagian kuota Rata-rata Antrian Ukuran pada bab ini. Probabilitas Drop Packet Kemungkinan drop packet didasarkan pada ambang minimum, ambang maksimum, dan mark probability denominator. Bila kedalaman antrian rata-rata di atas ambang minimum, RED mulai menjatuhkan paket. Tingkat drop paket meningkat secara linear karena ukuran antrian rata-rata meningkat sampai ukuran antrian rata-rata mencapai ambang maksimum. Penyebutan probabilitas mark adalah pecahan dari paket turun saat kedalaman antrian rata-rata berada pada ambang maksimum. Misalnya, jika penyebutnya adalah 512, satu dari setiap 512 paket dijatuhkan saat antrian rata-rata berada pada ambang maksimum. Bila ukuran antrian rata-rata berada di atas ambang batas maksimum, semua paket akan terjatuh. Gambar 9 merangkum probabilitas drop paket. Gambar 9 Probabilitas Drop Pack Mini Nilai ambang minimum harus ditetapkan cukup tinggi untuk memaksimalkan pemanfaatan link. Jika ambang minimum terlalu rendah, paket mungkin tidak diperlukan, dan link transmisi tidak akan sepenuhnya digunakan. Perbedaan antara ambang batas maksimum dan ambang minimum harus cukup besar untuk menghindari sinkronisasi global host TCP (sinkronisasi global host TCP dapat terjadi karena beberapa host TCP mengurangi tingkat transmisi mereka). Jika selisih antara ambang batas maksimum dan minimum terlalu kecil, banyak paket dapat dijatuhkan sekaligus, sehingga terjadi sinkronisasi global. Bagaimana TCP Menangani Catatan Rugi Lalu Lintas Bagian-bagian yang mengutip TCP Menangani Traffic Lossquot dan quotHow Router Berinteraksi dengan TCPquot berisi informasi rinci yang tidak perlu Anda baca untuk menggunakan WRED atau memiliki kemampuan umum tentang RED. Jika Anda ingin memahami mengapa masalah sinkronisasi global terjadi sebagai respons terhadap kemacetan saat drop ekor digunakan secara default dan bagaimana RED mengatasinya, baca bagian ini. Ketika penerima lalu lintas TCP menghubungi receiverreceives sebuah segmen data, ia akan memeriksa empat urutan oktet (32-bit) dari segmen tersebut terhadap jumlah receiver yang diharapkan, yang mengindikasikan bahwa segmen data diterima secara berurutan. Jika nomornya sesuai, penerima akan mengirimkan semua data yang dipegangnya ke aplikasi target, kemudian memperbarui nomor urut untuk mencerminkan nomor berikutnya secara berurutan, dan akhirnya keduanya mengirimkan paket acknowledgement (ACK) ke pengirim atau Itu jadwal ACK untuk dikirim ke pengirim setelah penundaan singkat. ACK memberitahukan pengirim bahwa penerima menerima semua segmen data sampai namun tidak termasuk yang ditandai dengan nomor urut baru. Penerima biasanya mencoba mengirim ACK sebagai respons terhadap segmen data bolak-balik yang mereka terima sehingga mereka mengirim ACK karena untuk banyak aplikasi, jika penerima menunggu penundaan kecil, secara efisien dapat memasukkan jawaban balasannya pada respons normal terhadap pengirim. Namun, ketika receiver menerima segmen data yang rusak, ia segera merespons ACK untuk mengarahkan pengirim agar mengirim ulang segmen data yang hilang. Ketika pengirim menerima ACK, itu membuat penentuan ini: Ini menentukan apakah ada data yang beredar. Jika tidak ada data yang beredar, pengirim menentukan bahwa ACK adalah keepalive, yang dimaksudkan untuk menjaga agar saluran tetap aktif, dan tidak melakukan apa-apa. Jika data beredar, pengirim menentukan apakah ACK menunjukkan bahwa penerima telah menerima beberapa atau tidak ada data. Jika ACK menunjukkan penerimaan beberapa data yang dikirim, pengirim menentukan apakah kredit baru telah diberikan untuk memungkinkannya mengirim lebih banyak data. Bila ACK menunjukkan penerimaan tidak ada data yang dikirim dan ada data beredar, pengirim menginterpretasikan ACK menjadi ACK berulang kali. Kondisi ini menunjukkan bahwa beberapa data diterima tidak sesuai, memaksa penerima untuk mengirimkan ACK pertama, dan bahwa segmen data kedua diterima tanpa urutan, memaksa penerima untuk mengirimkan ACK kedua. Dalam kebanyakan kasus, penerima akan menerima dua segmen yang rusak karena salah satu segmen data telah dibatalkan. Ketika pengirim TCP mendeteksi segmen data yang jatuh, ia mengirim ulang segmen tersebut. Kemudian menyesuaikan tingkat transmisi menjadi separuh dari apa yang sebelum penurunan terdeteksi. Ini adalah perilaku TCP back-off atau slow-down. Meskipun perilaku ini tepat responsif terhadap kemacetan, masalah dapat timbul saat beberapa sesi TCP dijalankan bersamaan dengan router yang sama dan semua pengirim TCP memperlambat pengiriman paket pada saat yang bersamaan. Bagaimana Router Berinteraksi dengan TCP Catatan Bagian-bagiannya mengutip TCP Menangani Traffic Lossquot dan quotHow Router Berinteraksi dengan TCPquot berisi informasi rinci yang tidak perlu Anda baca untuk menggunakan WRED atau memiliki kemampuan umum tentang RED. Jika Anda ingin memahami mengapa masalah sinkronisasi global terjadi sebagai respons terhadap kemacetan saat drop ekor digunakan secara default dan bagaimana RED mengatasinya, baca bagian ini. Untuk melihat bagaimana router berinteraksi dengan TCP, kita akan melihat sebuah contoh. Dalam contoh ini, rata-rata, router menerima lalu lintas dari satu aliran TCP satu sama lain, setiap 10, dan setiap pesan 100 atau 200 di antarmuka di MAE-EAST atau FIX-WEST. Router dapat menangani beberapa sesi TCP bersamaan. Karena arus jaringan aditif, ada kemungkinan tinggi bahwa bila lalu lintas melebihi Batas Antena Transmit (TQL) sama sekali, maka akan sangat melampaui batas. Namun, ada juga probabilitas tinggi bahwa kedalaman lalu lintas yang berlebihan bersifat sementara dan lalu lintas tidak akan terlalu jauh kecuali titik dimana arus lalu lintas bergabung atau pada router tepi. Jika router menjatuhkan semua lalu lintas yang melebihi TQL, seperti yang dilakukan saat drop ekor digunakan secara default, banyak sesi TCP secara bersamaan akan mulai lambat. Akibatnya, lalu lintas sementara melambat ke ekstrem dan kemudian semua mengalir lamban-mulai lagi aktivitas ini menciptakan kondisi sinkronisasi global. Namun, jika router tidak menjatuhkan lalu lintas, seperti yang terjadi saat fitur antrian seperti antrian yang adil atau custom queueing (CQ) digunakan, maka data kemungkinan akan disimpan dalam memori utama, menurunkan kinerja router secara drastis. Dengan mengarahkan satu sesi TCP pada suatu waktu untuk melambat, RED memecahkan masalah yang dijelaskan, memungkinkan penggunaan bandwidth secara penuh daripada utilisasi yang memanifestasikan sebagai puncak dan palung lalu lintas. Tentang WRED WRED menggabungkan kemampuan algoritma RED dengan fitur IP Precedence untuk memberikan penanganan lalu lintas istimewa dari paket prioritas yang lebih tinggi. WRED dapat secara selektif membuang lalu lintas prioritas yang lebih rendah saat antarmuka mulai mengalami kemacetan dan memberikan karakteristik kinerja yang berbeda untuk kelas layanan yang berbeda. Anda dapat mengkonfigurasi WRED untuk mengabaikan IP yang didahulukan saat membuat keputusan penurunan sehingga perilaku RED nonweighted tercapai. Untuk antarmuka yang dikonfigurasi untuk menggunakan fitur Resource Reservation Protocol (RSVP), WRED memilih paket dari arus lain yang turun daripada arus RSVP. Juga, IP Precedence mengatur paket mana yang diturunkan lalu lintas yang berada pada tingkat yang lebih rendah memiliki tingkat penurunan yang lebih tinggi dan oleh karena itu lebih mungkin dilontarkan kembali. WRED berbeda dengan teknik penghindaran kongesti lainnya seperti strategi antrian karena mencoba mengantisipasi dan menghindari kemacetan daripada mengendalikan kemacetan begitu terjadi. Mengapa Menggunakan WRED WRED membuat deteksi dini kemacetan mungkin dan menyediakan beberapa kelas lalu lintas. Ini juga melindungi terhadap sinkronisasi global. Untuk alasan ini, WRED berguna pada antarmuka output mana pun yang Anda harapkan terjadi kemacetan. Namun, WRED biasanya digunakan di router inti sebuah jaringan, bukan di pinggir jaringan. Router tepi menetapkan prioritas IP ke paket saat mereka memasuki jaringan. WRED menggunakan preseden ini untuk menentukan bagaimana memperlakukan berbagai jenis lalu lintas. WRED menyediakan batasan dan bobot terpisah untuk prioritas IP yang berbeda, memungkinkan Anda memberikan kualitas layanan yang berbeda sehubungan dengan penurunan paket untuk jenis lalu lintas yang berbeda. Lalu lintas standar mungkin akan turun lebih sering daripada lalu lintas premium selama periode kemacetan. WRED juga RSVP-aware, dan dapat memberikan layanan QoS dengan beban terkendali untuk layanan terpadu. Cara Kerja Dengan menjatuhkan paket secara acak sebelum periode kemacetan tinggi, WRED mengatakan sumber paket untuk menurunkan tingkat transmisi. Jika sumber paket menggunakan TCP, maka akan menurunkan tingkat transmisi sampai semua paket mencapai tujuannya, yang mengindikasikan bahwa kemacetan akan hilang. WRED umumnya menjatuhkan paket secara selektif berdasarkan IP precedence. Paket dengan IP yang lebih tinggi didahulukan cenderung tidak turun daripada paket dengan prioritas lebih rendah. Dengan demikian, semakin tinggi prioritas sebuah paket, semakin tinggi probabilitas bahwa paket akan dikirimkan. WRED mengurangi kemungkinan penurunan ekor dengan memasukkan paket secara selektif saat antarmuka output mulai menunjukkan tanda-tanda kemacetan. Dengan menjatuhkan beberapa paket lebih awal daripada menunggu sampai antrian penuh, WRED menghindari menjatuhkan sejumlah besar paket sekaligus dan meminimalkan kemungkinan sinkronisasi global. Dengan demikian, WRED memungkinkan jalur transmisi untuk digunakan sepenuhnya setiap saat. Sebagai tambahan, WRED secara statistik menurunkan lebih banyak paket dari pengguna besar daripada kecil. Oleh karena itu, sumber lalu lintas yang menghasilkan lalu lintas paling banyak cenderung diperlambat daripada sumber lalu lintas yang menghasilkan sedikit lalu lintas. WRED menghindari masalah globalisasi yang terjadi saat drop ekor digunakan sebagai mekanisme penghindaran kemacetan. Sinkronisasi global bermanifestasi ketika beberapa host TCP mengurangi tingkat transmisi mereka sebagai respons terhadap penurunan paket, kemudian meningkatkan tingkat transmisi sekali lagi ketika kemacetan berkurang. WRED hanya berguna bila sebagian besar lalu lintasnya adalah lalu lintas TCPIP. Dengan TCP, paket yang terjatuh menunjukkan kemacetan, sehingga sumber paket akan mengurangi tingkat transmisi. Dengan protokol lain, sumber paket mungkin tidak merespons atau mengirimkan ulang paket yang terjatuh dengan tarif yang sama. Dengan demikian, menjatuhkan paket tidak mengurangi kemacetan. WRED memperlakukan lalu lintas non-IP sebagai preseden 0, prioritas terendah. Oleh karena itu, lalu lintas non-IP, pada umumnya cenderung lebih rendah daripada lalu lintas IP. Gambar 10 mengilustrasikan bagaimana WRED bekerja. Gambar 10 Deteksi Dini Datar Rata-rata Tertimbang Rata-rata Antrian Router secara otomatis menentukan parameter yang akan digunakan dalam perhitungan WRED. Ukuran antrian rata-rata didasarkan pada rata-rata sebelumnya dan ukuran antrian saat ini. Rumusnya adalah: di mana n adalah faktor bobot eksponensial, nilai yang dapat dikonfigurasi pengguna. Untuk nilai n tinggi. Rata-rata sebelumnya menjadi lebih penting. Faktor besar menghaluskan puncak dan rendahnya panjang antrian. Ukuran antrian rata-rata tidak mungkin berubah sangat cepat, menghindari ayunan drastis. Proses WRED akan lambat untuk mulai menjatuhkan paket, tapi mungkin terus menjatuhkan paket untuk sementara waktu setelah ukuran antrian sebenarnya turun di bawah batas minimum. Rata-rata yang bergerak lambat akan mengakomodasi semburan lalu lintas sementara. Catatan Jika nilai n terlalu tinggi, WRED tidak akan bereaksi terhadap kemacetan. Paket akan dikirim atau dijatuhkan seolah-olah WRED tidak berlaku. Untuk nilai n yang rendah. Ukuran antrian rata-rata melacak ukuran antrian saat ini. Rata-rata yang dihasilkan mungkin berfluktuasi dengan perubahan tingkat lalu lintas. Dalam kasus ini, proses WRED merespon dengan cepat antrian panjang. Begitu antrian jatuh di bawah ambang minimum, proses akan berhenti menjatuhkan paket. Jika nilai n menjadi terlalu rendah, WRED akan bereaksi berlebihan terhadap semburan lalu lintas sementara dan lalu lintas yang tidak perlu. Pembatasan Anda tidak dapat mengkonfigurasi WRED pada antarmuka yang sama dengan CQ berbasis Route Switch Processor (RSP), antrian prioritas (priority queuing / PQ), atau weight fair queuing (WFQ). Deteksi Dini Terdistribusi Terdistribusi Terdistribusi Terdistribusi WRED (DWRED) adalah implementasi WRED untuk Versatile Interface Processor (VIP). DWRED menyediakan serangkaian fungsi lengkap untuk VIP yang diberikan WRED pada platform Cisco IOS standar. Fitur DWRED hanya didukung pada router seri Cisco 7000 dengan prosesor antarmuka RSP7000 berbasis RSP dan router seri Cisco 7500 dengan prosesor antarmuka VIP2-40 atau antarmuka VIP berbasis VIP. Prosesor antarmuka VIP2-50 sangat disarankan bila tingkat garis agregat port adapter pada VIP lebih besar dari DS3. Prosesor antarmuka VIP2-50 diperlukan untuk tarif OC-3. DWRED dikonfigurasi dengan cara yang sama seperti WRED. Jika Anda mengaktifkan WRED pada antarmuka VIP yang sesuai, seperti VIP2-40 atau lebih besar dengan minimal 2 MB SRAM, DWRED akan diaktifkan. Untuk menggunakan DWRED, penerusan Cisco Express Forwarding (dCEF) terdistribusi harus diaktifkan pada antarmuka. Untuk informasi tentang dCEF, simak Panduan Konfigurasi Layanan IOS Switching Cisco dan Rujukan Perintah Cisco Switching Services IOS. Anda dapat mengkonfigurasi DWRED dan distributed weighted fair queueing (DWFQ) pada antarmuka yang sama, namun Anda tidak dapat mengkonfigurasi distributed WRED pada antarmuka yang berbasis RQ, CQ, PQ, atau WFQ dikonfigurasi. Anda dapat mengaktifkan DWRED menggunakan fitur Modular Quality of Service Command-Line Interface (Modular QoS CLI). Untuk informasi konseptual dan konfigurasi lengkap mengenai fitur QoS CLI Modular, lihat bab quotModular Quality of Service Command-Line Interface Overviewquot buku ini. Cara Kerja Ketika sebuah paket tiba dan DWRED diaktifkan, kejadian berikut terjadi: Ukuran antrian rata-rata dihitung. Lihat bagian Kuantitas Queue Sizequot untuk rinciannya. Jika rata-rata kurang dari ambang antrian minimum, paket yang datang antri. Jika rata-rata berada di antara ambang antrian minimum dan ambang antrian maksimum, paket tersebut akan jatuh atau antri, tergantung pada probabilitas drop paket. Lihat bagian quotCacket-Drop Probabilityquot untuk rinciannya. Jika ukuran antrian rata-rata lebih besar dari ambang antrian maksimum, paket otomatis akan turun. Ukuran Antrian Rata-rata Ukuran antrian rata-rata didasarkan pada rata-rata sebelumnya dan ukuran antrian saat ini. Rumusnya adalah: di mana n adalah faktor bobot eksponensial, nilai yang dapat dikonfigurasi pengguna. Untuk nilai n tinggi. Ukuran antrian rata-rata sebelumnya menjadi lebih penting. Faktor besar menghaluskan puncak dan rendahnya panjang antrian. Ukuran antrian rata-rata tidak mungkin berubah sangat cepat, menghindari ayunan drastis. Proses WRED akan lambat untuk mulai menjatuhkan paket, tapi mungkin terus menjatuhkan paket untuk sementara waktu setelah ukuran antrian sebenarnya turun di bawah batas minimum. Rata-rata yang bergerak lambat akan mengakomodasi semburan lalu lintas sementara. Catatan Jika nilai n terlalu tinggi, WRED tidak akan bereaksi terhadap kemacetan. Paket akan dikirim atau dijatuhkan seolah-olah WRED tidak berlaku. Untuk nilai n yang rendah. Ukuran antrian rata-rata melacak ukuran antrian saat ini. Rata-rata yang dihasilkan mungkin berfluktuasi dengan perubahan tingkat lalu lintas. Dalam kasus ini, proses WRED merespon dengan cepat antrian panjang. Begitu antrian jatuh di bawah batas minimum, proses berhenti menjatuhkan paket. Jika nilai n menjadi terlalu rendah, WRED akan bereaksi berlebihan terhadap semburan lalu lintas sementara dan lalu lintas yang tidak perlu. Probabilitas Packet-Drop Probabilitas bahwa sebuah paket akan dijatuhkan didasarkan pada ambang minimum, ambang maksimum, dan probabilitas tanda. Bila ukuran antrian rata-rata di atas ambang minimum, RED mulai menjatuhkan paket. Tingkat drop paket meningkat secara linear karena ukuran antrian rata-rata meningkat, sampai ukuran antrian rata-rata mencapai ambang maksimum. Penyebutan probabilitas mark adalah pecahan dari paket yang jatuh ketika ukuran antrian rata-rata berada pada ambang maksimum. Misalnya, jika penyebutnya adalah 512, satu dari setiap 512 paket dijatuhkan saat antrian rata-rata berada pada ambang maksimum. Bila ukuran antrian rata-rata berada di atas ambang batas maksimum, semua paket akan terjatuh. Gambar 11 merangkum probabilitas drop paket. Gambar 11 Probabilitas Drop Packet Nilai ambang minimum harus ditetapkan cukup tinggi untuk memaksimalkan pemanfaatan link. Jika ambang minimum terlalu rendah, paket mungkin tidak diperlukan, dan link transmisi tidak akan sepenuhnya digunakan. Perbedaan antara ambang batas maksimum dan ambang minimum harus cukup besar untuk menghindari sinkronisasi global host TCP (sinkronisasi global host TCP dapat terjadi karena beberapa host TCP mengurangi tingkat transmisi mereka). Jika selisih antara ambang batas maksimum dan minimum terlalu kecil, banyak paket dapat dijatuhkan sekaligus, sehingga terjadi sinkronisasi global. Mengapa DWRED DWRED menghasilkan kinerja yang lebih baik daripada WRED yang berbasis RSP. Anda harus menjalankan DWRED pada VIP jika Anda ingin mencapai kecepatan yang sangat tinggi pada platform seri Cisco 7500 misalnya, Anda dapat mencapai kecepatan pada tingkat OC-3 dengan menjalankan WRED pada prosesor antarmuka VIP2-50. Selain itu, alasan yang sama Anda akan menggunakan WRED pada platform Cisco IOS standar berlaku untuk menggunakan DWRED. (Lihat bagian quotWhy Gunakan WREDquot di awal bab ini.) Misalnya, ketika WRED atau DWRED tidak dikonfigurasi, drop ekor diberlakukan selama periode kemacetan. Mengaktifkan DWRED meniadakan masalah sinkronisasi global yang terjadi saat drop ekor digunakan untuk menghindari kemacetan. Fitur DWRED memberikan manfaat arus lalu lintas yang konsisten. Saat RED tidak dikonfigurasi, buffer output mengisi selama periode kemacetan. Bila buffer penuh, drop ekor terjadi semua paket tambahan dijatuhkan. Karena paket dijatuhkan sekaligus, sinkronisasi global host TCP dapat terjadi karena beberapa host TCP mengurangi tingkat transmisi mereka. Kemacetan membersihkan, dan host TCP meningkatkan tingkat transmisi mereka, mengakibatkan gelombang kemacetan diikuti oleh periode ketika link transmisi tidak sepenuhnya digunakan. RED mengurangi kemungkinan penurunan ekor dengan memasukkan paket secara selektif saat antarmuka output mulai menunjukkan tanda-tanda kemacetan. Dengan menjatuhkan beberapa paket lebih awal daripada menunggu sampai buffer penuh, RED menghindari menjatuhkan sejumlah besar paket sekaligus dan meminimalkan kemungkinan sinkronisasi global. Dengan demikian, RED memungkinkan jalur transmisi untuk digunakan sepenuhnya setiap saat. Selain itu, RED secara statistik menurunkan lebih banyak paket dari pengguna besar daripada kecil. Oleh karena itu, sumber lalu lintas yang menghasilkan lalu lintas paling banyak cenderung diperlambat daripada sumber lalu lintas yang menghasilkan sedikit lalu lintas. DWRED menyediakan batasan dan bobot terpisah untuk presedensi IP yang berbeda, memungkinkan Anda memberikan kualitas layanan yang berbeda untuk lalu lintas yang berbeda. Lalu lintas standar mungkin akan turun lebih sering daripada lalu lintas premium selama periode kemacetan. Pembatasan Pembatasan berikut berlaku untuk fitur DWRED: DWRED berbasis antarmuka tidak dapat dikonfigurasi pada subinterface. (Sebuah subinterface adalah salah satu dari sejumlah antarmuka virtual pada satu antarmuka fisik.) DWRED tidak didukung pada antarmuka Fast EtherChannel dan terowongan. RSVP tidak didukung pada DWRED. DWRED berguna hanya jika sebagian besar lalu lintasnya adalah lalu lintas TCPIP. Dengan TCP, paket yang terjatuh menunjukkan kemacetan, sehingga sumber paket mengurangi laju transmisi. Dengan protokol lain, sumber paket mungkin tidak merespons atau mengirimkan ulang paket yang terjatuh dengan tarif yang sama. Dengan demikian, menjatuhkan paket tidak serta merta menurunkan kemacetan. DWRED memperlakukan lalu lintas non-IP sebagai preseden 0, prioritas terendah. Oleh karena itu, lalu lintas non-IP biasanya lebih cenderung turun daripada lalu lintas IP. DWRED tidak dapat dikonfigurasi pada antarmuka yang sama seperti RQ berbasis CQ, PQ, atau WFQ. Namun, keduanya DWRED dan DWFQ dapat dikonfigurasi pada antarmuka yang sama. Catatan Jangan gunakan perintah protokol kecocokan untuk membuat kelas lalu lintas dengan protokol non-IP sebagai kriteria pencocokan. VIP tidak mendukung pencocokan protokol non-IP. Prasyarat Bagian ini memberikan prasyarat yang harus dipenuhi sebelum Anda mengkonfigurasi fitur DWRED. Weighted Fair Queuing Melampirkan kebijakan layanan ke antarmuka menonaktifkan WFQ pada antarmuka itu jika WFQ dikonfigurasi untuk antarmuka. Untuk alasan ini, Anda harus memastikan bahwa WFQ tidak diaktifkan pada antarmuka semacam itu sebelum mengkonfigurasi DWRED. Melampirkan kebijakan layanan yang dikonfigurasi untuk menggunakan WRED ke antarmuka akan menonaktifkan WRED pada antarmuka tersebut. Jika salah satu kelas lalu lintas yang Anda konfigurasikan dalam peta kebijakan, gunakan WRED untuk drop paket, bukan tetesan ekor, Anda harus memastikan bahwa WRED tidak dikonfigurasi pada antarmuka yang ingin Anda lampirkan pada kebijakan layanan tersebut. Daftar Kontrol Akses Anda dapat menentukan daftar akses bernomor sebagai kriteria kecocokan untuk setiap kelas lalu lintas yang Anda buat. Untuk alasan ini, sebelum mengkonfigurasi DWRED Anda harus tahu cara mengkonfigurasi daftar akses. Cisco Express Forwarding Agar bisa menggunakan DWRED, switching dCEF harus diaktifkan pada antarmuka. Untuk informasi tentang dCEF, lihat Panduan Konfigurasi Layanan IOS Switching. Flow Based WRED Flow berbasis WRED adalah fitur yang memaksa WRED untuk memberi keadilan lebih besar pada semua arus pada sebuah antarmuka sehubungan dengan bagaimana paket dijatuhkan. Mengapa Menggunakan Flow Based WRED Sebelum mempertimbangkan keuntungan yang menggunakan penawaran WRED berbasis aliran, ada baiknya untuk memikirkan bagaimana WRED (tanpa konfigurasi berbasis arus WRED) mempengaruhi berbagai jenis arus paket. Bahkan sebelum flow-based WRED mengklasifikasikan arus paket, arus dapat dianggap sebagai salah satu dari kategori berikut: Aliran nonadaptif, yaitu arus yang tidak merespons kemacetan. Aliran yang kuat, yang rata-rata memiliki data rate yang seragam dan melambat dalam menanggapi kemacetan. Aliran yang rapuh, yang, meski macet-sadar, memiliki lebih sedikit paket yang disangga di gerbang daripada aliran kuat. WRED cenderung menuju bias terhadap arus rapuh karena semua arus, bahkan yang memiliki paket yang relatif lebih sedikit dalam antrian output, rentan terhadap penurunan paket selama periode kemacetan. Meskipun aliran rapuh memiliki paket buffer yang lebih sedikit, mereka turun pada tingkat yang sama dengan paket arus lainnya. Untuk memberikan keadilan pada semua arus, WRED berbasis arus memiliki beberapa fitur berikut: Ini memastikan bahwa arus yang merespons tetesan paket WRED (dengan melepaskan transmisi paket) dilindungi dari arus yang tidak merespons tetesan paket WRED. Ini melarang satu aliran dari memonopoli sumber daya penyangga pada sebuah antarmuka. Cara Bekerja Flow-based WRED bergantung pada dua pendekatan utama berikut untuk mengatasi masalah penurunan paket yang tidak adil: Ini mengklasifikasikan lalu lintas masuk ke arus berdasarkan parameter seperti alamat tujuan dan sumber dan port. Ini mempertahankan keadaan tentang arus aktif, yaitu arus yang memiliki paket dalam antrian output. Flow-based WRED menggunakan klasifikasi ini dan informasi negara untuk memastikan bahwa setiap aliran tidak mengkonsumsi lebih banyak daripada bagian yang diizinkan dari sumber buffer output. Arus berbasis WRED menentukan mana yang memonopoli sumber daya dan lebih banyak menghukum aliran ini. Untuk memastikan keadilan di antara arus, berbasis arus WRED mempertahankan hitungan jumlah arus aktif yang ada melalui antarmuka output. Dengan jumlah arus aktif dan ukuran antrian keluaran, berbasis aliran WRED menentukan jumlah buffer yang tersedia per aliran. Untuk memungkinkan beberapa burstiness, skala berbasis aliran WRED jumlah buffer yang tersedia per aliran oleh faktor yang dikonfigurasi dan memungkinkan setiap aliran aktif memiliki sejumlah paket dalam antrian output. Faktor penskalaan ini umum terjadi pada semua arus. Hasil dari jumlah skala penyangga menjadi batas per aliran. Bila aliran melebihi batas per aliran, probabilitas bahwa paket dari arus tersebut akan turun meningkat. DiffServ Compliant WRED DiffServ Compliant WRED memperluas fungsionalitas WRED untuk mengaktifkan dukungan untuk DiffServ dan AF Per Hop Behavior PHB. Fitur ini memungkinkan pelanggan menerapkan AF PHB dengan mewarnai paket sesuai dengan nilai DSCP dan kemudian menetapkan probabilitas drop preferensial ke paket tersebut. Catatan Fitur ini hanya bisa digunakan dengan paket IP. Ini tidak dimaksudkan untuk digunakan dengan paket Multiprotocol Label Switching (MPLS)-tersusun rapi. Kualitas Layanan Berbasis Kelas MIB mendukung fitur ini. MIB ini sebenarnya adalah dua MIB berikut: Fitur DiffServ Compliant WRED mendukung RFC berikut: RFC 2474, Definisi Bidang Layanan Diferensial (Bidang DS) di Header IPv4 dan IPv6 RFC 2475, Kerangka Arsitektur untuk Kerangka Kerja yang Diferensial RFC 2597, Tertentu Forwarding PHB RFC 2598, Sebuah Ekspedisi Forwarding PHB Cara Kerja DiffServ Compliant WRED fitur memungkinkan WRED untuk menggunakan nilai DSCP ketika menghitung probabilitas drop untuk sebuah paket. Nilai DSCP adalah enam bit pertama dari jenis layanan IP (ToS) byte. Fitur ini menambahkan dua perintah baru, random-detect dscp dan dscp. Ini juga menambahkan dua argumen baru, berbasis dscp dan prec-based. Ke dua perintah WRED yang ada terkait perintah acak-detect (interface) dan perintah random-detect-group. Argumen berbasis dscp memungkinkan WRED untuk menggunakan nilai DSCP dari sebuah paket saat menghitung probabilitas drop untuk paket. Argumen berbasis sebelumnya memungkinkan WRED untuk menggunakan nilai IP Precedence dari sebuah paket saat menghitung probabilitas drop untuk paket. Argumen ini bersifat opsional (Anda tidak perlu menggunakan salah satu dari mereka untuk menggunakan perintah) tetapi keduanya juga saling eksklusif. Artinya, jika Anda menggunakan argumen berbasis dscp, Anda tidak dapat menggunakan argumen berbasis sebelumnya dengan perintah yang sama. Setelah mengaktifkan WRED untuk menggunakan nilai DSCP, Anda kemudian dapat menggunakan perintah dscp acak-detect yang baru untuk mengubah batas paket minimum dan maksimum untuk nilai DSCP tersebut. Tiga skenario untuk menggunakan argumen ini disediakan. Usage Scenarios The new dscp-based and prec-based arguments can be used whether you are using WRED at the interface level, at the per-virtual circuit (VC) level, or at the class level (as part of class-based WFQ (CBWFQ) with policy maps). WRED at the Interface Level At the interface level, if you want to have WRED use the DSCP value when it calculates the drop probability, you can use the dscp-based argument with the random-detect (interface) command to specify the DSCP value. Then use the random-detect dscp command to specify the minimum and maximum thresholds for the DSCP value. WRED at the per-VC Level At the per-VC level, if you want to have WRED use the DSCP value when it calculates the drop probability, you can use the dscp-based argument with the random-detect-group command. Then use the dscp command to specify the minimum and maximum thresholds for the DSCP value or the mark-probability denominator. This configuration can then be applied to each VC in the network. WRED at the Class Level If you are using WRED at the class level (with CBWFQ), the dscp-based and prec-based arguments can be used within the policy map. First, specify the policy map, the class, and the bandwidth. Then, if you want WRED to use the DSCP value when it calculates the drop probability, use the dscp-based argument with the random-detect (interface) command to specify the DSCP value. Then use the random-detect dscp command to modify the default minimum and maximum thresholds for the DSCP value. This configuration can then be applied wherever policy maps are attached (for example, at the interface level, the per-VC level, or the shaper level). Usage Points to Note Remember the following points when using the new commands and the new arguments included with this feature: If you use the dscp-based argument, WRED will use the DSCP value to calculate the drop probability. If you use the prec-based argument, WRED will use the IP Precedence value to calculate the drop probability. The dscp-based and prec-based arguments are mutually exclusive. If you do not specify either argument, WRED will use the IP Precedence value to calculate the drop probability (the default method). The random-detect dscp command must be used in conjunction with the random-detect (interface) command. The random-detect dscp command can only be used if you use the dscp-based argument with the random-detect (interface) command. The dscp command must be used in conjunction with the random-detect-group command. The dscp command can only be used if you use the dscp-based argument with the random-detect-group command. For more information about using these commands, refer to the Cisco IOS Quality of Service Command Reference. Android vs iOS: how they compare (updated for Android Nougat and iOS 10) Android 7.x Nougat and iOS 10.x have been rolling out to devices around the globe, with the changes come new multi-tasking features for Android and some powerful developer APIs for iOS. We8217ve added some of the particulars below, otherwise, there are very few edits to our Android vs iOS article this month. Let me start with a simple truth, I am a fan of Android. I have such a passion for Google8217s mobile operating system that I worked my way to a job where I get to play with Android all day, and share my experiences with you, our faithful readers. Today I am going to talk about iOS as well, and I may have to say some nice things, hang in there and we8217ll get through this together. All joking aside, Android and iOS are the clear leaders in mobile operating systems around the globe, and the idea for each is to provide the fastest, smoothest and most robust performance and features as possible. With different approaches to these tasks, it is about time we did an official Android vs iOS comparison. The differences between these two operating systems goes well beyond the bits and bytes of it all, Android and Apple have both cultivated strong followers, please note that I said 8220Apple8221 on purpose, as 8220iOS8221 is not the term used with passion quite as much. This speaks to a larger difference in these two ecosystems, where Android users are loyal to the operating system, but iOS users are loyal to the company behind the OS, we8217ll explain more in a bit. These fans are people that are willing to camp out for days to get the next device, people that are willing to spend hundreds, if not thousands of dollars to enjoy the latest and greatest phones and tablets with each OS. Unfortunately, this also means that there are users on both sides that are quick to belittle the other. We are glad to see a greatly reduced frequency of such outbursts, but there was a time that you could often find crude and indecent conversations between the fans of each OS. The general dispute in days past is exactly what makes these two operating systems stand out from one another. On one hand, Android is a highly customizable system, with roots in Linux and code that can be found in the Open Source space for all to take and expand upon. On the flip side, iOS is a closed operating system. Without taking extreme actions, the average user will never know what tweaking the OS or alternate versions of the OS would look like. Bringing it back to the core of the user experience, Android is an excellent OS for those that like to get down and dirty with their devices, where iOS is made for simplicity, turn on any Apple mobile device and enjoy the exact same experience. There is no right or wrong option for all, one must decide what they want and need for themselves, then read articles like this one to learn which system will suit them best. Android 7.0 Nougat vs iOS 10 8211 the latest and greatest in 2016 Recent updates to both operating systems have added a ton of new functionality and features that out-do their respective predecessors. Multi-tasking is the name of the game on Android and APIs for Siri are the big news on the iOS side. There is way more to each OS update, but these are, I believe, the key features. Starting with iOS 10, which began hitting devices in September, there were many little improvements and more than a few updates to system apps like Safari, News, Music and more. Lift to wake uses sensors to identify when you lift the device up to face you, turning the display on for you. Handy, but, truth told, a feature that has been around in Android for a while, if only only a select few devices. APIs are the big winner here. as far as iOS 10 updates go, APIs are boring news right now for the most of us, but the new integration with Siri means that all of your favorite apps can build voice input functionality into the Siri input. Instead of Siri serving little more than a voice search tools, with the ability to open a few apps and other relatively limited functionality, stay tuned for the ability to reserve a table, order a burrito and so much more by voice, turning Siri into a personal assistant able to control things beyond the device in your hand. Moving over to Android Nougat, and more specifically Androi 7.1 as found on the Pixel phone announced in October, the personal assistant theme prevails with Google Assistant. What you may know as Google Now, a voice search tool with some basic functionality beyond search, the bump up to Assistant takes things to a similarly new world. We8217ve been waiting on this since Google teased it at Google IO earlier in the year, a voice search tool that can live on more than just your handheld device 8211 look for Google Home and more 8211 that can handle everything from reading you the news, reminding you your schedule for the day, all the way up to playing music or casting your favorite movie on the big screen. Android 7.1 Nougat may be the best of the best at this time, but Android 7.0 is the best to be found on non-Pixel phones. Updates to the OS, which are only a month old themselves, include muti-tasking features that include split-screen functionality, for some apps at least, and new functionality to the Recents button 8211 just double tap to jump between your two most recently used apps. The Notification Shade, Quick Settings and main Settings have been revamped for easier navigation and customization as well. It would be wrong of me to dive into the technical details on this next point, but it is important to mention that Google has opted to balance better between ART with its pre-load compiling and the more traditional JIT compiling. In plain terms, Android 6.x would pre-load most of the OS and your apps into RAM when the device started up, I8217m sure you recall the screen that just said 8220Optimizing app 73 of 210.8221 The new setup will get you going faster, doing this pre-load in the background as the OS becomes available to you sooner. The best of both worlds, I suppose. Android8217s double edged open source sword The ability to take the base version of Android and expand upon it has resulted in wonderful and diverse device experiences. Sadly, this has also meant some seriously strange and problematic situations. At the core of it is what is called AOSP, the Android Open Source Project, built and maintained primarily by Google. AOSP is, as the name implies, a free and open operating system that anyone is free to take and modify. This is most commonly performed by our favorite device manufacturers. Even Google develops the Nexus program, which is a fairly vanilla experience, just with the addition of Google8217s own suite of apps and services, which are not built into AOSP. In addition to the manufacturers creating unique skins for the OS, there is a vibrant community of smaller players making third-party (so to speak) ROMs for popular Android devices. For those unfamiliar, a ROM is what we typically refer to as the actual code for an Android OS, and it is possible to install this code to an Android device by a means called Flashing. Every one of these ROMs offers a unique and flexible set of design and features placed on top of the core layer of Android. While I believe that having options is a good thing, there are those that feel that there are just too many options available under the Android banner. With something north of 5000 unique Android devices available for purchase, it is no wonder that there is some confusion for consumers. Sadly, there is also no surprise that more than a few of these devices and ROMs are utterly useless. But that8217s why you are here, to learn the good from the bad, right The 8220iSheep8221 situation A commonly used term, meant as a derogatory description of an Apple user, 8220iSheep8221 implies that a person blindly follows wherever they are told to go with their iOS powered mobile devices. In stark contrast to the plethora of options on Android, iOS users have just a few options in front of them. In fact, I could name each and every mobile device made by Apple right here, and you wouldn8217t be overwhelmed. With now two current generation smartphones, but five up for sale on their website, plus three sizes of their tablet, Apple8217s latest and greatest offerings are easy to choose from. For many, there is no need for options or variables, they just want a simple device that gets the job done. More often than not, a person purchasing a newer iPhone or iPad will be found to already own an older version of the device. This is not to say that they are blindly following, just that they are comfortable with the type of device that they have, but need a newer version in a different size or with a little more horsepower. Sometimes these folks 8220need8221 a new version of their iPhone or iPad because they8217ve been told the new one is just better, but that holds true of flagship Android devices as well, doesn8217t it The main difference, at least in our little world of Android fandom here at Android Authority and TabTimes, is that us Android users care about the specs inside the devices, whereas, the average iOS user that I know personally just wants the device to be able to keep up with them, regardless if it has Intel, Snapdragon, Exynos, MediaTek, Kirin or Apple processor. Hint, your Apple product is likely to only contain one of these processors, can you guess which one Enough with the theory, let8217s look at the actual software. The basics The basic software experience is actually fairly similar between Android and iOS. Aside from the initial setup, users are greeted by a lock screen, requiring a swipe gesture or authentication challenge to enter the system. Once inside, you get a Homescreen or two and some apps. Everything from your system settings to your favorite game or social media program is made available through individually installed and updateable programs, and each ecosystem has an attached store to install from a collection of over a million other apps. Apps generally run in fullscreen mode and, for the most part, you can only really use one app at a time. That is not to say that you cannot multi-task, just that without the latest of iOS software and devices, specialized apps on Android or the latest Android 7 Nougat installed, only one app displays on screen, your other 8216multi-tasking8217 apps will need to run in the background. This is ideal for music players or file downloads, but means you cannot, generally speaking, have a spreadsheet and a text document on screen at the same time. Luckily, this is changing, as the latest versions of both operating systems are incorporating split screen app usage. One can quickly view their recently used apps from a dedicated list. This recent apps list also allows one to effectively close an app by swiping the app off of the screen from the list. Swipe down from the top of the screen to access what Android calls the Notification Shade. This is a drop down menu that houses current notifications from the apps and services on your device. Android includes a quick settings menu at the top, from a second downward swipe, and iOS put their quick settings panel at the bottom. Do you get my point yet In the big picture, things are very similar, much in the same way that most all cars on the road have four tires and a steering wheel. The differences are in the details. Where one can find options for fuel efficient small cars all the way through to jet engine equipped monster trucks, literally, so too can one find many differences in Android and iOS devices. Home screens The default location for all of your computing is the homescreen. Both Android and iOS have Home screens, and on each you can place links to apps, folders and more. The largest difference, at least for now, is that most Android builds include an app drawer in which the OS stores all of your app icons, though there are exceptions, with the LG G5 going completely app drawer-less, for example. In contrast to 8216stock8217 Android, iOS simply dumps all your apps onto the Home screen by default. Each operating system includes folders for better management and will add in extra screens as needed if you go over the default amount. Advantage Android 8211 Launchers . One key feature of Android, which goes well beyond the Homescreen, is the ability to install third-party Launchers. A Launcher is a full desktop environment for your device, you may have heard the term 8216skin8217 as well, which is appropriately descriptive of how a Launcher works. Providing different and extra tools for controlling apps, icons, folders, number of screens on your Homescreen layout and more, Launchers open a whole new world to the Android experience. Best of all, Android users can get their hands on Google8217s own Pixel Launcher as well. Formerly know as the Nexus Launcher, this is the home scree environment that Google has built for their Pixel phones, including a sideways swipe to a dedicated Google Search hub and page, known as Google Now and now Google Assistant. iOS also has a sideways swipe to a Siri powered news and search page, so this point is a tie, depending on your ecosystem of choice, of course. Advantage Android 8211 Widgets . Admitting that iOS has made some strides in this department, Android is still king of customization, particularly homescreen customization and utilities through interactive elements called widgets. Perhaps the best examples of widgets are a clock widget and a music widget. Where there is a full fledged app in the back end for the clock and music playback, widgets put small interactive graphical windows on your homescreen for quick actions like viewing the time or simply controlling your music playback. Lockscreen A dangerous topic for any computer related developer, user, tester or more, 8216what makes a device good8217 and 8216is yours good enough8217 Better yet, 8216who8217s device is better8217 There are two very distinct theories at work when you compare Android and iOS for performance, with Apple8217s tight control over all aspects of hardware and software differing greatly from Google8217s approach of building an OS and just putting it out there for the hardware manufacturers to have fun with. If you8217ve spent any time on our sites, you know already that there are in the ballpark of 5000 unique Android devices on the market. But you probably also know that there are only a handful of great devices, the flagships that shape the generation, each year. Apple8217s approach avoids the irrelevant devices, focusing only on the best phones and tablets that they can offer, but it is fair to say that Apple8217s best and Android flagships are in the same league for performance. When we put the average iOS powered device beside an average Android device, we still can8217t truly compare them fairly. Android manufacturers, acting on their own, and not always in the best interest of Google and Android, have the freedom to install any version of Android they wish, update it as they wish, and add in their own sets of apps and features. There are a few rules to follow to be eligible for Google8217s apps and services, but that takes this topic too deep for today8217s comparison. Truth is, for the average user who surfs the web, checks into social media a few times per day, pulls up a map and plays a small game or two, there is no point doing any performance battles. Your average iOS or Android device will work just fine. Good thing we are not your average users around here, let8217s dive in. First up, let8217s talk hardware. Looking for a 64-bit quad-core or larger processor, graphics processor capable of easily running full HD and beyond displays, 4GB of RAM, 64GB or maybe 128GB of internal storage space, fingprint scanners, a 12MP or greater camera sensor capable of 4K video capture What about high-fidelity audio Yup, Android and iOS have all that. Mostly, anyway. You really have to start looking at some of the gimmicks and party tricks of each device to decide what is more important to you for overall performance, but the truth is, deep down where it counts, the hardware available to Android and iOS users is largely the same. If the hardware is the same, the performance should also be equal, right Nope Don8217t be fooled by the spec sheets, and all that junk I just told you, there is a difference in performance across the devices. Dramatic differences, actually. We see this all the time just in Android devices, we8217ll have a Snapdragon powered device side-by-side a Kirin or MediaTek device. On paper the processors may be 8216equal,8217 but true usage of the processors tells an entirely different story. iPhones have long been touted as the best phones for photography, while that may have been true for a while, Android devices are beginning to steal that thunder. However, the 12MP, 16MP and even 21MP or larger camera sensors on these competing Android devices could be considered overkill compared to the long running 5MP, 8MP and now 12MP sensors on the Apple devices. Let8217s not get into it all, I just wanted to point out that Apple has figured out a trick, if only in the software side of things, that many Android manufacturers have either never bothered with or are only recently figuring out as well. The same specification does not mean you8217ll see the same performance. As you can see, for basic day-to-day tasks, our sample iOS and Android devices perform admirably. You need to get down and dirty, by loading heavy games or other large apps, before you really get a feel for the difference in performance here. Apple8217s latest does outperform a one year old Kirin device and a brand new Intel powered device, but that margin is reduced greatly when flagship Android devices are considered. Please do keep in mind that, although the speed tests above were performed as fair and accurate as we could, we did not account for many external factors such as network performance, device up-time or amount of other apps running and more. Point is: our tests are flawed in many ways, but they are great indicators of real world performance as calculated with no more than a basic stop watch. Also, the first 5 devices were tested by me, but the Note 5 and iPhone 6S were each tested by other members of our team, results may vary depending on how they performed these tests. Bottom line, we cannot definitively announce a best phone or OS here, please just use the data for some perspective. I8217ve added times for the iPhone 7. I know things look confusing based on this graph, but there is a speed bump over the older iPhone 6S, and we8217re pretty impressed by it. We8217ll be sure to jump back when we get the chance to test the Pixel phone to round out your perspective. Conclusions As we have said time and time again, your preferred ecosystem for apps and services should be your deciding factor between an Android or an iOS device purchase. Obviously, we prefer Android around here. We8217re assuming that most of you on our Android fan site are also Android fans, not that that matters. With two highly capable operating systems at your disposal, we truly feel the only reason to choose one over the other is out of personal preference, just please put in the time to figure out what will fit your needs best before you spend a ton of money on a device and accessories. While we prefer Android mainly because of its ability to mold to our liking, we cannot discount the value in the simplicity of iOS. Admitting that there is still a learning curve, and that the average Android user may be frustrated with the lack of features and options, many users out there appreciate the familiarity and thoughtlessness of using iOS. Let me say this again in one last way, this is something that I have been saying about Android vs iOS since the days of Froyo and is less true today that it was then, but I still stick with it: With iOS, you ask what your device can do and you stick with that, with Android, you ask yourself what you want to happen, then find out how Android can do it. Bottom line, iOS is a powerful tool, if you want to do what it wants to do, Android is a powerful tool no matter what you want to do. Final note: I hope that we8217ve provided a thorough overview of the major similarities and differences between Android and iOS. We recognize that there is so much more to each ecosystem than what we talked about here today, we also recognize that we are fairly biased in favor of Android, we can8217t help it, that8217s our passion. Please remember these things as you ponder the differences in these operating systems, luckily it is as easy as ever to bounce back and forth between the two these days, so don8217t be afraid to experiment. It8217s your turn, join us in the comments below for a thoughtful and polite conversation, even debate, over these two powerful operating systems. What do you think, Android vs iOS When you are ready to move forward, here are some resources to help you get started :Feb 21, 2017 7:51 am PST by Joe Rossignol The tentatively named Apple Watch Series 3 will feature a new glass-film touchscreen in place of the current touch-on-lens solution, with shipments to begin in the second half of this year, according to Taiwan-based DigiTimes . While it remains unclear if the switch to a film-based solution will have any obvious consumer-facing benefits, this is more interestingly the first rumor to surface about the supply chain ramping up for the next Apple Watch. The timeline matches a Chinese report last month that claimed the third-generation Apple Watch will be unveiled in the third quarter of 2017 with battery life and performance improvements. The report said Series 3 models, to be manufactured by Quanta, will lack any significant hardware changes. Few other details are known about the next Apple Watch models, which could feasibly launch alongside the iPhone 8 in September. KGI Securities analyst Ming-Chi Kuo and other sources have claimed the Apple Watch could gain an LTE chip for cellular capabilities as early as 2017, while a supply chain report last year said Apple may switch from OLED to micro-LED displays for the Apple Watch in the second half of 2017 at the earliest. Micro-LED displays have benefits such as thinness, lightness, improved color gamut, increased brightness, and higher resolutions. The panels do not require backlighting like traditional LCD displays, but they can be difficult and expensive to mass produce. Micro LEDs range in size from 1-micron to 100-micron. Apple has filed patents for a number of ideas that could eventually be included in an Apple Watch, such as a heart rate identification system. modular bands. haptic feedback band. and a band with a built-in charger. More significant health and fitness features could be added pending further FDA approvals. Ahead of Apple Watch Series 3 models, Apple is expected to introduce new bands at its rumored iPad Pro-focused event next month. Feb 21, 2017 7:01 am PST by Joe Rossignol The widely rumored 5.8-inch iPhone with an edge-to-edge OLED display will match the iPhone 7 Plus with 3GB of RAM and come in two storage options, 64GB and 256GB, according to Chinese research firm TrendForce . The report, which outlines several already-rumored features, added that the so-called iPhone 8 will not have a fully curved display due to production and drop test issues with 3D glass. Instead, the high-end device will adopt the same slightly curved 2.5D cover glass used since the iPhone 6 and iPhone 6 Plus in 2014. TrendForce said Apple will remove the Home button on the iPhone, as widely rumored, and integrate the related functions into the display. If that fact is accurate, it suggests rumored 3D facial recognition capabilities could supplement rather than fully replace Touch ID. which could be embedded into the display. TrendForce itself expects the iPhone 8 to incorporate 3D sensing technology that can be used for facial recognition and augmented reality features. The research note said the 5.8-inch iPhone will be accompanied by updated 4.7-inch and 5.5-inch models with LCD displays. The 5.5-inch model will allegedly have the same 3GB of RAM as the iPhone 7 Plus, while the 4.7-inch model is said to have 2GB of RAM. Both models are expected to include up to 256GB of storage. Rumors are generally shaping up to suggest the 5.8-inch iPhone with an OLED display will be a significant upgrade, but the model could cost upwards of 361,000 in the United States. Meanwhile, the new 4.7-inch and 5.5-inch models are expected to be iterative but less expensive upgrades to the iPhone 7 and iPhone 7 Plus. Last year, TrendForce accurately predicted the iPhone 7 and iPhone 7 Plus would be available in 32GB, 128GB, and 256GB storage capacities. Apple today has been granted a patent by the United States Patent and Trademark Office regarding an avatar editing environment , which is the companys patent terminology for a Mii-like app that users can visit to craft a digitized likeness of themselves to use throughout the Apple ecosystem. The patent was originally filed back in October 2011 but was just published by the USPTO today (via Patently Apple ). Apples patent explains that its avatar editing environment would let users create a representation of their alter ego. This includes a collection of editing features such as different eyes, ears, mouth, skin color, hair, teeth, smile, facial expressions, eyebrows, hair, beard, glasses, hats, and even more items related to the expression of each persons unique identity and fashion. While Apples new patent sounds like a basic Avatar editing system, the companys wording goes into deeper detail about how far and wide the digital personalities might be implemented across its services. The editor would primarily be its own application on iOS devices, but the patent also notes that Apple could add it as an online addition to its website and give its API to developers so they could implement the avatars into games, social networks, and more. Once an avatar is created, the user would then discover the character can be placed -- and even animated -- in a number of iOS locations, including in Messages, Address Book, and FaceTime. In Messages, users could set a specific animation of their avatar to trigger in response to certain events, so while youre waiting for a text from a friend your avatar could be animated on their screen to be tapping its foot in impatience, or sleeping. In execution, some of Apples avatar features sound similar to the popular Bitmoji app. The patent also describes a feature where a users face would be replaced in video chat, likely within FaceTime, by the avatar that they have created with Apples editing system. The character would then be able to track and replace the users expressions, eye movements, head, and body language, much like the technology created by Faceshift, which Apple acquired two years ago. Like all other patents, the avatar editing environment described here is unlikely to see the light of day any time soon, if ever. Although the patent mentions that users could manually and automatically generate an avatar, it never directly specifies if that would include using a future iPhones advanced camera system to map the users face and generate a close approximation in digital form. According to analyst Ming-Chi Kuo. the iPhone 8 s front camera will be able to fuel experiences just like that, and might lead to gaming-enhanced 3D selfies and even experiences in augmented and virtual reality. The rumored iPhone 8 with an edge-to-edge OLED display will gain a revolutionary front-facing camera system that consists of three modules that enable fully-featured 3D sensing capabilities, according to new predictions shared by KGI Securities analyst Ming-Chi Kuo. The upgraded camera system will be fueled by PrimeSense algorithms, which Apple acquired in 2013. The three modules include an existing front camera module of current iPhones, an infrared transmitting module, and an infrared receiving module. Using these advancements, the camera will be able to find the location and depth of objects placed in front of it, with potential applications including facial and iris recognition. The camera will function by merging the depth information captured by the IR transmitting and receiving modules with the traditional 2D images captured by the front camera. This not only could be used for the iPhone 8s long-rumored iris recognition feature. but even in some gaming applications -- and future ARVR experiences -- where users could place their own 3D-scanned face in the game using a quick selfie. Todays news of an overhaul to the front-facing camera of the iPhone 8 follows speculation surrounding the potential of Apple dropping Touch ID and instead focusing on either 3D facial recognition or iris scanning as the devices main security feature. JPMorgan analyst Rod Hall has stated that facial recognition could be a more secure alternative, and help increase Apple Pay adoption with retailers and financial institutions. According to Kuo, this three-module front-facing camera system will bring an innovative user experience to the OLED iPhone 8, but for now itll be reserved as exclusive to that model. Future iPhones may come with a similar system for the rear camera, the analyst noted. Feb 21, 2017 3:59 am PST by Tim Hardwick Popular podcast player Overcast has reached its long-awaited third iteration on the iOS App Store. with improvements to episode management and a slew of other UI enhancements. Designed by Instapaper developer Marco Arment. Overcast 3s most obvious change is that it adopts the design language of iOS 10. such as the use of stacked views which Apple introduced in Apple Music. so screens including Now Playing, settings, downloads, and recommendations, now appear as stacks that slide up from the bottom of the interface. Theres also a redesigned Now Playing view, in which users swipe right to adjust audio settings, and swipe left to view episode information. A new episode action tray features in the app, grouping actions that were previously hidden behind swipe gestures or other menus. Tapping an episode in a list now displays buttons to share, star, play, add to queue, and delete the selected podcast episode. Elsewhere, Peek and Pop 3D Touch gestures are now supported in episode list screens, allowing users to quickly preview episode contents and access play and delete shortcuts by sliding up the Peek card. An Overcast 3 widget for the home screen has also been developed, which allows users to see whats playing, resume playback, and see upcoming episodes in their Up Next queue. Also included in Overcast 3 is a redesign of its Apple Watch component, with the ability to view upcoming episodes from the wrist. Overcast 3 is available as a free ad-supported app, while an optional 369.99 in-app purchase gets users a premium ad-free version. Overcast 3 is available for iPhone and iPad from the App Store. Direct Link Feb 21, 2017 2:46 am PST by Tim Hardwick Apple has claimed that the European Commission made fundamental errors when it ruled last year that the company owed Ireland 13 billion euros (3613.7 billion) in unpaid taxes plus interest. Apple appealed the commissions decision in December, but on Monday the company published a piece in the Official Journal of the European Union detailing 14 pleas in law to support its action, according to The Irish Times . The European Commission argues that Irish revenue commissioners gave Apple unfair advantage between 1991 and 2007 by allowing the company to move income from the European market through two non-resident head office subsidiaries based in Ireland. Apple and the Irish government, which has also appealed the commissions decision. argue that the bulk of those profits are due in the U. S. The Commission made fundamental errors by failing to recognize that the applicants profit-driving activities, in particular the development and commercialization of the intellectual property (Apple IP), were controlled and managed in the United States, Apple said, according to the Official Journal. The profits from those activities are attributable to the United States, not Ireland. Apple maintained that the commission had failed to recognize that the Irish branches carried out only routine functions and were not involved in the development and commercialization of Apple IP, which drove profits. Cupertino also said that the commission failed to conduct a diligent and impartial investigation, and exceeded its competence as it relates to the Treaty on the Functioning of the European Union, by attempting to redesign Irelands corporate tax system. Apple CEO Tim Cook has called the ECs ruling total political crap and described the lower end 0.005 tax rate Apple is accused of paying as a false number. The Apple CEO believes that the decision will be reversed. Appeals by Apple and the Irish government have been made to the European Unions General Court, where proceedings may take up to two years to complete, after which the case is likely to go all the way to the European Court of Justice. Note: Due to the political nature of the discussion regarding this topic, the discussion thread is located in our Politics, Religion, Social Issues forum. All forum members and site visitors are welcome to read and follow the thread, but posting is limited to forum members with at least 100 posts. Feb 20, 2017 3:40 pm PST by Juli Clover As part of its ongoing Shot on iPhone advertising campaign highlighting the iPhones camera, Apple today uploaded four videos that belong to its new One Night series. Each of the 15 second ads features a compilation of photos and videos captured on a single night in New York, Johannesburg, Shanghai, and Tokyo and set to music. Designed to showcase the low-light capabilities of the iPhone 7 and the iPhone 7 Plus, all of the photos and videos in the One Night campaign were taken on November 5, 2016 in different places around the world. Last week, Apple uploaded a one minute compilation video featuring much of the same footage, but todays videos show more of the individual photos and videos taken in each different location. Though only four locations are shown in the videos uploaded today, the One Night ad campaign features images and videos taken by 16 photographers across 15 cities on six continents. Apple is also using the photographs as part of a One Night print and billboard campaign thats being showcased in 25 countries around the world. Update: Apple has also uploaded two new videos that are part of a separate ad campaign showcasing Portrait Mode in the iPhone 7 Plus. Each video offers a short tutorial on the benefits of Portrait Mode, showing how its able to blur the background to put the focus on the person in the photograph. Feb 20, 2017 12:11 pm PST by Juli Clover Apple today seeded the third beta of an upcoming macOS Sierra 10.12.4 update to developers, two weeks after seeding the second macOS Sierra 10.12.4 beta and just under a month after releasing macOS Sierra 10.12.3. The third macOS Sierra 10.12.4 beta is available for download through the Apple Developer Center or the software update mechanism in the Mac App Store for those who have previously installed a beta. macOS Sierra 10.12.4 brings iOSs Night Shift mode to the Mac for the first time. First introduced on iOS devices with iOS 9.3, Night Shift is designed to gradually shift the display of a device from blue to yellow, cutting down on exposure to blue light. Blue light is said to disrupt the circadian rhythm and is believed to interrupt sleeping patterns. Night Shift can be activated through the Displays section of System Preferences, where a setting to have it come on at sunset and turn off at sunrise is available. Night Shift can also be toggled on manually through the Notification Center or via Siri. Subscribe to the MacRumors YouTube channel for more videos. The 10.12.4 update focuses mainly on Night Shift, but also includes dictation support for Shanghainese, cricket scores for Siri, improved PDFKit APIs, and iCloud Analytics options. Feb 20, 2017 11:48 am PST by Juli Clover Both ING Direct and Macquarie have implemented support for Apple Pay in Australia, according to Apples updated Apple Pay website in the country. Starting today, both ING Direct and Macquarie customers can use Apple Pay for purchases in participating stores and locations with an eligible device. Apple Pay support at the two banks comes more than a year after Apple Pay first became available in the country through a partnership with American Express. The service is available in retail stores on iPhone SE. 6, 6s, 6 Plus, 6s Plus, 7, 7 Plus, and older devices using the Apple Watch. In-app and web purchases can also be made using the aforementioned devices, a supported iPad, or one of Apples new MacBook Pro s. While ANZ and many smaller banks support Apple Pay in Australia, three of the countrys major banks, including Commonwealth Bank, National Australia Bank, and Westpac, are currently embroiled in an ongoing dispute with Apple that has seen the banks refusing to accept Apple Pay. The banks have asked the Australian Competition and Consumer Commission (ACCC) to give them permission to negotiate with Apple to gain access to the NFC chip in the iPhone, allowing the iPhone to be used with the banks own NFC-based payment solutions. Apple does not allow third-party services to access the NFC chips built into its most recent devices for security reasons and has argued that the banks challenge is harmful to consumers and would stifle innovation in mobile payments. The ACCC sided with Apple in an initial ruling. but both sides are continuing to submit arguments and the banks recently re-submitted their application asking for permission to work together to make a deal with Apple. Apple Pay is available in 13 countries, including the United States, UK, China, Australia, Canada, Switzerland, France, Hong Kong, Russia, Singapore, Japan, New Zealand, and Spain. Feb 20, 2017 10:16 am PST by Juli Clover Apple today seeded the third beta of an upcoming tvOS 10 .2 update to developers for testing purposes, two weeks after seeding the second tvOS 10.2 update and nearly a month after releasing tvOS 10.1.1. the current release version of tvOS. Designed for the fourth-generation Apple TV. the third tvOS 10.2 beta can be obtained by connecting the Apple TV to a computer with a USB-C to USB-A cable, downloading and installing the software from a registered developer account via iTunes or Apple Configurator. Once a profile is installed, subsequent betas can be downloaded over the air. Given the tricky installation requirements, tvOS betas are limited to developers and will not be provided to the public. According to Apples release notes, tvOS 10.2 introduces improved scrolling behavior, allowing tvOS users to scroll through large lists of information more quickly. A large swipe on the Siri remote automatically activates the new scrolling mode, and a swipe on the far right side of the remote allows users to navigate specific indexes. Its likely there are other small feature tweaks and bug fixes included in tvOS 10.2, even though additional changes have not been specifically outlined by Apple. Well update this post should any new content be found in the third tvOS 10.2 beta. Feb 20, 2017 10:13 am PST by Juli Clover Apple today seeded the third beta of an upcoming watchOS 3.2 update to developers for testing purposes, two weeks after seeding the second watchOS 3.2 beta and nearly a month after the release of watchOS 3.1.3. the current public version of the operating system. The watchOS 3.2 beta can be downloaded through the dedicated Apple Watch app on the iPhone by going to General -- Software Update after installing the proper configuration profile on the iPhone. To install the update, the Apple Watch must have 50 percent battery, it must be placed on the charger, and it must be in range of the iPhone. Subscribe to the MacRumors YouTube channel for more videos. watchOS 3.2 requires an iPhone running iOS 10 to install and will only be available to developers. Apple does not make watchOS betas available to the public as there is no way to downgrade the software on an Apple Watch. watchOS 3.2 includes a Theater Mode designed to let customers quickly mute the sound on the Apple Watch and disable Raise to Wake, preventing the screen from lighting up with arm movement. Theater Mode, originally introduced in watchOS 3.1.3, is being made available in watchOS 3.2. Customers are still able to receive haptic feedback-based notifications, and information can be viewed by either tapping the screen or pressing down on the Digital Crown. watchOS 3.2 also brings Siri Kit to the Apple Watch, allowing customers to ask Siri to do things like send messages, send payments, book a ride, log a workout, make a call, or search through photos. SiriKit has been available on iOS devices since the release of iOS 10, but is new to the Apple Watch.
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